Non-solvent Induced Phase Separation Process Research Articles

Highly stretchable porous regenerated silk fibroin film for enhanced wound healing.

Silk fibroin (SF) has received interest in tissue engineering owing to its biocompatibility, biodegradability, and favorable mechanical properties. However, the complex preparation, brittleness, and lack of pores in the structure of the silk fibroin film limit its application. Herein, we show that facile dissolution of SF in aqueous phosphoric acid followed by regeneration in aqueous ammonium sulfate ((NH4)2SO4) could afford highly stretchable films with nano-pores formed in the nonsolvent-induced phase separation process. The named phase separation, which determines the morphology and mechanical properties of the regeneration silk fibroin (RSF) films, is highly dependent on the (NH4)2SO4 concentration as well as the initial concentration of the SF solution. Therefore, the RSF films exhibit a tunable pore size ranging from 230 to 510 nm and excellent stretchability with tensile strain up to 143 ± 16%. Most interestingly, the RSF films were shown to support the proliferation of human skin fibroblasts in vitro as well as speed up full-thickness skin wound healing in a rat model. This work establishes an easy and feasible method to access porous RSF membranes that can be used for wound dressing in clinical settings.

Towards superior permeability and antifouling performance of sulfonated polyethersulfone ultrafiltration membranes modified with sulfopropyl methacrylate functionalized SBA-15

A non-solvent induced phase separation (NIPS) process was used to fabricate a series of sulfonated polyethersulfone (SPES) membranes blending with different concentrations of SBA-15-g-PSPA with the applications in the ultrafiltration (UF) process. SBA-15 was modified with 3-methacrylate-propyltrimethoxysilane (MPS) to form SBA-15-g-MPS. It was further modified with the charge tailorable polymer chains by reacting with 3-sulfopropyl methacrylate potassium salt. The nanoparticles were uniformly dispersed and finger-like channels were developed within the membrane. The adding of surface modified SBA-15-g-PSPA nanoparticles has significantly improved membrane water permeability, hydrophilicity, and antifouling properties. The pure water fluxes of the composite SPES membranes were significantly higher than the pristine SPES membrane. For the membrane containing 5% (mass) of SBA-15-g-PSPA (MSSPA5), the pure water flux was increased dramatically to 402.15 L∙m –2 ∙h –1 , which is ∼ 1.5 times that of MSSPA0 (268.0 L∙m –2 ∙h –1 ). The high flux rate was achieved with 3% (mass) of SBA-15 nanoparticles with retained high rejection ratio 98% for natural organic matter. The results indicate that the fashioned composite membrane comprising SBA-15-g-PSPA nanoparticles have a promising future in ultrafiltration applications.

Fabrication of Polyarylate-Based Porous Membranes from Nonsolvent-Induced Phase Separation Process and Related Permeability and Filterability Characterizations

The stability demand of polymeric membrane separation systems used in harsh environments, including high temperature, high pressure, extreme acid, and high salinity, makes the role of polyarylate (PAR) porous membranes more and more crucial. Herein, the PAR ultrafiltration membrane is fabricated from the nonsolvent-induced phase separation (NIPS) method in a simple, high-efficiency way. In order to study the evolution mechanism of cross-sectional pore morphologies during the NIPS process, different coagulation conditions, including the PAR concentration in casting solution, the coagulation temperature, and the addition of different hydrophilic additives (PEG400, PEG4000, PEG20000, and PVP), are applied. Next, the morphologies and membrane performances of various PAR membranes are analyzed by scanning electron microscopy, porosity measurement, N2 isotherm adsorption–desorption measurement, water flux measurement, bovine serum albumin (BSA) separation measurement, and mechanical test. Based on these measurements, the formation rule of different pore morphologies in the cross section of PAR membrane was clarified, and the effects of different cross-sectional morphologies on the permeability, filterability, and mechanical properties of the resultant membranes are pointed out. The viscosity effect from a higher PAR concentration and a higher hydrophilic additive concentration in a casting solution can delay the formation of the outer layer and limit the nucleation growth process of the nonsolvent, then allowing the formation of near-surface sponge-like pores and fewer inner macropores. Moreover, not only the increase of the bath temperature but also the strengthening hydrophilicity of the casting solution can accelerate the double-diffusion rate and the growth process of nuclei, thereby promoting the formation of near-surface finger-like pores and more inner macropores. Combined with the enhancement of membrane hydrophilicity, these pores as channels can accelerate the passage of water through the PAR membrane. For the PAR16–PVP10-30 membrane, not only a 120 L·m–2·h–1·bar–1 of water flux but also a close to 100% of BSA rejection ratio is obtained. Although the formation of near-surface sponge-like pores and fewer inner macropores deteriorate the membrane’s permeability, the high BSA rejection ratio and the improved mechanical property can be maintained. Finally, the optimization component of the casting solution for fabricating a PAR ultrafiltration membrane with enough permeability, high selectivity, and suitable mechanical property adds 10 wt % PVP in the solution of 16 wt % PAR, ensuring the solid hydrophilic effect and moderate viscosity effect.

