Non-solvent Induced Phase Separation Process Research Articles

Tailoring of polysulfate/polyvinylpyrrolidone membrane structure via NIPS coupled physical aging technique for high-performance dye/salt separation

Tight ultrafiltration (TUF) membranes have been proposed as an effective candidate for the treatment of textile wastewater with high salinity. In this study, a novel polysulfate (PSE)-based TUF membrane was prepared by coupling the non-solvent induced phase separation (NIPS) process with the physical aging method. The polyvinylpyrrolidone (PVP) was adopted to tailor the micro-/nanostructure of the fabricated membranes. Accordingly, the molecular weight cut-off (MWCO) of the membrane can be tuned from 293.8 to 3.7 kDa. Endowed with the high porosity and small pore size, the optimized PSE/PVP blend membrane (a MWCO of 3.9 kDa) was applied for removal of dyes from dye/salt aqueous solution, which offered top-tier overall performance, e.g., a pure water flux of 70.7 L*m−2*h−1, CR/NaCl selectivity of 494.3, CR/Na2SO4 selectivity of 42.6, long-term running stability, and excellent antifouling performance. Therefore, our study establishes a simple avenue to fabricate a high-performance TUF membrane for practical textile wastewater treatment.

Development of low-fouling PVDF membranes blended with poly(2-methoxyethyl acrylate) via NIPS process

PVDF-based membranes with low-fouling and high permeability properties were developed by blending poly(vinylidene fluoride) (PVDF) with poly(2-methoxyethyl acrylate) (PMEA), a low-fouling polymer, via non-solvent induced phase separation (NIPS). Since PMEA suppresses protein adsorption and is insoluble in water, the PMEA homopolymer was used as an additive. Consequently, transparent dope solutions containing 15 wt% PVDF and 0–7 wt% PMEA were prepared using N-methyl-2-pyrrolidone as the solvent. The macrovoids in the blended membranes were larger than those in the pristine PVDF membrane and were probably attributed to the PMEA-promoted solvent exchange during the NIPS process. As a result, the pure water permeabilities of the blended membranes were 5–10 times higher than those of the pristine PVDF membrane. The ATR FT-IR characterization revealed that the PMEA composition of the membrane surfaces increased as the PMEA blend ratio in the dope solution increased. This resulted in the improvement of their low-fouling properties when used in 1000 ppm of bovine serum albumin (BSA) and lysozyme aqueous solutions. Additionally, the PMEA-blended PVDF membrane with the highest PMEA ratio showed the best low-fouling properties.

Asymmetric Solvent-Annealed Triblock Terpolymer Thick Films Topped by a Hexagonal Perforated Lamellar Nanostructure.

Asymmetric and nanostructured polystyrene-block-poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO or SVEO, S:V:EO ≈ 56:34:10, 79.5kg mol-1 ) thick films blended with 20 wt% of a short PS homopolymer (hPS, 10.5kg mol-1 ) are achieved by combining the non-solvent induced phase separation (NIPS) process with a solvent vapor annealing (SVA) treatment. Here, the NIPS step allows for the formation of a highly-permeable sponge-like substructure topped by a dense thin layer exhibiting poorly-ordered nanopores while the subsequent SVA treatment enables to reconstruct the material top surface into a porous monolayer of well-ordered hexagonal perforated lamellae (HPL). This optimized film architecture generated by NIPS-SVA shows a water permeability of 860 L h-1 m-2 bar-1 , which is roughly two times higher than the flux measured through NIPS made PS-b-P2VP-b-PEO/hPS materials having poorly-ordered nanopores. The post-SVA treatment is also revealed as a powerful tool to tailor the thickness of the nanostructure formed within the blended material because monoliths entirely composed of a HPL phase are produced by increasing the time of exposure to a chloroform stream. The water flux of such PS-b-P2VP-b-PEO/hPS monoliths is found to be an order of magnitude lower than that of their asymmetric film homologues.

