The effect of sulfonated polysulfone on the compatibility and structure of polyethersulfone-based blend membranes

Improving the bioactivity of cellulose acetate hemodialysis membranes through nanosilver modification

The effectiveness and safety of hemodialysis can be hindered by protein accumulation, mechanical instability of membranes and bacterial infection during the dialytic therapy. Herein, we show that cellulose acetate membranes modified with the low-fouling polymers (namely polyvinylpyrrolidone and polyethylene glycol), followed by the in situ reduction of different densities of silver oxide(I) nanoparticles, can effectively address these limitations. These improvements comprise the enhanced resistance to the protein fouling, improved antimicrobial capabilities against S. aureus, increased selectivity, and thermal stability and mechanical strength. The nano-enhanced membranes showed an improved albumin rejection rate of approximately 90 %, and the creatinine clearance rate ranged between 90 and 94 %. Our findings demonstrate that nanosilver-modified membranes can be readily prepared from precursor solutions to act as robust, biocompatible, and hydrophilic hemodialysis membranes with controlled bacteriostatic potential, antifouling properties and high toxin clearance.

Fabrication and Characterization of PPSU/PES Blend Nanofiltration Membrane via VIPS‐NIPS Method for Effective Dye Rejection

Industrial effluents, including dyes, pose a threat to the environment and human health, as they are resistant to reacting with oxygen; therefore, they are rarely biodegradable. Among the various processes, nanofiltration is an attractive process for separating dyes from water due to its economic efficiency. This work represents the fabrication of poly (phenyl sulfone) (PPSU)/poly (ether sulfone) (PES) blend nanofiltration membranes through vapor‐induced phase separation (VIPS) followed by immersion precipitation. The influence of polymer blend, exposure time, and coagulation bath composition on membrane characteristics and performance was studied. Results illustrate that an increment in exposure time caused a thinner top layer and changed the cross‐section morphology from finger‐like to sponge‐like. At PPSU:PES = 50:50 blend ratio, the pore radius significantly got larger than the neat polymers' fabricated membranes. The addition of N‐methyl‐2‐pyrrolidone (NMP) in the coagulation bath causes the formation of smaller finger‐like voids at the top layers and a sponge‐like structure in the sub‐layers of membranes. The optimal conditions for the nanofiltration membrane were determined at 28 s VIPS time, an equal ratio of polymers, and pure water as the coagulation bath. Under these conditions, the distilled water permeability and Rose Bengal rejection were determined as 63.6 L/m2 h and 77.11%, respectively.

Improving Hemocompatibility of Polysulfone Membrane by UV-Assisted Grafting of Sulfonated Chitosan

The most prevalent type of hemodialysis membrane is polysulfone (PSf). However, due to inadequate biocompatibility, it significantly compromises the safety of dialysis for patients. In this study, we modify the surface of the PSf membrane with 2,4-dihydroxybenzophenone (DBPh) groups to serve as anchoring sites during UV irradiation. Subsequently, a tailored sulfonated dihydroxy propyl chitosan (SDHPCS) is grafted onto the modified PSf membrane to compensate for the deficiencies in hydrophilic additives. The modified PSf membrane exhibits outstanding hydrophilicity and stability, as demonstrated by its characterization and evaluation. This paper focuses on investigating the interaction between platelet membrane formation, protein adsorption, and anticoagulant activity. The results show that the modified PSf membrane exhibits remarkable enhancement in surface hydrophilicity, leading to a significant reduction in protein and platelet adsorption as well as adhesion.

Poly(arylene ether)s-Based Polymeric Membranes Applied for Water Purification in Harsh Environment Conditions: A Mini-Review

Confronting the pressing challenge of freshwater scarcity, polymeric membrane-based water treatment technology has emerged as an essential and effective approach. Poly(arylene ether)s (PAEs) polymers, a class of high-performance engineering thermoplastics, have garnered attention in recent decades as promising membrane materials for advanced water treatment approaches. The PAE-Based membranes are employed to resist the shortages of most common polymeric membranes, such as chemical instability, structural damage, membrane fouling, and shortened lifespan when deployed in harsh environments, owing to their excellent comprehensive performance. This article presents the advancements in the research of several typical PAEs, including poly(ether ether ketone) (PEEK), polyethersulfone (PES), and poly(arylene ether nitrile) (PEN). Techniques for membrane formation, modification strategies, and applications in water treatment have been reviewed. The applications encompass processes for oil/water separation, desalination, and wastewater treatment, which involve the removal of heavy metal ions, dyes, oils, and other organic pollutants. The commendable performance of these membranes has been summarized in terms of corrosion resistance, high-temperature resistance, anti-fouling properties, and durability in challenging environments. In addition, several recommendations for further research aimed at developing efficient and robust PAE-based membranes are proposed.