Facile engineering of PES ultrafiltration membranes using polyoxometalates for enhanced filtration and antifouling performance

The pursuit of augmented membrane separation performance is mainly proceeded by breaking the permeability-selectivity trade-off and ameliorating the membrane fouling propensity. Here, we report the usage of phosphomolybdic acid (PMo12) as a functional additive to fabricate poly (ether sulfone) (PES) based composite ultrafiltration membranes via a non-solvent induced phase separation process. In contrast to the control PES membrane, the introduction of PMo12 endowed the composite membranes with increased surface pore density, porosity and selective layer thickness as well as the enhanced hydrophilicity and charge property through altering the phase inversion rate, thereby resulting in a significantly increased filtration performance. Specifically, the optimized composite membrane presented a water flux of 572.67 ± 21.73 L·m−2·h−1 and a bovine serum albumin rejection of 99.31 ± 0.22 %, which are ca. 340 % and 0.7 % higher than those of the control PES membrane, respectively. Importantly, the composite membrane also displayed enhanced anti-organic and anti-biofouling properties with the assistance of the introduced PMo12. This work provides an efficient pathway to simultaneously enhance the filtration and antifouling performance toward the further advancement of UF membrane for water purification.

Selective separation of dyes by green composite membrane based on polylactide with carboxylated cellulose microfiber from empty fruit bunch

A bio-based membrane was prepared by a non-solvent induced phase separation process. A polylactide (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) polymer blend was mixed with functionalized cellulose microfiber from empty fruit bunch (EFB) modified with maleic anhydride (MEFB). MEFB reduced the water contact angle and increased the porosity of the membrane. In a batch adsorption process, the pseudo-second order and Langmuir isotherm models best described the adsorption of the cationic dye methylene blue (MB) on PLA/PBAT and PLA/PBAT-MEFB membranes. In a dynamic adsorption process, pure water flux was higher through the PLA/PBAT-MEFB membrane (1214 L m−2 h−1) than the PLA/PBAT membrane (371 L m−2 h−1). The PLA/PBAT-MEFB membrane removed 97.2 % of MB while the PLA/PBAT membrane removed only 58.7 %. The hydrophilicity of the membrane and its adsorption efficiency toward MB were improved by the abundant carboxyl groups in MEFB. A filtration test using a mixed dye solution of anionic methyl orange (MO) and MB showed that the PLA/PBAT-MEFB membrane rapidly adsorbed MB while permitting MO to pass through. Moreover, this membrane could be easily regenerated and maintained a satisfactory separation performance over several cycles. Based on the membrane performance and its economical preparation, the proposed biocomposite membrane could be used for selective filtration and wastewater treatment.

Tight UF membranes with ultrahigh water flux prepared by in-situ growing ZIF particles in NIPS process for greatly enhanced dye removal efficiency

Tight ultra-filtration (TUF) membranes with in-situ grown zeolitic imidazole framework (ZIF) particles embedded in and packed under porous polysulfone (PSF) separating layers were prepared using non-solvent induced phase separation (NIPS) processes. Imidazole ligands contained in casting solutions were released and reacted with divalent Zn2+ cations pre-loaded on non-woven fabric supporting layers. The capillary filling pore size and molecular-weight-cut-off (MWCO) Stokes solute rejection pore size of the formed ZIF/PSF TUF were tuned by varying the loading levels of Zn (II), polyvinylpyrrolidone (PVP) and imidazole, as well as the NIPS reaction time. With thinned PSF separating layer (200–500 nm) and embedding water permeating short-cuts from the ZIF particles, ZIF/PSF TUF membranes showed 7 times higher water permeance (up to 250 L/(m2 h bar)) and greatly enhanced dye/salt retention selectivity, bearing high potential for applications in dye and textile waste water treatment processes.

