BSA Rejection Research Articles

Micro-patterned membranes prepared via modified phase inversion: Effect of modified interface on water fluxes and organic fouling

The introduction of patterns on a membrane-solute interface has been suggested as an effective method to tackle the reduced flux and fouling issues. Herein, the effectiveness of using spray-modified non-solvent induced phase separation (s-NIPS) to create a variety of micrometer-level structured interfaces is now studied. Circular, triangular and rectangular patterns with different dimensions were successfully created on polyacrylonitrile membranes. The rectangular pattern height was varied from 500 to 1500 µm, which resulted in a proportional increase in clean water permeance from 590 ± 47 L m−2 h−1 bar−1 to 1345 ± 108 L m−2 h−1 bar−1 respectively. This coincided with some BSA rejection loss for the highest patterns, indicating the fragile nature of these tall features. No significant rejection losses were found for the smaller pattern heights (145–250 µm) as compared to flat membranes, while fluxes more than doubled still. The critical pressure was also increased substantially for patterned membranes and showed a proportionality with the pattern height. These experimental findings were correlated with the reduced foulant adhesion due to a shear-induced slip boundary layer at the membrane-solution interface. Computational fluid dynamics simulations further showed higher shear stress values due to flow constriction within the membrane’s valley regions. These findings indicate the high potential of s-NIPS patterned membranes in long-term industrial applications by requiring less membrane area for a given application and reducing cleaning interventions.

Antifouling and photocatalytic properties of 2-D Zn/Al layered double hydroxide tailored low-pressure membranes

In this study, Zinc-Aluminium layered double hydroxide (LDH) was synthesized to fabricate membranes with superior hydrophilic and photocatalytic characteristics. The prepared LDH was extensively characterized and employed for the preparation of polyetherimide mixed matrix ultrafiltration (UF) membranes, which displayed > 96 % BSA rejection and a flux recovery ratio of 88 % even after 3-cycles. M-1 (UF, 1 wt. %) displayed a 94 % degradation of organic dye (methylene blue) in 120 min when irradiated with UV-light. Further, nanofiltration (NF) membranes were prepared by incorporating Zn/Al LDH into the polyamide (PA) layer during the in-situ interfacial polymerization to prepare thin-film nanocomposite membranes. MT-2 (NF, 0.4 wt.% LDH in PA layer) displayed improved hydrophilicity (lower water contact angle), > 94.5 % rejection of cationic dye (Methylene blue), > 91 % rejection of inorganic salt (CaSO4) with an 80 % flux recovery after long-term filtration. The LDH holds an auspicious potential to tune the properties of UF and NF membranes to be used in the treatment of industrial effluents.

Polyethersulfone-polyvinylpyrrolidone composite membranes: Effects of polyvinylpyrrolidone content and polydopamine coating on membrane morphology, structure and performances

Hydrophilic modification is a promising method to inhibit fouling formation on ultrafiltration membrane. In this work, different mass concentrations (1%–16%) of hydrophilic polyvinylpyrrolidone were incorporated into polyethersulfone (PES) membranes fabricated by none-solvent induced phase separation. Then, polydopamine (PDA) coating on the surface of prepared membrane was carried out at pH 8.5. The morphology and structure, surface hydrophilicity, permeation flux, BSA rejection, antifouling and stability performances of PES and PDA/PES modified membranes were investigated in detail. The results indicated that PDA was successfully attached onto the membranes. Membrane hydrophilicity was evaluated by water contact angle measurement. The contact angles of modified membranes reduced remarkably, suggesting that the membrane hydrophilicities were significantly increased. The results of filtration tests, which were done by dead-end filtration of bovine serum albumin solution, showed that the properties of permeability and fouling resistance were obviously improved by PDA modification. When polyvinylpyrrolidone mass content reached 10%, flux recovery ratio of modified membrane was up to 91.23%, and its BSA rejection were over 70%. The results of stability tests showed that the modified membranes had good mechanical stability and chemical stability. This facile fabrication procedure and outstanding performances suggested that the modified membranes had a potential in treating fouling.