Shutdown-Functionalized Poly Ethylene-Vinyl Alcohol Sulfonate Lithium and Poly (Vinyl Alcohol) Composite Lithium-Ion Battery Separator

The thermal shutdown of the separator is the crucial feature for hindering thermal runaway of lithium-ion batteries. Because the temperature within the cell continues to rise rather than drop immediately after shutdown, the separator should be capable of maintaining adequate dimensional stability up to a specific range above the shutdown temperature to prevent internal short circuits. Based on this, a composite separator with high shutdown temperature and a wider shutdown temperature window was fabricated based on the non-solvent induced phase separation process of poly ethylene-vinyl alcohol sulfonate lithium (EVOH-SO3Li) and poly (vinyl alcohol) (PVA). The scanning electron microscope, pore size analysis, and wettability test results show that the composite separator possesses a uniform micron-sized porous structure and excellent electrolyte affinity owing to the abundant hydroxyl and sulfonic acid groups. Hence, the composite separator obtains the optimized electrochemical performances. The cell assembled with the composite separator also exhibits superior discharge C-rate capacity and cycle stability. In addition, the composite separator displays a higher shutdown function of 155 °C and maintained sufficient dimensional integrity below 213 °C, which is conducive to fabrication of lithium-ion batteries with adequate security feature and ideal cycle ability.

Hydrophilic nano-aluminum oxide containing polyphenylsulfone hollow fiber membranes for the extraction of arsenic (As-V) from drinking water

In the present work, hollow fiber ultrafiltration membranes were fabricated by incorporating intensified dosages of nano‑aluminum oxide (nano-Al2O3; 0.6 wt%, 1.0 wt% and 1.5 wt%) into cellulose acetate (CA)/polyphenylsulfone (PPSU) and cellulose acetate phthalate (CAP)/PPSU by non-solvent induced phase separation (NIPS) process. The topological structures and the morphologies were investigated using atomic force microscope (AFM) and scanning electron microscope (SEM). The crystalline and morphological structures of the nano-Al2O3 were investigated using X-ray diffraction (XRD) and transmission electron microscope (TEM) respectively. Fourier transform infra-red spectroscope (FTIR) and x-ray photoelectron spectroscopy (XPS) analysis have been carried out to validate the dosages of nano-Al2O3, CA and CAP on PPSU membranes. The membrane's surface charge measurement of 1.5 wt% of nano-Al2O3 in CA/PPSU (ALCA-1.5) was scrutinized by zeta potential analysis. Membranes removed more arsenate oxide as the removal rate from membranes ALCA-1.5 and 1.0 wt% of nano-Al2O3 in CA/PPSU (ALCA-1) was 98.67% and 94.89% with retention permeabilities of 88.41 L/m2h bar and 53.53 L/m2h bar respectively from laboratory prepared 1 ppm of aqueous arsenic solution with pH in the range 6.8 ± 0.2 at 1 bar transmembrane pressure. In addition, membrane's antifouling analysis was performed using laboratory prepared 0.8 g/L (Bovine Serum Albumin) BSA as standard protein solution.

Advancements in Sustainable PVDF Copolymer Membrane Preparation Using Rhodiasolv® PolarClean As an Alternative Eco-Friendly Solvent

In this work, Rhodiasolv® PolarClean was employed as a more sustainable solvent for the preparation of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) flat sheet membranes via phase inversion technique by coupling vapour induced phase separation (VIPS) and non-solvent induced phase separation (NIPS) processes. Preliminary calculations based on Hansen solubility parameters well predicted the solubilization of the polymer in the selected solvent. The effect of exposure time on humidity and the influence of polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP) and sulfonated polyether sulfone (S-PES) on membrane properties and performance, were evaluated. Three different coagulation bath compositions were also explored. The obtained membranes, prepared using a more sustainable approach, were compared with those produced with the traditional toxic solvent N-methyl-2-pyrrolidone (NMP) and characterised in terms of morphology, porosity, wettability, pore size, surface roughness and mechanical resistance. The potential influence of the new solvent on the crystallinity of PVDF-HFP-based membranes was also evaluated by infrared spectroscopy. The adjustment of the parameters investigated allowed tuning of the membrane pore size in the microfiltration (MF) and ultrafiltration (UF) range resulting in membranes with various morphologies. From the water permeability and rejection tests, performed with methylene blue dye, the prepared membranes showed their potentiality to be used in MF and UF applications.

