Poster session 3

End stage renal disease (ESRD), with its increasing prevalence and high mortality rate, is an important public concern. Polymer membranes used for dialysis have a wide range of pores, tortuous paths and some materials like polysulfone are non-biocompatible. Hence, we intend to develop cost effective, portable teflon based dialysis devices with efficient silicon dialyzers. Composite membranes of microporous and nanoporous silicon have been fabricated to separate blood cells from plasma and to clear uremic toxins respectively.

Silicon Nanoporous Membranes (SNMs) of 15 nm thickness, with an average pore diameter of 8 nm were fabricated in-house by batch mode microelectronic processes. They were functionalized to prevent surface binding. Porous silicon (PS) membranes of 50 µm depth and 1-2 µm diameter was formed by electrochemical etching followed by a lift-off method. Using arrays of 9 SNMs (3×3), teflon devices were tested with 30 ml of mock fluid and blood serum. A custom made teflon setup was made containing two reservoirs- cis having fluid with uremic toxins and trans with dialysate, separated by silicon membranes at the center. The filtration experiments were carried out with diluted heparin treated human blood.

PS membrane efficiently separated the plasma from whole blood within 10 minutes of peristalsis. Using an SNM array, 50% of urea and creatinine were eliminated from mock fluids within 15 minutes of peristalsis. Under similar conditions, 42% of urea and 48% of creatinine were cleared from 30 ml blood plasma.

Affordable and portable hemodialyzers can significantly impact patients with renal failure. Efficient filtering by the PS membranes followed by the clearance of uremic toxins by the SNMs indicates that the silicon-based membranes can be an alternative to the polymeric ones for hemodialysis and it can be reused.

Membrane technologies in the last few years have significantly grown in diverse market segments. However specific, attractive applications such as purification of bio-fluids for extracellular vesicles (EVs) isolation have not systematically been explored yet. EVs have recently captured a lot of interest due to their diagnostic significance as biomarkers for diseases, or their potential as drug delivery vehicles and therapeutic agents. The major challenges faced by current membranes are non-specific binding of matrix compounds such as proteins and hence fouling, or the affinity of negatively charged EVs towards the membranes, both result in a very low recovery. The aim of this work is to develop functionalized polymeric membranes, scalable using an industrial approach in an attempt to enhance the recovery of EVs from biofluids.

For this purpose, hydrophobic poly(vinylidene difluoride) (PVDF) depth filter membrane is modified into a surface filter by cross-linking it with different building blocks, hydroxyethylmethacrylate and acrylic acid or polyvinylpyrrolidone, using free radical grafting-cross-linking polymerization to obtain 3 prototypes with different surface chemistry (Figure 1). These membranes were evaluated to explore their potential for EVs, with a designed filtration tool which included fluorescent particles of various sizes towards understanding the blocking mechanism to identify the factors affecting efficiency of filtration.

Successful functionalization of PVDF with different degrees of grafting and change in morphology were verified by Fourier Transform-Infrared spectroscopy and Scanning Electron Microscopy, respectively. The grafted membranes showed enhanced hydrophilicity (contact angle less than 10° from 110° before modification) and change in surface charge (Figure 2). Flux study provided evidence of reduced pore size of the grafted membrane with dependence on solution pH for acrylic acid-grafted membranes (Figure 3). The decrease in flux was potentially caused by the swelling of grafted hydrogel matrix. Interestingly, filtration results showed that grafted membranes have higher recovery of particles compared to the control membranes manufactured by blending of the polymer with a hydrophilic additive.

This study not only provided PVDF membranes with different surface properties potentially useful for various bio-medical applications, but also proposed a novel scalable functionalization approach to enhance the performance of advanced functionalized polymeric membranes.

Acknowledgements

The project has received funding from the European Union´s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 722148.

Introduction:

Extracellular environments significantly affect cell proliferation, differentiation, and functions. The extracellular environment changes dynamically during many physiological and pathological processes such as embryo development, wound healing, and tumor growth. To mimic these changes, we have, for the first time, developed novel clickable thiol–maleimide microcapsules via “in situ conjugation” of cysteine-terminated biomimetic peptides to maleimide-modified alginate (Alg-Mal), even in serum-containing cell culture media. The cysteine-terminated peptides diffuse into Alg-Mal microcapsules and bind to immobilized maleimide groups via a thiol–maleimide reaction. To demonstrate switching cellular function by utilizing this microcapsule culture system, the induction of cell differentiation via in situ conjugation of BMP-2 mimetic peptides to Alg-Mal microcapsules was investigated.

Methods:

Alg-Mal was synthesized via carbodiimide-mediated reaction, followed by the microcapsule fabrication using a coaxial two-fluid nozzle. Then the in situ conjugation process in Alg-Mal microcapsule was quantified via fluorescence by incubating them with model thiolated dye. In addition, the kinetics of the in situ conjugation was calculated based on a reaction-diffusion mass transport model. Furthermore, osteogenic differentiation of preosteoblastic cells was evaluated by in situ conjugation of cysteine-terminated BMP-2 mimetic peptides, DWIVA and BMP-2 knuckle epitope peptide.

Results and discussion:

Alg-Mal microcapsules were successfully obtained with the diameter of 490 μm. Added thiolated dyes were rapidly introduced and concentrated into Alg-Mal microcapsules, which was consistent with simulated results. This was because the penetrated thiolated dye was rapidly consumed by the conjugation, thereby maintaining the concentration gradient from outside to inside the microcapsules. Encapsulated preosteoblastic cells started osteogenic differentiation via in situ conjugation of the peptides, while BMP-2 did not induce the differentiation possibly due to inactivation of BMP-2 before its diffusion into Alg-Mal microcapsules. We believe this in situ conjugation approach can be applied for various bioactive peptides, and thus will become a useful platform for biomedical applications.

There is huge interest in the development of useful in vitro Blood-Brain Barrier (BBB) models to help biomedical researchers and save costs during the development of new drugs targeted to CNS (Central Nervous System) [1]. In our previous works, polycaprolactone (PCL)/graphene-based nanomaterials membranes improved the differentiation of neural progenitor stem cells [2], and PCL HFs were promising substrates for blood vessel regeneration [3].

In this work, PCL and PCL/G HFs with interconnected porous morphology (Figure 1A and 1B) were produced and mechanical, electrical and chemical characterizations were performed. PCL/G HFs showed significantly higher C6 cells adhesion (Figure 1C) and differentiation towards astrocytes (Figure 1D), maybe attributed to the higher electrical conductivity in comparison to PCL HFs. On the other hand, the presence of graphene produced a cytotoxic effect on the endothelial cell line (HUVEC) (Figures 1E and 1F, respectively).

These results highlight the potential of a double-layered HF membrane, i.e. internal PCL-layer and external PCL/G layer to favor simultaneously the proliferation of HUVEC cells and C6 differentiation towards neuronal cell lineages to recapitulate in vitro BBB models. Furthermore, the positive role of graphene in PCL/G HFs on neural cell differentiation open the opportunity to explore their application on other type of neural models, i.e. co-culture of motorneurons and muscle cells.

Figure 1. ESEM images of the cross section of (A) PCL and (B) PCL/G HFs. (C) Adhesion and (D) differentiation assay of C6 cells and (E) adhesion and (F) proliferation assay of HUVEC cells on TCP, and PCL and PCL/G HFs.

[1] S. Bagchi, et al., Drug Des. Devel. Ther. 13 (2019) 3591–3605.

[2] S. Sánchez-González, et al., Macromol. Biosci. 18 (2018) 1–8.

[3] N. Diban, et al., Acta Biomater. 9 (2013) 6450–6458.

Financial support from IDIVAL (INNVAL 17/20), and MINECO/EIG-Concert Japan (PCI2018-092929 project) is gratefully acknowledged.

Monophasic hybrid cellulose acetate/silica (CASiO₂) integrally skinned membranes with tailored hemocompatible surfaces and permeation properties that assure the kidney metabolic functions of preferential permeation of urea and the retention of albumin were synthesized by an innovative method which combines the phase inversion and sol-gel techniques.

The morphological and topographical characterization of the hybrid CASiO₂ membranes with silica contents between 5 and 18 wt.% was performed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Static contact angles were measured through the sessile drop method and permeation experiments were performed to determine the hydraulic permeability and rejection coefficients to reference solutes pertaining to the metabolic functions of the kidney.

SEM confirmed asymmetric membrane cross-section structures (Figure 1) and AFM showed that the introduction of silica reduced the submicron surface roughness at least 3 times when compared to the pure CA membrane, reaching a roughness mean value below 2.5 nm.

Fig. 1 SEM micrographs obtained for the (a) active layer surface, (b) bottom porous surface and (c) cross-sections of the CASiO_2cmembrane containing 5wt.% SiO₂.

Contact angles revealed that the wettability increased for membranes containing 11 and 18 wt.%. Permeation studies show that the integration of silica into CA membranes increased the hydraulic permeability of the hybrid CASiO₂ membranes by a factor of ~2 and that all hybrid membranes fully permeated urea and completely rejected bovine serum albumin (BSA) (Figure 2). In terms of hemocompatibility, all CASiO₂ membranes were non-hemolytic, low thrombogenic and did not promote the highest stages of platelet activation.

Fig. 2 (a) Hydraulic permeability of the CASiO₂ membranes, (b) Rejection coefficients of the CASiO₂ membranes for glucose, PEG 1000, PEG 2000, PEG 10000, PEG 20000, and dextran T40, and (c) Rejection coefficients to urea and BSA and MWCO of the CASiO₂ membranes.

Acknowledgements

Funding by FCT through PTDC/CTM-BIO/6178/2014.

Liver cancer is a high incidence and malignancy disease with difficulty to be diagnosed in the early stage. With the development of clinical science, alpha-fetoprotein (AFP) in blood has been confirmed to serve as a specific marker of liver cancer, which plays an important role in the early screening of liver diseases. Currently in hospital, serum immunofluorescence is most applied to determine AFP level, however, it always cost quite long time with the multiple and complex manipulations to receive the result report. In order to address above issue, we proposed a novel electrochemical AFP biosensor based on a density controllable metal-organic hybrid microarray. Highly oriented hybrid material of Ni(en)₃Ag₂I₄ was fabricated by a facile and reliable method on the 1, 4-benzenendithiol modified Au substrate through the Ag-S covalent interaction (Fig. 1a). In addition, the density of the microarray could be controlled by adjusting the distribution of the 1, 4-benzenendithiol layer. In addition, the DNA probe assisted immune recognition strategy was applied to improve the selectivity and operability of the analysis process. The as-prepared DNA biosensor enables to assay AFP within 20 min in a wide linear range from 0.1 pg/mL to 176 ng/mL with an ultrasensitive detection limit of 33 fg/mL (Fig. 1b). The as-prepared biosensor also showed a promising potential for the application in rapid diagnosis and early detection of disease in the future.

Fig. 1 (a) SEM images of highly oriented hybrid material of Ni(en)₃Ag₂I₄; (b) DPV curves of AFP detection results.

Proteins have a wild variety of (biological) functions. The incorporation of proteins into polymer membranes to impart their biochemical functionality onto the membranes has proven to be tricky and not easily accomplished. Part of the reason is that proteins do not typically survive the membrane-production process.

We propose a method that produces membranes via polyelectrolyte complexation via an aqueous phase inversion from high to low pH. This phase inversion allows a selection of proteins to survive the production process. Additionally, polyelectrolyte complexes are known to be favourable or even preferable environments to some proteins.

We created polymer membranes via polyelectrolyte complexation and aqueous phase inversion that contains functional protein. Future prospects include the addition of anti-fouling and anti-bacterial proteins to create water filtration membranes with these inherent properties.

Biological cell membranes are composed of lipid bilayers and have excellent functions such as selective transportation. A supported lipid bilayer (SLB), in which a planar lipid bilayer is immobilized on a flat substrate, has attracted attention as a platform to immobilize lipophilic biomolecules due to its high physical stability. SLB formation is generally performed by a liposome rupture method, in which liposomes are adsorbed onto a flat substrate, ruptured, and transformed into a flat lipid bilayer. However, the process of the rupture and the transformation behavior of liposomes have not been explored. In this study, we evaluated the effect of the lipid composition and fusion-inducing reagents on the SLB formation behavior.

To form an SLB, a cationic flat substrate was immersed in an anionic liposome suspension. The liposome suspension was prepared with a phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or 1,2-dioleoyl-sn-glycero-3-phosphoethanoamime (DOPE), and an anionic phospholipid, 1,2-dioleoly-sn-glycero-3-phospho-rac-1-glycerol sodium salt (DOPG) or 1,2-dioleoyl-sn-glycero-3-phosphate sodium salt (DOPA), by an ultrasonic emulsification method. Calcium chloride was added as a fusion-inducing agent. To evaluate the adsorption state of lipid molecules on the substrate surface, the lipid fluidity was determined by using a fluorescence recovery after photobleaching (FRAP) assay.

The FRAP results showed that the liposomes prepared with anionic lipids were adsorbed onto the cationic substrate. Especially, the DOPC/DOPA-SLB showed the higher fluidity than others, indicating the planar lipid bilayer formation. The smaller hydrophilic group of DOPA probably caused the destabilization of the vesicular structure. The fusion-inducing agent, no further increase of the lipid fluidity of the DOPC/DOPA-SLB was observed with the addition of the agent. On the other hand, the lipid fluidity of the DOPE/DOPG-SLB was increased by Ca²⁺ addition, indicating the facilitation of the planar lipid bilayer formation.

Numerous separation processes, such as fruit juice concentration and bioresource processing, entail the removal of amphiphilic molecules from aqueous feeds. To this end, direct contact membrane distillation (DCMD) has been proposed as a solution. DCMD utilizes hydrophobic membranes, typically comprising perfluorocarbons, that robustly entrap air inside their pores, thereby preventing the mixing of aqueous feed and permeate solutions. In this presentation, I will demonstrate the vulnerability of DCMD to organic fouling using a broad set of techniques, including surface force apparatus, contact angle goniometry, and molecular dynamics simulations. Key factors and mechanisms underlying the time-dependent loss of the membrane hydrophobicity due to the preferential adsorption of amphiphilic solutes at the water-hydrophobe interface will be discussed. Specifically, organic fouling of perfluorinated surfaces and membranes on submersion in water-alcohol solutions (0.1-100 % v/v). Our results will thus provide molecular to macroscale insights into the fouling events that eventually leading up to the process failure. In response to this critical weakness of DCMD, we will unveil a new class of membranes - gas entrapping membranes (GEMs) – developed in our Group. GEMS can perform the functions of hydrophobic membranes, such as the robust entrapment of air on submersion in water, despite their water-loving composition. Thus, GEMS might facilitate the development organic fouling resistant DCMD membranes; insights into the functioning of GEMs that achieve their functions due to their microtexture instead of their surface make-up will also be provided.

Fouling represents one of the biggest bottlenecks in membrane technology. To tackle this problem, we seek inspiration in the kidney, a remarkable organ capable of producing over four million litres of effectively protein-free urine over a lifetime with no significant fouling(1). The glomerulus is a bundle of specialized blood vessels, which carries out the first stage of kidney filtration. Within the lumen of these blood vessels, a brush-like structure is present, composed of proteoglycans and glycoproteins, which are responsible for the overall negative charge and hydrophilicity of this layer. The combination of the brush structure, hydrophilicity and charge are believed to be key causes behind the superior anti-fouling properties of the kidney.

To translate this source of inspiration into the context of artificial membranes, the design employed here involves the grafting of polyelectrolyte polymer brushes as an anti-fouling layer onto track-etched polyester (PET) membranes. This grafting is achieved through Surface-Initiated Controlled Radical Polymerization (SI-CRP) using Activators Regenerated by Electron Transfer Atomic Transfer Radical Polymerization (ARGET ATRP). The stimuli-responsive polymer brushes reduce fouling through the formation of a hydration layer, steric repulsion and electrostatic interactions, due to the negative charge of the layer at pH above its pKa. This has been demonstrated thus far in the filtration of bovine serum albumin. The flux decline for the modified membranes showed a significant improvement over unmodified membranes with maximum flux declines of 24% and 60% over 0.5 h, respectively. This is related to the enhanced hydrophilicity of the membranes seen in Figure 1. Further optimization of the polymer brush anti-fouling layer has the potential to leverage the superior anti-fouling properties of the kidney.

Figure 1: Water contact angles of unmodified PET and subsequent grafting of polyacrylic acid brushes.

1. Hausmann R et al., Curr. Opin. Nephrol. Hypertens., 2012, 21(4), 441–9.

Biomimetic nanoporous membranes with the similar structures and functions of biological membranes, which could realize the precisely and fast gating and controlling transport specific ions/molecules, have caused a worldwide research interest. Recently, some artificial porous nanomaterials, such as zeolites, carbon nanotubes, graphene/ graphene oxide, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), have been utilized to fabricate separation membranes with nanopores. In this study, we report a facile and universal method for fabricating ultrafast molecular/ion sieving nanoporous membranes through zwitterionic dopamine nanoparticles (ZDNP) induced the in-situ growth of MOFs on polysulfone ultrafiltration (PSF-UF) membrane. The membrane thickness and nanoporous structure could be easily controlled by manipulating the membrane formation process. Our ZDNP@MOF membrane shows a super-high water permeance over 1800 L.m^-2.h^-1.MPa^-1, which is nearly 1~2 orders of magnitude higher than most of commercial nanofiltration membranes, simultaneously exhibiting high organic molecules/ inorganic salts separation performance. Moreover, the excellent compatibility and interaction between nanoparticles and substrates endows the resultant membrane having good stability. The ¹H time-domain nuclear magnetic resonance spectrum and positron annihilation spectroscopy demonstrates that the existence of nanoscale pores in the ZDNP@MOF membrane provide preferential flow paths for water molecules transporting, thus fostering the remarkable water permeance coupled with high organic molecules/ inorganic salts selectivity and good stability. Therefore, this study not only provides a novel candidate nano-based membrane for organic molecules/ inorganic salts separation, but also opens up an innovative approach to construct nanoporous membranes under simple operation and mild conditions.

The recovery of biomolecules from microalgae is gaining interest as new applications are developed in various industrial fields. However, one of the challenges remains the development of cost-effective processes for the extraction, separation and purification of these valuable compounds. To this aim, membrane filtration is a promising separation technology. Nevertheless, few works deal with membrane regeneration after filtration, which still requires large volumes of alkali solutions associated with important costs. Corbatón-Báguena et al. (2015) have successfully used NaCl solutions to clean ultrafiltration membranes fouled with whey proteins. The aim of this work was to test this innovative procedure on membranes fouled with an emulsion representative of microalgae lipid extracts and get more insight into how salt promotes changes in the fouling structure. Fouling experiments were conducted using a cross-flow filtration pilot and a 2% oil-in-water emulsion developed by Clavijo Rivera et al. (2018). Polyethersulfone 0.1 µm membranes were fouled with the emulsion, and then cleaned testing 2 concentrations of saline solutions (5 and 7.5 mM NaCl) and 2 temperatures (37.5°C and 50°C). Saline solutions cleaning efficiency was evaluated using water permeability recovery. The impact of salt on membrane fouling was then studied by characterizing the surface of (i) virgin membrane, (ii) fouled membrane and (iii) fouled and cleaned membrane, using tangential electrokinetic measurements, ATR-FTIR, HRFESEM and AFM analysis. The NaCl cleaning procedure was highly effective on lipid fouling, with water permeability recovery between 95 and 100% without additional alkali solutions or surfactants. ATR-FTIR and tangential electrokinetic measurements revealed that some lipids were still present on the membrane surface after NaCl cleaning. However, AFM and HRFESEM analysis highlighted that their organization was modified. Further works will allow better understanding of foulant compounds behaviour during cleaning and help developing cost-effective and eco-friendly cleaning procedures for the separation processes used in microalgae biorefining.

2,3-Butanediol (2,3-BDO) is an attractive renewable resources from microbiological fermentation process, which can be used as versatile raw materials in manufacturing of chemicals and food as well as being a fuel blend since its high heat capacity or further converted to other fuel additive solvent. In this study, we used three dense membranes (reverse osmosis and nanofiltration) to separate the targeting promising platform molecule (2,3-BDO) from salts and impurities presenting in the downstream of fermentation. Individual desalination performances of NF (ESNA1-K1) and RO (SWCS and PROC10) membranes were investigated by single salts (e.g. NaCl, MgSO₄, MgCl₂, Na₂SO₄) and mixture (recipe was simulating the effluent of fermentation process). A mathematical model, namely Donnan steric pore model with dielectric exclusion (DSPM-DE), based on MatLAB^TM software was applied to take an insight of mass transfer within these dense membranes during this application. Two diafiltration (DF) modes, i.e. constant volume diafiltration (CVD) and variable volume diafiltration (VVD), were experimentally tested the feasible range in efficiently harvesting this bioresource with limiting dilution and operation time. Moreover, various process designs via integrating NF and RO as a membrane cascade were simulated and prospects the potentials and benefits of downstream separation and resource recovery.

The downstream process of valuable biorefinery products severely affects the production costs. An example is biosuccinic acid (bio-SA) production, which is one of the top twelve bio-building blocks in biorefinery, with estimated downstream costs up to about 70% of the whole process. Membranes are key technologies currently used in industrial production and purification of bio-SA. For bio-SA production, membranes are used as (I) bioreactors, (II) for cell removal, (III) clarification of bio-SA and (IV) removal of pigments. Optimized technological integration e.g. membrane crystallization etc. and insights in membrane selectivity come as promising and rapid solutions to lower the downstream costs for commercial bio-SA production. Since the complex interaction between used feedstock, applied pretreatment, host microorganism, fermentation method and downstream technologies, this work analyses the bio-SA production process under different angles.

Therefore, studies on both fundamental phenomena affecting membrane selectivity and fouling, together with process simulation for optimal bio-SA production pathways were conducted in this work, which consisted of three sequential steps:

1) First, a literature revision of the state of the art suggested the best feed-stocks, microbial host and technologies for bio-SA production and purification. 2) Consequent simulation studies suggested that microfiltration for cell removal (particularly in situ), is a key step when CO₂ with glycerol or corn stover are used as feed-stocks and the host microorganism is E. coli. 3) Further studies on E. coli fermentation broths with various ultrafiltration (UF) and NF membranes suggest potential optimal bio-SA production processes, while NF tests with model organic acid solutions shows that thermodynamic phenomena can severely influence the flux and partly the retention.

It has been demonstrated that membranes can be used in different stages of the bio-SA production process, as well as for other fermentation products, potentially lowering the number of required units and consequently the production costs.

Biopolymers are gaining great importance from an environmental point of view, because of their biodegradability, and from an economical point of view, as their production follows a biorefinery approach of the valorization of low cost products. Corn fiber, a by-product from the wet-milling of corn for food applications is used in animal feed. However, it is composed by valuable components that should be valorized, such as arabinoxylans for biopolymers applications.

Arabinoxylans were obtained after an alkaline extraction of corn fiber followed by ultrafiltration operated in a concentrate mode, for concentration and partial removal of small compounds. The further purification of the arabinoxylans fraction was assessed by ultrafiltration operated in a dia-filtration mode, at different temperatures (see Figure 1), at different operation regimes (under controlled transmembrane pressure conditions and under controlled permeate flux conditions) and at different Reynolds number on the upstream side. The performance of purification of the arabinoxylans was assessed by the permeate flux and the % of removal of small contaminants (both desirably high).

Figure 1: % of removal of small contaminants (in this case compounds responsible for the color, in [Ferulic acid]_equivalents); (B) extracts produced during the purification process

The obtained arabinoxylans, with the optimized parameters of the purication step, were used to produce edible films, with different plasticizer content (glycerol, 15, 30 and 50% dry basis), and citric acid as crosslinking agents. In addition, films with the incorporation of ferulic acid (which was not purified in this work) were developed, in order to obtain active barriers with antioxidant activity. The films were characterized in terms of mechanical properties (tensile tests), water adsorption capacity, permeability to water vapor, oxygen and carbon dioxide. The prepared films presented a good potential to be used as packaging materials for food products with low water content.

Viral safety is one of the major concerns in the production of mammalian cell and plasma derived biotherapeutic products. A demonstration of virus clearance is required by the regulatory agencies. Virus filtration can provide a robust removal of virus. Here the effects of solution condition and process interruption on the fouling behavior and virus retention during virus filtration are systematically investigated for the filtration of an Fc-fusion protein and two monoclonal antibodies spiked with minute virus of mice (MVM) using three commercially available virus filters. A combined pore blockage and cake filtration model was found to describe well the fouling behaviors of the three filters for all the solution conditions and for all three biomolecules. The fouling of the virus filters is dominated by the pore blockage mechanism during the initial stage of the filtration and transformed to the cake filtration mechanism during the later stage of the filtration. Both flux and transmembrane resistance can be described well by this model. The pore blockage rate and the rate of increase of protein layer resistance over blocked pores are found to be affected by membrane properties as well as the solution conditions resulting from the modulation of interactions between virus, protein and membrane by the solution conditions. Our study shows that virus breakthrough is complex, but strongly filter and solution condition dependent. Surprisingly, virus breakthrough appears to be most severe under the relatively low membrane fouling conditions for one of the commercial filters investigated.