Explorations of complex thermally induced phase separation (C-TIPS) method for manufacturing novel diphenyl ether polysulfate flat microporous membranes

A complex thermally induced phase separation (C-TIPS) method combining the advantages of non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS) was proposed to prepare novel diphenyl ether polysulfate (De-PSE) flat membranes, using a good solvent Dimethyl acetamide (DMAC) and a neutral solvent Triethyl phosphate (TEP) as mixed solvents and a non-solvent Polyethylene glycol (PEG-400) as additive. The competition between NIPS and TIPS processes was regulated by adjusting the composition and temperature of quenching bath, so as to achieve fine tuning of membrane surface pore size, morphology, as well as permeability and mechanical property. The membrane cross section exhibited the coexistence of bi-continuous and finger-like pore structures. Compared with membranes prepared by the mainstream NIPS method, the pure water flux improved from 187.62 to 945.27 L m−2 h−1·bar−1 with a mean pore size increased from 30 nm to 195 nm, while the tensile strength enhanced from 2.31 to 5.89 MPa. This work demonstrated a simple strategy to improve the comprehensive performances of De-PSE membranes. Coupled with the strong acid-alkali resistance of the membrane, it greatly expanded the membrane application prospect, especially in the treatment of high polymer textile and papermaking wastewater with large volumes and strong alkalinity.

In-situ construction of water capture layer through reaction enhanced surface segregation for pervaporation desalination

Membranes with dense water capture layer and porous support layer hold great promise for achieving high flux in pervaporation desalination. Such membranes are usually fabricated by two-step methods, which often suffer from poor interfacial compatibility and membrane pore blockage. Herein, we fabricated a hetero-structured membrane with a dense water capture layer and a porous support layer in one step by reaction enhanced surface segregation (RESS) method. During the fabrication of polyether sulfone (PES) support layer via non-solvent induced phase separation (NIPS) process, the amphiphilic copolymer F127 in the casting solution and tannic acid (TA) in the coagulation bath migrated and reacted rapidly to each other, in-situ forming a TA-F127 water capture layer. The composition and structure of the water capture layer were tuned by controlling F127 content, TA concentration and reaction time. The optimal flux of 49.04 kg m−2 h−1 with the rejection of 99.99% was realized when treating 3.5 wt% NaCl solution at 70 °C. The membrane showed great adaptability for treating different concentrations of saline water. This study may provide a facile and scalable method for fabricating hetero-structured membranes toward efficient desalination.

Application of dextran to manipulate formation mechanism, morphology, and performance of ultrafiltration membranes

In this study, dextran polysaccharide was used as a hydrophilic non-solvent additive at different molecular weights and concentrations to prepare novel flat sheet PES membranes through non-solvent induced phase separation process. Formation mechanisms of the PES membranes were assessed thermodynamically and kinetically to verify the influence of dextran polysaccharide on evolving porous media. The obtained results revealed that, in the presence of dextran, the thermodynamic instability of the dope solutions could be remarkably enhanced, leading to a rapid instantaneous demixing during the phase inversion process. Morphologically, the long channel-like macrovoids of the sublayer were also transformed to a disordered structure and concave shapes were emerged on the membrane surface at high concentrations of dextran polysaccharide. Based on the obtained results, not only significant enhancements were achieved in membrane fluxes, but also BSA protein rejections and antifouling properties were improved by increasing the dextran concentration at either molecular weight. Accordingly, the experimental results indicated that the dextran polysaccharide could be employed in practice to achieve scalable high-quality UF membranes through simple NIPS method.

Strategy to prepare skin-free and macrovoid-free polysulfone membranes via the NIPS process

The non-solvent induced phase separation (NIPS) process applied to polysulfone (PSf) casting solutions traditionally leads to the formation of membranes decorated with large macrovoids in their cross-section on top of which lies a dense skin offering a significant resistance to flow. Macrovoids, are considered weak points. They are prone to compaction leading to poor filtration performance over time. Here, we used 2-pyrrolidone (2P) to prepare skin-free PSf membranes by NIPS, and studied the effect of water as an additive to help suppress the formation of macrovoids. The surface images showed the presence of multiple pores while the cross-section images exhibited the successful suppression of macrovoids. The latter was attributed to the enhancement of the solution viscosity causing the mass transfer kinetics to be slowed down, consequently affecting the demixing rates. Moreover, the rheological behavior of the casting solutions revealed that high degree of chain entanglement helped mitigate macrovoid formation. Using 2P as the solvent for PSf permitted the retention of interconnected pores from the top surface, due to the high viscosity of the solution which prevented coarsening. The high porosity (>75%) and large pores (>0.3 μm) of the PSf membranes were still maintained. The permeability of membranes was maintained after suppressing the macrovoids but their mechanical attributes were improved. The feasibility of utilizing water to eliminate macrovoid growth was further validated when applied to other PSf/solvent systems which showed similar trends in the SEM images. These results imply that water as a casting solution additive can provide a highly cost-effective and simple strategy to obtain macrovoid-free p olysulfone membranes.