Interfacial polymerization of thin film selective membrane layers: Effect of polyketone substrates

Thin film composite (TFC) membranes are the most widely used technology in reverse osmosis (RO)-based desalination processes, due to their desirable separation performance derived from the combined structure of the porous support and thin film active layer. Typically, TFC membranes are fabricated via an interfacial polymerization (IP) technique, where the porous substrate plays an indispensable role in forming the thin film layer. In this study, a porous polyketone membrane with a fibrous structure and intrinsically moderate hydrophilicity prepared using non-solvent induced phase separation (NIPS) was employed as the substrate to explore its suitability for fabricating high-performance TFC membranes. Investigations on structure control and chemistry regulation via the NIPS process and in-situ post-treatment revealed that porous polyketone substrates display different morphologies and chemistries, significantly altering the thin layer formation during IP. The resulting TFC membranes exhibited up to 14-fold permeance difference, which was attributed to the variance of “ridge-and-valley” structures in different thin film layers formed on different polyketone substrates. It was found that a polyketone membrane with an appropriate surface roughness could generate favorable “ridge-and-valley” structures in the thin film layer to enhance the surface area, realizing high water permeance as well as high salt rejection in reverse osmotic desalination of NaCl solution.

Electrostatic enhanced surface segregation approach to self-cleaning and antifouling membranes for efficient molecular separation

Membranes with excellent antifouling properties and persistent high permeance are eternal pursuits in membrane technology. Herein, we proposed an electrostatic enhanced surface segregation approach toward the antifouling and self-cleaning membranes for molecular separation. A copolymer containing quaternary ammonium (QA) segments was designed as the surface segregation agent in the casting solution, while polysulphonic acid (PSA) was designed as the crosslinking agent in the coagulation bath. Driven by the electrostatic interactions between the positively charged QA and negatively charged sulphonic groups, the copolymer and PSA were in-situ assembled during the non-solvent induced phase separation (NIPS) processes, generating a selective separation layer on the polymeric matrix. The segregation of copolymer was enhanced, leading to a high surface coverage of ionic QA and sulphonic groups and a significantly improved surface hydrophilicity. Accordingly, the membrane exhibited a high water permeance up to 124 Lm−2h−1bar−1 with dye rejection over 95%. Moreover, the membrane exhibited excellent antifouling performance with the ultralow total permeance decline of 1.2% and the ultrahigh permeance recovery ratio of 99.8% against emulsified oil, as well as the self-cleaning property against crude oil. Hopefully, this study can afford a novel and generic approach to antifouling and self-cleaning membranes for diverse separations.

Enhanced water permeability and fouling resistance properties of ultrafiltration membranes incorporated with hydroxyapatite decorated orange-peel-derived activated carbon nanocomposites

Hydroxyapatite-decorated activated carbon (HAp/AC) nanocomposite was synthesized and utilized as a nanofiller to fabricate a novel type of polyethersulfone (PES) nanocomposite ultrafiltration (UF) membranes. Activated carbon (AC) derived from orange peel was synthesized by low-temperature pyrolysis at 400 °C. A hydroxyapatite/AC (HAp/AC) nanocomposite was developed by a simple one-pot hydrothermal synthesis method. The UF membrane was fabricated by intercalating HAp/AC fillers into PES casting solution by the non-solvent induced phase separation (NIPS) process. The prepared membranes exhibited a lower water contact angle than the pristine PES membrane. The hybrid membrane with 4 wt% HAp/AC nanocomposite displayed 4.6 times higher pure water flux (~660 L/m2 h) than that of the pristine membrane (143 L/m2 h). In static adsorption experiments, it was found that the amount of humic acid (HA) and bovine serum albumin (BSA) adsorbed by the HAp/AC-PES hybrid membrane was much lower than that of the original membrane due to the electrostatic repulsive forces between them and the surface of the membrane. Irreversible fouling was reduced from 33 to 6 % for HA and from 46 to 8 % for BSA after HAp/AC was incorporated into the PES matrix. After 7 cycles of water-BSA-water, the HAp/AC-PES hybrid membrane maintained a high pure water flux of 540 L/m2 h with an excellent flux recovery ratio (FRR), demonstrating the long-term stability of the membranes. The developed UF membranes outperformed the original PES membranes in terms of permeability, selectivity, and antifouling.