Increases in product titre during cell culture operations has led to significant challenges during the downstream purification of these products. In the case of the bioreactor harvesting step, a high product titre is accompanied by a rather high cell density which places a significant burden on traditional clarification operations. Depth filtration, centrifugation and tangential-flow filtration (TFF) have been used to remove cells, cell debris and other impurities from the product stream. Depth filters consist of a thick porous bed that can trap particles within the filter in contrast to screen type filters that largely reject particulate matter based on surface exclusion. On the other hand, the tangential flow of the feed relative to the membrane surface leads to the suppression of cake growth.

BioOptimal MF-SL from Asahi KASEI operates as a hybrid TFF-depth filter. The membrane is asymmetric where the more open pore surface faces the feed stream. The plugging mechanism(s) for BioOptimal MF-SL and other hybrid filters are poorly understood. Here a combined pore blockage and cake filtration model has been developed in order describe the fouling mechanism of this hybrid filter in normal flow mode whereas a resistance in series model has been able to predict performance of the filter operated in the TFF mode. Experiments with yeast and CHO cell confirm the results of the modelling work. Significant insights have been obtained in understanding the fouling mechanism and optimal operation condition of this hybrid filter.

Full utilization of side streams in biorefineries is crucial for the material efficiency, because of economic and environmental reasons. Similarly, efficient recycling of materials used in the production processes is essential. Deep eutectic solvents (DES) are promising reaction media for the pretreatment of cellulosic side streams since they have good dissolving properties and they are easily prepared from non-toxic, low cost bulk raw materials. However, impurities can accumulate into the DES during the pre-treatment process and disturb the process itself. To prevent the accumulation and to further maximize the material efficiency of biorefineries, the used DES must be purified to enable its recycling back to the process. Membrane technologies are promising separation methods for many biorefinery applications due to e.g. their ability to accurately fractionate components, mild operation conditions and modularity. The aim of this research was to find suitable ultrafiltration and nanofiltration membranes to remove impurities from a deep eutectic solvent used in the production of cellulose nanofibers from cellulosic side streams.

The resistance of the membranes was first tested by exposing the membranes to choline chloride-urea (ChCl-urea) DES for 5 days at 40 ℃. FESEM images were taken to observe the possible changes on the membrane surface caused by ChCl-urea. 1H NMR analyses were performed to reveal whether ChCl-urea had dissolved the polymers existing in the membrane structures. Membranes resistant to ChCl-urea were selected to the filtration experiments with model solutions of ChCl-urea and sugars.

The results show that membranes tolerating ChCl-urea have been found and these membranes could be suitable for purification of the used ChCl-urea solution. Further research is still, however needed. Literature on purification and recycling of ionic liquids, as well as recycling of DESs can be found at present. However, to the knowledge of the authors, purification of DESs is not comprehensively studied yet.

Membrane processes have been identified as key separation processes for the transformation of the traditional paper and packaging orientated pulping industry to future lignocellulosic biorefineries.

This paper will provide an update on the status of pressure driven membrane processes in lignocellulosic biorefineries and the challenges ahead. The focus is on the integration of membrane processes in the three key pulping processes: thermo-mechanical pulping, kraft (sulphate) pulping and sulphite pulping. For each of the pulping processes membrane concepts to upgrade current processes to produce new products from side-streams will be presented and the challenges for integration of membranes will be discussed.

For thermo-mechanical pulping processes, the focus will be on the process water and the opportunity to purify and concentrate hemicelluloses from this stream by using a cascade of membrane processes consisting of microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF). Recovering hemicelluloses from this stream does not only reduce wastewater treatment costs but also provides an interesting raw material for packing and bio-chemical conversions.

In the kraft pulping process, the removal of lignin from the cooking chemicals by UF/NF opens not only the perspective to extend the capacity of kraft mills by increasing the reboiler capacity but provides a by-product which can be used to supply lignin-oil for e.g. renewable fuel production.

Finally, in the sulphite pulping process UF/NF can be utilised to recover hemicelluloses from sulphite streams at the pre-hydrolysis pulping stage. This does not only produce hemicelluloses as raw material for further processing but also upgrades sulphite streams for recycling to the process.

Overall, this paper will underline the great potential of membrane processes in the transformation of the pulping industry towards lignocellulosic biorefineries.

UiO-66 and functionalized materials with -NH₂ and-(CF₃)₂ groups were successfully synthesized by solvothermal method. The purpose was to study the effect of modified UiO-66 materials on the separation performance of xylene isomers. The crystal structure and morphology of these materials were characterized by XRD and SEM; the adsorption isotherms and rate curves of the single component xylene isomer on these materials were measured; the dynamic breakthrough experiments were used to investigate the effect of temperature on the adsorption performance of ternary equimolar mixtures. The results show that the adsorption of xylene isomers by UiO-66 and UiO-66-NH₂ conforms to the second-order kinetic model, while UiO-66-(CF₃)₂ is more in line with the first-order kinetic model due to the steric hindrance of the larger side chain. All three materials have reverse shape selectivityd and preferentially adsorb o-xylene. The sorption selectivity hierarchy follows: o-xylene(OX)> m-xylene(MX)> p-xylene(PX). As the temperature increases, the sorption selectivity increases, and the selectivities of UiO-66-NH₂ and UiO-66-(CF₃)₂ for OX/PX and OX/MX at 398 K are higher than that of UiO-66. Therefore, functional UiO-66 is a feasible method for separating xylene isomers and obtaining high adsorption separation performance in industrial processes 

Chilled ammonia process (CAP) is absorption method which can be used among others for post-combustion carbon capture from flue gas. It has several advantages compared to scrubbing by aqueous alkanolamine solutions considered as a reference process. One of the advantages is the higher absorption capacity, avoiding of agent degradation, absorption of other sour gases. Main disadvantage is the possible ammonia losses into the treated gas. The ammonia losses are minimized by regenerative cooling and heating of the input/output stream by direct contact heater (DCH) and cooler (DCC). The used medium is water which absorbs rest of ammonia in DCH and rest of SO₂ in DCC. Our goal is to use electrodialysis with bipolar membranes to treat the aqueous solution in the loop of DCH and DCC in order to recover ammonia and separate the additional anions coming from absorption by sour gases in DCC.

We estimate the composition of the aqueous solution by published values and according to known composition of the flue gas entering the DCH. The model solution consists of dissolved ammonia, SO₄^2-, NO₃^- and Cl^-. We used heterogeneous bipolar membranes as well as heterogeneous ion exchange monopolar membranes in two different stack configurations: (i) BAB (bipolar - anion – bipolar membrane) and (ii) CAB (cation – anion - bipolar membrane). Electrode compartments were separated by bipolar membranes in order to avoid contaminations by cations. Experiment were performed at different levels of feed solution dilution.

Results show that BAB configuration has lower separation performance. Configuration CAB has the ammonia yield about 89 % and level of anion removal above 77 % for Cl^-, above 92 % for NO₃^- and above 93 % for SO₄^2-. The higher ED performance at higher feed concentrations was expected and verified. Results confirm that ED could significantly lower ammonia losses in CAP.

Introduction:

Membrane separation using ion exchange membranes (IEMs) is an economical and environmentally friendly separation method for aqueous solutions. In this sense, it represents an alternative to recover and reuse nitrogen from wastewater in a sustainable way, being a promising solution to shift the standard wastewater treatment to current emphasis on sustainability. However, its current limitations in terms of selective separation ability and membrane high cost hinder its application for nitrate recovery in the wastewater. This work shows a simple, low cost and scalable method for the preparation of nitrate-selective anion exchange membranes (AEMs).

Methods:

In this study, nitrate-selective heterogeneous AEMs have been prepared by dispersing an anion exchange resin in a polymeric solution (polyvinylchloride dissolved in tetrahydrofuran). Three different anion exchange resins have been tested. For membrane preparation, a recycled pressure filtration membrane with ultrafiltration properties has been used as mechanical support. In separation performance experiments, an equimolar mixture of anions (chloride, nitrate and sulphate) has been employed as feed.

The effects of the type of anion exchange resin used in membrane preparation, the use of the recycled membrane support and the influence of the current density in the separation efficiency have been tested.

Results:

Figure 1. Selective separation at 5 mA·cm^-2; a) AEM without mechanical support, b) AEM with recycled membrane, “t” transport number.

Discussion:

The results revealed that prepared membranes can effectively facilitate the transport of nitrates over other monovalent and multivalent anions. The use of the recycled membrane did not increase the ion fractionation efficiency; however it provides mechanical stability to the prepared membranes. Finally, the use of low current density significantly improves the separation efficiency and facilitates the transport of nitrates through the membrane. The selectivity of the membranes for target ions could be easily tuned up by selecting the appropriate ion exchange resin.

A charged mosaic (CM) membrane consists of a structure in which cation and anion-exchange regions arrange in parallel to the membrane thickness direction. Due to this specific structure, the membrane can selectively permeate electrolytes against the non-electrolytes. Therefore, the membrane has a potential usage for desalination and concentration of salty solution in food and water treatment applications. Although there are various reports about preparation methods of CM membranes, the membranes have not been practically used yet because of their low mechanical strength and low ion permeation performance. In this study, we prepared CM membranes by using two-step ion-track graft polymerization method. A CM membrane prepared by this method will be expected to have high ion permeability because it nano-order size ionic channels with high charge density.

Fig.1 shows the preparation process of a CM membrane using two-step ion track graft polymerization method. Poly(ethylene-co-tetrafluoroethylene) (ETFE) used as a base film was irradiated with a 310 MeV ⁸⁴Kr ions from a cyclotron with 3.0×10⁸ of the ion-beam fluence. After the irradiation, the membrane was immersed in a solution of chloromethyl styrene (CMS) for graft polymerization of negatively-charged chains. And then, the chloromethyl groups of the graft polymer chains were quaternized with 30% trimethylamine to introduce anion exchange domains (P-domain) into the membrane. The membrane was irradiated with 3.0×10⁸ of the ion-beam fluence again. After the irradiation, the membrane was immersed in a solution of p-styrenesulfonate (SSS) for graft polymerization of negatively-charged chains (N-domains), which has opposite charges to the P-domains, to form CM structure inside the membrane with P-domains.

A piezo-dialysis system with the CM membrane desalinated salt solutions at least less than 6000 ppm. Therefore, the prepared CM has potential application to desalination process of salt solutions with low concentrations.

Fig. 1 Schematic diagram of the preparation process of a CM membrane using two-step ion track graft polymerization method.

In various applications of ion-exchange membranes (IEMs) such as electrodialysis (ED) and reverse electrodialysis (RED), IEMs having low membrane resistance, high permselectivity for counter-ions and low water permeability are needed. In general, the transport properties of IEMs depend on their water content. Hence, the control of the water content is one of the important points to prepare IEMs with high performance. In this study, we prepared novel high performance IEMs by ion-track irradiation graft polymerization technique. A heavy ion with huge kinetic energies can pass through a polymer material and induce a continuous trail of excitation and ionizations, leaving a latent track. The latent track contains high-density and localized macromolecular radicals, which can act as an initiator of graft polymerization. Here, we prepared cation-exchange membranes (CEMs) by using ion-track graft polymerization to control their water content. IEMs prepared by this method will be expected to have high ion permeability because it has nano-order size ionic paths with high charge density.

Fig. 1 Schematic diagram of a preparation process of a CEM by the ion-track grafting technique. (a) a base film after ion-beam irradiation, (b) a CEM after the grafting of cationic monomers that was initiated from the radicals in the base film.

Poly(ethylene-co-tetrafluoroethylene) (ETFE) films with a thickness of 25m were irradiated with a 560 MeV ¹²⁹Xe ion beam from a cyclotron. The irradiated films were immersed into mixed solutions of ethyl p-styrenesulfonate (EtSS) monomer and 1,4-dioxane to prepare base-membranes for CEMs. Finally, the EtSS-grafted membranes were hydrolyzed in ultrapure water at 80 ^°C for 24 h to remove the ethyl groups.

The obtained CEMs showed the ion exchange capacity (IEC) ranging from 0.38 to 1.70 mmol/g. The membrane resistance of the CEM with the IEC of 1.70 mmol/g was 0.18 Ω cm², which was only around one tenth of that of a commercial CEM, Neosepta® CMX.

Therefore, the prepared CEMs have potential application to an ED desalination for high salt concentrations.

Membrane capacitive deionization (MCDI) for water desalination has emerged as an innovative technique to help tackle global water scarcity. The employment of ion selective membranes with high ion-exchange capacity has the potential to markedly increase salt removal during MCDI desalination.

Dope solutions based on polybenzimidazole (PBI) and branched polyethylenimine (PEI) of various mass loadings were systematically prepared and membranes were precipitated using phase inversion. Both polymers possess a high number of nitrogen atoms; which can undergo quaternization to impart anion-exchange character.

Membranes were quaternized by surface modification with methyl groups and their structure and composition was characterized using various spectroscopic methods. Electrochemical properties (ion-exchange capacity, permselectivity) were determined and the membranes were employed as an anion-exchanhe membrane (AEM) in a bench-scale MCDI configuration using brackish water. The desalination performance was quantified in terms of salt adsorption capacity and charge efficiency.

Owing to the combination of nitrogen-rich PBI/PEI, all blend membranes displayed high quaternization degree as confirmed by NMR and elemental analysis. Further, all membranes displayed high ion-exchange capacity (outperforming some commercial membranes) and permselectivity; making them ideal candidates for MCDI anion-exchange membranes. The membranes produced a significantly higher salt adsorption capacity and charge efficiency than conventional CDI without membranes, whilst outperforming similar membranes in literature.

For the first time, this study fabricated quaternized membranes based on blends of PBI/PEI and were applied as AEMs in MCDI. The membranes exhibited over a 4x increase in salt adsorption capacity and charge efficiency compared to CDI. This was attributed to greatly enhanced chloride ion removal through the highly quaternized anion-exchange membranes. The use of such membranes will help to establish the industrial application of MCDI for water desalination.

Salinity gradient power (SGP), which is generated by mixing saline water and fresh water, has potential to recover energy in reverse osmosis (RO) brine from desalination plants. Reverse electrodialysis (RED) is one of the techniques for SGP generation. Nevertheless, the fouling of the ion exchange membranes may be a critical issue to reduce RED efficiency.

This study intended to compare pretreatment methods for fouling control in RED systems. Secondary effluent from a full-scale wastewater treatment plant was used as the low-salinity feed solution and synthetic RO brine was used as the high salinity feed solution. Commercial ion exchange membranes were used in a laboratory-scale RED experimental set-up. Cartridge filter (CF), microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), activated filter media (AFM), and granular activated carbon (GAC) were applied as the pretreatment methods. Open circuit voltage (OCV) and power density were measured in each case. The pressure drop inside the stack was also monitored. Theoretical energy consumption by the pretreatment method and the energy generation from RED were calculated to estimate the theoretical net energy production.

Results showed that the RED efficiency was affected by the pretreatment types. It is evident that the RED recovered more energy from the RO brine by the pretreatment method resulting in higher water quality. There were correlations between the power density of the RED and the water quality after the pretreatment. However, the theoretical net energy production showed the maximum when the optimum pretreatment was applied. Since the fouling was attributed to the organic matters and divalent ions in the low-salinity feed (reclaimed wastewater), it is recommended to select pretreatment methods that can selectively remove such foulants.

Nitrate, arsenic (V) and fluoride are three of the most common contaminants in ground waters worldwide, posing a significant risk to human health [1]. WHO has proposed maximum contaminant levels of 50 mg/L, 10 µg/L and 1.5 mg/L for nitrate, arsenic and fluoride, respectively [1]. Seeing all of these contaminants are dissociated and charged in the pH range typical in natural waters, electrodialysis (ED) is a possible treatment process [2]. ED for drinking water production has to date been little studied [2]. Previous studies have shown the possibility of inorganic contaminant removal by ED, whereas this study explains the main mechanisms of mass transfer and ion removal in ED process.

To elucidate the removal mechanism of different contaminants from brackish water in varying conditions, a number of experiments were carried out in this study [3], investigating the effects of operational and water quality parameters on the removal of electric conductivity (EC) and contaminants. A Deukum lab-scale 100 Quadro module was used. The membrane stack consisted of 10 anion exchange (Neosepta AMX) and 11 cation exchange membranes (Neosepta CMX) (total effective area of 0.1 m²). Flowrate, electric potential, salinity, pH and initial contaminant concentration was modified. Ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) were used to determine concentration of contaminants in samples.

Normalized concentration of contaminants in the diluate tank as a function of time is presented in Figure 1. Nitrate and fluoride transfer are pH-independent, while arsenic (V) transfer decreases with increasing pH. It is demonstrated that with decreased ionic mobility and diffusivity and increased hydration energy of arsenic (V) ions due to increasing pH [4, 5], its removal is decreased from 75% at pH 2 to 25% at pH 12.

Figure 1 Normalized concentration of contaminants in diluate tank in pH 2, 8 and 12 (NaCl: 5 g/L, NaHCO₃: 1 mmol/L, flow rate: 50 L/h, electric potential: 15 V)

[1] J.F. Terrence Thompson, D.J. Shoichi Kunikane, Stephen Appleyard, Philip Callan, Jamie Bartram, Philip Kingston and WHO, Chemical safety of drinking-water: Assessing priorities for risk management, in, 2007.

[2] C. Onorato, L.J. Banasiak, A.I. Schäfer, Inorganic trace contaminant removal from real brackish groundwater using electrodialysis, Separation and Purification Technology, 187 (2017) 426-435.

[3] M. Aliaskari, A.I. Schäfer, Electrodialysis (ED) for nitrate, arsenic and fluoride removal from brackish ground water, (2020).

[4] R. Epsztein, E. Shaulsky, M. Qin, M. Elimelech, Activation behavior for ion permeation in ion-exchange membranes: Role of ion dehydration in selective transport, Journal of Membrane Science, 580 (2019) 316-326.

[5] M. Tanaka, Y. Takahashi, N. Yamaguchi, K.-W. Kim, G. Zheng, M. Sakamitsu, The difference of diffusion coefficients in water for arsenic compounds at various pH and its dominant factors implied by molecular simulations, Geochimica et Cosmochimica Acta, 105 (2013) 360-371.

Bipolar membrane electrodialysis (BMED) uses electrical energy to produce acidic and alkaline solutions by water dissociation. Its great versatility has increasingly gained the interest in chemical/biochemical industry and in environmental protection. Co-ion leakages through the membranes and shunt currents pose major issues leading to significant drops in current efficiency.

This work focuses on the development of a novel model based on a multi-scale approach. Four different dimensional scales were fully integrated within a comprehensive simulating tool with distributed parameters. The lowest scale, which is represented by the channel, includes two sub-models. The CFD simulations sub-level estimates polarization phenomena and pressure losses, while the other sub-level calculates the physical properties of the solutions. The middle-low level simulates the triplet, i.e. the repetitive unit of the stack, by computing mass balances, membrane fluxes, electrical resistance and electromotive force. The middle-high scale, represented by the stack model, is made up of two sub-levels: one is intended to compute the shunt currents through the manifolds, the other one aims at calculating pressure losses in the whole stack. Finally, the highest level simulates the external hydraulic circuit accounting for external pressure losses and dynamic mass balances in the tanks.

The model was experimentally validated with both an original campaign and literature data, showing a good agreement. A sensitivity analysis was performed in order to assess the behavior of BMED systems. The process performance was evaluated by comparing current efficiency and power consumption in different scenarios. The outcome of the analysis illustrates the influence of operating variables (e.g. current density and mean flow velocity) and of the system geometry. Results highlight the key role of the manifolds features on the process efficiency.

In the last years, the Electrodialysis (ED) process has drawn much attention for drinking water production from saline water desalination. Electrodialysis is an electro-driven, membrane based process, where water desalination is achieved by applying an external electrical voltage and employing Ion Exchange Membranes (IEMs), which allow for a selective transport of ions. In ED units, IEMs are separated by means of net spacers or built-in profiles, which create the channels where the solutions flow.

In the literature, several studies have highlighted the detrimental effects of membrane deformation on the performance of many membrane-based processes. However, membrane deformation has been poorly investigated in ED applications. On the other hand, membrane deformation may occur in ED units due to an uneven pressure distribution between the two fluid channels facing an IEM, thus giving rise to a transmembrane pressure (TMP) distribution. Despite TMP is usually small in parallel flow arrangement, non-negligible local TMP values could exist in non-parallel configurations, e.g. cross-flow arrangements.

This work presents a novel multi-scale 2-D process model of ED cross-flow units, including the effects of membrane deformation induced by TMP. The model employs correlations obtained from small-scale numerical simulations (structural mechanics and computational fluid dynamics) to solve the fluid-structure interaction problem (flow redistribution induced by membrane deformation). Then, the model couples these effects with transport and electrochemical phenomena describing the ED process at the scale of an entire cell pair.

Mild membrane deformations were found to alter only slightly the ED process performance. However, larger membrane deformations, which may occur, e.g., with thin membranes, had more significant effects. For example, the specific energy consumption was increased by 6% compared to that predicted by neglecting membrane deformation.

Research is being conducted to determine the ability of electrodialysis metathesis to separate and recover rare earth elements (REE) and uranium and to determine the feasibility of geothermal waters as a source of these elements. Identifying untapped sources of REE and uranium and methods to obtain them are areas of growing interest due to current and expected supplies not projected to meet future demand. The demand for REE is due to it many uses such as microchips, magnets, and catalysts. Uranium’s classification as a clean energy due to its low footprint, minimal waste production, and zero-emission to the atmosphere is the main reason for projected increase in demand. Geothermal waters are readily available untapped sources of REE and uranium. EDM, a membrane-based technology, was selected as the technology for this research due to its ability to selectively separate ions and run for long periods of time without scaling. Cationic and anionic ion exchange membranes are placed in a repeating order that form compartments, with every four compartments being one quad. Each quad contains four streams: a feed, substitute, and two concentrates. Current applied to the system is the driving force for ion movement. The substitute solution is selected based on the feed composition to ensure the metathesis reaction. The metathesis reaction, selectivity, mass transport, kinetics, and process modelling for REE and uranium within EDM are being studied. Membrane type and solution pH are also being studied to determine the best conditions to produce high purity products. Laboratory research identified a correlation between solution pH and the amount of precipitate recovered, with higher pH values producing larger amounts of precipitate. Successful implementation of EDM to recover REE and uranium could lead to both an overall increase in the global supply and better sustainability by removing heavy metals from water sources.

Recently, in electromembrane processes including electrodialysis (ED), the use of overlimiting currents has been spotlighted with accelerated ion transport the ion exchange membranes by electroconvection (EC). EC plays the most important role in enhancement of mass transfer through ion exchange membrane at overlimiting current regimes. One of the most tantalizing problems in the use of overlimiting current is how can we initiate EC with a low voltage. Generally, a relatively high voltage (>1.5V) is required to generate EC. Common strategies for passive control of electroconvection include utilizing heterogeneous or patterned membranes of the ion selective interface. These strategies reduced the plateau length (25% to 60%) of limiting current regime so, there’s a limit that cannot accelerate the occurrence of EC any further from existing limiting current area. Here we suggest the way to accelerate the occurrence of EC by utilizing chemical energy from redox potential. To consume majority salts in seawater (i.e. and ), we use redox reaction of Zinc- iodine couple. During the desalination process, zinc anode consumes chloride ions to make zinc chlorides, and as a cathodic feed stream, sodium triiodide consumes sodium ions to make sodium iodides. We compared the I-V curves of fabricated devices using zinc as anode and using both zinc anode and sodium triiodide as cathodic feed stream. The overlimiting current regime is started at -0.4V and 0.2V respectively while normal ED is at 1.6V. Also with zinc-iodine coupled device, non linear ion concentration polarization is occurred at 0V and EC is clearly visualized at 0.5V. With this EC enhancement and operating voltage drop by chemical energy, the required energy per ion removal (EPIR) with 85% of salt removal ratio is only 65% compare to the typical ED system. These results show that this method is effective as a low energy method for desalination.

Introduction:

Due to the increasing number of yearly discarded Reverse Osmosis (RO) modules, intensive research is being conducted in developing suitable membrane recycling techniques. Among other alternatives, the use discarded RO membranes as mechanical support for anion exchange membrane (AEM) preparation has been recently proposed for the first time. The recycled AEMs have a good permselectivity but a high electrical resistance. In an effort to reduce the electrical resistance of the recycled AEMs, this work proposes an activation treatment consisted on the subsequent immersion of the membranes in diluted acid and alkali solutions. This treatment promotes the complete dissociation of the functional groups in the membrane, making them more reactive to the counter ions.