Effect of Polyethylene Glycol Additive on the Structure and Performance of Fabric-Reinforced Thin Film Composite

Fabric-reinforced thin film composite (TFC) membranes exhibit outstanding mechanical durability over free-standing membranes for commercial applications. In this study, polyethylene glycol (PEG) was incorporated to modify the polysulfone (PSU) supported fabric-reinforced TFC membrane for forward osmosis (FO). The effects of PEG content and molecular weight on the structure, material property and FO performance of the membrane were investigated comprehensively, and the corresponding mechanisms were revealed. The membrane prepared by using 400 g/mol PEG exhibited better FO performances than those of membranes with 1000 and 2000 g/mol PEG, and 20 wt.% was demonstrated to be the optimal PEG content in the casting solution. The permselectivity of the membrane was further improved by reducing the PSU concentration. The optimal TFC-FO membrane had a water flux (Jw) of 25.0 LMH using deionized (DI) water feed and 1 M NaCl draw solution, and the specific reverse salt flux (Js/Jw) was as low as 0.12 g/L. The degree of internal concentration polarization (ICP) was significantly mitigated. The membrane behaved superior to the commercially available fabric-reinforced membranes. This work provides a simple and low-cost approach in the development TFC-FO membrane and shows great potential in the large-scale production for practical applications.

Delayed Solvent-Nonsolvent Demixing Preparation and Performance of a Highly Permeable Polyethersulfone Ultrafiltration Membrane

Membrane performance optimization is a critical preparation step that ensures optimum separation and fouling resistance. Several studies have employed additives such as carbon and inorganic nanomaterials to optimize membrane performance. These particles provide excellent results but are rather costly, unstable and toxic to several biological organs. This study demonstrated that performance enhancement can also be achieved through delayed solvent−nonsolvent demixing during phase inversion membrane preparation. The rate of solvent−nonsolvent demixing was delayed by increasing the concentration of the solvent in the coagulation bath. This study employed synthetic and real water samples and several analytical techniques to compare optimized performances and properties of membranes prepared in this study with that of nanoparticle-embedded membranes in the literature. Pure water flux and BSA rejection of the membranes prepared in this study were comparable to those of nanoparticle embedded membranes. This study also shows the influence of delayed solvent−nonsolvent demixing on membrane properties such as morphology, wettability, surface roughness and porosity, thereby showing the suitability of the technique in membrane optimization. Furthermore, fouling studies showed that membranes prepared in this study have high flux recovery when fouled by humic acid feed water (>95%) and above 50% flux recovery with real water samples.

Synthesis and characterization of sulfonated poly(eugenol-co-allyleugenol) membranes for proton exchange membrane fuel cells

The research of sulfonated eugenol-allyleugenol copolymer (SPEAE) based membrane for fuel cell from eugenol derivate had been conducted. First, eugenol was reacted with various weights of allyl eugenol to form eugenol-allyleugenol copolymer (PEAE). Determination of the optimum composition of PEAE was done by testing the swelling properties. Then, PEAE was sulfonated using concentrated sulfuric acid with time variations of 1, 2, 3, 4, and 5 h to form SPEAE. The SPEAE produced was tested for the degree of sulfonation, water uptake, cation exchange capacity, and membrane proton conductivity. In addition, the characteristics of the PEAE and SPEAE copolymer membranes were also analyzed using FTIR spectrophotometers, 1H-NMR, TGA, and DSC. The results showed that the copolymerization of eugenol:allyleugenol (EG:AEG) with a ratio of 10:1 gave the lowest swelling degree. The best SPEAE copolymer was obtained from sulfonation for 2 h with yield, degree of sulfonation, water absorption value, proton conductivity, and cation exchange capacity of 90.6%, 12.87%, 50.7%, 1.83 × 10^-5 S cm^-1 and 0.356 meq/g, respectively. FTIR analysis shows the formation of PEAE with the loss of the vinyl eugenol groups used to form the polymer and shows the formation of SPEAE in the presence of sulfonate groups from the sulfonation reaction. ¹H-NMR also confirmed the presence of the PEAE and SPEAE copolymers. In addition, analysis of thermal properties with TGA and DSC also showed that sulfonate treatment could improve membrane stability.