Ultralow Ti3C2TX doping polysulfate membrane for high ultrafiltration performance

Incorporating hydrophilic nanomaterial fillers into a polymeric matrix enables a high-performance ultrafiltration membrane. 2D Ti3C2TX nanosheets are promising candidates due to their hydrophilic nature and good dispersion ability in the organic solvent. In this study, novel polysulfate (PSE)/Ti3C2TX ultrafiltration membranes were prepared by non-solvent induced phase separation (NIPS) method. The phase inversion process of the PSE/Ti3C2TX casting membranes was visualized. Ti3C2TX nanosheets could tune the phase inversion process effectively and promote the phase inversion speed with an ultralow content of 0.05 wt%. As a result, the hydrophilic property and porosity of PSE/Ti3C2TX membrane could be improved. The skin layer thickness was significantly reduced, resulting in saliently ultrafiltration performance, i.e., a pure water flux (PWF) of 685 L*m−2*h−1 (LMH) with a bovine serum albumin (BSA) rejection of 97%. The proposed ultralow Ti3C2TX doping in the casting solutions method offers a versatile platform to manipulate the phase inversion progress during the industrially NIPS process, and enhanced the separation performance of ultrafiltration membranes.

Simultaneous alkaline hydrolysis and non-solvent induced phase separation method for polyacrylonitrile (PAN) membrane with highly hydrophilic and enhanced anti-fouling performance

Microporous membranes are now favorably used as a separation tool for the purification of water and wastewater containing fine particles and macromolecular contaminants. However, organic fouling has often become one of the major problems hindering the wider applications of these membranes. In this study, a highly hydrophilic polyacrylonitrile (PAN) membrane with excellent anti-fouling performance was prepared from a method simultaneously combining alkaline hydrolysis and non-solvent induced phase separation (NIPS) processes together. The interplay of the PAN alkaline hydrolysis and NIPS was examined for its effects on both the structural and chemical properties of the prepared membranes. Morphological and porometric analyses confirmed that the new method produced PAN membranes with less macrovoids but highly ordered narrow flow channels in the cross-section structure, as well as a much denser selective surface layer with small and greatly uniform pore sizes. Characterizations in membrane surface wettability and chemical compositions revealed that the new preparation approach can endow the obtained membranes with significantly enhanced surface hydrophilicity as well as oleophobicity within a much shorter preparation time, in comparison with other conventional preparation methods, including the post alkaline hydrolysis of PAN membranes. Filtration experiments for oil (hexadecane)-in-water emulsion, NOM (humic acid) or protein (BSA) solutions have all confirmed that the developed membranes showed remarkably slow flux declining during filtration operation and high flux recovery by simple water flushing for membrane cleaning. Hence, it is anticipated that there is a great potential for the new approach to fabricate anti-fouling PAN membranes, especially for more challenging separation applications in water and wastewater treatment.

Preparation of porous fluorinated polyimide separator for lithium-ion batteries by non-solvent induced phase separation process

A series of novel porous fluorinated polyimide (FPI) separators containing trifluoromethyl group (–CF3) were prepared by the non-solvent induced phase separation (NIPS) strategy. The prepared FPI separator with 60% molar content (fluorinated dianhydride: non-fluorinated dianhydride: diamine = 60: 40: 100) of fluorinated groups (FPI-60%) could stably exist in the electrolyte as a LIBs separator. The resultant FPI-60% separator possesses high thermal stability with the Tgof 289.4°C and exhibits no shrinkage even at 200°C. The morphologies of the FPI-60% separators were adjusted by introducing small molecular non-solvent additives-ethanol, and the FPI-60% separators present the spongy-like and interconnected structure with different porosity as the amount of ethanol changed from 1 wt% to 10 wt%. The FPI-60% separators display excellent electrolyte uptake with 170%–200% and the ionic conductive could reach 1.17 mS/cm which is four times approximately than that of the PP separator. The lithium-ion batteries (LIBs) using FPI-60% separators with 10 wt% ethanol added show better rate capacities (102.8 mAh/g, 70.8 mAh/g of PI-10 and PP separator at 2 C, respectively) and the capacity retention rate is 93.2% after 50 cycles. The results prove that the porous FPI separator is a promising candidate for high-performance LIBs.