Figure 1. Graphical abstract

Methods:

The recycled AEMs were prepared by dispersing an ion exchange resin into a polymeric solution (polyvinylchloride dissolved in tetrahydrofuran). The mixture was extended on the membrane support and the solvent was evaporated. The resulting AEMs were subjected to the activation treatment. The effects of acid and alkali concentrations and exposition times on membrane properties were studied and the most suitable combination was selected. The performance in electrodialysis of AEMs before and after the activation treatment was compared.

Results:

Figure 2. Performance in ED and electrochemical characteristics (R, electrical resistance; α, permselectivity) of AEMs.

Discussion:

The results showed that the electrical resistance of the membranes can be reduced in 37% without compromising the permselectivity by using 0.01 M solutions with 2 h of exposition cycles. The performance of the recycled membranes in electrodialysis was considerably improved after the activation treatment by increasing the flux of fresh water, reducing the energy consumption and enhancing the current efficiency. This work shows a simple, green and low cost methodology for the improvement of the electrochemical properties of recycled electromembranes and thus, their performance in electrodialysis.

The positive effects of pulsed electric fields (PEF) on the performance of electrodialysis (ED) have been known for about twenty years. This branch of ED technology continues to evolve at a laboratory scale, although some effects, and especially their cumulative action, could significantly improve desalination, concentration and separation processes. It is established that this ED mode allows mitigation of fouling and scaling [1,2], an increase in mass transfer rate [2], a partial suppression of water splitting [3]. In addition, PEF affects specific permselectivity, as a function of pulse/pause combination, such as the selectivity of transport of Ca²⁺ compared to Na⁺ [4,5]. However, the understanding of the mechanisms behind the above effects are not sufficiently clear. Some ideas were developed by N. Mishchuk et al. [6], who associated these effects with electroconvection. More details in this regard were reported in [7].

In the actual contribution, a review of the known and some new experimental findings will be made along with the modern theoretical understanding of the PEF effects. We believe that the impact of PEF on ED performance is underestimated by industrials and that this contribution can change this view.

Acknowledgements. We thank RFBR (project #19-48-230023) and NSERC (Grant IRCPJ 492889-15 to Laurent Bazinet) for their financial supports.

References

1. Lee, H.-J., Moon, S.-H., Tsai, S.-P., Separation&Purification Technology 27 (2002) 89-95.

2. Ruiz, B., Sistat, P., (...), Bazinet, L. J. Membr. Sci. 287 (2007) 41-50.

3. Malek, P., Ortiz, J.M., Richards, B.S., Schäfer, A.I., J. Membr. Sci. 435 (2013) 99-109.

4. Lemay, N., Mikhaylin, S., N., Bazinet, L., J. Membr. Sci. 2020, in press.

5. Dufton, G.; Mikhaylin, S.; Bazinet L. Membranes, 10 (2020) 14.

6. Mishchuk, N., Koopal, L.K., Caballero, F.G., Physicochem.&Eng. Asp. 176 (2001) 195–212.

7. Uzdenova, A.M., Urtenov, M.K., Nikonenko, V.V., Electrochem. Commun. 51 (2015) 1-5.

Reverse electrodialysis (RED) is an emerging, membrane-based technology for harvesting salinity gradient energy. In RED, fouling, scaling, channels clogging, and uphill ionic transport are undesirable operation constraints since they lead to a decrease in the obtainable net power density. A practical overview of current problems and challenges of operating and monitoring RED under real conditions will be discussed based on our experience, as well as on literature review. However, comparison of different studies is not straightforward due to different operating conditions employed, as well as different chemical and physical characteristics of saline streams used. For example, although an increase of pressure drop is a good indicator of channel clogging, pressure drop depends also on stack geometry and flow rate of saline streams, which are different among studies reported in the literature. Thus, we “normalised” the pressure drop data [1], reported in five works [2-6] when natural saline streams were employed longer than 20 days, by dividing them by respective flow rates and channels lengths.

There is an enormous margin of progress for future research. The still insufficient permselectivity towards monovalent ions and high commercial costs of the currently used ion-exchange membranes, combined with their rapid fouling when operating with natural saline streams seem to be the major challenges although, if an efficient pre-treatment and appropriate in-situ cleaning strategies are applied, the performance of RED has already shown to be stable for relatively long periods.

[1] Pawlowski et al., Desalination 476, 2020, 114183.

[2] Vermaas et al., Water Res. 47, 2012, 1289-1298.

[3] Moreno et al., Water Res. 125, 2017, 23-31.

[4] Pawlowski et al., Water Res. 88, 2016, 184-198.

[5] Tedesco et al., J. Memb. Sci. 500, 2016, 33-45.

[6] Di Salvo et al., J. Environ. Manage. 217, 2018, 871-887.

Bipolar membrane (BPM) synthesis and its application is gaining much attention these days due to its unique property of electrodialytic water dissociation into H⁺ and OH^- ions under reverse bias electrical potential. Ion exchange membranes (IEMs) are classified into homogeneous and heterogeneous depending on the distribution of ion exchange sites in membrane matrix. Homogeneous membranes are superior in their electrochemical performance, but undergo number of synthesis steps and accounts for higher cost. While, heterogeneous membranes are low cost and easy to synthesize, with moderate electrochemical performance. Here in this work, Homogeneous BPMs are synthesized using SPEEK as CEL and quaternized Polysulfone as AEL. Similarly Heterogeneous BPMs are synthesized using cation and Anion resin particle of 40µm size in the PVC matrix for CEL and AEL, respectively. Both the membranes are synthesized by Layer by layer casting method and comparison study is performed systematically for both monopolar and BPMs, starting from its surface morphology, mechanical properties, physicochemical and electrochemical properties. Further its performance is studied through BPM electrodialysis (BMED) experiments to understand extent of Acid and base production form salt solution. Water dissociation potential and BMED experiments confirms that the performance is superior with homogeneous membranes, but still heterogeneous BPMs perform its role in water splitting at higher potential confirms possibility of developing heterogeneous BPMs operating at lower over potential. This comparison study helps in extending further research on modifying heterogeneous BPMs with improved properties.

Water resources and water quality worldwide are facing higher pressure because of continuing population growth and industrialization. In addition to water scarcity, available water quality itself exacerbates severe issues. Unfortunately, many resources of water are contaminated with harmful inorganic compounds like heavy metals.

In this work, the focus is given to the modification of a conventional electrodialysis (ED) system configuration by integrating bipolar membranes in the feed cells. The new system, named feed side bipolar membrane electrodialysis (fBMED), has an acidic and basic feed channels and concentrate cells. The main aim of this study is to improve the performance of ED to remove heavy metals and other inorganic components by insuring higher electrical current flow during the process and by complexing the contaminants without addition of chemicals. The fBMED is applied to a highly loaded aqueous solution with heavy metals. The influence of applied electrical potential, ionic strength and flow rate of the feed solution on electrical current flow through the ED stack is monitored.

The results showed, that the applied potential revealed an increase of current flow in the system and higher contaminants removal was achieved. Higher ionic strength resulted also in higher current flow in comparison to the conventional ED at given electrical potential. Moreover, it was noticed that the fBMED performance is better evaluated based on contaminants removal rate rather than electrical conductivity removal. While the conductivity removal was delayed and lower; heavy metals and other inorganic compounds removal was higher. The kinetic of inorganic components removal was quicker compared to conductivity one.

The fBMED process was found to be a good strategy to mitigate the ED stack resistance by maintaining higher electrical current flow and to delay or even avoid reaching the limiting current density that are challenging phenomena in ED process.

Ion-exchange membranes (IEMs) with fixed ions have been widely employed in various water treatment processes for the efficient separation of ionic substances. Recently, IEMs have also been investigated to be applied in several electrochemical energy conversion processes. Among them, reverse electrodialysis (RED) is one of the promising processes for generating electricity from the salt concentration gradient between river and sea water. A RED stack contains alternately arranged anion- and cation-exchange membranes that separate salt solutions of different concentrations. The power generation performance of REDs significantly depends on the characteristics of IEMs. The main membrane properties dominating the power generation in RED processes are the ion-exchange capacity, swelling degree, electrical resistance, permselectivity, thickness, and surface morphology, etc. Moreover, the cost-effectiveness of IEMs is very important for the successful commercialization of RED process. In recent years, pore-filled IEMs (PFIEMs) in which an inert porous substrate provides excellent stabilities while a filling ionomer selectively transports ions through the membrane have been receiving great interest in the application to various energy conversion processes such as fuel cells and redox flow batteries. Simple and cheap mass production by a roll-to-roll process is one of the main advantages of PFIEMs. In this work, we have investigated the surface modification of PFIEMs for successful application to a RED process. The simple surface modification was conducted with polypyrrole (Ppy) and reduced graphene (rGO) as the base materials. The results revealed that the membrane surface properties are effectively controlled by introducing the Ppy/rGO surface layer and can determine the selective transport of specific ion species. The surface-modified PFIEMs have also been applied to water-splitting electrodialysis (WSED) and all-vanadium redox flow battery. The detailed results will be presented at the conference. This work has supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2019R1A2C1089286).

Agro-industrial by-products represent great potential as innovative sources of bioactive molecules. The development of technologies to promote their valorization and address waste management constraints is a priority. Electrodialysis with ultrafiltration membranes (EDUF) were used to separate peptides from a complex spent brewer’s yeast hydrolysate (SBYH) previously fractionated by ultrafiltration (UF) using 15, 8 and 1 kg.mol^-1 molecular weight cut-off (MWCO) membranes. Antioxidant, anti-diabetic and anti-Alzheimer activities in the fractions were investigated. Three polyethersulfone (PES) UF membranes (1, 10 and 100 kg.mol^-1) were tested in an electrodialysis system, resulting in the simultaneous separation of positively (p⁺) and negatively (p^-) charged peptides of different molecular weight distribution (MW) and bioactivity profile. Whatever the initial feed composition and UF membranes in the EDUF system, feed peptide concentration significantly decreased whereas it increased in p⁺/p^- compartments. Superior migration rates were observed for the cationic one, revealing the presence of more mobile p⁺ and free basic amino acids in the SBYH. Highest concentrations of anionic (10x) and cationic (24x) peptides were obtained using a 15 kg.mol^-1 permeate as initial feed and a 100 kg.mol^-1 MWCO membrane. The corresponding migration rate of anionic and cationic peptides was 0.22 and 0.30 g.m^-2.h^-1, respectively. Overall, anionic peptides had MW higher than 4 kg.mol^-1, whereas cationic peptides were smaller (~1 kg.mol^-1). The separation of bioactive peptides was shown to be dependent on the EDUF conditions applied. Interestingly, both recovery compartments using a 10 kg.mol^-1 MWCO membrane (1 kg.mol^-1 permeate as initial feed) could increase by 2.7 and 3.4 fold the inhibition of α-amilase activity, demonstrating an in vitro anti-diabetic effect. No effect on the inhibition of acetylcholinesterase activity (anti-Alzheimer effect) was reported for any fraction. Finally, all collected fractions presented antioxidant properties. This study demonstrated the potential of SBYH specific peptide fractions for the prevention of the metabolic syndrome.

Bipolar membranes (BPMs) in which the anion- and cation-exchange layers are adjoined together in series can easily dissociate water molecules into hydrogen and hydroxyl ions under a reverse bias condition. As well known, water-splitting electrodialysis (WSED) employing BPMs can efficiently recover acid/base products from waste salt solution without the production of undesirable by-products. The process performances including acid/base production, desalination efficiency, power consumption and so on are largely dependent upon the properties of BPMs. Therefore, BPMs should possess excellent electrochemical properties (high permselectivity, low water-splitting resistance, etc.) for efficient water dissociation. In addition, the cost-effectiveness of the membranes is one of the major factors determining the successful commercialization of the electro-membrane processes utilizing BPMs. In this work, therefore, we have developed a novel type of BPMs with a thin membrane thickness of about 50 μm for efficient electro-membrane processes. The BPMs were prepared via a pore-filling method and shown to possess excellent water-splitting efficiency under a reverse bias condition and mechanical properties. In addition, efficient and durable metal complexes were examined as the catalysts for facilitating water-splitting in BPMs. Membrane characterizations and water-splitting experiments were also conducted to determine the optimum metal catalyst and loading amount. As a result, it was confirmed that the BPM prepared under the optimum condition showed excellent stability as well as a better water-splitting flux than that of the commercial BPM (BP-1E, Astom Corp.). The detailed results will be presented at the conference. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2019R1A2C1089286).

Electrodialysis (ED) process using ion-exchange membranes (IEMs) have been used in various industrial applications such as salt production from seawater. There are many papers on simulations of ED processes; however, there are few reports on simulation in a multi-component ion system. In this study, we simulated the ionic transport of an ED process in multicomponent ion system, and conducted ED tests using commercially available IEMs to evaluate the validity of the simulation.

Fig. 1. Time course of ion concentrations in the diluted compartments of the ED stack with CMX-AMX.

In the simulation of the ionic transport in an ED system consisting of cation-exchange membranes (CEMs) and anion-exchange membranes (AEMs), the chambers I and II of the system filled with model seawater consisting of various kinds of cations and anions. In this system, the concentration of these ions inside an IEM was calculated by using Donnan equilibrium equation, and the flux of each ion was obtained by substituting the concentrations into the equation of flux based on the Goldman assumption.

In an ED test, we used an ED stack with commercial CEM (CMX, ASTOM Corp., Japan) and AEM (AMX, ASTOM Corp., Japan). The electrodes and the electrolyte of the stack were Pt and 2.0 M NaCl, respectively. The ED test was performed at a constant current density (18.2 mA/cm²) and 25 ^°C.

Fig. 1 shows an example of the ED test using salt solutions containing five kinds of cations (Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺)^. The plots and curves show the experiments and the simulations of the change in the concentration at the diluted compartments of the ED test system, respectively. The experiments and the simulation agreed quantitatively with each other. Therefore, the simulation will help the prediction of optimal ED operation conditions to reduce the running cost and/or to increase product purity. 

Recent studies showed that electrically conductive ultrafiltration membranes exhibit several advantages regarding fouling and rejection behavior due to the application of a cathodic electrical potential onto the membrane surface. A repulsive force is induced when the membrane is charged negatively due to the likewise negative charge of most dissolved organic water compounds such as natural organic matter (NOM). We used sputter deposition of ultra-thin gold layers (15 nm) to generate an electrically conducting gold-polymer-gold flat sheet membrane by coating the active and the support layer of a commercial polymer membrane (pore size ~ 50 nm, pure water permeability 1200 L/(m² h bar)). Due to the duplex-coating, no additional counter electrode is necessary. The novel approach of this study is the application of positive (+2.5 V anodic cell potential) charge to the active layer to induce electrosorption of NOM onto the membrane surface. Desorption of the NOM is achieved by changing the potential periodically (e. g., after 30 min filtration) to negative charge (-2.5 cathodic cell potential). The present results showed that UV254 reduction of Suwannee River NOM is achieved to an extent of 80% whereas no reduction of flux of the membrane was observed. Moreover, permeate was almost colorless after electrosorption measured as 95% reduction of UV-absorption at a wavelength of 436 nm. Application of negative potential led to desorption of NOM. Due to a low current density of 0.6 A/m² at a flux of 100 L/(m² h), the additional energy consumption of electrosorption and desorption process was low with 0.01 kWh per cubic meter of permeate. By the novel approach of membrane-electrosorption, an electrical conduction membrane with energy consumption between microfiltration and ultrafiltration is achieving the NOM rejection of nanofiltration and is so breaking the selectivity-permeability trade-off.

Fig. 1: Graphical abstract of membrane-electrosorption of NOM

Organophosphates (OPs) are hazardous molecules that have found applications both as pesticides and nerve gases. The intensive use of OPs to support agriculture causes pollution of vegetable products, aquifers and air, while nerve gases accumulated during the cold war represent a threat to citizen security. Therefore, it is urgent to find applicable strategies to destroy these poisonous compounds. In this work, a robust bioremediation system was designed by using an inherently stable enzyme (a thermophile) able to hydrolyze OPs. The enzyme was further strengthened by immobilization on membranes to develop a biocatalytic membrane reactor (BMR) operating in contaminated aqueous streams. Freshwater and agro-food industry wastewaters (i.e. olive mill wastewater, OMWW) were selected as model streams, to simulate their contamination the paraoxon pesticide was added as model organophosphate. The enzyme immobilization was obtained covalently in mild conditions by exploiting aldehyde groups created on purpose in the polymeric membranes. The biofunctionalization was initially carried out using three different membranes based on polyvinylidene fluoride, polyethersulfone and regenerated-cellulose. The obtained biocatalytic membranes where characterized by FT-IR, immunoelectron microscopy, enzyme catalytic activity and stability. The regenerated-cellulose membrane was selected to develop the BMR since the enzyme immobilized on this polymer showed the highest performance. Optimizing enzyme amount and residence time the BMR was able to carry out high percentage of paraoxon degradation both in surface-water (85%) and in agriculture wastewater (70%). Kinetic studies demonstrated that the lower enzyme performance in OMWW respect to surface-water was due to competitive inhibition given by biophenols. However, by using the surfactant SDS, which increases the protein flexibility and then its substrate affinity, it was possible to improve the enzyme activity even in OMWW. To our knowledge, this is the first BMR operating OPs degradation in real matrices, the high degradation capacity and stability make it promising for environmental bioremediation.

Considering the increasing occurrence of complex, hazardous compounds in waters, the need of defining new strategies to address such challenge is more and more obvious. Enzyme immobilization on membranes has been suggested as one of the most promising technologies to this purpose in the past several years, and the interactions between enzymes and support materials are at the core of this technology. Suitable supports should be characterized by biocompatibility, presence of key functional moieties, high porosity and proper 3D-structure, so enzyme immobilization and in turn extended catalytic activity should be guaranteed. Electrospinning is a promising technique that enables to design and produce materials from various polymers and biopolymers and complies with the requirements to become an optimal material for enzyme immobilization.

The main aim of the presented study concerns preparation of electrospun material from polystyrene/poly(D,L-lactide-co-glycolide) (PS/PDLG) for using it as a potential support for immobilization of oxidoreductases i.e. laccase and alcohol dehydrogenase. In order to investigate the properties of the synthesized electrospun materials before and after enzyme immobilization, SEM, FTIR, and contact angle measurements were performed. To evaluate the catalytic activity of immobilized and native enzymes, model reactions with 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and formaldehyde were conducted at key operational conditions.

After immobilization of both enzymes, it should be noted that laccase possessed the highest catalytic activity at pH 5 and 25 °C, whereas alcohol dehydrogenase at pH 6.5 and 25 °C. What is more, immobilized enzymes possessed also higher catalytic activity for about 60% at more extreme conditions compared to the enzymes in free solution, which confirms that obtained electrospun material has a great potential as supports for enzyme immobilization.

Acknowledgement:

This work was supported by the Polish National Agency for Academic Exchange as part of the Iwanowska Programme

The production of waste gases and odorous compounds by industrial operations and the threats represented by hazardous substances that can be released in air by non-conventional event (terrorist act or industrial incidents) stimulates research to develop innovative and sustainable decontamination processes of gaseous stream. Bio-based strategies are appealing solutions particularly in intensified systems such as biocatalytic membrane reactors (BMR). In this work, an alternative BMR will be presented in which the substrate and the product are in gaseous state, while the biocatalyst is in solid phase. Lipase from candida rugosa and vaporized ethyl acetate were selected as model enzyme and gaseous substrate, respectively. Lipase was immobilized on functionalized PVDF membranes by using two different chemical interactions. In the first case, the negatively-charged Lipase was immobilized by electrostatic interaction on PVDF membrane functionalized with positively-charged amino groups. In the second case, Lipase was immobilized covalently on aldehyde-functionalized membranes with or without surface-immobilized polyacrylamide microgels. The biocatalytic membranes were tested in the BMR working in gas phase, by studying enzyme specific activity, catalytic activity and volumetric reaction rate. In particular, during experiments carried out at temperature of 50 °C, lipase covalently immobilized in presence and in absence of microgels mediation showed catalytic activity of 4.4 μmol/h and 2.2 μmol/h, respectively. This outcome indicates that the local hydrated microenvironment provided by hydrophilic microgels improves lipase activity. Lipase immobilized by electrostatic bond, showed the same specific activity (1.5 mmol/h·g_enz) of the system using microgels due to a higher enzyme degree of freedom coupled with an analogously enzyme hydration, anyway its catalytic activity was lower (3.5 vs 4.4 μmol/h). Using the optimized operating conditions (enzyme loading and molar flow rates of ethyl acetate and water) all the BMRs demonstrated long-term stability (5 months) and better performance respect to the free enzyme in water/ethyl acetate emulsion.

Chromium salts, in particular trivalent Cr (III) chromium salts, are widely present in tannery effluents, thus contributing for the toxicological impact of these effluents in ecosystems[1,2]. Therefore, the development of efficient pre-treatment processes, allowing for the recovery and use of chromium salts for reuse is essential to reduce the hazardous impact of tannery effluents.

This work shows selective recovery of chromium from synthetic and real tannery effluents using chitosan-based membranes prepared by coating of a chitosan layer on the top surface of a microfiltration polyether sulfone support(Figure 1A). An integrated 2-steps membrane process was implemented combining reserve osmosis (RO) and diafiltration (DF) (Figure 1B). Real and synthetic tannery effluents were pre-treated by RO using a SW30 membrane. The RO was conducted at the natural effluent pH of 3.6, thus assuring an almost total chromium rejection (> 99%), while the rejection of other divalent and monovalent ions, e.g. Na⁺, K⁺, NH₄⁺, Ca²⁺ and Mg²⁺, presented in the effluent was > 95%.

Figure 1(A) SEM image of the chitosan-based membrane, (B)diagram of the integrated RO + diafiltration process, (C) % mass of each element present in the permeate, retentate and membrane after diafiltration.

The RO concentrates were finally processed by diafiltration, through the chitosan-based membrane, which allowed for a high chromium rejection > 95% for a real concentrate(Figure 1C) with a selectivity of ~2 in reference to the divalent cations (Mg²⁺ and Ca²⁺). These results could be explained by the high chelating capacity of chitosan towards chromium ascribed to the presence of amino and hydroxyl groups in the polymer chain[3] and competing transport of other cations. Chromium recovery can thus be achieved by reducing the pH, taking advantage of the pH responsiveness of chitosan.

References:

[1] Kiliç et al. J. Hazardous Materials 185 (2011) 456‑462

[2]Vignati et al. Science of the Total Environment 653 (2019) 401‑408

[3] Baroni et al. J. Hazardous Materials 152 (2008) 1155–1163

Acknowledgements to LAQV-REQUMTE financed by FCT/MCTES (UID/QUI/50006/2019).

Modelling and optimizing food processes is a complicated task due to the high complexity of the food product, the lack of knowledge about mechanisms limiting process performances, and the heterogeneity of the involved variables (ordinal, cardinal, discrete or continuous variables). This is the case for skim milk crossflow microfiltration with 0.1 µm pore size (MF 0.1 µm). This operation is commonly used in dairy industry to separate proteins: native casein micelles (retentate) are used in cheese making while serum proteins (permeate) are mainly used in food formulations for specific populations (elderly people, infants, etc.). Despite the high interest in MF 0.1 µm in the dairy sector, this process has not been optimized yet regarding stakeholder's objectives. The choices of membrane configurations, processing designs and operating conditions are mainly based on the know-how of equipment manufacturers and the available expert knowledge. In the literature, the optimization of MF 0.1 µm is performed as mono-objective empirical problem or as the specific influence of one variable of interest on a group of chosen variables. This work aims to optimize skim milk crossflow MF 0.1 µm from design to product composition with conflicting optimization objectives. The considerate objectives are to maximize the composition of retentate and permeate fractions, to maximize the protein recovery in permeate fraction and to minimize the economic costs. The applied methodology can be divided in three parts. First, the acquisition of scientific and expert knowledge about the objectives of the optimization, second, the modeling of objectives as computable functions, then the solving of the optimization problem by using an adapted metaheuristic multiobjective optimization algorithm.

This paper reports the application of the fluid dynamic gauging (FDG) technique to assess the fouling and cleaning behaviours of regenerated cellulose acetate (RCA) membranes fouled by filtering orange juice. In this study, RCA membranes at different molecular weight cut-off were fouled with orange juice over two fouling-cleaning cycles. Each fouling and cleaning cycle consists of 30 min of pure water flow, 60 min of fouling and 10 min of cleaning. The initial permeate flux decreased gradually with filtration time until it reached a steady-state value. The permeate flux of RCA 10 kDa and RCA 30 kDa dropped to 22 L m^-2 h^-1, indicating a flux decline of 24% and 44%. The RCA 10 kDa membranes exhibited the best separation of sterols from protein in orange juice with a selectivity factor of 16 ± 3. The permeate stream was found to be relatively high in sterols and low in protein. In the FDG testing, the fouling layers were removed by fluid shear stresses caused by suction flow and the cleanability was characterised by using ImageJ analysis. Membranes that were fouled after two cycles showed higher surface coverage compared to one fouling cycle. The surface coverage for RCA 10 kDa and RCA 30 kDa decreased from 81 ± 1 % to 5 ± 2 % and from 89 ± 3 % to 8 ± 3 % with increasing shear stress from 0 to 3.9 Pa. The RCA 30 kDa membrane showed higher surface coverage compared to RCA 10 kDa membrane. These results show that the fouling layer on RCA membranes can be removed by applying the FDG technique, without affecting the membrane surface modification caused by chemical cleaning.