Phenolphthalein polyethersulfone bearing carboxyl groups: Synthesis and its separation-membrane applications

A series of phenolphthalein polyethersulfones, containing varying contents of carboxyl groups, were synthesized via SN2 nucleophilic reaction. Structure of the prepared copolymers was confirmed by 1H NMR and FTIR. The phenolphthalein polyethersulfone comprising carboxyl groups exhibited excellent hydrophilicity and mechanical properties in the fabrication of ultrafiltration membrane. The properties of the membrane were measured using scanning electron microscopy and ultrafiltration membrane evaluator. The membrane showed superior ultrafiltration performance with a pure water flux of 399 (L·m− 2·h− 1), which was 1.9 times higher than that of the pristine phenolphthalein polyethersulfone. The pure water flux of the membrane with the pore-forming agent Tween 80 was up to 1082 (L·m− 2·h− 1), and its BSA rejection was up to 97% at 0.1 MPa. This work provided a new resin material with better performance for water treatment membrane.

Preparation and antifouling performance of thin inorganic ultrafiltration membrane via assisted sol-gel method with different composition of dual additives

A novel TiO2 thin film was prepared on the ceramic hollow fiber by the sol-gel method using poly(vinylpyrrolidone) (PVP) and polyvinyl alcohol (PVA) as additives. SEM images verified the formation of TiO2 layer with various thickness using different composition of titania sols. The effect of the PVP and PVA contents on the TiO2 sol properties, the separation and the antifouling performance of the ultrafiltration membranes were investigated thoroughly. When the contents of PVP and PVA were 1.0 wt% and 0.8 wt%, respectively, the resultant membrane showed a thickness of 0.55 μm with a pure water flux of 255 L m−2 h−1. In addition, the adherent foulant bovine serum albumin was applied to evaluate the antifouling performance. During the three fouling-recovery cycles, the flux recovery ratio and the flux decay ratio maintained about 99% and 30%. The BSA flux and rejection were still 169 L m−2 h−1 and 96.9% after the cycles, indicating a superior antifouling property.

In Situ Growth of Cationic Covalent Organic Frameworks (COFs) for Mixed Matrix Membranes with Enhanced Performances.

Covalent organic frameworks (COFs) are increasingly utilized as doping agents for the design of advanced ultrafiltration mixed matrix membranes, thanks to their prominent nanoporosity and excellent polymer compatibility. However, current strategies are largely limited in the complicated postaddition of neutral COF particulates. Herein, cationic COFs, namely, TpEB, with sizes down to ∼39 nm are in situ synthesized in polyacrylonitrile (PAN) solution as crystalline fillers for the production of highly permeable TpEB-PAN ultrafiltration membranes. After the condensation of monomer pairs, the growth of cationic TpEB crystallites is restrained due to the electrostatic interaction with negatively charged PAN chains, leading to the formation of a homogeneous TpEB-incorporated casting solution. During the subsequent nonsolvent-induced phase separation process, TpEB crystallites facilitate exchange between the solvent and the nonsolvent because of their hydrophilic and nanoporous nature, accelerating the rate of phase inversion to form a highly porous membrane surface. Thus-prepared TpEB-PAN membranes deliver a tight rejection of BSA with water permeance of up to 380 L m-2 h-1 bar-1, which is 35.6% higher than that of the original PAN membranes prepared without TpEB. The TpEB-PAN membranes also exhibit enhanced operation stabilities and fouling resistances. This in situ growth strategy suggests a new avenue for the preparation of advanced mixed matrix membranes.

Antifouling PES/Cu@Fe3O4 mixed matrix membranes: Quantitative structure–activity relationship (QSAR) modeling and wastewater treatment potentiality