Preparation and Properties of Thin-Film Composite Forward Osmosis Membranes Supported by Cellulose Triacetate Porous Substrate via a Nonsolvent-Thermally Induced Phase Separation Process.

A porous substrate plays an important role in constructing a thin-film composite forward osmosis (TFC-FO) membrane. To date, the morphology and performance of TFC-FO membranes are greatly limited by porous substrates, which are commonly fabricated by non-solvent induced phase separation (NIPS) or thermally induced phase separation (TIPS) processes. Herein, a novel TFC-FO membrane has been successfully fabricated by using cellulose triacetate (CTA) porous substrates, which are prepared using a nonsolvent-thermally induced phase separation (N-TIPS) process. The pore structure, permeability, and mechanical properties of CTA porous substrate are carefully investigated via N-TIPS process (CTAN-TIPS). As compared with those via NIPS and TIPS processes, the CTAN-TIPS substrate shows a smooth surface and a cross section combining interconnected pores and finger-like macropores, resulting in the largest water flux and best mechanical property. After interfacial polymerization, the obtained TFC-FO membranes are characterized in terms of their morphology and intrinsic transport properties. It is found that the TFC-FO membrane supported by CTAN-TIPS substrate presents a thin polyamide film full of nodular and worm-like structure, which endows the FO membrane with high water permeability and selectivity. Moreover, the TFC-FO membrane supported by CTAN-TIPS substrate displays a low internal concentration polarization effect. This work proposes a new insight into preparing TFC-FO membrane with good overall performance.

Influence of the formed interface during preparation of poly(vinylidene fluoride) blend cation exchange membrane on the electro-chemical properties and performance

Cation exchange membrane containing low fraction of charge moiety is beneficial as it minimizes the water swelling and back diffusion of ions, increases the mechanical property and lowers the cost. However, moderate to high extent of ion conducting group in a membrane is necessary for the effective ion exchange and good electrodialysis performance. To address this issue, we report a non-solvent (water) induced phase separation process where solid-water interface is generated and helps to migrate the ionic moieties on the surface and transport of ions, while a solid-air interface is formed in the solvent evaporation process which partially hinders the migration of the ionic moieties (high surface energy) on the membrane surface and ion transport property. Cation exchange membranes of the blend of poly(vinylidene fluoride) and poly(methyl methacrylate)-co-poly(styrene sulfonic acid sodium salt) have been prepared by both non-solvent induced phase separation and solvent evaporation process. Membrane containing about 5% (w/w) anionic polymer and prepared by non-solvent induced phase separation process exhibits high transport number (t+ = 0.93), good water desalination performance with power consumption of 1.15 KWhKg−1 and current efficiency of 90% than that of the membrane prepared by solvent evaporation process (power consumption = 1.58 KWhKg−1 and current efficiency = 58%).

High-performance thin-film composite forward osmosis membranes with hydrophilic PDA@TiO2 nanocomposite substrate for the treatment of oily wastewater under PRO mode

The applications of thin-film composite (TFC) forward osmosis (FO) membranes are limited by low flux and strong internal concentration polarization (ICP). In this study, a simple, facile, and eco-friendly approach to improve the wettability of the FO membrane substrate using hydroxyl- and amino-functionalized TiO2 nanocomposites by polydopamine (PDA) coating on TiO2 particles is demonstrated. In our research, a composite membrane substrate was fabricated by incorporating PDA@TiO2 into polyethersulfone (PES) through the non-solvent induced phase separation (NIPS) process. Then, a selective active polyamide layer was formed by interfacial polymerization on top of the PES-PDA@TiO2 membrane substrate to obtain the resulting TFC-FO membrane. The composite membrane substrate exhibited higher hydrophilicity (about 25% lower contact angle) and higher porosity than the pristine membrane substrate. The water flux (Jw) of 34.3 L/m2h and 60.1 L/m2h was achieved for the resulting TFC-PDA@TiO2 FO membrane under FO and pressure retarded osmosis (PRO) modes which was ~174% and ~183% higher than that of the pristine TFC-FO membrane under FO and PRO modes respectively. Furthermore, the TFC-PDA@TiO2 membrane exhibited enhanced selectivity, as expressed by the decrease in the specific salt flux (Js/JW) values (from 0.48 g/L and 0.53 g/L of pristine TFC to 0.27 g/L and 0.28 g/L for TFC-PDA@TiO2 under the FO and PRO modes respectively). More importantly, the TFC-PDA@TiO2 membrane exhibited better fouling behavior with the organic foulant solution. These results demonstrate that the fabricated TFC-FO membranes have significant potential for sustainable water reclamation from oily wastewater via FO under the PRO mode.