This work was aimed at investigating a sustainable process for the purification of biologically active compounds from goji berry (Lycium barbarum) fruit extracts. It was based on a ‘green’ aqueous extraction of fruits, a clarification step of the extract with microfiltration (MF) and ultrafiltration (UF) membranes and a fractionation/concentration step of the clarified extract through the use of tight UF membranes. The aqueous extraction was studied in order to obtain the maximum yield of biologically active compounds. At this purpose, different parameters including extraction time, temperature and solid/liquid ratio, were optimized. Polymeric membranes with molecular weight cut-off (MWCO) from 0.5 to 3.5 kDa (GE, GH and GK from GE Osmonics) were tested in the fractionation step. The performance of selected membranes was evaluated in terms of productivity and selectivity towards target compounds. To fulfil the final aim to purify polyphenols from carbohydrates the membrane process was also studied in a diafiltration mode. Fouling index and cleaning efficiency were analysed in order to determine process feasibility at industrial scale.

The GH membrane with a MWCO of 2.5 kDa exhibited the best separation efficiency of polyphenols from carbohydrates. For this membrane an improved purification of polyphenols from carbohydrates by increasing the diafiltration volume (D) was observed: at a D of 5 the removal of carbohydrates in the UF retentate was higher than 90%; on the other hand, the loss of polyphenols in the permeate was lower than 20%.

The investigated work allowed to obtain two distinct natural aqueous extracts from goji berries: a concentrated extract enriched in polyphenols with high antioxidant activity of interest for pharmaceutical, cosmetic or nutraceutical applications and a purified extract enriched in carbohydrates useful in the food industry.

Fig. 1- Retentate concentration of polyphenols and carbohydrates for the GH membrane as a function of the diafiltration volume (D).

Introduction:

Mango is a tropical and seasonal fruit with high nutritional value and a good source of vitamins and minerals. In many countries, this fruit is found as backyard trees or along the roadside. In order to give a value-added, this work aims to concentrate the mango juice using membrane distillation (MD) process for obtaining sugar crystals.

Methods:

Mango fruits were collected from different cities of Paraguay and characterized in order to determine the content of sugars (sucrose, glucose and fructose). Mango fruits were peeled, and the pulp was extracted in a filter press. Then, the extracted was centrifugated and micro filtrated. The mango juice obtained was concentrated by membrane distillation process using the commercial module MD020CP2N. Feed temperature was at 45°C and the feed flow rate at 80 L/h.

Results:

Mango extracted obtained has a concentration of 17°Brix. This extracted was analyzed by HPLC and Table 1 shows the content of sugars (sucrose, glucose and fructose).

Table 1. Content of sugars in mango extracted.

The permeate flux was maintained constant along the experiment at 1,25 L/m²h. It was possible to achieve 40°Brix. Permeate stream did not show ionic conductivity neither °Brix concentration.

Discussion:

As it can be seen, the initial sugar concentration is high and has potential to be concentrated for posteriorly crystallizing sugar. Despite this low flux, better organoleptic characteristics have obteined than conventional vacuum evaporation. The last process requires higher temperatures promoting the caramelization of sugars, Maillard reactions and changes in color and flavor.

Membrane distillation is suitable to concentrate the mango juice in order to achieve high sugar concentration and a better quality. This concentrated juice will be crystallized in order to obtain sugar from mango, and this will give a value-added to this fruit.

In a multi-channel membrane, individual channels contribute unevenly to the total flux of the module. Due to the longer flow path of the permeate from the inner channels to the edge of the module, their contribution to the total flux is smaller than the outer channels because of the higher pressure on permeate side. 

If multi-channel modules are used for milk protein fractionation it is to be expected that the advective transport of proteins to the membrane surface will have a different effect due to different permeation rates in the inner or outer channels. Therefore, the phenomenon of fouling by retained biopolymers should also show up to different degrees. Moreover, the homogeneity of the permeate flow should depend on the number of channels. 

Thus, milk protein fractionation was investigated using ceramic modules with 1, 7, 19 or 37 channels under variation of transmembrane pressure (0 – 4.0 bar) and wall shear stress (50 – 200 Pa). The calculation of the whey protein mass flow resulted in an optimum efficiency for the milk protein fractionation - independent of the channel configuration - at low transmembrane pressure and high wall shear stresses. Operated in this optimum, the 7-channel membrane shows the highest area-specific permeate flux. However, if the module-specific permeate volume or the module-specific mass flow is considered, the 37-channel membrane shows a better performance due to the larger membrane area. 

However, if these correlations are considered in relation to transmembrane pressure, the variation in the number of channels has no influence at the optimum of the mass flow at low transmembrane pressure. Consequently, the 37-channel membrane will have the highest mass flow per module because of the higher flux. Though at high transmembrane pressure the increase in the number of channels has a positive influence on the mass flow for the entire module. 

Polychlorinated biphenyls (PCBs) are classified as: Level 1 carcinogens for humans, Super-Hydrophobic organic compounds (SHOC) and Persistent organic pollutants (POP). Additionally, their Octanol-Water coefficient is > 6, which makes them highly lipophilic substance. Thus, they tend to concentrate in adipose tissues when ingested by animals and then, following the trophic chain, PCBs are consumed by humans from products of animals origin such as meat, milk or eggs.

With the aim of designing a process to extract the compounds (PCB) from milks, a perstraction system has been proposed using an ionic liquid (ILs) as the extractive phase, both are separated by a polymeric membrane. The polymeric membrane and ILs are selected by their high affinity and selectivity for the PCB, both properties are determinated by distribution coefficients and selectivity.

For this, we will use COSMO-RS, which predicts activity coefficients in the balance between solute-solvent and solute-membrane from the density charge distribution around a molecule. Then, it is possible to design an ILs and a membrane that have an affinity to the PCB under study and low affinity to the rest of the components. (table 1). The optimal configuration of the system allows the selective diffusion of PCBs through the polymeric dense membrane and then towards the ILs.

COSMO-RS allows to predict the activity coefficients and selectivity from reported values. Table 2 and Table 3 show polymers and IL that are selective for PCB. In the case of polymers, polybutadiene and polychloroprene are preferable, and for ILs, [Tetrabutyl-Phosphonium][I₃] is the most acceptable. As a rule of thumbs, it can be argued that: 1) The lower the value of Ln(ϒ), the higher the affinity of PCBs and 2) the greater the differences between Ln(ϒ) values of the components, the higher the selectivity.

A multiple membrane process aimed at reutilization of plating combined wastewater after physical and chemical pretreatment in mechanical industry was developed for selective separation to reduce cost and mitigated the increasing heavy metal pollution.

Realizing the present growing trend in many countries and the very strict environmental norms implicated in discharging wastewater to the environment, we felt it essential to utilize the hybrid ED and NF process for an effective treatment of effluent wastewater collected from plating industry and its recirculation as a process water. Specifically, we focused on the removal of copper (Cu²⁺) and nickel (Ni⁺) ions from the plating wastewater because all these ions are strictly regulated when discharged into watershed in Korea.

The process was divided into three stages: firstly, coagulation–flocculation was used to separate the possible organic and suspended solids, secondly, electrodialysis (ED) was carried out for effective desalination, and thirdly, the concentrate from ED was treated by nanofiltration (NF) separately to increase the recovery rate of water. The recirculation of process water was studied using the indigenously built ED and NF hybrid pilot plant under process variables such as feed pressure, initial feed concentration, applied voltage and flow rate.

Thus, this work is a demonstration of the combined ED/NF process at the pilot-scale, which could offer the collective information on a large scale treatment of the waste water.

The development of the electronic and medical industries has led to a sharp increase in the demand for xenon, which modern industry cannot provide, due to its dependence on oxygen demand (xenon is a byproduct of its production), therefore, a more energy-efficient method for Xe recovery from natural gas has been proposed. This method implemented in one mass transfer apparatus, including gas hydrate crystallization and membrane gas separation, and allows to separate hard-to-separate natural gas components. Based on the results of theoretical calculations and experimental studies, a comparative characteristic of continuous gas hydrate crystallization and membrane-gas hydrate crystallization is carried out.

The hybrid membrane-gas hydrate crystallization (Fig.1) is a new process for the gas mixtures separation [1]. Unlike rectification, it has higher energy efficiency due to the process at temperatures above 273 K. A particularly promising application of this method is the recovery and high purification of low-boiling components (for example, Xe). Currently, Xe recovery from the air is expensive. Xe recovery from natural gas is especially effective due to the fact that Xe concentration in natural gas [2] is four orders of magnitude higher than in the air [3]. And the use of hybrid membrane-gas hydrate crystallization for Xe separation and purification is quite effective due to differences in gas hydrate dissociation pressures and gas permeabilities of the natural gas components. The hybrid membrane-gas hydrate crystallization consists in the conversion of gases with a low dissociation pressure into the gas hydrate phase, the presence of gases with a high dissociation pressure in the gas phase, and gases with different gas permeabilities can be separated using membrane gas separation.

Figure 1 - Scheme and photo of the experimental setup.

Mathematical modeling was carried out on the basis of three model gas mixtures:

1. CH₄ (94.85 vol.%), CO₂ (5.00 vol.%), Xe (0.15 vol.%);

2. CH₄ (94.85 vol.%), H₂S (5.00 vol.%), Xe (0.15 vol.%);

3. CH₄ (94.85 vol.%), H₂S (2.50 vol.%), CO₂ (2.50 vol.%), Xe (0.15 vol.%).

It was established that Xe is most efficiently concentrated in the gas hydrate phase, CH₄ is in the gas phase, and H₂S and CO₂ predominantly permeability through the membrane.

Two types of the most widely used industrial elastomeric membranes are theoretically examined: polydimethylsiloxane (PDMS) and cellulose triacetate (CTA). It was found that the most efficient Xe - CH₄ and Xe - H₂S gas mixtures separation using PDMS membrane, and Xe - CO₂ gas mixture separation using cellulose triacetate (CTA) membrane.

A comparative analysis was also carried out of continuous gas hydrate crystallization and membrane gas hydrate crystallization based on CH₄ (94.85 vol.%), CO2 (5.00 vol.%), Xe (0.15 vol.%) gas mixture with the addition of the kinetic promoter SDS. Composite membrane of the organosilicon type MDK-1 (silicon based polymeric membrane) was chosen as the membrane.

It has been shown that the membrane-gas hydrate crystallization is more than 20% effective compared to the continuous gas hydrate crystallization under the same conditions. It was found that CH4 recovery weakly depends on the used method and the conditions for its implementation and varies in the range of 22-27%.

It was found that the lower the temperature and the higher the ratio of the proportion of the outflow to the gas hydrate flow, the higher process efficiency. It was shown that during the implementation of membrane-gas hydrate crystallization and continuous gas hydrate crystallization (at T=272 K, p=26 bar, the ratio of the outflow to the gas hydrate flow=3), the maximum Xe recovery was 99% and 82%, Xe separation factor was 4.23 and 3.77, respectively.

As a result of theoretical and experimental studies, it was found that the use of the membrane-gas hydrate crystallization allows more efficient Xe recovery from natural gas compared to the individual method of gas hydrate crystallization or membrane gas separation.

This work was supported by the Russian Science Foundation under Grant number 17-79-20286.

1. Sergeeva M., Petukhov A., Shablykin D. et al. Separation Science and Technology, 2019. DOI: 10.1080/01496395.2019.1577454.

2. Patent RU2466086C2, 2010.

3. Godish T., Davis W.T., Fu J.S. Air Quality. – Boca Raton: CRC Press, 2014. – 542 p.

To reduce the fresh water consumption in steel industry and reach the goal of "zero liquid discharge", process water treatment is an important topic. In this work we focus on the development of a reverse osmosis (RO) membrane to recycle acidic washing water containing hydrofluoric and nitric acid from the picking line.

We developed a composite membrane on tubular ceramic support with a tailored layer-by-layer polyelectrolyte coating performing in the range of RO, which can withstand these harsh conditions. Membranes were tested with the real process water on lab scale. The membrane synthesis was then scaled up on multichannel pilot scale supports and are tested at the picking line of the steel company "Deutsche Edelstahlwerke AG".

Methods

As support α-Al2O3 ceramic tubular membranes with a pore size of 150 nm were used. The RO polyelectrolytemultilayer build-up was performed by the layer-by-layer technique. As polycation polystyrene sulfonate, as polyanion polyallylaminhydrochloride and additional covalent crosslinking glutaraldehyde was used.

For characterization water permeability, the molecular weight cut off and salt retentions were measured. Filtrations of the real acidic process water were performed for different membranes at transmembrane pressures up to 40 bar.

Results and discussion

The coating of a polyelectrolytemultilayer on ceramic support results in a dense layer, performing in the range of RO with NaCl retentions above 90 % and MWCO down to 150 Da. Filtrations of real process waters show rejections of the acid residue ions up to 98 % of fluoride and 95 %, while metal anions are completely removed. The scale-up to multichannel pilot scale membranes deliver a very high reproducibility and are tested recently on site at the picking line on in pilot scale containing three multichannel membranes in a module. Through the filtration of the washing water, the water can be reused and the overall fresh water input can be reduced.

Currently, membranes prepared from glassy polymers are utilized for natural gas sweetening, such as Ethyl Acetate (CA), and polyimides. However, gas separation performance of these polymers degrades significantly in the presence of water liquid and heavy hydrocarbons. For example, CA membrane is damaged in the presence of water liquid. Therefore, significant efforts have been devoted to the pretreatment for the natural gas feed stream to remove heavy hydrocarbons and prevent liquid water formation. This stringent pretreatment significantly increases the membrane process cost and makes the process much more complicated.

Recently, Air Liquide has developed a new simple and robust membrane process that essentially eliminates the pretreatment for natural gas sweetening and the process has been successfully commissioned at a petroleum facility in Hungary. Two types of membranes are utilized in the process. The first type of membrane is made of poly(ether ether ketone) (PEEK-Sep), which is very durable towards harsh organic compounds. PEEK-Sep membrane selectively removes heavy hydrocarbons, hydrogen sulfide, and water, providing protection for the subsequent membranes. The second type of membrane is a high performance polyimide, which exhibits very high CO2/CH4 selectivity. The membrane process contains only simple coalescing filter as the pretreatment and is sweetening natural gas from 30% CO2 down to 5%.

Nanoprecipitation has been introduced in the late 1980s for the manufacturing of nanoparticles. Until now, its use at industrial scale is still hindered by the lack of a robust technique able to translate the results from laboratory scale to mass production. In the last years, an innovative method for the production of polymeric nanoparticles (NPs) by combining membrane contactors (MC) with nanoprecipitation has been introduced. In this case, two miscible phases are separated by the membrane and meet each other at the pore exit where the mixing of the polymer solution (in an organic solvent) with the non-solvent phase (water) occurs. The emerging study of nanoprecipitation in combination with MC has opened a new window on the application of membrane science in the production of NPs. The challenges in this field are: 1) to achieve a fine control of the mixing processes in order to tune with good accuracy, the size and physicochemical properties of NPs; 2) to design new processes to reach large-scale production with high reproducibility.

In this work, the powerful of MC in combination with nanoprecipitation for the production of polymeric NPs will be demonstrated. Two case studies will be described: the production of 1) hydrophobic PLGA-PEG NPs (by using acetone and water as solvent and non-solvent, respectively) and hydrogel PVA NPs (by using water and ethanol as solvent and non-solvent, respectively). To the best of our knowledge, the proposed method combination has never been reported for the manufacturing of hydrogel-based NPs. The influences of parameters related to formulation composition (solvent, polymer concentration, phases ratio), membrane (surface wettability, pore size) and operative conditions (shear stress, flux) to develop a scalable continuous formulation method will be presented. Results demonstrated that the method is highly promising as a reproducible, productive and low-energy method for the production of drug-loaded NPs.

Introduction

Biogas is a renewable energy source composed mostly of carbon dioxide CO₂ and methane CH₄. It can be used in many applications such as the production of heat and steam. However, the presence of CO₂ decreases the calorific value of the biogas. With membrane technology, biogas can be upgraded to obtain biomethane with similar quality compared to natural gas.

This work focuses on the CO₂ capture in the CO₂/CH₄ separation. Biogas upgrading requires a 2% vol CO₂ content to be reached (from a typical 40% content in the feed mixture) for connection to the grid. Among different gas separations technologies (adsorption, cryogeny, membrane gas separation), gas-liquid absorption in a physical solvent is considered as promising [1]. The possibility to achieve process intensification of gas-liquid absorption processes thanks to membrane contactors has been intensively investigated for chemical solvents [2], but it is almost unexplored for physical solvents (such as water, Selexol, propylene carbonate, methanol, NMP…). This study intends to achieve a systematic parametric analysis of membrane contactors for biogas upgrading, in order to evaluate the best operating conditions and maximal intensification factor, compared to the baseline technology (i.e. packed column).

Methods

A study was performed to determine the influence of different membrane contactor parameters on the energy requirements and the intensification factor (i.e. volume reduction compared to a packed column). The inlet gas is composed of CO₂ and CH₄ at a 40/60 ratio. The aim is to obtain an outlet gas composition of 2% in CO₂ with a counter-current gas-liquid membrane contactor. Figure 1 shows a membrane contactor and the associated parameters related to the membrane, the contactor, the solvent and the operating conditions. In this work, we investigated the influence of the following parameters: the mass transfer coefficient of the membrane Km, the conformations: liquid in or liquid out, the length of the contactor L, the packing factor of the fibers φ, the CO₂ solubility in the solvent He, the solvent viscosity μ and the velocity of the liquid phase u_l.

Figure 1 : Membrane contactor and related parameters

Results

The efficiency of the separation is determined through the CO₂ transferred molar flow as a function of the energy consumption (i.e. the pressure drop in the liquid phase).

It was observed that the efficiency of the solvent decreases with an increase of its viscosity (methanol > NMP > propylene carbonate > selexol). Moreover, the CO₂ solubility appears to be a critical parameter. A low CO₂ solubility will lead to higher impact on the efficiency than a high viscosity.

The choice of the conformation - liquid in the lumen (called liquid in conformation) or in the shell side (liquid out conformation) - has an influence on the optimal packing factor. For the liquid in conformation, the higher the packing factor, the better the transfer is. On the other hand, an optimum in the packing factor value is observed for the liquid out conformation, depending on the solvent used.

The efficiency of the membrane contactor was compared with packed column. Looking at the CO₂ transferred molar flow, intensification factors up to 30 can be obtained. This suggest that physical capture of CO₂ by membrane contactor could be efficient for CO₂/CH₄ separation. Finally, the results obtained by simulation are critically discussed in terms of process feasability and limitations (e.g. fiber resistance, volatility of solvent, …).

[1] I. Angelidaki, L. Treu, P. Tsapekos, G. Luo, S. Campanaro, H. Wenzel, P. G. Kougias, Biogas upgrading and utilization: Current status and perspectives, Biotechnology Advances 36 (2018) 452–466.

[2] Favre, E., Svendsen, H.F. Membrane contactors for intensified post-combustion carbon dioxide capture by gas-liquid absorption processes (2012) Journal of Membrane Science, 407-408, pp. 1-7.

This paper involves the development of a novel Thermal Induced Phased Separation (TIPS) Polyvinylidene Fluoride (PVDF) hollow fiber membrane contactors used for the reduction of ammonia from wastewater. This membrane contactor allows the ammonia gas transfer between two separate liquid phases without mixing them. Compared to current nitrification and denitrification processes, it will not require additional space or nutrient addition.

The TIPS membrane tested displayed higher mechanical strength and chemical resistance compared to other commercial membrane contactors. The membrane had an air bubbling point in water of 0.03MPa, pure air flux of 6926LMH/bar, water breakthrough pressure of 0.27MPa and a contact angle of 77^o.

Sulfuric acid was used as the absorbent to strip ammonia from wastewater, which is present in gaseous form in alkaline conditions. The concentration of ammonia used during the experimental trial varied from 50ppm to 500ppm to mimic municipal and industrial wastewater respectively. Experimental results demonstrated that highest ammonia removal achieved was up to 99%. The highest flux achieved was up to 20 LMH. 

Natural gas usually contains water vapour that corrodes pipelines and forms hydrates blocking pipes and installations. The high-pressure gas stream needs to be dehydrated before transportation and a specified water content is required to meet the pipeline specifications. Compared to conventional dehydration processes, the novel membrane absorption process offers a larger contact area, less methane loss, high modularity and compact design[1]. The objective of this work was to test membrane materials and process solutions to evaluate the feasibility of the novel membrane absorption system for high pressure subsea gas dehydration.

A flat sheet membrane contactor module was employed in this study. A composite membrane was used as a membrane interface. Teflon AF2400 was coated on a commercial polyvinylidene fluoride porous support (Figure 1(a)). Polymer selection was performed based on compatibility of polymer and Triethylene glycol (TEG). The selective layer was faced to the liquid side. The module was operated with saturated methane flowing counter-current to pure (less than 20 ppm H₂O) TEG. The experimental flux and outlet dew point was measured at different pressure, temperature, liquid and gas flow rate, and inlet dew-point of gas stream. A novel (2D,1D) model was developed, implemented, and solved using orthogonal collocation approach coupled with regression analysis in order to estimate the membrane permeability and overall mass transfer coefficient.

The defect free composite membrane was characterized, and the gas permeation tests were carried out at aforementioned operating conditions. Figure 1(b-c) shows the highest flux was obtained at highest gas flow rate and lowest temperature. The effect of pressure shows a linear increase in water flux by increasing the pressure from 2-10 barg. The overall mass transfer coefficient and membrane permeability was estimated by optimizing the continuum model with experimental outlet gas concentration data. This study shows the membrane contactor enables to separate water effectively.

Figure 1: Membrane contactor characterization, (a) SEM image of composite membrane, (b) effect of gas flow rate, (c) effect of temperature, and (d) modeling water concentration profile in gas and liquid side along the membrane

References

1-Dalane, K., Svendsen, H. F., Hillestad, M., & Deng, L. (2018). Membrane contactor for subsea natural gas dehydration: Model development and sensitivity study. Journal of membrane science, 556, 263-276.

Ammonia contamination in wastewater is a growing problem that causes serious environmental problems, such as eutrophication. Traditionally, ammonia was removed to avoid its discharge into the environment. However, in recent years, ammonia is no longer considered a problem but a potential source of N for fertilizer production.

The purpose of this work is to obtain the maximum ammonia recovery from urban wastewater using hollow fiber liquid-liquid membrane contactors (HF-LLMCs) as liquid fertilizers, based on ammonium salts. For that, different operation conditions were tested in order to evaluate its performance.

An urban wastewater stream from a pilot plant located in Murcia-East, previously treated by an adsorption/desorption process was used. This stream contained 4.2 g/L- 4.8 g/L of NH₃ (pH>12), among other ions, such as Na⁺, K⁺, SO₄^2-. HNO₃ was used as acid stripping solution in the ammonia recovery process by HF-LLMC to enable the direct production of ammonium nitrate salts. Experiments were carried out in one or two stages. Those trials in two stages consisted on the performance of the same process twice, changing the initial acid solution once the process was stabilized.

Three main studies were carried out: (i) the influence of cleaning the contactor between stages (ii) the influence of having two contactors in series, both studies maintaining a constant flow rate on both sides (450 mL/min); (ii) the optimum flow rate in feed and acid streams, while working with a single stage HF-LLMC.

Results indicated that the maximum ammonia recovery was reached working by two HF-LLMCs in series, in a single stage, without a cleaning procedure at 450 mL/min and 770 mL/min of feed and acid, respectively. Best results showed that it was possible to recover 89.6 % of ammonia in 14 h and obtaining a liquid fertilizer with a composition of 4.1 % N.

The accumulation of ammonia in water bodies can cause eutrophication and reduce water quality. Thus, a concentrated ammonia effluent from a Vilanova i la Geltrú (Barcelona) wastewater treatment plant was treated. This urban wastewater contained approximately 3.4 - 5.4 g/L of NH₃, among other chemical species, such as Na⁺, K⁺, Cl⁻, Mg²⁺, Ca²⁺, PO₄^-3, SO₄^-2, at pH=12.

The experimental part of this work was based on testing different contactor operational configurations: (i) the position (vertical or horizontal) and (ii) the entrances (shell and fibres) of the liquid-liquid membrane contactor (LLMC). In addition, experiments in two stages, which simulated two contactors in series, were tested. The X-50 PP fibre 3M LLMC (USA) was used to treat 60 L of concentrated ammonia stream with 0.5 L of acid stripping solution (0.4 M HNO₃). Both streams were pumped at 450 mL/min in a closed-circuit mode. The acid solution converts ammonia into ammonium salts, which can be used as liquid fertilizers.