Polyethersulfone hybrid ultrafiltration membranes fabricated with polydopamine modified ZnFe2O4 nanocomposites: Applications in humic acid removal and oil/water emulsion separation

This study explored the impact of eco-friendly polydopamine (PDA) coated ZnFe2O4 nanocomposites (PDA@ZnFe2O4 NCs) as nanofillers to fabricate a new class of polyethersulfone (PES) hybrid ultrafiltration (UF) membranes for wastewater treatment applications. The hybrid UF membrane was prepared by incorporating PDA@ZnFe2O4 NCs into PES via the non-solvent induced phase separation (NIPS) process. The PDA@ZnFe2O4 NC was characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Additionally, the morphology and performance of the prepared hybrid membranes were characterized by SEM, contact angle, surface charge, and thermogravimetric analysis (TGA). The incorporation of PDA@ZnFe2O4 NC into the PES membrane affects the porosity, mean pore radius, hydrophilicity, and thermal stability of the developed hybrid membranes. The pure water flux of the PES hybrid membrane with 4 wt% PDA@ZnFe2O4 reached ∼687 L/m2 h, which is about 188% higher than that of the pristine PES membrane. The performance of the PES/ PDA@ZnFe2O4ultrafiltration hybrid membrane was also investigated using humic acid (HA) foulant and oil/water emulsion individually. Compared to the pristine PES and PES/ZnFe2O4 membranes, the developed hybrid membranes showed enhanced permeability and HA foulant removal. HA's removal efficiency has improved from ∼65% in the pristine PES membrane to ∼94% in the 4 wt% PDA@ZnFe2O4 hybrid membrane. The abundant functional groups on the PDA@ZnFe2O4 NC surface also enhanced the separation of the oil/water emulsion (96%). In both the HA and oil/water emulsion separation tests, the flux recovery ratio (FRR) and reversible fouling ratio (Rr) were also significantly improved, suggesting that the PES/PDA@ZnFe2O4 membrane was a very promising candidate for HA removal and treatment of oily wastewater.

Extraction of penicillin-G from pharmaceutical wastewaters via a developed hydrophobic PVDF-HFP hollow fiber membrane contactor and process optimization

Discharge of pharmaceutical wastewaters can cause substantial environmental impacts. Since the conventional wastewater treatment processes are not efficient for comprehensive separation of pharmaceutical substances, a non-dispersive solvent extraction via a hollow fiber membrane contactor can be a promising alternative. In the present study, a structurally developed poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) hollow fiber membrane was fabricated via a non-solvent induced phase separation (NIPS) process to enhance extraction of penicillin-G (Pen-G) from the wastewater. Response surface methodology (RSM) was used for optimization of the main operating variables in the liquid–liquid membrane contactor process. From FESEM examination, the prepared membrane showed an open structure with large finger-likes, ultra-thin outer skin, and inner skinless layer. The membrane presented a narrow pore size distribution with mean pore size of 0.038μm, water contact angle of about 94°, critical water entry pressure of 350 kPa, and overall porosity of about 84 %. Extraction of Pen-G from the aqueous phase by 5 wt% organic solution of Aliquat 336 was performed. The feed concentration of 218 ppm, temperature of 41 °C, flowrate of 51 ml/min, and the organic phase flowrate of 144 ml/min were the optimum values predicted by the model. A maximum Pen-G extraction flux of 1.55×10−3 kg/m2 s was predicted at the optimum operating conditions. The value of error between the experimental and predicted fluxes was about 3.23% which confirmed accuracy of the model. Due to the developed membrane structure, the prepared PVDF-HFP hollow fiber membrane showed a considerably higher Pen-G extraction flux compared to the PP commercial membranes.