Innovative mixed matrix membranes were fabricated from blending of both polyethersulfone (PES) and Cu@Fe3O4 core–shell nanostructure (NS) using facile wet phase inversion method. Brunner-Emmett-Teller (BET) surface area, Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDX), and scanning electron microscopy (SEM) analyses of Cu@Fe3O4 NS all confirmed that it was fabricated satisfactorily. Besides, a theoretical model is also constructed for studying the interaction between the proposed compounds. Theoretical results ensure that the feasibility of blending Cu and Fe3O4 with PES polymer, since it is indicating the formation of more reactive structures. This explains their incredible capacity for usage in water/wastewater treatment applications. Resultant data show also the hydrophilic nature of the formed blends agrees with the presented experimental results. Then, the as-prepared membranes were evaluated by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), SEM, atomic force microscopy (AFM), contact angle, thermal gravimetric analysis (TGA), and tensile strength techniques. The obtained characterization results demonstrated that the embedding of Cu@Fe3O4 core shell NS inside PES polymer matrix has caused various significant changes on morphology and membrane chemistry. Such changes are reflected in enhancements of both separation and antifouling features due to the porous and hydrophilic nature of Cu@Fe3O4 NS. Furthermore, enhancements in both thermal stability and the mechanical strength (36%) of the modified membrane compared to the bare PES membrane, proving the existence of a strong interaction resulting from hydrogen bonding between hydroxyl group of Cu@Fe3O4 NS and sulfonic group of PES polymer matrix interface as demonstrated from modeling results. In terms of performance, water flux has been boosted 4-fold after adding small quantities of Cu@Fe3O4 to PES polymer while keeping BSA and MB rejection high (up to 90%) which explains the potentiality of the fabricated UF membranes for wastewater treatment.

Metal organic framework nanoparticles loaded- PVDF/chitosan nanofibrous ultrafiltration membranes for the removal of BSA protein and Cr(VI) ions

The UiO-66 NH2 and ZIF-8 metal organic framework nanoparticles (NMOFs) were incorporated into the polyvinylidene fluoride (PVDF) nanofibrous membrane. Then, the chitosan nanofibers were coated on the PVDF nanofibers to produce the PVDF/chitosan nanofibers. The performance of synthesized PVDF/NMOFs single layer and PVDF/chitosan/NMOFs two layers nanofibrous membranes was investigated for BSA protein molecules and Cr(VI) ions separation via ultrafiltration membrane process. The potential of synthesized nanofibers was also examined for BSA and Cr(VI) adsorption in a batch system. The characteristics of synthesized nanofibrous membranes were determined using SEM, EDX, TGA, BET, porosity and water contact angle measurements. The PVDF/chitosan nanofibrous membrane containing 20 wt% UiO-66-NH2, exhibited the maximum water flux of 470 L.m−2 h−1, 98.1% BSA rejection and 95.6% Cr(VI) rejection. The nanofibers were sucessfully regenrated for five adsorption-desorption cycles. The maximum sorption capacities of BSA and Cr(VI) were found to be 574.5 and 602.3 mgg−1, respectively. The obtained results revelaed the high potential of PVDF/chitosan/UiO66-NH2 nanofibers for membrane separation and adsorption of BSA molecules and Cr(VI) ions.

Synthesis of patterned PVDF ultrafiltration membranes: Spray-modified non-solvent induced phase separation

Patterned membranes have been attractive for the mitigation of fouling in membrane processes, but existing patterning methods are rather in-effective in terms of scalability and performance due to pore-size reduction and patterning at the non-selective membrane side. Polyvinylidene fluoride (PVDF) was used now to synthesize patterned membranes via the spray-modified non-solvent induced phase separation (s-NIPS), a recently developed technique that avoids the current drawbacks of patterned membranes. However, PVDF intrinsically suffers from a slow phase separation, while very fast fixation of the patterns is crucial with this synthesis method. Therefore, the casting solution was optimized towards an accelerated process of phase inversion by systematically studying the effect of polymer concentration, addition of poly(vinylpyrrolidone) (PVP), addition of non-solvent (H2O) and use of different casting solvents for adequate patterning of the membranes. SEM analysis and pure water permeance of the synthesized membranes assessed the homogeneity and pattern formation for each membrane. The most optimal casting solution composition comprised of 20 wt% PVDF, 6.7 wt% PVP and 1 wt% H2O which resulted in homogenously patterned PVDF membranes. The optimized patterned membrane showed a 9 fold increase in PWP as compared to the reference flat membrane thanks to the addition of PVP and H2O as well as the additional surface area. In the filtration of proteins, the water permeance of the membranes improved drastically (+140%) upon patterning with only a moderate loss of BSA rejection (from 90% to 71%) as compared to the corresponding flat membrane. Realisation of patterning via the s-NIPS method resulted in a higher effective membrane surface area combined with an increased membrane porosity. Reduced flux decline of the patterned membrane (52%) as compared to the flat membrane (62%) during continuous BSA filtration also proved the anti-fouling potential of the created patterns.