Results showed that the entrances presented a strong effect on the LLMC process. When the feed solution was circulated by the shell side and the acid solution by the fibres, in horizontal position, the recovery percentage of ammonia was 74.2% with the shortest time (13 h). On the other hand, the vertically position of the LLMC provided the optimal working conditions based on ammonia recovery (74.8%) and liquid fertilizer composition (7.7% N(NH₄⁺) and 5.7% N(NO₃^-)). Additionally, the highest percentage of ammonia recovery (83.1%) was obtained with the LLMC experiments in two stages using HNO₃ as acid stripping solution under the mentioned optimal conditions of position and entrances.

Following the circular economy framework, as well as the enhance of nutrient resources from wastewater, LLMC is proposed as an eco-friendly technology for ammonia revalorization as liquid fertilizers.

Shear and dilatational forces during premix membrane emulsification (PME) of protein stabilised emulsions have an impact on the protein structure. The protein structure, on the other hand, affects the characteristics of an emulsion throughout formation and storage. Relevant structural features range from the amino acid sequence to the quaternary structure, i.e., the spatial arrangement of multiple molecules.

With respect to the emulsion formation via PME, three phases may be distinguished: (I) migration of the protein through the bulk continuous phase, (II) adsorption to the oil-water-interface, and (III) interfacial rearrangement with protein film formation. The aim of this work was to investigate the effects of the protein structure on the three phases (I)-(III) at the oil-water interface.

Structural variants of the model dairy protein beta-Lactoglobulin (BLG) with changes in the amino acid sequence were recombinantly derived and kindly provided by the group of Prof. Krull and Dr. Biedendieck (Technical University Braunschweig, Germany). The behaviour of the protein during phase (I) and (II) was investigated by measurements of the interfacial tension (drop tensiometer) and during phase (III) by measurements of the response of the protein film to shear and dilatational forces (dilatational rheology).

In general, changes in the structure had a high impact on the adsorption character of proteins (I + II). In all cases, a protein film was developed, but films showed different viscous and elastic properties (III).

Differences in the adsorption behaviour will affect the macroscopic behaviour of the emulsion and its kinetic stability. The research is the first step towards a fundamental understanding of the protein structure on interfacial stabilization mechanism at the oil-water interface, necessary to characterise and control the PME process.

Membrane-based gas separation is an important process in chemical industries due to its simplicity, easy operation, lower energy consumption and compact structure [1]. For gas separation, new studies were carried out by synthesizing enzyme stabilization systems consisting of supported liquid membranes (SLMs) wherein their pores were impregnated with water-in-oil (W/O) nanoemulsions produced by direct membrane emulsification, a mild and low energy intensive technique, suitable for sensitive enzymes. The oil phase of the nanoemulsion is a low cost, low toxic oil and the aqueous phase is the enzyme in water; the support of the SLM is a porous hydrophobic PVDF membrane.

This study is focused on the capture of CO₂ by the enzyme carbonic anhydrase (CA). The composition of the oil phase was optimized among various edible oils aiming their highest CO₂ sorption capability. The water phase was optimized according to the stability of CA enzyme in aqueous phase, in the presence of various surfactants. The optimized nanoemulsions consisted of 2% wt. Tween 80 in corn oil as continuous phase and the dispersed phase of 1 g.L^-1 CA enzyme and 5% wt. PEG300 in aqueous solution (see Fig 1.A), These nanoemulsions were prepared with selected MicrodynNadir UP020 membrane and were impregnated in a hydrophobic PVDF membrane (0.22 m).

Permeation experiments mimicking different biogas compositions were performed with the SLMs, using online mass spectrometry. The permeabilities of CO₂, CH₄ and the selectivity of CO₂ in relation to CH₄ (α_CO2-CH4) were calculated.

The presence of CA enzyme significantly improved the selectivity towards CO₂. Although selectivities are not high, it must be considered that a very small amount of enzyme was used. The improvement of selectivity with increasing amounts of CA enzyme is currently under study.

Reference:

[1] S.P. Nunes et al., Membrane Technology in the Chemical Industry, WILEY-VCH (2001).

Low-molecular weight perfluorocarbons (PFCs) are chemically and biologically inert, having high affinity for several gases. Using PFC-in-Water emulsions for O₂/CO₂/NO capture/delivery systems, such as blood substitutes face problems related to low emulsion stability, wide size distribution and reduced shelf-live [1]. These limitations were overcome with nanoemulsions with a larger surface-to-volume ratio, enhanced stability and more efficient gas capture/delivery features [2].

1% (v/v) PFC-in-water nanoemulsions were produced by membrane emulsification and compared with traditional ultrasound emulsification (500W) and characterised by Dynamic Light Scattering. Tween 80 and phosphocholine ‘FC8’ fluorinated surfactant system was subjected to surface tension and interfacial tension measurements. Eight flat-sheet polymeric membranes ranging from 30 nm to 200 nm nominal pore size were screened for nanoemulsions production.

The membrane emulsification technique used allowed to produce 103±0.7 nm PFC-in-water nanoemulsions, using 1.1x10^-5 moles of the surfactant system with a 23% enhanced stability compared to emulsions with an average size of 175±1.4 nm and requiring 4.1x10^-4 moles of surfactant, produced by ultrasound emulsification (see Figure 1). A Whatman® Nuclepore track-etched 30 nm isoporous polycarbonate membrane emulsification procedure was optimised at 1.5 ml.min^-1 dispersed phase flowrate and at 0.34 m.s^-1 continuous phase cross-flow velocity (see figure 2). Membrane emulsification witnessed significant energy saving, requiring only 0.29 kW.h to produce 1m³ of nanoemulsion, compared to a 33.4 kW.h energy expenditure when ultrasound emulsification is used.

Fig 1. Z_avg mean droplet size of emulsions

Fig 2. SEM image of selected membrane

As future work, PFC (core)/silica (shell) nanocapsules will be prepared by membrane emulsification, encapsulating the nanoemulsion droplets with silica. Then, the resultant nanocapsules containing PFCs will be evaluated in terms of solubility coefficients for O₂ and CO₂, aiming their use for gas capture and delivery in biomedical applications.

References

[1] M.P. Krafft et al., doi.org/10.1016/S1359-0294(03)00045-1

[2] E. Piacentini et al., doi.org/10.1016/j.memsci.2014.05.059

Introduction

Membranes bioreactors (MBRs) combine active sludge treatments with membrane technology and currently it is broadly used for industrial and urban wastewater treatments. One of the principal difficulties that those systems have to deal with is the fouling generated onto the membranes surface. Commercial MBR systems require the replacement of the fouled membranes which contributes to increase the operational cost. The present work studies the use of recycled ultrafiltration membranes (coming from end-of-life reverse osmosis (RO) membranes) on aerobic membrane bioreactor (aMBR). Furthermore, a comparison between commercial and recycled membrane for aMBR is also investigated.

Methods

End-of-life reverse osmosis membrane was firstly recycled into ultrafiltration membrane by means of sodium hypochlorite. Subsequently, this recycled ultrafiltration membrane was assembled to a commercial flat sheet MBR support. The process performance of both membranes was tested in a laboratory scale aMBR. Table 1 shows the initial characteristics of the membranes.

Table 1 Membrane characteristics

Table 2 shows the average values of the synthetic wastewaters (SWW) used in the experiments. 

Table 2 Synthetic wastewater 

Results

Results obtained in this pioneering study are shown in Figure 1. Recycled membrane permeate values are similar to those obtained treating the SWW influent with a commercial MBR membrane. Moreover, in some specific parameters the water quality achieved with the recycled ultrafiltration membrane is slightly higher than commercial ones. 

Figure 1 aMBR permeate values

 Discussion

Obtained results were very promising and open a window for innovative studies regarding indirect use of recycled membranes. Further experimentation is required to assess the behaviour of the recycled membrane in long term experiments. 

Introduction

Anaerobic wastewater treatment is the core process for valorizing wastewaters of high strength, including those encountered in dairy and other food-processing plants; however, an aerobic post-treatment process-step is necessary when high-quality effluent is required for recycling/reuse. This study aims at demonstrating valorization of dairy-industry effluents, whereby bio-gas is produced and good quality treated-water for reuse, through a novel continuous-process involving integration of anaerobic and aerobic membrane bioreactors (MBR).

Methods

A lab-scale two-stage anaerobic/aerobic MBR pilot system was built and operated for processing dairy-effluents. Initially, biomass acclimatization took place and process adjustments (including automatic periodic membrane back-washing) that permitted long-term continuous process operation. Four experimental campaigns were performed, the first with synthetic lactose-solution as feed, characterized by high organic content (TOC= 14.3 g/L) and the rest with real effluents from a local dairy-industry (MEVGAL). TOC concentration in 2nd, 3rd and 4th campaigns were 1.9, 2.6, 4.5g/L, respectively.

Results

The performance of anaerobic/aerobic MBR pilot during the 4^th-campaign is summarized in Figure 1 and Error: Reference source not found The produced-biogas volumetric-rate (Figure 1) varied between ~9.7 and 15.4 Ndm³/d, whereas the average rate during the 4^th-campaign was ~12.5 Ndm³/d. Based on theoretical methane yield per unit organic-matter removed, the estimated methane production-rate is ~10.53 Ndm³/d, whereas measured average methane production-rate is 7.95 Ndm³/d. Thus, actual to theoretical methane yield reached 75.5%.

Concerning TOC removal, the pilot operation was very satisfactory, with removal-efficiencies of anaerobic and aerobic stages at ~99%, and ~83%, respectively, thus, leading to overall removal ~99.9%. The average TOC of pilot-unit effluent was 6.2 mg/L (Figure 2), rendering it appropriate for recycling.

Discussion

The overall performance of integrated anaerobic/aerobic MBR pilot is considered satisfactory, for valorizing dairy-effluents with significant organic load, producing biogas and good quality effluents for reuse. The integrated MBR process is undergoing further development through industrial-scale pilot-demonstration.

Figure 1 Biogas daily volumetric rate and its composition

Figure 2 Overall performance of organic matter removal of the lab-scale anaerobic/aerobic MBR unit.

An increase in the atmospheric concentration of CO₂ would cause environmental disasters making CO₂ separation necessary. Among different techniques, membrane separation by polymeric materials has been widely studied owing to their ease of processability in addition to their relatively high CO₂ permeability and selectivity. In this case, multiblock copolymers of poly(ether-amide), termed as Pebax^@, suggested relatively excellent gas separation performance by circumventing the Robeson’s trade-off. However, the membrane technology such as other separation approaches would encounter a major issue for the management of collected CO₂ after separation. Therefore, the CO₂ conversion techniques to other chemicals or fuels should be developed. In this regard, photocatalytic CO₂ conversion can be an interesting process due to low energy consumption and useful products. Considering different photocatalysts, titanium dioxide (TiO₂) due to its high quantum efficiency is attractive, but the adverse phenomena such as recombination of the photogenerated charge carriers (electrons and holes) would decrease its performance. To address this problem, vanadium/titanium (V/Ti) bimetallic compounds will be deposited on the activated carbon cloths (ACCs) via a magnetron sputtering technique. Then, they will be anodized and annealed to fabricate type II heterostructures suggesting narrower band gaps in comparison to each of the single metallic oxides. Subsequently, Pebax^@1657 block copolymer will coat the surface of ACCs as the support of catalysts to form a dense selective layer by a solution-casting method to synthesize membrane photocatalytic reactor. The prepared three-layer composite structure will be examined by different characterization methods to determine their morphology, crystalline structure, photocatalytic, and gas separation performance.

The results reveal that the porous tubular structure of the anodized film for the bimetallic oxides would yield 67±3 ppm of carbon monoxide. At the end, the gas separation performance for the neat Pebax^@1657 exhibits the CO₂ permeability and CO₂/N₂ selectivity of approximately 40.5 Barrer and 53.5, respectively.

Key issues for membrane technology in harvesting microalgae are to reach high fluxes and to alleviate fouling by microalgal cells and extracellular organic matter (EOM). Controlling the interaction between the membrane surface and the microalgal broth is the key to mitigate fouling. Many studies using hydrophilic and negatively charged membranes have been reported, because most EOM is hydrophobic and the microalgal surface charge is negative. The topography of the membrane surface (i.e. patterned membranes) offers an emerging hydrodynamic method to mitigate fouling as a simple and low-cost approach without chemical treatment. Besides, the patterned membranes have a higher surface area offering a higher flux. Shear-enhanced dynamic filtration by introducing vibration is also suggested as a feasible approach to vigorously reduce fouling. 

Therefore, it is now hypothesized that membrane performance can be improved by combining shear at the membrane surface with a negative membrane surface charge to minimize fouling, hence further reducing energy input and decreasing costs.

To achieve this goal, three favorable approaches (membrane surface charge, patterned membranes and shear-enhanced dynamic filtration) were thus for the first time combined to improve membrane performance in microalgae harvesting. Negatively charged patterned membranes were prepared from polysulfone/sulfonated polysulfone (PSf/sPSf) blends using a spray-modified phase inversion method to create surface corrugation, and the effect of sPSf on the membrane morphology and filtration performance was investigated. The patterned membrane with highest sPSf concentration exhibited the highest clean water permeance (2420±260 L/m² h bar), lowest membrane intrinsic resistance (6.1 m^-1) and highest critical flux (55 L/m² h) for harvesting microalgae. Membrane vibration could mitigate membrane fouling both for the patterned and flat membranes. The vibration system can easily achieve turbulent conditions at frequencies higher than 7 Hz. The synergy between membrane vibration, surface pattern and charge thus resulted in a clearly enhancedmembrane performance.

As membrane bioreactor (MBR) technology for wastewater treatment has developed and controversy with other technologies has always existed, knowing the whole cost, operating energy efficiency and sustainability of MBR applications is important, both economically and environmentally.

In this work, considering that the wastewater treatment will produce undesired output---sludge, we build a whole cost analysis framework and apply a data envelope analysis (DEA) methodology based on the non-radial direction distance function (NDDF) to calculate the whole cost and the wastewater treatment efficiency of MBRs for sampling of wastewater treatment plants (WWTPs) located in China. We further analyze the factors affecting the efficiency of MBRs by the pooled econometric model and panel econometric model.

The results show that the emission reduction efficiency of wastewater treatment plants after the application of MBR is significantly higher than before. The benefits of the improvement of effluent water quality can cover the increase in energy consumption costs. We also find that geographic location, effluent standards, and treatment capacity can significantly affect MBRs' wastewater treatment performance, while the type of wastewater treated (municipal wastewater or industrial wastewater) is not a determining factor.

Lastly, based on the cost-efficiency analysis and the development trend of MBRs, we analyze the driving force and sustainability of MBR applications from the perspective of supply and demand, and identify the short-term effects of environmental regulation policies.

Hydrogen can be produced by the catalytic decomposition of ammonia, where ammonia is employed as a hydrogen carrier (i.e. 17.8 wt. % of hydrogen)¹. The main drawback of the ammonia decomposition reaction is that it is thermodynamically limited at low temperature (i.e. Conv_NH3 = 100% at T ≥ 400 °C). Hence, this work focuses on the use of a catalytic hollow fibre Pd/Ag-based membrane reactor (HFMR), which is able to overcome thermodynamic equilibrium limitations. Over the last decade Garcìa-Garcìa et al.² has shown that hollow fibres can be efficiently used as support for both catalysts and membranes. The deposition of the catalyst inside the micro-channel structure of the hollow fibre increases its efficiency by minimising both internal and external diffusion limitations. Moreover, catalytic hollow fibre reactors enhance the residence time distribution, overcoming the three typical issues faced by packed bed reactors: i) preferential pathways, ii) recirculation, iii) stagnant regions. Likewise, hollow fibres can be also used as support of ultra-thin Pd/Ag membranes due to the narrow pore size distribution of their outer surface (i.e. 0.1 μm)³.

In this work a series of Ru-based catalysts supported on carbon xerogels were tested in a packed bed reactor (PBR). The reactions were carried out between 200 °C and 600 °C, at atmospheric pressure, flowing 100 mL/min of 10% vol. ammonia in argon. Then, the most active catalyst (i.e. k= 30 min^-1 at 400 °C) was deposited inside the micro-channel structure of the hollow fibre via sol-gel method. SEM and EDX images in Fig.1A show that the deposition of the catalyst was homogeneous. As can be observed in Fig.1B, the performance of the hollow fibre reactor (HFR) at 500 °C was 11 times higher than that of the PBR. The schematic diagram of the HFMR currently under investigation is showed in Fig. 1C.

Figure 1. A) SEM and EDX images of a multichannel hollow fibre after impregnation with a Ru/carbon-based catalyst, B) Performance in a PBR and the HFR during the ammonia decomposition reaction, C) Schematic representation of the catalytic hollow fibre Pd/Ag-based membrane reactor.

References

1. García-García, F.R. et al., 2011. Physical Chemistry Chemical Physics, 13(28), pp.12892-12899.
2. García-García, F. et. al,(2012). Catalysis Today, 193(1), pp.20-30.
3. García-García, F.R. et. al, 2013. Applied Catalysis A: General, 456, pp.1-10.

Narrowing the molecular weight (Mw) distribution of oligosaccharides greatly influence their value in the pharmaceutical industry. Enzyme membrane reactors (EMR) have shown promise to achieve this objective via a coupled bioreaction-separation process. Mutual dependence between enzyme kinetics and mass transfer/fouling during filtration influence the overall performance of the symbiotic system.

Most of previous studies on oligosaccharides production by EMR have focused either on optimal operation of the enzyme reaction or the membrane filtration separately, but none of them have considered the implications of coupling both steps together. It is our motivation in this study to critically assess such interactions from a novel point of view: by paying special attention to the interactions enzyme reaction-membrane filtration, which are critical for high performance of the overall process. Depending on the conditions of the reaction, the generated fouling directly affecting filtration performance will vary. Such fouling depends on the membrane type and operation mode, which will in turn have an influence on the enzyme performance. In order to assess such interactions, an EMR with free enzymes has been designed, and the mechanisms have been evaluated to produce a stream of narrow Mw distribution of products by controlling the operational conditions. Enzyme immobilization via a ‘fouling-induced’ method has been identified as a promising strategy to promote the uniformity of the products. The main weakness of the method has been however the membrane fouling (pore blocking) caused by enzyme immobilization, which led to high filtration resistance and therefore lower the permeate yield. To address this limitation, covalent and cross-linking enzyme-attachment alternatives has been be carried out on modified membrane surfaces, providing better results in terms of for enzyme stability and less pore blocking. A discussion about how the operation modes and conditions affect fouling and optimize e productivity has been also considered.

Enzyme immobilization on membranes offers several important solutions in the development of sustainable processes. Notably, both biocatalysis and membrane processes are typically operated at moderate process conditions. Furthermore, the coupling of the two processes allows a continuous operation, as the enzymes can be sterically retained within the bioreactor while the products are continuously removed from the reactor. Simultaneously, the downstream steps of inactivating and removing the enzymes from the products are eliminated. The result is an intensified process with economic and environmental benefits.

A main objective of enzyme immobilization is to stabilize the enzymes to enable their efficient use in continuous processes. However, enhanced enzyme stability often comes at the cost of decreased enzyme activity retention, and the main challenge is to balance enzyme stability and activity upon immobilization.

We have investigated current enzyme immobilization systems for applications in membrane bioreactors, and we have identified design objectives with the aim of implementing biocatalytic membranes in industrial processes. Besides high enzyme stability and activity retention, the simplicity of the immobilization method and ability of regeneration of the membrane substrate are important factors to take into consideration. Based on these design objectives, we have developed methods for fabrication of inorganic nanofiber membranes with ultra-high surface areas and tailor-made surface properties, which can be used as scaffolds for enzyme immobilization. The inorganic nanofiber membranes allow high enzyme loading as well as regeneration of the native membrane properties. In a different approach, we applied surface modification to commercial polymeric membranes that promote favourable conditions for the enzymes and result in high enzyme loading and activity retention. Here we focused on implementing the enzymes in the membrane skin layer by incorporating the enzymes in the membrane fabrication procedure, e.g. by the polyelectrolyte layer-by-layer assembly method, interfacial polymerization, or a combination of the two methods.

A novel concept has been proposed for the implementation of unsteady-state gas separation in a membrane gas separation module based on the process of pulsed retentate withdrawal [1, 2]. Both experimentally and through multi-parameter semi-empirical modelling, it was shown [1, 2] that the influence of the operating parameters is complex and multidirectional. It is critically important to understand the dynamics of the process involving the dynamics of establishing the concentration profile along the membrane during closed-mode operation, as well as the process of “relaxation” after disturbance caused by pulsed retentate withdrawal for rigorous optimization.

As a basis for the development of the model, the general problem of removing highly penetrating components from a slow-permeant matrix gas in a radial membrane module with a counter-current flow was considered. The developed model reflects the dynamics of establishing the concentration profile in the module when operating in closed-mode mode and takes into account the relationship between coordinate and time, as well as the effect of axial mixing present in the real process.

The mathematical model was successfully verified (Fig. 1) by experimentally investigating the separation of several binary diluted mixtures (He/C₄H₁₀, CO₂/N₂ and N₂O/N₂) using methods based on periodic withdrawal for gas chromatographic analysis and online mass spectrometric monitoring [3].

It should be noted that the developed model includes an analytical solution to the problem, which is important in terms of understanding the phenomena arising from unsteady state gas separation, and can serve as an effective tool for optimization of module design, as well as the operating conditions of the process of pulse retentate withdrawal.

Figure 1. The dependence of separation factor (F) from the retentate flow. Lines – simulation, dots – experimental results.

The reported study was funded by Russian Foundation of Basic Research, project № 18-38-20163.

1. M.M. Trubyanov et al., J. Memb. Sci. 530 (2017).

2. S.V. Battalov, et al., Petrol. Chem. 58 (2018).

3. M.M. Trubyanov et al., J. Memb. Sci. 587 (2019).

Kraft black liquor lignin is an underutilized resource from the pulp and paper industry with the potential of being a significant raw material for renewable fuels and chemicals. The SunCarbon process utilizes ultrafiltration to produce a lignin-rich retentate, which is subjected to lignin depolymerisation to produce lignin-oil. Remaining is a lignin lean permeate, containing low molecular weight (MW) lignin, usually returned to the cooking chemical recovery cycle. However, recovery of the remaining lignin will both produce a concentrate of potentially valuable low molecular weight lignin and a permeate clean enough to probably bypass the energy intensive evaporators and recovery boiler in the cooking chemical recovery cycle.

This work therefore evaluates nanofiltration for the separation and concentration of low MW lignin from the ultrafiltration permeate. Eight flat sheet membranes, two ceramic membranes and one hollow fibre membrane, with MW cut-offs ranging from 100 to 2000 Da were tested. The nanofiltration tests were conducted at 50 °C, 2.5-35 bar, and cross flow velocity of 0.3-0.5 m/s. The hollow fibre membrane showed a high flux of 82.3 L/m²·h, but only a 23.5% lignin retention. The SolSep NF09081 and Microdyn-Nadir NP030 membranes showed high lignin retentions (90.4% and 80.8%, respectively), but their fluxes were low (37 and 28.7 L/m²·h, respectively). Both high fluxes (72 and 165.9 L/m²·h, respectively) and high lignin retentions (83.7% and 71.4%, respectively) were obtained for the Koch Membrane System MPS36 and Microdyn-Nadir NP010 membranes. Overall, it was shown that the nanofiltration process is able to produce a permeate stream which could be suitable for bypass of the evaporators and a concentrated lignin fraction, which can either be used to produce valuable chemicals or blended into the lignin-oil.

The transformation of the pulping industry into lignocellulosic biorefineries is essential to establish a circular bioeconomy. These lignocellulosic biorefineries will not only produce cellulose and electricity but compounds for the production of biochemicals, biofuels and advanced materials as well. In particular lignin, hemicelluloses and extractives are promising wood compounds currently discharged in process water from pulping plants e.g. thermomechanical pulping (TMP) mills. They can be recovered by using efficient separation methods.

The pressure-driven membrane processes microfiltration (MF) and ultrafiltration (UF) have been identified as key technologies for this task. However, membrane fouling is still a major obstacle. Especially the widely used polysulfone UF membranes are prone to the adsorption of wood chemicals altering the membrane performance during operation either as a reduction in flux or an increase transmembrane pressure. Both changes are common indicators of membrane fouling but do not provide any information on the fouling layer composition and the interactions of the compounds involved in its formation. Ex situ analysis reveals some of this information but the time dependence of the fouling process remains unknown.

Alternatives are in situ real-time monitoring technologies that provide a deeper understanding of the fouling processes. Quartz Crystal Microbalance with Dissipation (QCM-D) is such a technology allowing investigations of membrane fouling at an early-stage.