Enhanced performance of superhydrophobic polyvinylidene fluoride membrane with sandpaper texture for highly saline water desalination in air-gap membrane distillation

Here, we report a simple and cost-effective process to fabricate a superhydrophobic Polyvinylidene Fluoride (PVDF) membrane. Four different PVDF membranes were investigated using sandpaper (SP), polydimethylsiloxane (PDMS), stainless steel mesh (SSM), and tempered glass as casting substrate in a non-solvent induced phase separation process. Sandpaper-like texture was replicated on a PVDF membrane using a PDMS template prepared via soft lithography technique. Interestingly, PDMS-based membrane reveals surface with textures depicting the lotus effect. The developed membranes were characterized in terms of their morphology, bulk properties, wetting behavior and MD performance. Among all the membranes developed, PDMS-based textured membrane showed excellent MD performance with high and stable salt rejection at 99.99%, and permeate flux reaching 21 kg m−2 h−1 after a 40-hour test using highly saline water (70 g/L NaCl) in Air-Gap Membrane Distillation (AGMD). Notably, the PVDF membranes developed in this study showed an increase in permeate flux with time due to a decrease in the air gap width as a result of membrane stretching. The textured PVDF membrane that was developed using sandpaper features offers a promising alternative for treating highly saline water in the MD system.

One-Step Water-Induced Phase Separation Simultaneously Triggering Polymer Solidification and Polyelectrolyte Complexation for Porous Ultrafiltration Membranes.

Functional additives have been widely utilized for the membrane structure modulation and performance improvement during the nonsolvent-induced phase separation process, but the resulted membranes easily suffer from additives' inhomogeneous dispersity and compatibility with the polymer matrix. Herein, a facile and robust strategy, i.e., one-step water-induced phase separation, was proposed for the preparation of polyelectrolytes-contained composite membranes. Polyanion (dopamine modified polyacrylic acid) and polycation (quaternized chitosan paired with bis(trifluoromethane-sulfonyl)imide) were first premixed in dimethyl sulfoxide and used as polyelectrolyte additives in a polysulfone (PSF) solution, and then a uniform PSF-based casting solution was readily obtained. During the solvent-water exchange process, polymer solidification and polyelectrolyte complexation were simultaneously triggered, in situ generating a polyelectrolyte complex fixed within the membrane matrix. Ultrafiltration membranes with hierarchical structures were notably tailored through altering the concentration, molecular weight, and type of polyelectrolytes. The obtained membrane exhibited a water flux of 672 L·m-2·h-1, three times over the raw PSF membrane, while almost maintaining high bovine serum albumin (BSA) rejection. This work paves a straightforward and convenient path for the preparation of composite membranes with tunable architecture and properties.

Comprehensive Analysis of Spinel-Type Mixed Metal Oxide-Functionalized Polysulfone Membranes toward Fouling Resistance and Dye and Natural Organic Matter Removal.

Nanostructured polymeric membranes are of great importance in enhancing the antifouling properties during water filtration. Nanomaterials with tunable size, morphology and composition, surface modification, and increased functionality provide considerable opportunities for effective wastewater treatment. Thus, in this work, an attempt has been made to use spinel-structured MnCo2O4 as a nanofiller in the fabrication of nanostructured polysulfone (PSF) mixed matrix membranes and is investigated in terms of morphology, hydrophilicity, permeability, protein and natural organic matter separation, dye removal, and, finally, antifouling properties. The MnCo2O4 nanomaterials are synthesized and characterized via X-ray diffraction and field emission scanning electron microscopy and are loaded into a membrane matrix with varied concentrations (0 to 1.5 wt %). PSF nanocomposite membranes are prepared via a nonsolvent-induced phase-separation process. The results show an enhancement in hydrophilicity, porosity, and permeability with respect to the modified nanocomposite membranes because of oxygen-rich species in the membrane matrix, which increases affinity toward water. It was also found that the modified membranes display remarkably greater pure water flux (PWF) (220 L/m2 h), higher Congo red rejection coefficient (99.86%), higher humic acid removal (99.81%), higher fouling resistance, and a significant flux recovery ratio (FRR) (88%) when tested with bovine serum albumin protein when compared to a bare PSF membrane (30 L/m2 h PWF and 35% FRR). This is because the addition of MnCo2O4 nanoparticles into the polymeric casting solution yielded tighter PSF membranes with a denser skin layer and greater selectivity. Thus, the enhanced permeability, greater rejection coefficient, and antifouling properties show the promising potential of the fabricated PSF-spinel nanostructured membrane to be utilized in membrane technology for wastewater treatment.

Nanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV‐Mediated Cross‐Linking Strategies

Front Cover: A block copolymer containing UV-addressable benzophenone moieties within the hydrophobic block is synthesized via atom transfer radical polymerization (ATRP). The block copolymer is utilized in a self-assembly non-solvent induced phase separation process to obtain an integral asymmetric membrane, which can be stabilized upon UV- irradiation revealing enhanced solvent and pressure resistance. This work is featured in article number 2100632 by Bizan N. Balzer, Markus Gallei, and co-workers.

A Contrastive Study of Self-Assembly and Physical Blending Mechanism of TiO2 Blended Polyethersulfone Membranes for Enhanced Humic Acid Removal and Alleviation of Membrane Fouling.

In this study, membrane fabrication was achieved by two different methods: (i) self-assembly and (ii) physical blending of TiO2 in PES membrane for humic acid filtration. The TiO2 nanoparticles were self-assembled by using TBT as the precursor and pluronic F127 as triblock copolymers around the membrane pores. This was achieved by manipulating the hydrolysis and condensation reaction of TBT precursors during the non-solvent induced phase separation (NIPS) process. On the other hand, the TiO2 was physically blended as a comparison to the previous method. The characteristic of the membrane was analysed to explore the possibility of enhancing the membrane antifouling mechanism and the membrane flux. The membrane morphology, pore size, porosity, and contact angle were characterised. Both methods proved to be able to enhance the antifouling properties and flux performance. The HA rejection increased up to 95% with membrane flux 55.40 kg m−2 h−1. The rejection rate was not significantly improved for either method. However, the antifouling characteristic for the self-assembly TiO2/PES membrane was better than the physically blended membrane. This was found to be due to the high surface hydrophilicity of the MM membrane, which repelled the hydrophobic HA and consequently blocked the HA adsorption onto the surface.

Carbon Black/Polyvinylidene Fluoride Nanocomposite Membranes for Direct Solar Distillation

Water reclamation is becoming a growing need, in particular in developing countries where harvesting the required energy can be a challenging problem. In this context, exploiting solar energy in a specifically tailored membrane distillation (MD) process can be a viable solution. Traditional MD guarantees a complete retention of non-volatile compounds and does not require high feed water temperatures. In this work, a suitable amount of carbon black (CB) was incorporated into the whole matrix of a polymeric porous membrane in order to absorb light and directly heat the feed. The mixed matrix membranes were prepared forming a uniform CB dispersion in the PVDF dope solution and then using a non-solvent induced phase separation process, which is a well-established technique for membrane manufacturing. CB addition was found to be beneficial on both the membrane structure, as it increased the pore size and porosity, and on the photothermal properties of the matrix. In fact, temperatures as high as 60 °C were reached on the irradiated membrane surface. These improvements led to satisfactory distillate flux (up to 2.3 L/m2h) during the direct solar membrane distillation tests performed with artificial light sources and make this membrane type a promising candidate for practical applications in the field of water purification.

Asymmetric block copolymer membrane fabrication mechanism through self-assembly and non-solvent induced phase separation (SNIPS) process

In this paper, the concept of the functional mechanism of copolymer membrane formation is explained and analyzed from the theoretical and experimental points of view. To understand the phase inversion process and control the final membrane morphology, styrene-acrylonitrile copolymer (SAN) membrane morphology through the self-assembly phenomena is investigated. Since the analysis of the membrane morphology requires the study of both thermodynamic and kinetic parameters, the effect of different membrane formation conditions is investigated experimentally; In order to perceive the formation mechanism of the extraordinary structure membrane, a thermodynamic hypothesis is also developed based on the hydrophilic coil migration to the membrane surface. This hypothesis is analyzed according to Hansen Solubility Parameters and proved using EDX, SAXS, and contact angle analysis of SAN25. Moreover, the SAN30 membrane is fabricated under different operating conditions to evaluate the possibility of morphological prediction based on the developed hypothesis.