High-performance chlorinated polyvinyl chloride ultrafiltration membranes prepared by compound additives regulated non-solvent induced phase separation

To enable wider deployment of ultrafiltration (UF) membrane technology, novel advanced membrane materials are still highly desired. Chlorinated polyvinyl chloride (CPVC) shares most of the outstanding features of polyvinyl chloride (PVC) and possesses improved thermal stability, indicating a promising material for UF membrane. To date, however, the separation performance of the current CPVC UF membranes is far below the requirements for application. In this study, propylene glycol and polyoxyethylene-20-sorbaitan monolaurate (Tween-20) were selected as compound additives to manipulate the structure and separation performance of CPVC membrane fabricated by the non-solvent induced phase separation process. The results demonstrated that the synergistic effect of compound additives led to instantaneous demixing to increase the ratio of polymer lean phase in the initial casting film, and the rapid precipitation fixed the phase separation structure immediately. Consequently, the prepared membranes possessed improved porosity and pore size uniformity. The obtained CPVC UF membranes exhibited a high pure water flux up to 955.2 L m-2 h-1·bar-1 with a BSA rejection above 95.0%, which is 11 times higher than CPVC membrane fabricated without additive and comparable to that of commercial UF membranes. In addition, thanks to the more uniform pore size distribution and smooth top surface, the obtained CPVC membranes also exhibited good antifouling performance. Moreover, the CPVC UF membrane showed good thermal stability and reuse performance, which would facilitate its post-functionalization and practical application.

Catalytic performance of polyvinylidene fluoride (PVDF) supported TiO2 additive at microwave conditions

TiO2 is widely used additive material in order to improve properties of filtration membranes. As far as its contribution to filtration performance, TiO2 acts as catalytic agent.In this study, catalytic activity of TiO2 added PVDF flat sheets (membranes) prepared by phase inversion method, and they were performed on benzyl alcohol oxidation at microwave radiation. Structure, thermal behaviors and morphology of samples were investigated by FTIR, TG-DTA and SEM analysis respectively. Hydrophilicity was determined by contact angle measurements. Interaction between TiO2and PVDF chain was evidenced. TiO2 added PVDF membranes had improved filtration and rejection performance. 32.4% BSA rejection was obtained with composites while it was 7.5% of pristine membrane. 93.86% conversion and 56% selectivity were obtained with composites in microwave-assisted batch reactor. Decomposition of polymer increased when 6% additive due to catalytic effect of TiO2 then, it decreased with further loading.Detailed evidences were obtained by activation energies (Ea) of decomposition calculated by Kissinger method. Microwave-assisted catalytic effect of TiO2inside polymeric matrix promise to obtain fast, high yielded and disposable membrane materials for catalytic reactors to in-situ production of fine chemicals.

Improved water flux and antifouling properties of cardo poly(aryl ether ketone) ultrafiltration membrane by novel sulfobetaine polyimides additive

To improve the water flux and antifouling properties of cardo poly(aryl ether ketone) (PEK-C) ultrafiltration membrane, a novel amphiphilic zwitterionic polymer sulfobetain polyimide (sPI) is introduced into the membrane matrix. A series of PEK-C blend membranes were prepared via non-solvent induced phase separation. Sulfobetain polyimide can migrate and enrich on the surface of membranes/pores due to hydrophilic-hydrophobic structure transformation, which achieved the pore-forming and antifouling dual function. Surface chemical compositions and wettability of the membrane are characterized. The blend membrane sPI/PEK-C membranes exhibited significantly pure water flux (up to 220.65 L/m2h), which was almost 3 times that of the pristine PEK-C membrane (73.68 L/m2h), whereas the BSA rejection of sPI/PEK-C blend membrane was still maintained at a high level (99.1%). Moreover, the sPI/PEK-C blend membranes exhibited improved antifouling performance. Specifically, the higher flux recovery ratio (FRR) (up to 91.56%) and low irreversible fouling (Rir) (15.35%) after three sequential dead-end filtration cycles were observed. This could be attributed to the formation of the hydration layer near the surface via hydrogen bond between water molecules and the hydrophilic sulfobetain groups in zwitterionic polymer. Overall, the novel zwitterionic copolymer is a promising candidate for developing antifouling membrane due to its high water flux and long-term stability in the membrane.