In the presented study, QCM-D was used to investigate adsorption of raw and MF pre-treated TMP process water on polysulfone model surfaces representing commercial membranes. This presentation will demonstrate that a link between the observed fouling behaviour of the tested solutions and the main foulants – colloidal extractives and hemicelluloses – can be established. The gained knowledge will contribute to membrane fouling reduction in lignocellulosic biorefineries in an efficient and sustainable way and thus support the further dissemination of membrane processes in this industry.

Liposomes are spherical vesicles based on a central aqueous core surrounded by a phospholipid bilayer. They are used to encapsulate compounds for various applications [1]. The conventional ethanol injection technique for liposome preparation presents many advantages such as reproducibility, its fast implementation and the possibility of scale up. In parallel, the use of the membrane contactor method based on microengineered membranes (figure 1) to prepare liposomes offers a fine control of liposome size distribution and therefore the possibility of scale up. Cysteamine, a hydrophilic molecule, has a radioprotective, anticancer and anti-malarial effects, it is used for cystinosis treatment and as depigmenting agent. Its encapsulation could increase its stability in solutions and improve its organoleptic and pharmacokinetic behaviours.

The organic phase containing lipoid S100 and cholesterol was injected through the membrane using a syringe pump at a flow rate of 1 mL/min and the cell was filled with 20 mL of ultrapure water or cysteamine solution to obtain the blank or cysteamine loaded liposomes. The obtained liposomes were characterized for their size, polydispersity index (PdI) and zeta potential by diffusion light scattering and for their morphology using transmission electron microscopy. The encapsulation efficiency of cysteamine in liposomes was also determined.

With the conventional ethanol injection method, two populations (nanometric and micrometric) were observed in blank and cysteamine-loaded liposomes. The liposomes were homogenous (PdI close to 0.2) with a negative charge and an oligolamellar spherical-shape. The encapsulation efficiency varied between 12 and 40% for the different formulations. The encapsulation of cysteamine improved the stability of this drug in all the conditions assessed. The same characterization was conducted with the membrane contactor method to evaluate its effect on all these parameters. The effects of lipid and cholesterol concentrations and the membrane microstructure on the characteristics of the vesicles were studied as well.

Figure 1: Schematic diagram of the membrane contactor.

[1] Laouini, A., Jaafar-Maalej, C., Limayem-Blouza, I., Sfar, S., Charcosset, C., & Fessi, H. (2012). Preparation, Characterization and Applications of Liposomes: State of the Art. Journal of Colloid Science and Biotechnology, 1(2), 147–168. https://doi.org/10.1166/jcsb.2012.1020

Diclofenac is a nonsteroidal anti-inflammatory drug, which is rated as a “contaminant of emerging concern” and was included in the previous Watch List of EU Decision 2015/495. Due to the constant entry and stability, diclofenac has been even found in fruits and vegetables.

The need to remove diclofenac from waste water before it can reach the environment is high and requires advanced treatment systems. Conventional methods include ozonation, activated carbon or membrane technologies, which all have certain disadvantages like the generation of toxic products or high energy consumption. Diclofenac is also naturally degraded in the environment via UV-light (photolysis). We propose a new method using UV-light and a PVDF membrane to remove diclofenac from water at high speed. The photolysis of diclofenac is hindered and slowed down by the formation of intermediates (see Figure 1, left picture). By introducing a PVDF membrane, less intermediates (Figure 1, right picture) were found in the solution, thus diclofenac degradation was increased and removal of total organic carbon was enhanced.

A simple setup was used to proof the concept. A solution of diclofenac with 25 mg L^-1 diclofenac sodium salt was added to a petri dish with and without a PVDF membrane (Roti®- Polyvinylidene Difluoride 0.45 µm). The system was irradiated with UV light (Heraeus Original Hanau OH M 21/25 R Slim 25 W Tanning Tubes, 300 - 440 nm) over different time scales. The degradation of diclofenac was analysed using HPLC, GC-MS, TOC and DFT calculations. Dark-adsorption was always performed.

Figure 1. Schematic graph of the photolysis of diclofenac without (left) and with a PVDF membrane (right).

Crystallization is an important unit operation in process engineering as it allows the production, purification or separation of solid compounds. However, crystallization, driven by the supersaturation, includes complex phenomena that occur simultaneously or consecutively and can induce polymorphism. Amongst several supersaturation techniques, reverse antisolvent appears as the one able to limit phases transition, control polymorphism and crystal size distribution (CSD). In this process, the solute is dissolved in a good solvent-antisolvent mixture and the good solvent has to be evaporated to supersaturate the solution (usually by heating).

This study intends to study reverse antisolvent crystallization using pervaporation. Pervaporation allow a better control of the mass transfer, by the selective evaporation of the good solvent. A fine control of the mass transfer across the membrane induces a better control of the CSD and the polymorphism. Furthermore, membranes provide a greater surface area per unit volume of equipment and may reduce energy consumption and improve the operability and controllability of the process.

To reach the aim of this study, a semi-continuous experimental set-up (figure 1) is developed. Two membrane materials have been selected: polydimethylsiloxane membrane and HybSi hybrid membrane and two different membrane modules are studied: a plan and a tubular module for the separation of water/ethanol mixtures. The permeate is analyzed by refractometry. L-glutamic acid is chosen as model compound as it crystallizes under two well-known monotropic polymorphs: the stable polymorph β and the metastable polymorph α. The polymorphic form is determined by X-ray diffraction and Scanning Electron Microscopy and the CSD is measured by laser diffraction. The influence of permeate pressure and temperature of the feed reactor are studied to investigate the process performances.

Figure 1: Experimental set-up

Current phase separation techniques for the production of polymeric membranes mostly involve the use of toxic solvents. Many alternatives for the solvent have been investigated, however, a recent breakthrough has found that membranes can also be produced through an aqueous phase separation (APS) approach, utilizing a pH gradient [1]. A downside of the approach is that quite extreme pH values are needed to obtain the desired precipitation rates. Here, we propose an alternative APS approach that relies on a salinity gradient. Two oppositely charged polyelectrolytes (PEs) in aqueous solution are mixed at a high salinity where the PEs do not complex. Casting of the mixture and immersion in a low salinity coagulation bath result in the formation of a water-insoluble polyelectrolyte complex (PEC). The resultant PEC membranes are in the nanofiltration (NF) range with <300 Da of molecular weight cut-off and ≤1 L·m⁻²·h⁻¹·bar⁻¹ permeability. First, the effects of PE molecular weight (MW) and total PE concentration were investigated. The optimum casting solution was selected based on membrane water permeability and simplicity of the membrane formation procedure. Then, the effect of coagulation bath salinity was investigated. While the MW and the polymer concentration do not affect the membrane structure significantly, the coagulation bath salinity affects both the membrane structure and performance. High salinity coagulation baths led to thicker skin layers, lower permeabilities and higher MgSO₄ retentions (up to 80%). Besides the separation performance, stability of the membranes under high pressures and after long-term tests confirmed that these membranes are suitable for NF applications.

A highly desirable feature of PECs is that they are insoluble in an apolar media making PEC membranes suitable for organic solvent nanofiltration applications. This work shows that it is possible to prepare polymeric membranes in a simple and sustainable way and the resultant membranes can perform in both aqueous and organic solvent filtrations.

Figure 1. An illustration for preparation, structure and performance of the NF membranes obtained with complexation induced aqueous phase separation.

[1] Baig M.I., Durmaz E.N., Willott J.D., de Vos W.M., Adv. Funct. Mater., 2019, 1907344

Synthetic membranes, largely made of polymers, are widely used in various industries, such as water purification, bioprocessing, and food processing. The commercial polymeric membranes are generally recognized to have negative environmental impact as membranes need to be replaced and abandoned after reaching the end of their life. Recycle of end-of-life synthetic polymeric membranes is of great significance for environmental sustainability. However, only techniques of downcycling of end-of-life high-pressure membranes to low-pressure membranes are available, resulting in a current unfavourable route of membrane material reuse (Fig. 1A).

Figure 1 The schematic of TFC PA membranes upcycled from biopolymer fouled substrates for water purification

Here, we propose to upcycle fouled microfiltration membranes for fabricating polyamide (PA) thin-film composite (TFC) nanofiltration membranes (Fig.1B). Cross-linked, defect-free, and ultrathin PA active layers were formed via interfacial polymerization (IP) on substrates fouled by vacuum filtration of biopolymers (Fig. 1C), which were characterized by scanning electronic microscopy, X-ray photoelectron spectroscopy and atomic force microscopy. In contrast to the decreased pure water flux of microfiltration substrates by biopolymer fouling, the upcycled membranes show excellent water permeability (~30 L^-1 m^-2 h^-1 bar^-1) and Na₂SO₄ rejection (~95%) upon nanofiltration tests, significantly higher than those of the control membrane. It is demonstrated that the biopolymer foulants regulate the IP process and the formation of PA layer, ensuring the high rejection performance. The foulants between PA layer and substrate can induce additional channels for water transport, evidenced by gold nanoparticle filtration and transmission electronic microscopic characterization. Further, a contribution analysis via spray-coating experiment revealed the role of foulants at different positions in the improved performance of upcycled membranes. This proof-of-concept study paves the way of upcycling fouled/end-of-life low-pressure membranes to fabricate new high-pressure membranes (Fig. 1B), forming a closed eco-loop of membrane material recycling (Fig. 1A).

Membranes are often used in environmentally friendly applications and as a sustainable alternatives to conventional processes. Unfortunately, the vast majority of polymeric membranes are produced via an unsustainable and environmentally unfriendly process that requires large amounts of harsh reprotoxic chemicals like N‑methyl‑2‑pyrrolidinone (NMP) and dimethylformamide (DMF). In this work, we investigate an aqueous phase separation (APS) system that uses weak polyelectrolytes, whose charge is dependent on the pH (weak polyelectrolytes) to produce membranes. Specifically, the copolymer polystyrene-alt-maleic acid (PSaMA) is used. PSaMA contains responsive monomers required for the aqueous phase separation and also unresponsive hydrophobic monomers that provide mechanical stability to the resultant membranes. This work demonstrates that by controlling the precipitation of PSaMA, it is possible to prepare a wide range of membranes, from open microfiltration membranes capable of treating oily waste water, to dense nanofiltration-type membrane with excellent micropollutant retentions and high mechanical stability. The only solvents used in this APS system are water and the green solvent acetic acid, thus making our APS process significantly more sustainable and environmentally friendly compared to conventional membrane fabrication methods.

Ceramic silicon carbide (SiC) membranes are useful for water treatment due to their chemical resistance and high permeate flux. The addition of photoactive TiO₂ layers can be beneficial to control their porosity, increase hydrophilicity, decrease fouling and improve the overall water quality produced. In previous work, SiC membranes were modified with silicon dioxide (SiO₂) and TiO₂ Degussa nanoparticles by the sol-gel process, using ethanol as a solvent, and photocatalytic membranes with high potential to degrade organic contaminants were obtained [1]. This modification procedure was further improved and new membranes were prepared at low temperature and under solvent-free conditions, exhibited a narrow pore size distribution and homogeneity without cracks [2]. These surfaces have shown a highly efficient and reproducible behaviour for the degradation of methylene blue.

Finally, a new hybrid photocatalytic membrane reactor that can easily be scaled-up was designed, assembled and used to test the photocatalytic membranes developed [3]. Extremely high removals of total suspended solids, chemical oxygen demand, total organic carbon, phenolic and volatile compounds were obtained when the hybrid photocatalytic membrane reactor was used to treat olive mill wastewaters.

The photocatalytic membranes were also tested in combination with diodes that emit light at different wavelengths that proved to be effective to inactivate different Aspergillus species [4]. The combined process was extremely effective to retain and inactivate total coliforms, E. coli and fungi present in wastewater effluents.

The submerged photocatalytic membrane reactor proposed and the modified membranes represent a step forward towards the development of new advanced treatment technology able to cope with several water and wastewater contaminants.

References

[1] Huertas R. M. et al. Sep. Purif. Technol. 180 (2017) 69.

[2] Huertas R. M. et al. Molecules 24 (24) (2019) 4481.

[3] Fraga M. C. et al. Catalysts 9(9) (2019), 769.

[4] Oliveira, B. et al. Water Research 168 (2020), 115108

Acknowledgements

PTDC/ EAM-AMB/30989/2017; Águas do Tejo Atlântico; INTERFACE Programme.

Polymeric membranes are typically prepared using a technique called Non-solvent induced phase separation (NIPS). Unfortunately, this technique relies on large amounts of aprotic organic solvents such as N‐methyl‐pyrrolidone (NMP). NMP is reprotoxic and unsustainable and recently, its use has been restricted within the European Union. Here, we report a new and sustainable approach to produce polymeric membranes. The new Aqueous Phase Separation (APS) technique relies on polyelectrolyte complexation for the phase inversion. A homogeneous solution of a strong polyanion, poly(sodium 4‐styrenesulfonate) (PSS), and a weak polycation poly(allylamine hydrochloride) (PAH), is prepared at high pH. The solution is then cast as a thin film and immersed in a pH ~ 1 coagulation bath. At this low pH, PAH becomes charged and complexes with PSS to form a water-insoluble polyelectrolyte complex film, a membrane. The structure and morphology of the resulting membranes is tuned by varying the polyelectrolyte solution concentrations, molecular weights of the polyelectrolytes, and the salinity of the coagulation bath. This allows the production of microfiltration membranes that can remove dispersed oil from waste‐water, ultrafiltration membranes that are able to concentrate dilute protein solutions, and nanofiltration membranes that effectively remove small organic molecules from water streams. The new APS technique also provides a new type of separation where it is important to retain organics without retaining salts. To retain the salts, layer-by-layer coating is performed with three different types of polyelectrolyte pairs. MgCl2 retentions in excess of 97% are obtained upon coating the APS membranes with only 4.5 bi-layers of PSS and polyethyleneimine (PEI). With the demonstrated control over pore size and membrane structure that allows the production of membranes with excellent separation properties, the completely water‐based APS technique is truly an alternative to the now dominant solvent‐based NIPS approach.

The current membrane fabrication methods mainly require the use of fossil derived polymers and toxic solvents. Hence, because of the rising environmental issues, new strategies to develop greener membrane processes are emerging and the use of renewable and non-toxic materials are part of them [1,2]. It is herein proposed a new sustainable membrane fabrication approach by combining the use of a polyhydroxyalkanoate (PHA) as biopolymer matrix and Cyrene™ as biosolvent by phase inversion.

The membranes were made by dissolving poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) into Cyrene™ and inducing the phase inversion by a first partial evaporation (EIPS) followed by a non-solvent bath (NIPS). The influence of the evaporation time and dope solution composition were studied. The mechanical properties and microstructures of the membranes were analysed and linked to the process conditions. Pure water permeability and pervaporation tests were carried out to highlight the membranes application areas (Figure 1).

Figure 1: Overview of the sustainable process development. With the biomaterials chemical structures, membranes SEM cross-section images and porosities. PWP: pure water permeability, J: thickness normalized total flux and α: methanol selectivity.

By increasing the evaporation time, the membrane porosity was decreased but the tensile strength was improved. While an evaporation time of 1.5 min led to porous membranes intended for microfiltration, a time of 5 min led to dense asymmetric membranes for pervaporation. The addition of polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG) as pore forming additives was also evaluated.

By acting on polymer composition and preparation conditions, new biobased membranes were successfully produced. The membranes demonstrated promising results for microfiltration and pervaporation applications. This process has proven its potential to make greener membranes.

[1] A.G. Livingston et al., Green Chem. 16 (2014) 4440.

[2] F. Galiano et al., J. Memb. Sci. 564 (2018) 562–586.

There are some 50 quadrillion tons of minerals and metals dissolved in all the world’s seas and oceans. Thus uranium, calcium, magnesium, potassium, sodium, lithium represent a much bigger amount of storage compared to the land and underground resources. Nano/ultrafiltration process using inorganic membranes can concentrate multivalent metal ions by rejection attributed to a combination of various mechanism including steric, Donnan, dielectric and transport effects. Our goal is to investigate the possibility to use inorganic membrane in order to concentrate valuable metals from seawater by a nanofiltration process.

For this purpose, a laboratory scale pilot was used (see Figure 1) with membranes with a molecular weight cut-off of 1 to 8 kDa, a multilayer structure with a TiO2/ZrO2 active layer and a tubular channel titanium support.

Nanofiltration experiments were investigated in a 1 L volumetric reactor on synthetic aqueous solutions in order to concentrate valuable metal ions.

The results show that by electric effect, inorganic membrane can selectively reject the metal ions with different rejection in different pH and concentration conditions as illustrated in Figure 2 for the Cu. The results have been correlated to speciation studies with Phreeqc, which help to describe the species distribution in solutions and to explain the rejection of metals by electric effect. In alkaline environment close to seawater conditions, due to their special species distribution we can specifically perform the separation of targeted ions which allows us to consider the implementation of a concentration process on seawater. Additionally, when the electric effect cannot reject the metal ions, the use of water-soluble complexing agents, which can change the ion size and the speciation of the solute, is investigated.

Hydrothermal liquefaction (HTL) of sewage sludge leads to the production of a liquid phase by-product containing high concentration of organic compounds, which shall be recovered back to the HTL process. In the framework of this study, the performance of several membranes in the range from ultrafiltration to reverse osmoses whilst filtration of the liquid phase was investigated.

Experiments were carried out the following polymeric membranes: NF-270, NF-245, NF-90, BW-30 (DuPont Water Solutions) and HYDRACoRe 10 and HYDRACoRe 50 (Hydranautics). Samples from the feed and the permeate were taken for measuring electrical conductivity, pH value, concentrations of dissolved organic carbon (DOC), total nitrogen, volatile fatty acids (VFA) and selected inorganic ions.

Feed solution showed high DOC-concentration (30 g/L), which enhanced fouling, leading to a fast drop in permeability. The DOC consisted of small organic compounds, e.g. VFA, phenols, organic compounds of sulphur and nitrogen. The decrease in permeability was higher for sulfonated poly ether-sulfone membranes in comparison to polyamide membranes. Interactions between membrane materials and dissolved compounds play a key role, influencing membrane performance.

The feed solution had a high electrical conductivity (62 mS/cm), generated mainly from monovalent ions. Thus, filtration with NF 90 and BW 30 was done at 40 bar due to high osmotic pressures produced by the ion-rejection. Filtration with the other membranes having low retention of monovalent ions induced low osmotic pressures and a pressure of 20 bar was applied. NF 90 and BW 30 showed high retention of DOC (70-80 %) but extremely low permeability in comparison to the other membranes.

For practical applications, only NF 270 and NF 245 can offer an acceptable permeability with low DOC rejection (30 %). A combination of membrane processes (pressure driven membranes and membrane distillation) seems to be the optimal option to treat this kind of industrial waste streams.

Due to increasing shortage of fresh water, seawater desalination has become important source of fresh water. However, large amounts of concentrated seawater brines pose significant environmental and economic thread. Nevertheless, brines can be a convenient source of minerals, like magnesium. Thanks to a very low solubility, magnesium hydroxide can be precipitated from concentrated brines by alkaline reactant.

In this work, a crystallizer with anion-exchange hollow-fibres is presented. In the module, 0.5 M MgCl₂ and 1 M NaOH solution, flowed on the opposite sides of the hollow-fibres. Cl^- and OH^- exchanged between the solutions through the hollow-fibres, and Mg(OH)₂ precipitated. Impact of number of hollow-fibres in modules and flow regime on conversion and particle size distribution was studied. Experiments with model solutions of seawater brines were conducted as well.

Conversion increased with increasing number of hollow-fibres in modules. For 135 hollow-fibres the conversion was 71% while the conversion in 275 hollow-fibres module was 88%. In co-current flow arrangement the conversion was 91% for 135 hollow-fibres module. In module with higher number of hollow-fibres the exchange of anions was faster and therefore lot of smaller crystals of Mg(OH)₂ was created. Median in 275 hollow-fibres module was 7.56 µm, in 135 hollow-fibres module was 9.86 µm. Purity of Mg(OH)₂ was crucial in tests with model seawater brines since brines contain other minerals that can precipitate. Nonetheless, the purity of Mg(OH)₂ was 98.6%.

Goal of this work was to study membrane crystallization of Mg(OH)₂ with anion-exchange hollow-fibres. The highest achieved conversion was 91% in co-current arrangement. However, conversion could increase, if the drawbacks of this process, like scaling of the module, solve out. Under the right process condition Mg(OH)₂ can be produced from brines with high purity. Moreover, this process can find application in other fields such as production of low soluble organic acids.

Recovery and re-use of reactive nitrogen from aqueous wastes streams such as urine or digestate is gaining attention, for both environmental and economic reasons. A high TAN (Total ammonia nitrogen, ammonium and ammonia) recovery can be achieved using a hydrogen recycling electrochemical system (HRES). When a current is applied, a concentration gradient of cations builds up between catholyte and feed solution due to their separation by a cation exchange membrane (CEM). When no current is applied, cations (Na⁺ and K⁺) can diffuse back to the feed solution through the CEM as a result of the concentration difference. These cations will be exchanged for other cations (NH₄⁺ and H⁺) to maintain electroneutrality: a phenomenon known as Donnan Dialysis. In this study, Donnan Dialysis was explored as a strategy to enhance the TAN recovery efficiency in an HRES. Our system achieved 87% TAN recovery efficiency. In continuous operation Donnan Dialysis did not clearly affect TAN recovery, although it improved the ammonium transport at a lower load ratio (L_N=1). During continuous operation, protons were also transported from feed to cathode, which resulted in a lower catholyte pH and consequently led to a lower ammonia transport over the gas permeable hydrophobic membrane. In batch operation, Donnan Dialysis increased the TAN recovery efficiency by 10% compared to operation without Donnan Dialysis. By analysing transport numbers of the different cations we show that in batch mode Donnan Dialysis exchanges mostly Na⁺ and K⁺ with NH₄⁺. Moreover, batch operation with Donnan Dialysis achieved similar recovery as in continuous operation but consumed less energy, between 7.8 kJ g_N^-1 and 10.1 kJ g_N^-1 compared to 9.7 kJ _gN^-1 to 14.2 kJ g_N^-1 in continuous. Donnan Dialysis is thus a good strategy to enhance TAN recovery in batch operation mode as it enhances ammonium recovery while consuming less energy.

Sugar beet molasses is an underutilized by-product obtained from sugar mills, which is today mainly used for animal feed. The sugar compounds in the beet molasses, such as sucrose, are suitable raw materials for biorefinery processes. Among the different platform chemicals which can be produced in biorefineries, 5-Hydroxymethylfurfural (5-HMF) is a promising candidate for creating several different chemical building blocks and polymers. However, the 5-HMF formation process is affected by the purity and concentration of the raw materials used. In this study, two membrane processes, ultrafiltration (UF) and nanofiltration (NF), were studied for the purification of the sucrose fraction in the molasses.

Two ceramic tubular modules were evaluated for the concentration of diluted molasses in cross-flow filtration mode. An UF membrane (Atech, Germany) with 10kDa MWCO and a NF membrane (IKTS Fraunhofer, Germany) with 200Da MWCO were used. During the concentration studies of the molasses, high normalised fluxes of 11-34 L/(m²h bar) (UF) and 14-27 L/(m²h bar) (NF) were achieved at 60˚C under volume reductions of 65-85%. During the trials significant membrane fouling was observed which resulted in pure water flux declines of 35 – 65%. However, it was possible to closely recover the original pure water flux (>80%) with optimised sequences of acid, alkaline and enzymatic cleaning agents.

During the analysis of the retention of the different membranes using HPLC, significant differences for the sugar components were observed. Therefore, Dynamic Light Scattering was used to determine aggregate formations of the feed solution which revealed large variations of particle sizes distribution depending on molasses concentration. The purified molasses from both UF and NF was concentrated by evaporation and tested for 5-HMF production. The results from the 5-HMF production based on the purified and raw molasses were assessed and compared in a techno-economical evaluation.

The oxidation under pressure (POX) process used in the gold’s beneficiation consumes a lot of water and, consequently, generates a large volume of aqueous effluent’s (63 m³/h) composed of high sulfuric acid concentration (11540 mg/L; pH 0.8), which promotes several metal ions solubilization, such as Ni (169.30 mg/L), Co (115.40 mg/L) and Cu (171.57 mg/L), that can be toxic to the environment and human health. The traditional POX effluent’s treatment requires larger area and results in a lot of waste generation. The situation is even more challenging considering the growing in water’s scarcity. In this context, the direct contact membrane distillation (DCMD) highlights for its effluent’s treatment efficiency retaining, theoretically, 100% of non-volatile compounds. Thus, this study aims to propose a treatment in order to generate industrial reuse water from POX effluent. For this, DCMD tests were performed on a bench scale (Figure 1) applying PTFE membrane and its costs was estimated evaluating its operational expenses (OPEX).

Figure 1. DCMD set up. P01 and P02: peristaltic pumps; HE01: shell and tube heat exchanger.

Until 30% recovery rate (RR) the DCMD had metals ions retentions >99.8%, but after this the conductivity increases demonstrating membrane wetting as can be seen in Figure 2.