Fabrication of high-flux asymmetric polyethersulfone (PES) ultrafiltration membranes by nonsolvent induced phase separation process: Effects of H2O contents in the dope

A series of asymmetric polyethersulfone (PES) membranes were fabricated using non-solvent induced phase separation (NIPS) process from the system of water/GBL/PVP/PES at 40 °C. Water, acting as the nonsolvent, was added in different amounts to the dope solution to modify the porous structure and enhance the permeability of the membranes. The fabricated membranes were tested systematically for their morphologies, physical properties, pure water fluxes, and rejection capacities against bovine serum albumin molecules (BSA). The SEM images indicated that the pore size and porosity of the top surface increased with increasing water content in the dope, and when 1.5 phr of water was incorporated, the macrovoids in the cross section disappeared and the pores interconnected to form numerous continuous channels within the PES matrix. This membrane exhibited a pure water flux of 642 L m−2h−1bar−1 and a tensile strength as high as 5.6 N/mm2. The dead-end filtration experiments indicated a very high BSA rejection of ~98% for membranes prepared from dopes containing ≤1.0 phr of water, and a moderately high (85%) rejection for that with a higher dope water content.

Fabrication of novel polyethersulfone (PES) hybrid ultrafiltration membranes with superior permeability and antifouling properties using environmentally friendly sulfonated functionalized polydopamine nanofillers

Developing hybrid ultrafiltration (UF) membranes with high permeability and low fouling tendency is important for a wide range of wastewater treatment applications. Herein, we report the synthesis of novel environmental-friendly sulfonated functionalized polydopamine (SPDA) nanocomposite as a nanofiller for UF membranes. Firstly, mussel-inspired PDA nanoparticles (NPs) were synthesized based on oxidation and self-polymerization of dopamine monomer. PDANPsweresubsequentlysulfonatedwith3-mercapto-1-propanesulfonicacid(athiolwith –SO3H group)throughMichael's addition reaction to produce the SPDA nanofiller. Fourier transform infrared spectroscopy and zeta potential measurements verified the functionalization of the PDA. Hybrid UF membranes were then fabricated via the non-solvent-induced phase separation process (NIPS), using polyethersulfone (PES) as a matrix and SPDA nanofiller at different loading levels (0–4 wt%). The water contact angle values showed an increase in the hydrophilicity of the fabricated UF membranes. The water permeability and antifouling capability of the hybrid UF membranes were dependent on the nanofiller's loading quantity. At 1 bar feed pressure, the pure water flux of the 2 percent SPDA nanofiller membrane was 2.7 times higher than that of the pristine membrane. Foulant solutions have been used to determine the antifouling efficiency of the hybrid membranes using sodium alginate (SA), humic acid (HA) and bovine serum albumin (BSA). The antifouling properties of the PES membranes have been significantly improved by incorporating the SPDA nanofillers in accordance with the foulant rejection and flow recovery ratios. The results indicated that SPDA nanofillers have great potential to improve the permeability and antifouling properties of PES membranes.Capsule: High-flux and antifouling PES hybrid membranes fabricated using environmentally-friendly sulfonated functionalized polydopamine nanofillers.

Janus polyvinylidene fluoride membranes with controllable asymmetric configurations and opposing surface wettability fabricated via nanocasting for emulsion separation

Janus membrane (JM) with opposite wettability has great potential in separation of oil-in-water (O/W) and water-in-oil (W/O) emulsions. In this work, we have reported a simple, low cost nanocasting/NIPS strategy for preparation of the superhydrophobic and underwater oleophobic surface of JM for the first time. Poly (vinylidene fluoride) (PVDF) and polyethylenimine (PEI) blend membranes were fabricated on PDMS modified non-woven fabric by non-solvent induced phase separation (NIPS) process. Then the as-prepared membranes were further modified with hydrophilic nano-SiO2 to improve the hydrophilicity of the top surface. Peel off PDMS modified non-woven fabric, parts of PDMS chains were imprinted to the membrane bottom surface with micro-nano three-dimensional microstructures, resulting in superhydrophobic property. The as-prepared JM exhibits an asymmetric wettability with the water contact angle of 35.3° and 151.8° of the opposite surfaces. By changing the orientation of the membrane, oil or water can be filtered respectively. The as-prepared JM shows excellent separation performance for both O/W emulsion and W/O emulsion, the separation efficiency reached 99.72 % and 99.68 %, respectively, as well as good long-term stability. This work is expected to yield a new way to fabricate the superhydrophobic surface of JM.