The hierarchical flower-like MoS2 nanosheets incorporated into PES mixed matrix membranes for enhanced separation performance

Membrane fouling is an issue of concern due to the hydrophobic properties of polyethersulfone (PES) membrane when applied in water treatment. In this work, a facile hydrothermal method was utilized to synthesize hierarchical flower-like structured molybdenum disulfide nanosheets (HF–MoS2 NSs) that then incorporated into PES membranes as composite membranes. We characterized their permeability, the separation performance, the antifouling performance, and the antibacterial activity systematically. Results showed that composite membranes exhibited a better pure water flux (286 LMH/bar) at the HF–MoS2 NSs content of 0.4 wt%, which was 1.8 times higher than the control membrane. Also, composite PES membranes achieved 98.2% and 96.9% rejection of BSA and HA in comparison with the control PES membrane (87.3%, and 84.5%, respectively). Compare to the control PES membrane, the flux recovery ratio of the composite membrane increased from 69% to 88% for BSA fouling and increased from 84% to 93% for HA fouling. The retention rate for the organic dyes also improved slightly after HF–MoS2 NSs incorporation into the membrane. Additionally, the composite membranes exhibited a relatively high antibacterial activity against E. coli and B. subtilis with antibacterial rates of 67.8% and 82.5%, respectively. In conclusion, HF–MoS2 NSs incorporated composite membranes were shown to have outstanding filtration performance and could be a promising candidate for practical application in water filtration.

Improving the hydrophilicity of polyethersulfone membrane by the combination of grafting technology and reverse thermally induced phase separation method

AbstractIn this work, surface grafting modification technology was combined with reverse thermally induced phase separation (RTIPS) method in order to improve the structure and permanent hydrophilicity of polyethersulfone (PES) membranes. Acrylic solution with different concentrations was grafted on the surface of PES membranes while grafting temperature and grafting time were also varied. The modified PES membranes were characterized in all aspects. Attenuated total reflectance Fourier transform‐infrared confirmed successful modification of the PES membrane by grafting acrylic acid. Scanning electron microscopy revealed that homogeneous porous top surface as well as spongy‐like cross‐section structure appeared in the membrane by RTIPS procedure. Moreover, porosity was affected by changes of acrylic acid concentration, grafting temperature, and grafting time. Atomic force microscopy showed that grafting acrylic acid gave a reduction in roughness of PES membrane. Combined with the decreased values of contact angle, the hydrophilicity and antifouling performance of the PES membrane were improved. The pure water flux and BSA rejection rate of the grafted PES membranes were remarkably improved for pure PES membrane and attained a maximum, which was 1,646.24 L/(m2h) and 94.5%, respectively. The long‐term test demonstrated that grafting membranes exhibited outstanding elevated water flux recovery ratio (>85%).

Effect of oxidation degree of GO nanosheets on microstructure and performance of polysulfone-GO mixed matrix membranes