Figure 2. DCMD profile test at 60 °C and 0.30 L/min.

The DCMD energy requirement is low since the POX effluent residual heat can ensure an adequate driving force. The cleaning agent presented the lowest contribution, due to no representative fouling or scaling occurrence, but membrane replacements were the main contributors to OPEX in the first two years as shown in Figure 3.

Figure 3. System requirements and their contribution to OPEX.

Thus, considering the average permeate flux of 0.033 m³/h.m², the system would be capable of supplying 3,483.41 m³ of high-quality water for reuse annually.

Nowadays, any polluted water can be separated to gain the products with the desired quality by using the conventional processes like distillation, crystallization, adsorption, chemical and biological treatment, if the cost and energy intensity of such treatment are not subject of interest.

The advantage of membrane separation is to operate the process even in the case of shortage or no power supply by using low-grade heat or solar energy. Besides, some membrane processes can be operated without phase transition at the relatively low-pressure difference.

The goal of this work is to develop membrane-based processes that can significantly reduce the energy consumption and the cost or to be operated independently for effective operation in the remote areas to produce the clean water and recovery of organic and inorganic components together with clean water from the polluted water.

In this project, scientific approaches are being developed on the combination of electrodialysis and reactive electrodialysis for the effective separation of nitrate ions with their subsequent reduced to nitrogen. Ion-exchange membranes are being developed that fractionate phosphate and nitrate from the other components in the contacting brine solution. The use of membrane extraction is being investigated for the preliminary separation of metal ions, as well as for the preparation of metal ion concentrates. Membrane crystallization method based on membrane distillation together with crystallization process is being developed to effectively split the concentrated stream after nanofiltration, reverse osmosis or electrodialysis to two streams – pure water and the salts of presented metals in the form of crystals.

This project was founded by RFBR (№ 18-58-80031), NSFC (51861145313), DST (DST/IMRCD/BRICS/PC2/From waste to resources/2018 (G)), NRF (No: 116020), CNPq (CNPq/BRICS-STI-2-442229/2017-8).

Lithium is one of the most sought after metals. It is required for production of electrical batteries, glasses, ceramics and lubricants. The high demand of lithium feedstock is conditioned by the recent rapid growth in the market of lithium batteries, which are used in almost all modern portable devices and electro cars. Despite the relatively high lithium abundance on Earth, its production is difficult because of its low concentration in raw materials. One of the main sources of lithium is geothermal brines.

In the present work, a novel integrated process to the concentration and extraction of lithium compounds from geothermal waters is proposed. The novelty of this method is a unique way of brines pre-concentration by means of thin-film evaporation with vapor condensation on a porous membrane. The technique provides high performance (more than 20 kg m^-2 h^-1 of water), low metal and energy demand since the process is being carried out at atmospheric pressure, and the driving force may be created by using geothermal water internal heat. An important advantage of our method is the fact that the high process efficiency does not depend on the quantitative and qualitative salts composition in concentrate. Fundamentally new approach is merging two membrane processes (concentration and extraction) in one. The pre-concentration stage allows significant intensification of lithium compounds extraction, which results in decreased separation costs and allows to enhance the process performance, to achieve deeper hydrothermal feedstock recovery and to obtain pure water as an extra product.

This project was founded by RFBR (№ 20-58-53038) and NSFC (No. 51861145313, 5191101572).

MEWLIFE is a LIFE project aiming to demonstrate the environmental benefit and economic feasibility of an innovative approach to produce microalgal biomass in an integrated phototrophic – heterotrophic cultivation system using preconcentrated olive oil wastewaters as carbon source for growing algae, thus contributing to waste reuse and valorisation.

The concentrated feedstream are membrane concentrates that are produced during the purification of the wastewater. In this insight, the treatment pant has to accomplish two targets, that is to permit discharge of purified after in the municipal sewer system and at the same moment, prepare suitable feedstocks to the subsequent bioreactors.

The latter requirement requires to maintain the organic matter and in particular the polyphenols in the waste stream almost intact. After an acid flocculation process, that do not affect much the content of polyphenols, ultrafiltration and nanofiltration are employed in series. Due to the light pretreatment of the feed stream, fouling is of major concern.

To overcome operation failures, a pilot plant was provided by an automatic control system including both feedback and advanced control systems. The latter relies on the concept of the boundary flux to permit operation at sub-boundary conditions, where fouling is strongly inhibited.

Finally, reverse osmosis is used to reach the target purification level of the wastewater.

This work will report about the preliminary runs and experimental campaign performed during the first year of the MEWLIFE project on the pilot plant, reporting productivity, selectivity and longevity of the membranes.

The European Union is ranked second in pork meat production after China which naturally signifies the substantial use of antibiotics (ABs) in the region to enhance the growth and feed efficiency of pigs. Pig farming industry uses largest amount of ABs followed by poultry farms across the world. Hence, a significant amount of ABs which cannot be metabolized completely, are excreted as manure and spread in soil and water body. Most studies have found the notable presence of tetracycline and sulphonamide group of ABs in pig manure. Meanwhile, recent literatures are showing that the sorption of ABs in manure depend on the physiochemical properties such as organic content and pH of the manure.

In this particular study, detail characteristics analysis of different pig manure samples from the diverse locations of Germany is done with great focus on the nature of their organic content followed by identification of Abs. The liquid chromatographic organic carbon detector (LC-OCD) showed a narrow size distribution (400 to 500 Dalton) of organic matters present in pig manure.

Keeping that into account, pig manure slurry is filtered by ceramic microfiltration membranes (50 to 200 nm pore sizes) as primary treatment. Cake formation and biofouling are the main drawbacks for the microfiltration treatment and represent major challenge for long term applications. Further, the permeate is filtered by low molecular weight cut off ultrafiltration and loose nanofiltration membranes for complete removal ABs and reuse of the rich ammonia stream.

Initial results of organic and AB analysis and the consequent analytical approach will be discussed that will also help to evaluate ABs from pig manure.

Figure 1. Dissolved organic carbon concentration signals of different pig manure in LC-OCD

Very narrow size distribution of organic matter presents in different pig manure and their corresponding dissolved organic carbon (DOC) signals are represented.

Introduction: Tomato is the second most economically important crop worldwide. In tomato glasshouses substantial quantities of leaf waste (LW) are produced to maintain optimal plant architecture and minimise fungal disease. LW is used for low value applications, e.g. composting or anaerobic digestion. However, LW is a rich source of important phytochemicals. The first step for recovering added-value compounds from LW is the initial water extraction. This leads to cloudy tomato leaf extract (TLE) with suspended solids ranging to 1-5% w/w. TLE clarification from the particulates is a crucial step for the subsequent recovery of phytochemicals. Membrane separations are advantageous for clarifying TLE and recover phytochemicals under mild conditions.

Membrane fouling as well as the partitioning of micropollutants (MPs) with organic matter and polymeric membrane materials are two major challenges to overcome for the effective application of ultra (UF) and naonofiltration (NF) in water treatment and reuse. A major source of MPs like steroid hormones in the environment is the discharge of treated wastewater [1]. MIEX is applied in pre-treatment [2-3], or integrated in processes to reduce fouling of UF and NF membranes [4-7]. However, partitioning of micropollutants occur due to the affinity with the polymeric resin [8]. Such complex partitioning is quantified with MP estradiol (E2) in a MIEX-membrane process (UF or NF), where E2 partitioning with membrane materials, organic matter and ion exchange resins might occur.

E2 uptake by MIEX is measured in batch at different operative conditions (e.g. ionic strength, calcium and pH) and combined with NF or UF in one single process, where the resin is added directly in the membrane system. E2 partitioning with the membrane, humic acid (as organic matter) and MIEX is evaluated at different water pH and in presence of fouling (in the case of NF membrane).

Results show strong E2-MIEX partitioning especially at alkaline pH due to charge interaction. This results in significant (up to 80%) E2 uptake in the combined MIEX-UF process [9]. In presence of fouling, E2-HA partitioning is low due to interference of calcium, which reduced the number of HA molecules available to interact with E2, especially at alkaline pH. In the combined MIEX-NF process, E2-MIEX interaction occurs at all pH conditions resulting in high (40% of total mass) E2 uptake [10].

This study is significant to understand accumulation and potential accidental release of contaminants when treating waters containing organics and micropollutants with polymeric materials such as MIEX and membranes.

Figure 1. E2 uptake in hybrid MIEX-NF and MIEX-UF process (data adapted from [9-10])

[1] Luo, Y, Guo, W., Ngo, H. H., Nghiem, L. D., Hai, F. I., Zhang, J., Liang, S., Wang, X. C. A review on the occurrence of micropollutants in the aquatic environment and their fate and removal during wastewater treatment, Sci. Tot. Environ., (2014), 473, 619-641;

[2] T.V. Nguyen, R. Zhang, S. Vigneswaran, H.H. Ngo, J. Kandasamy, P. Mathes, Removal of organic

matter from effluents by Magnetic Ion Exchange (MIEX®), Desalination, 276 (2011) 96-10;

[3] T.H. Boyer, Removal of Dissolved Organic Matter by Magnetic Ion Exchange Resin, Curr. Poll.

685 Rep., 1 (2015) 142-154;

[4] J. Kaewsuk and G.T. Seo, Verification of NOM removal in MIEX-NF system for advanced water treatment, Sep. Purif. Technol. (2011), 80, 11–19.

[5] H. Son, Y. Hwang, J. Roh, K. Ji, P. Sin, C. Jung and L. Kang, Application of MIEX pre-treatment for ultrafiltration membrane process for NOM removal and fouling reduction, Water Sci. Tech.: Water Supp. (2005), 5, 15–24.

[6] E. Cornelissen, D. Chasseriaud, W. Siegers, E. Beerendonk and D. Van der Kooij, Effect of anionic fluidized ion exchange (FIX) pre-treatment on nanofiltration (NF) membrane fouling, Water Res. (2010) 44, 3283–3293

[7] Imbrogno, A., Tiraferri, A., Abbenante, S., Weyand, S., Schwaiger, R., Luxbacher, T., Schäfer, A.I. J. Membr. Sci. (2018), 549:474-85

[8] Neale, P.A., Mastrup, M., Borgmann, T., Schäfer, A.I. Sorption of micropollutant estrone to a water treatment ion exchange resin, J. Environ. Mon. (2010),12(1):311-7

[9] Imbrogno, A., Biscarat, J., Schäfer, A.I. Estradiol uptake in a combined magnetic ion exchange-ultrafiltration (MIEX-UF) process during water treatment. Curr. Pharmac. Des. (2017), 23(2):328-37

[10] Imbrogno, A., Samanta, P., Schäfer, A. I. Fate of steroid hormone micropollutant estradiol in a hybrid magnetic ion exchange resin-nanofiltration process, Environ. Chem. (2019), 16(8)

In nearly all European streams, dissolved organic micropollutants can be found nowadays. Examples are pharmaceuticals, hormones, pesticides, and industrial chemicals, which despite of their low concentration in the micro- to nanogram per litre-range are detrimental to aquatic ecosystems. Wastewater treatment do not fully degrade harmful micropollutants, even if the state-of-the-art activated sludge technology is applied. In the past decades, membrane technology has grown to be one of the most important technologies to remove colloids and dissolved substances from water. According to the principle of size exlusion, the feed solution is separated into permeate and retentate. However, for the removal of these micropollutants via membrane technology, very small pore sizes and, consequently, high energy cost would be required.

A novel and promising approach is the combination of micropollutant adsorption and membrane technology for particulate matter in one single step. The adsorbent is embedded directly into the polymeric membrane matrix, obtaining a mixed-matrix-membrane. The pore size is in the micro- to ultrafiltration range in order to reduce the pressure loss. Hence, colloid and micropollutant removal could be combined resource-efficiently, for example in a membrane bioreactor.

First results showed that it is possible to manufacture such membranes in flat sheet configuration with an adsorbent (activated carbon – AC) content of over 100% based on the membrane matrix (Fig. 1). The matrix polymers used were polyethersulfone as main polymer and polyvinylpyrrolidone as the pore forming additive. In retention tests with highly concentrated (1,000 to 10,000 times the ambient concentration) diclofenac – a common pain reliever – a removal of up to 50% was found, the retention decreasing over time due to the increasing loading of the adsorbent (Fig. 2). The promising approach of mixed-matrix membranes for micropollutant removal could offer an alternative to separate activated carbon adsorbers or to the use of ozone in the future.

Fig. 1: Scanning electron micrographs of (a) pristine membrane and (b) 20% AC mixed-matrix membrane

Fig. 2: Diclofenac (DCF) removal over time with mixed-matrix membranes of different AC contents

Available drinking water resources are increasingly limited. Water quality requirements are increasing as well as consumption. Therefore, much attention is being paid to developing a technology that is cheap and effective in water treatment. Membrane technology is considered as one of these methods. This technology removes most contaminants from the water without any chemicals. However, this technology has its limitations, which are related to the phenomenon of fouling. The natural organic matter (NOM) that is an integral part of water is considered to be the main cause of fouling. Due to the great diversity in the composition of NOM, the challenge remains to development of technology to remove these compounds as effectively as possible. The most common solution used in practice is to combination of coagulation and membrane technology. The integration of different pre-treatment strategies to improve the performance of membrane is one of the most frequently analysed solutions. Another solution is to modify the membrane structure. One of the new technologies implemented into water treatment is electrospinning nanofibers membranes.

This paper presents the results of bench-scale research on electrospinning nanofibers efficiency in NOM removal. PAN solution of the concentration 12 wt% was electro-spun and carbonized. Experiments were conducted using water samples (collected from the Ontario Lake, Canada). The general rejection trend of NOM varies between 66% up to 79%. The process can be studied further for high performance membranes and alternative energy sources to obtain low cost treatment systems.

According to the pessimistic forecasts by the 2018 edition of the United Nations World Water Development Report, by 2050, 6 billion people in 58 countries will suffer from chronic water deficiency. This problem may be associated with hydrological drought, which has a destructive effect on the environment and economics. Therefore, the growing attention is paid to recycling water and recovering raw materials from wastewater. On 2 December 2015, the European Commission presented the new circular economy package, which committed to develop a number of actions to promote water reuse and recovery from treated wastewater at EU level.

This study aims at developing an integrated membrane technology for recovering water from secondary effluent at the Wrocław Wastewater Treatment Plant (Poland) in accordance with the assumptions of the circular economy. The main goal of the study is the production of cooling water for sludge drying system at WWTPs. For this purpose, integrated membrane technology in a quarter-technical scale is used.

The prototype of the installation includes microfiltration/ultrafiltration (MF/UF), nanofiltration (NF) and reverse osmosis (RO). The first stage was the separation of suspended solids and COD via dead-end/cross-flow ultrafiltration system. In the next stage, permeate from UF entered first nanofiltration and then reverse osmosis. The tests comprise measurements of permeate and retentate streams in time and calculation of the retention rates of the main contaminants of treated wastewater. The retention degree of all measured contaminants in the three-stage integrated process exceeded 80%. Suspended solids and Humic acids are removed by UF in 100 and 70%, respectively. While NF almost completely separates COD, phosphorus, sulphur and magnesium ions. The research carried out so far, shows that purified water from subsequent stages could be used as cooling medium in the sludge drying system at the WWTP.

Since irrigation constitutes the greatest pressure on freshwater resources, it is crucial that different water sources, such as treated wastewater, start being used for irrigation. However, in order to protect consumers, effective treatment approaches must be developed to cope with the presence of contaminants (such as antibiotics) and pathogens (e.g. antibiotic resistant bacteria and pathogenic viruses) in wastewater effluents.

In this study, different methods were tested to detect the presence of different antibiotics (quinolones and carbapenems), antibiotic resistance genes/bacteria and viruses, at occurrence levels, in wastewater effluents and after nanofiltration treatment. To detect the antibiotics ciprofloxacin, levofloxacin, meropenem, imipenem and ertapenem, solid phase extraction was followed by detection by liquid chromatography with tandem mass spectrometry. For resistance genes detection and quantification, three in-houseTaqMan multiplex qPCR protocols for five carbapenem (blaKPC, blaOXA-48, blaNDM, blaIMP and blaVIM) and three quinolone (qnrA, qnrB and qnrS) were applied. Regarding the pathogenic viruses, six genomes were identified and quantified (adenovirus, polyomavirus, norovirus GI and GII and hepatitis A virus and hepatitis E virus) by two multiplex qPCR protocols.

Pilot scale nanofiltration assays using a Desal 5DK membrane were conducted to test the feasibility of the proposed solution to upgrade conventional wastewater treatment plants and achieve high quality water that could be used for irrigation. The rejections of the target contaminants were monitored at occurrence levels and compared in different assays conducted under controlled permeate flux and controlled pressure difference, with pre-defined recovery rates. The best operating conditions were found at a controlled pressure difference of 6 bar and a recovery rate of 72%, with an average permeate flux of 120 L/h. The untreated and treated effluents will be used for irrigation of raspberries and the fruit uptake of the contaminants evaluated after irrigation with the different water sources.

Acknowledgments:

The authors would like to acknowledge Águas do Tejo Atlântico for providing the real secondary effluent samples for the laboratory assays and for the assistance in the operation of the pilot plant in their wastewater treatment plant utility. Financial support from Fundação para a Ciência e a Tecnologia through the project PTDC/CTA-AMB/29586/2017 is gratefully acknowledged. We also acknowledge the financial support from Fundação para a Ciência e Tecnologia and Portugal 2020 to the Portuguese Mass Spectrometry Network (LISBOA-01-0145-FEDER-402-022125). iNOVA4Health - UID/Multi/04462/2013, a program financially supported by Fundação para a Ciência e Tecnologia/Ministério da Educação e Ciência, through national funds and co-funded by FEDER under the PT2020 Partnership Agreement is gratefully acknowledged. Associate Laboratory for Green Chemistry LAQV - Requimte which is also financed by national funds from FCT/MEC (UID/QUI/50006/2013) and co-financed by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER - 007265) is gratefully acknowledged. Funding from INTERFACE Programme, through the Innovation, Technology and Circular Economy Fund (FITEC), is gratefully acknowledged.

The prevalence, persistence and development of antibiotic resistance genes (ARGs) in the aquatic environment has attracted widespread concern, since surface water bodies are important water sources and the ARGs in drinking water can induce direct threats to public health. Thus the prevention of the persistence and dissemination of ARGs in water treatment system becomes necessary. Various solutions, including conventional and advanced treatment processes, have been tried to lessen the ARGs in drinking water. However, limited efforts have been achieved [1-2], and some treatments even favor the diffusion of ARGs [3-4]. Recently membrane separation technology has been demonstrated to be a promising method which can remove most emerging contaminants, especially the combination of coagulation and membrane filtration exhibits superior effluent quality. In this study, the combined coagulation-UF-NF was adopted to remove the ARGs for Taihu Lake water treatment. The concentrations of two typical ARGs (sul1, sul2), class 1 integron (intI1) and 16S rRNA gene were determined by a quantitative polymerase chain reaction (qPCR) method. The results showed that the concentrations of the detected genes were effectively reduced with the combined coagulation-UF-NF processes. Specifically, with UF the removal efficiency of the detected genes were 0.94-2.23 log value, while it could be enhanced to 2.24-3.39 log value with combined coagulation-UF. While the UF-NF exhibited the highest reduction rate of the target ARGs concentrations, with the removal efficiency ranging from 1.97-4.60 log value. In conclusion, the coagulation-UF-NF is an effective method to reduce the ARGs and lesson the antibiotic resistance risk in drinking water system.

References

[1] X. Guo et al. 2014. Sci. Total Environ. 493, 626-631.

[2] Y. Hu et al. 2018. J. Hazard. Mater. 360, 364-372.

[3] S. Jia et al. 2020. Water Res. 176, 1-11.

[4] J. Zheng et al. 2018. Sci. Total Environ. 612, 1-8.

Gravity-driven membrane (GDM) filtration has shown a great potential as an extremely low-energy surface water treatment process because of water gravity (40-100 cm) as a driving force. Importantly, GDM filtration can achieve relatively stable flux without any physical and chemical cleaning during a long period of operation time. Although the gravity-driven membranes, i.e., microfiltration (MF) or ultrafiltration (UF), are capable to highly reject most of algal cells in the surface waters due to their special nature (fine pore size, surface property), the effects of these algal metabolic products on the GDM water quality have not been well illustrated.

This study aims to study the effects of algal species (Chlorella vulgaris (green algae) and Phaeodactylum tricornutum (diatom)) and amounts in the surface water on the performances of different GDM systems (MF and UF membranes) in terms of permeate flux and permeate water quality. To further explore GDM fouling mechanisms, the characteristics of the cake layer foulants were examined after 35-day of operation.

The results showed the cake layer fouling was predominant in the UF-GDM systems, while irreversible fouling contributed majorly to the MF-GDM fouling. As a result, the UF-GMD systems achieved >1.5 time higher permeate flux compared to the MF-GDM systems in treating algae-polluted lake water. Compared to the green algae, the presence of the diatom cells in the feed water had more negative impacts on the UF permeate flux (increasing the cake layer resistance) and water quality (producing more low molecule weight neutrals in the permeate water). The analysis of cake layer foulants revealed that more aromatic protein-based biopolymers were accumulated on the membranes during filtration of algae-polluted lake water and the biopolymer amounts were almost linearly associated with membrane fouling potential of the GDM systems.

Direct membrane filtration (DMF) is a relatively new concept for municipal wastewater treatment plants (WWTPs) in contrast to the widely accepted membrane bioreactor (MBR). While the MBR process combines a biological process with membrane filtration, the DMF concept involves abiotic processes. Thus, DMF processes has the potential to be more compact and less energy demanding than MBRs.

This presentation compares the results/experiences from three pilot tests in Norway and Sweden. The test sites were municipal WWTPs in Lund, Svedala (both Sweden) and Fredrikstad (Norway). The pre-treatment in all cases was a combination of coagulation/flocculation and microsieving (100 μm mesh) optimised to the local conditions. All pilot units used 0.2 μm polyvinylidene difluoride (PVDF) microfiltration (MF) membranes in flat sheet modules (Alfa Laval, Denmark) as reference. However, to investigate the impact of the membrane selection the pilot in Svedala was additionally equipped with a 10 kD hydrophilised polysulphone (PS) ultrafiltration (UF) membrane in parallel to the MF membrane. Even though the UF membrane showed higher retentions than the MF membranes, the permeates from all membranes had similar high qualities. Furthermore, to meet future tightening discharge limits two different post-treatments for DMF permeate were tested: (1) forward osmosis at the Lund WWTP which has a coastal discharge and (2) activated carbon for micropollutant removal at the Svedala WWTP. Both post-treatments demonstrated the opportunity to further improve the permeate quality.

Overall, all three pilot studies demonstrated that the DMF concept can achieve high reductions in suspended solids (SS), dissolved organic carbon (DOC) and phosphorus, and also has the potential to meet future and stricter discharge demands in combination with suitable post-treatment methods. Since DMF is a compact and low energy demanding wastewater treatment technology it is particularly suitable for upgrading of WWTP in densely populated areas with space limitations.

Introduction:

Antimony is highly toxic and carcinogenic to the human body and its effective removal is significantly important to aquatic environment. Complexation-ultrafiltration (UF) process, which is based on the principle that the polymers with larger molecular weights than molecular weight cut-off (MWCO) of UF membranes can bind heavy metals to form macromolecular complexes and be retained by UF membranes, can effectively remove heavy metals from wastewater. However, membrane fouling is a big issue. In this study, a one-step mussel-inspired hybrid coating method was used to modify polyethersulfone (PES) membrane for highly hydrophilic surface. The modified membrane was characterized and applied in complexation-UF process for antimony removal. Its anti-fouling property and stability were also studied.

Methods:

The dopamine-based one-step hybrid coating was applied with various chemical dosage and modification time. The modified membranes were characterized by XPS, water contact angle (WCA) and water absorbing capacity. The modified membrane with the highest hydrophilicity was chosen. Complexation-UF experiments with polyethyleneimine (PEI) as complexation agent was conducted with optimized pH and loading ratio (C_PEI/C_Sb). Complexation-UF experiments were conducted for three cycles (each lasted 1 h) to evaluate the membrane’s effective removal for antimony, anti-fouling property and stability.

Results:

The hydrophilization modified PES membrane has WCA of 17.5°, much lower than that of pristine one at 63.1°. Its anti-fouling property was also dramatically improved with much lower flux decreasing during three cycles of complexation-UF process when antimony removal was still kept constant. In addition, the membrane flux could be completely recovered with simple water flushing after each cycle.

Discussion:

The one-step mussel-inspired hybrid coating method was simple and effective for hydrophilization modification. The modified membrane with good anti-fouling property was effective in complexation-UF process for antimony removal. Results furthered the application potential of modified PES membrane in wastewater treatment.