Metal-organic framework/zeolite nanocrystal/polyvinylidene fluoride composite ultrafiltration membranes with flux/antifouling advantages

In this study, hydrophilic zirconium 1,4-dicarboxybenzene (UiO-66) and chromium (III) terephthalate (MIL-101) metal-organic frameworks (MOFs) and faujasite (FAU) zeolite nanocrystals were synthesized successfully and incorporated into polyvinylidene fluoride (PVDF) matrix as nanofillers to fabricate mixed matrix membranes (MMMs) via non-solvent induced phase separation (NIPS) process. The effects of casting solution temperature and casting speed as two important factors in membrane fabrication via phase inversion method on performance and structure of the neat PVDF membrane were investigated. Then, various contents of the synthesized nanofillers were loaded into the PVDF matrix and the effects of the synthesized nanofillers on hydrophilicity, pure water flux (PWF), morphology and antifouling properties of the fabricated MMMs were explored. Antifouling studies were also performed using Bovine serum albumin (BSA). The obtained results demonstrated that incorporation of the synthesized nanofillers into the PVDF membrane has positive effect on performance and structure of the fabricated MMMs and the MMM containing 0.1 wt% MIL-101 showed the best performance with water flux of 360 LMH, BSA rejection of 100%, irreversible fouling of 22.2% and flux recovery ratio of 77.7%. This work highlighted the potential application of the MOFs as effective nanofillers for MMM fabrication.

Spraying of Ultrathin Isoporous Block Copolymer Membranes-A Story about Challenges and Limitations.

Isoporous membranes can be prepared by a combination of self-assembly of amphiphilic block copolymers and the non-solvent induced phase separation process. As the general doctor-blade technique suffers from high consumption of expensive block copolymer, other methods to reduce its concentration in the casting solution are sought after. Decreasing the block copolymer concentration during membrane casting and applying the block copolymer solution on a support membrane to obtain ultrathin isoporous membrane layers with e.g., spraying techniques, can be an answer. In this work we focused on the question if upscaling of thin block copolymer membranes produced by spraying techniques is feasible. To upscale the spray coating process, three different approaches were pursued, namely air-brush, 1-fluid nozzles and 2-fluid nozzles as generally used in the coating industry. The different spraying systems were implemented successfully in a membrane casting machine. Thinking about future development of isoporous block copolymer membranes in application it was significant that a continuous preparation process can be realised combining spraying of thin layers and immersion of the thin block copolymer layers in water to ensure phase-separation. The system was tested using a solution of polystyrene-block-poly(4-vinylpyridine) diblock copolymer. A detailed examination of the spray pattern and its homogeneity was carried out. The limitations of this method are discussed.

Improved surface properties in spray-coated PU/TiO2/graphene hybrid nanocomposites through nonsolvent-induced phase separation

Herein, superhydrophobic and antibacterial polyurethane (PU) nanocomposite films loaded with titanium dioxide (TiO2) nanoparticles and graphene nanoplatelets were fabricated via a spray coating technique. The nonsolvent-induced phase separation (NIPS) process increased the films' roughness and hydrophobicity. In addition to the effective role of nonsolvent in phase separation, graphene also played the nucleating role and promoted the NIPS process. Based on scanning electron microscopy, atomic force microscopy, and optical microscopy results, it was found that the combinational use of TiO2, graphene, and nonsolvent leads to a hierarchical structure with a high extent of uniform surface roughness resulting in a superhydrophobic/roll-off behavior (water contact angle = 159°, sliding angle < 5°). The antibacterial activity was profoundly increased to ca. 99% against S. aureus and E. coli bacteria and was attributed to the induced superhydrophobicity and also the surface localization of TiO2 as a biocidal agent. An attempt was also made to present a mechanism for the NIPS process in the presence of TiO2 and graphene nanoparticles.