Graphene oxide with increasing degree of oxidation (GO-x) were incorporated in polysulfone (PSF) mixed-matrix ultrafiltration membranes. Synthesized GO-x were characterized for average particle size by AFM and DLS method; oxygen functionalities and nanostructure properties by XPS, FT-IR, XRD, Raman analysis, TEM, and elemental analysis; surface charge by zeta potential. Increasing oxidation degree, increased the proportion of carbonyl functional groups, exfoliation, lowered zeta potential and particle size in GO. GO-x with higher oxidation degree showed significantly improved dispersibility in N-methyl-2-pyrrolidone and polysulfone matrix. Blending hydrophilic GO-x, enhanced phase-separation kinetics improving porosity, tensile strength, permeability, protein rejection, and fouling resistance of membranes. With the increase in the oxidation degree of the matrix, contact angle and surface charge on the membranes decreased. 2%-GO-7/P membrane showed permeate flux of 352 kg m−2 h−1 bar−1 while, 1%-GO-7/P membranes acquired permanent negative charge and displayed permeability of 250 kg m−2 h−1 bar−1 with BSA rejection of about 97%, compared to control membrane permeability of 102 kg m−2 h−1 bar−1 with BSA rejection of about 91%. Thus, the membrane flux-rejection trade-off is overcome. 1%-GO-7/P membrane displayed exceptional flux recovery of over 99% on simple DI water flushing. The superior performance of GO-x/P membranes is attributed to faster diffusion rate of water across GO matrix over that through the polymer solution, which increased the number of thermodynamic instabilities giving higher rate of phase inversion resulting in narrow pore size distribution and higher pore density, demonstrating simple approach for enhancing performance of UF membranes.

Pressure-assisted in-depth hydrophilic tailoring of porous membranes achieving high water permeability, excellent fouling resistance and superior antimicrobial ability

Biofouling occurs at any wet structure including external surface and internal pore walls. Although the external surface biofouling can be limited by conventional methods, mitigating biofouling on the internal pore walls is still challenging. To address this issue, a novel pressure-assisted strategy was designed to tailor porous membrane surface for forming an in-depth multifunctional coating layer. The built ultrathin coating (ca. 26.3 nm) with hydrated and antimicrobial functions emerged on both external surface and inner pore walls of membranes via π-π interaction, hydrogen bonding and entanglements under unique pressure assistance. Such in-depth surface tuned porous membrane can achieve high separation performance (water flux ~ 519.7 L m−2 h−1, BSA rejection ~95.1%), excellent fouling-resistance (FRR~94.2%) and superior antimicrobial effects (>99%) simultaneously. Our pressure-assisted in-depth modification strategy can open a new door to constructing omni-directional anti-fouling membrane towards highly efficient water treatments, and inspire abundant porous material modifications for diverse applications such as marine anticorrosion, adsorption separation and drug controlled release.

Improvement of PVDF nanofiltration membrane potential, separation and anti-fouling performance by electret treatment

Electret treatment was a simple method to enhance the charge-electrode properties of polyvinylidene fluoride (PVDF) materials due to the increase of space charge and polarization charge of PVDF materials. The polarization charge was due to the electric dipole orientation change in loose nanofiltration PVDF membrane, which increased the electric dipole moment and improved the polarity of surface potential. Importantly, electret charges were less affected by ambient humidity. Therefore, the electret treatment could improve the surface negative potential of loose nanofiltration PVDF membrane, so as to improve its anti-fouling performance under certain conditions. Based on the above theoretical analysis, the influence and mechanism of the electret treatment on the surface potential, morphology, structure, hydrophilicity and anti-pollution performance of PVDF membrane were studied in this manuscript. When the electret time was 7.5 min and the electret voltage was 30 kV, the surface negative potential was the highest. The content of β phase crystals was 39.1%, which was 12.18% higher than that of untreated membrane. In addition, the surface morphology of PVDF membrane did not change significantly, but the water contact angle decreased slightly, and the pore size increased by 0.36–0.75 nm. Importantly, the flux and the rejection of dye and BSA increased to some extent, and the maximum rejection rate and water flux were increased by 10.34% and 20.25%, respectively. Through the cyclic filtration test and analysis, the anti-fouling performance of membrane was increased due to electrostatic repulsion.