In the present study, LaCu_xMn_1-xO₃ perovskite-like oxide (x=0.2, 0.4, 0.6, 0.8) was employed as a heterogeneous catalyst for the degradation of acrylonitrile by catalytic peroxidation in the presence of hydrogen peroxide as an oxidant. The perovskite-like oxide was synthesized by sol-gel method and further characterized by XRD, FTIR, BET, Fe-SEM, TEM and XPS. The acrylonitrile degradation study was carried out for various parameters viz., catalyst dose (100-1200 mg/L); stoichiometric molar ratio of H₂O₂/acrylonitrile (0.5-3); pH (2.5-10); temperature (30-75 ºC) and initial acrylonitrile concentration (100-1000 mg/L). The kinetic study for the degradation of acrylonitrile at various temperatures and various concentrations were performed and well-represented by 1^st order and n^th order kinetic models. The plausible reaction mechanism for acrylonitrile degradation at optimum operating conditions were proposed according to intermediates detected by GC-MS analysis. Scavenging studies were performed to investigate in situ-generation of reactive oxygen species (ROS) with their respective quenchers during catalytic peroxidation of acrylonitrile. This study demonstrates that ROS scavengers inhibit the acrylonitrile degradation during catalytic peroxidation process. The catalyst reusability study was performed at optimum operating conditions and remarkable results were obtained after five cycles of experiments for the degradation of acrylonitrile. Thermodynamic parametric study was performed at various temperatures for catalytic peroxidation of acrylonitrile, which reveal that catalytic peroxidation of acrylonitrile is feasible and spontaneous.

By 2025, more than two million of end-of-life (EoL) reverse osmosis (RO) modules will be generated. Several EoL-RO management alternatives of valorisation are being researched to approach RO technology to Circular Economy such as RO reuse, direct recycling into nanofiltration (NF) and ultrafiltration (UF), indirect recycling of plastic components, or combined strategies such as the semiconservative recycling into forward osmosis (FO). Nonetheless, according to the Directive on Waste (WFD-2008/98/ EC), in order to generate a specific waste hierarchy, the environmental outcome of the alternatives must be evaluated. In this sense, Life Cycle Assessment (LCA) methodology has been mentioned to be the most suitable tool.

In this study, LCA studies regarding different EoL-RO management routes have been compiled and harmonised. Those technologies include: RO reusing, direct recycling into NF and UF, semiconservative recycling into FO, plastic recycling, incineration or landfilling. Results were aggregated to the management of one EoL-RO module (functional unit). A substitution approach was considered for the recycling alternatives. For each technology, a substitutability ratio has been developed according to the International Life Cycle Data system (ILCD) handbook. In this sense, recycled membrane performances have been compared with commercial homologue ones.

Results provides an overview of the most preferable recycling options based on the environmental feature. They show that recycling into UF membranes, followed by the recycling into NF are the most important alternatives in several impact categories. However, some of the limitation found during the LCA were the lack of inventories of real membrane production processes and the fault of standardised methodologies when measuring certain parameters such as the membrane lifespan. In addition, those results are discussed with other important techno-economic parameters related to the suitability of their implementation. Those results will also drive the introduction of Life Cycle Thinking into membrane technology sector.

Biomaterial supported neural stem cell (NSC)-based therapies have the potential to address central nervous system (CNS) injuries, such as neuro-degenerative diseases and traumatic injuries. However, NSC are relatively rare in the human body, requiring ex-vivo cultivation combining soluble factors with scaffolds that mimic the cells natural niche.

Membrane nanofiber scaffolds for neural regeneration are particularly attractive as they are powerful physical guides for neuronal tissue. The nanofiber mesh provides an extracellular geometry at the cell scale, with advantageous porosity, high surface-to-volume ratio, and permeability, contributing to cell attachment and orientation, as well as effective nutrient feeding and oxygen diffusion.

Stem cell culture within nanofiber scaffolds is usually performed in static systems, often neglecting the scalability required for a systematic production of tissue transplants, or tissue engineered platforms. Effective supply of adequate factors (nutrients, cytokines, growth factors, oxygen), cell interactions and shear forces are also critical for adequate cell growth.

A bioreactor able to accommodate a scaffold platform is a promising approach to enhance stem cell culture, while functionalized materials are required to promote a specific cell response or function, such as tissue organization or cell differentiation prior to transplantation.

In this study, a novel “plate and frame” membrane nanofiber system was developed, aiming to scale NSC expansion and differentiation. The flow structure and wall shear stress were investigated by computational fluid dynamics (CFD) and NSC were experimentally cultivated on poly-ε-caprolactone nanofiber membranes in the designed vessel. A Sherwood Number of about 152 was found optimal for NSC growth. After a 10-day dynamic culture, the cells grew uniformly and homogeneously distributed along the nanofibers and maintained the expression of specific NSC markers (Nestin and Sox2). These results are promising for scaling up the production of neural tissue constructs for regenerative medicine and disease models.

Acknowledgements for Fundação para a Ciência and Tecnologia funding (UID/BIO/04565/2020, PTDC/CTM-CTM/30237/2017) and PORL2020 (PAC-PRECISE-LISBOA-01-0145- FEDER-007317).

Figure 1: Top Right: Vessel with Nanofiber Membranes; Bottom Right: Number of Viable cells per frame at the end of expansion; Top Left: Cells with phalloidin/DAPI staining along fibers orientation (Fluorescent Microscopy); Bottom Left: Cells in Electrospun Membrane (Optical Microscopy).

A new type of membrane is urgently needed to address the increasing concentrations of harmful organic micropollutants (e.g. pharmaceuticals, pesticides and plasticizers) in our surface and drinking water. These micropollutants have potential negative effects on human health and the environment and long-term effects are still unknown for the majority of micropollutants. Conventional wastewater treatment plants (WWTPs) are not capable of fully removing micropollutants from wastewater streams. Using reverse osmosis type membranes, the densest available membranes, micropollutants can be removed. However, this comes with many disadvantages like a low permeability, high energy demands and the removal of minerals.

During this project we aim to design and fabricate a new type of membrane which is specifically designed for the removal of micropollutants while maintaining a high permeability and salt flux. Using a so-called Layer-by-Layer assembly, alternatingly polycations and polyanions are exposed to a porous support membrane creating a polyelectrolyte multilayer (PEM). A large advantage of this approach is that the properties of the PEM layer, responsible for the separation properties of the membrane, can be tuned by choice of polyelectrolyte and by the employed coating conditions such as pH and ionic strength. Using a novel approach of asymmetric coating, we first coat an open permeable PEM onto our support membrane. On top of this open PEM we coat a very thin dense selective layer of only 4 nm. By applying a novel asymmetric PEM we are able to remove up to 98% of the micropollutants while maintaining a high permeability.

In conclusion, we created a membrane with reverse osmosis type micropollutant retention, nanofiltration type permeability and tight ultrafiltration type salt retention.

The development of catalytic membranes as heterogeneous catalysts provides an opportunity to reduce the cost of biodiesel production, as well as being environmentally and eliminating the catalyst separation step [1]. Membrane catalysts can be obtained by polymer modification or blending a good film-forming polymer, such as poly(vinyl alcohol) (PVA) or polyacrylonitrile (PAN), with other active components [2]. Poly (2-acryloamido-2-methylpropane sulfonic acid) (PAMPS) has interesting properties that may lead to many potential application due to its higher proton conductivity and swelling behavior. PAMPS homopolymer is generally water swollen to the point of being soluble; hence, it can only be used in gel forms, copolymerized or crosslinked to control swelling. In this work, we report the preparation of new catalytic membranes from PAMPS-b-PHEMA copolymer at different composition of PAMPS and poly (2-hydroxyethyl methacrylate) (PHEMA), crosslinked with sulfosuccinic acid (SSA). Moreover, we present a detailed characterization of the structure and properties of the membranes, including swelling properties, ion exchange capacity (IEC, mmol/g) as well as the effect of these properties on the catalytic performance of the PAMPS-b-PHEMA membranes for the biodiesel production by transesterification of soybean oil in the presence of methanol.

The synthesis of copolymers was carried by sequential polymerization of second monomer 2-hydroxyethyl methacrylate (HEMA), respectively, via the direct fresh feed into the PAMPS prepolymer solution in DMF at 80 ºC using ruthenium(II) complexes as catalyst. Membranes were prepared by casting a 6% (wt/v) solution of PAMPS-b-PHEMA in water. The membranes were heated at 120°C for 1 h under vacuum to crosslink the membrane. Swelling was determined gravimetrically and ion exchange capacity (IEC) was measured using an acid/base titration method. The transesterification reaction was carried out in a series of 12 mL screw-cap vials under stirring at 60 °C, with 0.068 mmol/g oil of membrane and 6 mL of MeOH. The reaction was started with the addition of 0.5 mL of vegetable oil. Biodiesel conversion was monitored periodically by ¹H-NMR.

Crosslinked PAMPS-b-PHEMA catalytic membranes as heterogeneous catalyst for biodiesel production were successfully prepared with different PAMPS/PHEMA molar composition (1:2.5, 1:2, 1:1.25) and crosslinked with 15% sulfosuccinic acid (SSA) at 120 ºC. FTIR confirmed the successful crosslinking by esterification of the -OH groups in PHEMA with SSA (see Figure 1). The compositions of the copolymers were obtained by ¹H-RMN indicating 37.5, 60 and 65% of PAMPS block.

Fig. 1. IR spectra of crosslinked PAMPS-b-PHEMA membranes at different composition of PAMPS.

The ion exchange capacity (IEC) of a membrane indicates the number of acid groups available in the membrane for catalyzing the reaction. Table 1 present IEC values for the PAMPS-b-PHEMA membranes. The acidity of the membranes increases significantly with increasing PAMPS content due to the greater number of sulfonic acid groups present. The experimental IEC values of the membranes remained within a 2.18-3.10 mmol g^-1 range very close to the theoretical values.

Table 1. Experimental and theoretical IEC of the PAMPS-b-PHEMA membranes

PAMPS-b-PHEMA membranes crosslinked with 15 % SSA were highly effective as heterogeneous catalysts for the transesterification of soybean oil with methanol. The performance of the catalytic membranes is well correlated with the acid capacity (IEC) and swelling properties.

Acknowledgment: Ciencia Basic CONACYT No. 286973.

References

1. Casimiro, M.H.; Silva, A.G.; Alvarez, R.; Ferreira, L.M.; Ramos, A.M.; Vital, J.; Radiat. Phys. Chem. 2014, 94, 171.

2. Zhu, M.; He, B.; Shi, W.; Feng, Y.; Ding, J.; Li, J.; Zeng, F.; Fuel 2010, 89, 2299.

Herein, we present the fabrication of new biomimetic membranes for wound dressing applications (See scheme. 1). The membranes were prepared using polymer blends of poly(vinyl alcohol) (PVA) with different poly(2-acryloamido-2-methyl-1-propanesulfonic acid) (PAMPS) ratios (15, 10 and 5 %), crosslinked with succinic acid (SA) at 100 °C for 1 h. The scanning electron microscope (SEM) showed a bilayer structure membrane (dense and porous layers). According with EDX and XPS, the dense layer is composed of PAMPS and the porous layer, layer with size pore between 6-40 μm of PVA/PAMPS blends. The dense layer protects the wound from micro-organisms, infections or contaminations, while the porous layer provides functions such as cell proliferation (fibroblasts) and biocompatibility. We present a detailed characterization of the structure and properties of the PVA/PAMPS blend membranes, including PBS swelling properties, ion exchange capacity (IEC, mmol/g) as well as their effect on the mechanical properties, biocompatibility and cell proliferation testing.

Scheme 1 Biomimetic membranes of PVA/PAMPS blend

First, a 12% (wt/v) polymeric solution of PVA/PAMPS blends and SA (10% with respect to PVA) was dissolved in water and molded using a film casting knife. After that, the dope solution was immersed into a ethanol/2-propanol (90/10 %v/v) bath to obtain asymmetric membranes. Finally, the membranes were crosslinked for 1 h at 100 ° C. Membranes were characterized by SEM and XPS and and ion exchange capacity (IEC) was measured using an acid/base titration method. The biological tests was carried out according to ISO 10993-1 2009 using human fibroblasts with a count of 3,000 cells per sample. The cell proliferation was quantified by measuring the UV absorbance at 570 nm througth resazurin assay. Dilution method with E.Coli and S. Aureus were used in antimicrobial assays.

XPS test were performed to measure the sulfur content in each layer. Both, sulfur measurement and ion exchange capacity (IEC) were used to determine the PAMPS content in the membranes. As can be seen in Fig. 1 and 2, the higher PAMPS content was found in the dense layer and it was observed to increase from 1.26 to 3.33 atomic % with increasing PAMPS content. The porous layers present pores in the range of 6 to 40 µm.

The elastic modulus (E) values of the previously swollen cross-linked PVA/PAMPS membranes are similar to the value reported for the skin. Thus, the introduction of PAMPS enhances the mechanical properties in comparison with de pure PVA membrane. Moreover, the membranes present PBS uptakes around of 398 to 565 %. The proliferation of human fibroblasts on the porous layer was evaluated for 72 h. All membranes presented biocompatibility and cell viability. As can be seen in Fig. 3, the amount of fibroblasts increases with increasing PAMPS content in membranes with no significant difference with the negative control.

Fig. 3- Cell proliferation assay in porous layer of the membranes PVA and PVA/PAMPS

Membrane dense layers and pure PVA membrane were exposed to E.Coli and S. Aureus as model bacterias. Membrane with 15 % PAMPS presented superior antimicrobial performance (Fig. 12) against both bacterias at 24 and 48 h. Membrane with 5% of PAMPS only present inhibition against E. Coli. Pure PVA membrane did not show bactericidal activity over this time.

Acknowledgment: Ciencia Basic CONACYT No. 286973.

Reference [1]E. A. Kamoun, E. S. Kenawy, and X. Chen, “A review on polymeric hydrogel membranes for wound dressing applications : PVA-based hydrogel dressings,” J. Adv. Res., vol. 8, no. 3, pp. 217–233, 2017.

Micropollutants in water are a major global challenge [1]. Photocatalytic membranes combine photocatalysis that degrade micropollutants with membranes that remove pathogens and other contaminants, thus integrating two water treatment processes[2]. Such photocatalytic membrane operating under flow-through conditions are a promising for continuous single-stage technology.

Anodized aluminium oxide membranes with pore sizes of 20 nm and 200 nm were coated with a titanium dioxide (TiO₂) photocatalyst via atomic layer deposition [3]. The impact of operational parameters on the photocatalytic efficiency of these membranes was examined using a photocatalytic membrane filtration system with a custom built membrane cell (active membrane area of 2 cm²) and a ultraviolet (UV) 365nm light source. Performance was investigated using methylene blue (MB) as a model contaminant. Parameters investigated included light intensity, coating thickness and flow rate and initial MB concentration investigated [3].

Convective flow through the coated membrane pores enhanced the accessibility of MB resulting in effective mass transfer and, hence, improved photodegradation. MB removal increased up to 50% with increasing coating thickness (up to 6 nm) and light intensity (2 mW/cm²). Above these values, the degradation was no longer limited by these parameters. The high degradation of MB was even achieved with a light intensity (2 mW/cm²) less than the UV content of terrestrial sunlight (3.65 mW/cm²). This signifies that even a nanometer-thin coating of TiO₂ inside the membrane pores can achieve significant removal as a photocatalyst operating under direct sunlight [3]. Convective MB molar flux, under low membrane flux or low MB concentration, limits the reaction rate, but results in a high removal (up to 80%). Thus photocatalysis integrated with membrane filtration exhibits a novel means for treating water contaminated with organic micropollutants.

Figure Schematic showing the photocatalytic cell, membrane in use and degradation mechanism.

References

[1] R.P. Schwarzenbach, B.I. Escher, K. Fenner, T.B. Hofstetter, C.A. Johnson, U. von Gunten, B. Wehrli, The challenge of micropollutants in aquatic systems, Science, 313 (2006) 1072.

[2] S. Leong, A. Razmjou, K. Wang, K. Hapgood, X. Zhang, H. Wang, TiO₂ based photocatalytic membranes: A review, Journal of Membrane Science, 472 (2014) 167-184.

[3] T. Berger, C. Regmi, A. Schäfer, B. Richards, Photocatalytic degradation of organic dye via atomic layer deposited TiO₂–ceramic membranes in single-pass flow-through operation, Journal of Membrane Science, (2019),(Under revision).

One attractive topic on lithium-ion batteries (LIBs) is developments of suitable electrolytes with satisfied properties and performance to replace the conventional liquid electrolytes and porous polyolefin. Gel polymer electrolytes (GPEs) have received considerable studies as they have shown attractions for both battery safety and performance. Porous structured polymer matrixes have been widely applied to GPEs for warranting lithium ion mobility through the GPEs. Nevertheless, the relatively low lithium ion conductivities of the GPEs are critical. In this work, the two fields, membrane structure design and GPEs, have been integrated for the developments of high performance GPEs. Ion-conducting channels have been introduced to GPEs with employing porous membranes prepared with nonsolvent-induced phase separation. A graft copolymer possessing poly(ethylene glycol) (PEG) side segments has been used as the raw material. The PEG segments would cover on the pore walls of the obtained porous membranes to create hydrophilic domain and lithium-ion conducting channels in the corresponding GPE matrix. Compared to the ion conductivity of 0.57 mS cm^-1 recorded on the GPE based on the PEG-free precursor, introduction of PEG ion-conducting channels to the GPE matrix increases the ion conductivity to 1.86 mS cm^-1. A discharging capacity of 150 mAh g^-1 and 72 mAh g^-1 has been recorded with batteries employing the prepared GPE at a charging rate of 0.2C and 10C, respectively. Based on the membrane formation technique, this work has demonstrated an effective approach on designing porous membranes based GPEs for high-rate lithium ion batteries.

Abstrat

Acrylamide (AA, 2-propenamide, C₃H₅NO, (Mw=71.09) is an unsaturated amide, occurs in various thermally processed (baked/fried) foods. It is generated by baking / cooking of food items that are rich in reducing sugars yielding starch and proteins containing asparagines (amino acid), at high temperature under low moist condition. The consumption of processed food items containing acrylamide is responsible for various types of toxicity. therefore, it is necessary to detect acrylamide concentration in thermally processed foods. Various types of detection methods are available for the detection of acrylamide. Membrane technology is being an important alternative to classical separation processes such as distillation, crystallisation, solvent extraction, precipitation, etc. Among membrane-based separation processes, the use of supported liquid membranes (SLMs) has received growing attention during recent years. The aim of this work was to recover an organic compound metabolite (AA) from aqueous solution by SLM using ionic liquid as carrier. The effect of different parameters on transport efficiency have been studied : pH of the feed phase, the nature of the strippant, the nature of the diluent,the concentration of the strippant, the nature of the support ,the initial concentration of the AA in the feed phase and the stability of the system.

Currently, most commercial nanofiltration membranes are flat sheet membranes because the fabrication process is less complex. However, hollow fiber membrane modules are backwashable and higher packing densities can be achieved.

So far with our chemistry in a spinneret concept, we can directly fabricate composite hollow fiber membranes in a single step process by combining two phenomena. The conventional phase inversion of an inert polymer during dry-jet wet spinning is superimposed either by a covalent (Roth et al. 2018) or ionic cross-linking (Gherasim et al. 2016). While the inert polymer precipitates as a porous support structure, the cross-linking reaction forms the dense separation layer on the lumen-side.

Going one step further, we now increase the complexity of the chemistry in a spinneret concept and master three processes at once. Ionic cross-linking between oppositely charged polyelectrolytes is superimposed with a covalent cross-linking while phase inversion of an inert membrane forming polymer is happening simultaneously. The amine component as reactant is added to the membrane forming polymer solution, while the bore fluid is blended with a cross-linker and a negatively charged polyelectrolyte.

Surface morphology, surface elementary composition and surface charge analysis proof the successful formation of the cross-linked polyelectrolyte separation layer on the lumen channel surface of the fabricated fibers. The fibers show nanofiltration properties regarding high salt retentions and a low molecular weight cut-off of 280 Da.

Concluding, the application of the chemistry in a spinneret approach proves to be robust for the here presented complex material system with overlapping diverse phenomena. Stable separation layers with unique properties evolved. We now envision to transfer the technology to further material systems with similar or even higher complexity.

Soon, we expect the technology base to be ready to provide an efficient and low-cost alternative to the multistep fabrication methods of flat sheet nanofiltration membranes.

In presented research hybrid membranes composed of alginate matrix and oxides or chitosan micrparticles fillers were prepared, characterized and used in pervaporative separation of ethanol/water azoetrope. The aim of our study was to boost the transport properties of alginate membranes and correlated the filler’s dispersion with separation effectiveness by means of fractal analysis.

The results of pervaporation experiments of azeotrope ethanol/water mixture were analysed, providing extensive characterization of the transport phenomena through investigated membranes. The research showed that presence of oxide in polymer matrix has a significant influence on the transport of water and ethanol. The PSI values of all membranes filled with oxides, besides magnetite, were very similar. However, for the magnetite distinctly different changes can be observed. In this case the perceived increase in PSI was rapid and much higher than the relevant values obtained for other oxides (Fig.1).

Fig.1. Dependence of PSI on the oxide content

The effect of chitosan microparticles, i.e. neat (CS), phosphorylated (CS-P), glutaraldehyde crosslinked (CS-GA), and glycidol modified (CS-G) on membrane’s separation properties is presented in Fig.2. The results indicated that the newly developed membranes had dehydration performance superior to other membranes. The best effectiveness was achieved for membrane filled with 10 wt% of CS-P.

Fig.2. Variation of PSI for Alg membranes with the type and content of fillers

To summarize, hybrid composite materials made from renewable biopolymers and accurately selected fillers can serve as effective membranes in the ethanol dehydration process, providing both high flux and selectivity. The best efficiency are obtained in case of membranes filled with magnetite and phosphorylated chitosan. In the first case, the magnetic properties of filler are responsible for the superior separation, whereas in the second case – the good dispersibilty and compatibility of polymeric filler with the host matrix benefiting from the attributes of both polymers.

Sodium alginate seems to be the promising membrane material for the pervaporative dehydration of ethanol because of its excellent permselectivity toward water. Hybrid alginate membranes filled with various amount of magnetite (Fe₃O₄) and crosslinked using four different agents, i.e. calcium chloride (AlgCa), phosphoric acid (AlgP), glutaraldehyde (AlgGA) and citric acid (AlgC) were prepared and applied in pervaporative dehydration of ethanol [1]. In this paper, the correlation between chemical composition, structure and morphology, and transport properties of membranes is discussed. We started with the investigation of patterns formed by magnetite in the alginate membrane matrix. We studied the optical microscopy images of cross-sections of alginate membranes cross-linked by different agents and containing various amount of magnetite particles. Morphological properties were expressed in terms of observed amount of polymer matrix, sizes of polymer matrix domains, fractal dimension and others. Next step was to study the possibility of using numerical modelling in the process of design a membrane of prescribed morphology and transport properties. Two different methods of generating models of such were discussed and properties of such prototype membranes were analysed. After choosing the best models based on its morphological similarities to the real hybrid alginate Alg/Fe₃O₄ membranes, we studied transport properties of real and prototype membranes in terms of Brownian diffusion.

[1] G. Dudek, et al., Structure, morphology and separation efficiency of hybrid Alg/Fe₃O₄ membranes in pervaporative dehydration of ethanol, Sep. Purif. Technol. 182 (2017) 101-109

The purpose of this research was to study the influence of particular iron-containing fillers on the transport properties of hybrid alginate membranes in the process of ethanol dehydration by means of pervaporation and water/ethanol permeation .

To study the pervaporation process, we used the apparatus shown in Fig.1. As fillers the following iron-containing compounds were selected: magnetite, hematite, Prussian blue and [Fe₄(acac)₆(Br-mp)₂] molecular magnet.

Fig.1. Scheme of the pervaporation setup: 1 feed tank, 2 circulation pump, 3 separation chamber, 4 vacuum gauge, 5 traps, and 6 vacuum pump.

Membranes filled with Prussian blue and molecular magnet showed the best separation efficiency. They were characterized dually by high flux (Fig.2) and PSI (Fig.3). The membranes' high hydrophilicity and compatibility of the fillers with polymer matrix are accountable for such results. In case of membranes containing iron oxides it is not possible to obtain such uniform dispersibility in polymer matrix due to their particle size and tendency to agglomeration of them. The experiments clearly showed that the PSI coefficients increase for the fillers with better dispersion. Additionally, the magnetic properties bearing by a molecular magnet filler improve the separation ability of membrane, that’s why the best results were obtained for membrane containing [Fe₄(acac)₆(Br-mp)₂].

Based on the results, it can be concluded that the organo-magnetic [Fe₄(acac)₆(Br-mp)₂] complex has the greatest influence on the enhancement of selectivity of the ethanol/water separation process on alginate hybrid membranes.

Fig.2 The variation of evaluated fluxes with increasing filler content in alginate matrix.

Fig.3 The variation of evaluated PSI with increasing filler content.