Membrane modification with semiconductor diode laser to reduce membrane biofouling for external MBR system and modelling study

Membrane biofouling is one of the major problem for membrane-based wastewater treatment. In this study, we used laser technology to modify ultrafiltration polyethersulfone (UP150) membrane in order to decrease membrane biofouling. Semiconductor laser diodes with different wavelengths of 405, 520, and 658 nm and different power density of 1.5, 2.0, 2.5 mW were used to improve membrane structure against biofouling. The pure water permeability (Lp), contact angle, porosity, and the average pore size were determined for pristine and modified membranes. Lp value of the pristine UP150 membrane (721.18 L/(m2 h bar)) was higher than modified membrane (22.08 L/(m2 h bar)). The contact angle values were presented that hydrophilicity was decreased from 75.1° to 61.2° for 2 h at 2.5 mW laser irradiation. Membrane porosity increased from 63.2 to 67.7%; however, the average pore size decreased from 88 to 23 nm after laser modification. The impact of laser wavelength and irradiation time on the rejection of protein (bovine serum albumin, BSA) and the fractions of soluble microbial products (as protein and carbohydrate) was systematically investigated. A maximum rejection of 32.17% and 41.86% was obtained for carbohydrate and protein when activated sludge was filtrated through modified membrane. Moreover, 100% BSA rejection was obtained by the modified membrane when BSA solution was filtrated. The modified membranes were extensively characterized by AFM, FTIR, SEM, and mechanical strength test analyses to observe morphological changes of the membrane before and after modification. The results showed that laser irradiation was changed the membrane morphology. Our results presented that laser-modified membranes with red wavelength changed the pore size, porosity, hydrophilicity of the pristine membrane. Also, membrane surface melting was revealed with a study called “Thermal Analysis on Membrane Surface Modelled 3D” using Solidworks CAD/CAM software. The results obtained from Solidworks thermal analysis was presented with 98.7% ratio of successful approach.

Preparation and characterization of novel nanoporous SBA-16-COOH embedded polysulfone ultrafiltration membrane for protein separation

Polysulfone ultrafiltration membrane was modified by novel nanoporous SBA-16-COOH during the membrane preparation via the phase inversion. The pure water flux and bovine serum albumin (BSA, as the foulant) flux were measured at 2 bar and the membranes’ antifouling behavior were analyzed. The membranes showed higher water flux after SBA-16-COOH addition up to 2 wt% and after that the flux slightly decreased which is attributed to the aggregation of SBA-16-COOH particles at the higher concentrations. SBA-16-COOH addition improved the surface hydrophilicity and led to elongated finger-like pores within the membranes cross section structure. The water flux after BSA flux was still higher than the one before BSA, thereby SBA-16-COOH addition resulted in better antifouling properties. In terms of BSA rejection, the nanocomposite SBA-16-COOH-based membranes outperform the pristine PSf membrane with rejection values up to 98.9%. The water contact angle confirmed the enhanced hydrophilicity of the membranes’ surface due to COOH functional groups of the nanomaterials which led to a higher permeability and an enhanced fouling resistance.

Improving the perm-selectivity and anti-fouling property of UF membrane through the micro-phase separation of PSf-b-PEG block copolymers

PSf-b-PEG block copolymers with different PEG contents were synthesized to fabricate the highly perm-selective and anti-fouling ultrafiltration (UF) membranes. PEG homopolymer was also blended into the polysulfone casting solutions to fabricate the control (PSf/PEG blend) membranes. The membrane pore structure, surface properties and separation performances of PSf-b-PEG block copolymer membranes and PSf/PEG blend membranes were investigated to identify the role of PEG block for the pore formation. Our results find that the higher PEG content in the PSf-b-PEG block copolymer and in the PSf/PEG blend system was favorable to form more pores and thinner top skin layer with the slightly larger pore size and the higher MWCO of the fabricated membranes. But under the same content, PEG in the block copolymer could help to generate more pores but with similar pore size than PEG in the blend system during the phase-inversion process, which is because of the micro-phase separation of PSf block and PEG block. The fabricated PSf-b-PEG21 (PSf-b-PEG having 21 wt% PEG) membrane had a high water permeation coefficient of 980.0 ± 33.0 LMH/bar and a high BSA rejection above 98%, succeeding the current perm-selectivity upper-bound of the reported polymeric UF membranes. Antifouling experiments confirmed that the PSf-b-PEG21 membrane exhibited a slow and less flux decline during the fouling stage, but a fast and high flux recovery after the backwash cleaning. Our work provides some insights on the relationship of PSf-b-PEG block copolymer composition and membrane structure-separation properties.