Ultrastable Super-Hydrophobic Surface with an Ordered Scaly Structure for Decompression and Guiding Liquid Manipulation

Directional droplet manipulation is very crucial in microfluidics, intelligent liquid management, etc. However, excessive liquid pressure tends to destroy the solid-gas-liquid (SAL) composite interface, creating a highly adhesive surface, which is not conducive to liquid transport. Herein, we propose a strategy to enhance the surface durability, in which the surface cannot withstand liquid pressure only by "blocking" but must instead guide liquid transport for "decompression". Learning from the water resistance of water strider legs and the drag reduction of shark skin, we present a continuous integrated system to obtain an ultrastable super-hydrophobic surface with a highly ordered scaly structure via a liquid flow-induced alignment method for lossless unidirectional liquid transport. The nonwetting scaly structure can both buffer liquid pressure and drive droplet motion to further reduce the vertical pressure of the liquid. Moreover, droplets can be manipulated unidirectionally using a voice. This work could aid in manufacturing scalable anisotropic micro-nanostructure surfaces, which inspires efforts in realizing lossless continuous liquid control on demand and related microfluidic applications.

Molecular Compatibility and Hydrogen Bonding Mechanism of PES/PEI Blends

The development of high-performance polymer membranes has sparked a lot of attention in recent years. Polymer blending is a potential method of modification. A limitation, however, is the compatibility of blends at the molecular level. In this investigation, polyethersulfone/polyetherimide hollow fiber membranes were prepared by the solution blending method. Compatibility, hydrogen bonding, crystallinity, microstructure, hydrophilicity, mechanical properties, and transmissibility of blended membranes were also characterized. The compatibility and hydrogen bonding action of the two components were confirmed by DSC, FTIR, XPS, and XRD. The structure exhibits a C−H···O interaction motif with the sulfone group acting as a hydrogen bond acceptor from a methyl C−H donor. The π–π stacking between the two polymers arranged molecules more orderly, resulting in enhanced intermolecular interactions. Compared to polyethersulfone hollow fiber membranes, the hydrophilic, mechanical properties, and rejection rate of the blended membranes are more effectively enhanced. Self-assembly of the host polymer with a polymer capable of forming hydrogen bonds to construct controllable blends is a crucial and proven method.

Metal organic framework UiO-66 incorporated ultrafiltration membranes for simultaneous natural organic matter and heavy metal ions removal

In this work, a new type of UiO-66 incorporated polysulfone (PSf) ultrafiltration (UF) membranes was fabricated to enhance antifouling properties and heavy metal ions removal efficiency. The UF membranes incorporating different loadings of the UiO-66 filler were prepared via the classical phase inversion process. These membranes unveiled enhanced hydrophilicity, porosity, water uptake, zeta potential, mechanical strength, permeability, and HA removal ratios due to the incorporation of hydrophilic UiO-66 fillers. Particularly, HA rejection ratios were observed to be approximately 93% for all the modified membranes, which was attributed to electrostatic repulsion interactions between the hydrophilic groups of HA and UiO-66. Moreover, the antifouling abilities of the modified membranes were evaluated and found to be much better with a high flux recovery ratio (FRR) of about 88% when compared to the blank PSf membrane (only around 34%). Moreover, the UiO-66 incorporated membranes were highly-effective in the removal of contaminants like heavy metal ions (Sr²⁺, Pb²⁺, Cd²⁺, and Cr⁶⁺) and HA at the same time. Overall, the PSf UF membranes incorporating UiO-66 opened up a new avenue to enhance the membrane hydrophilicity, permeability, antifouling properties as well as heavy metal ions removal abilities.

Preparation of Small-Pore Ultrafiltration Membranes with High Surface Porosity by In Situ CO2 Nanobubble-Assisted NIPS

The fabrication of ultrafiltration (UF) membranes with a small pore size (<20 nm) and high surface porosity is still a great challenge. In this work, a nanobubble-assisted nonsolvent-induced phase separation (BNIPS) technique was developed to prepare high-performance UF membranes by adding a tiny amount of CaCO₃ nanoparticles into the casting solution. The phase inversion occurred in a dilute-acid coagulation bath to simultaneously generate CO₂ nanobubbles, which regulated the membrane structure. The effects of the nano-CaCO₃ content in the casting solution on the structure and performance of poly(ethersulfone)/sulfonated polysulfone (PES/SPSf) UF membranes were studied. The UF membrane prepared from a casting solution with 0.3% nano-CaCO₃ achieved a surface porosity of 12%, a pore diameter of 10.2 nm, and a skin-layer thickness of 80.3 nm. The superior structure of the UF membrane was mainly attributed to the in situ generation of CO₂ nanobubbles because the CO₂ nanobubbles were amphiphobic to water and solvents to delay the phase inversion time and acted as nanosize porogens. The produced membrane showed an unprecedented separation performance, achieving a pure water permeance of up to 1128 L·m^-2·h^-1·bar^-1, 2.5 fold that of the control membrane. Similarly, a high bovine serum albumin rejection of above 99.0% was obtained. The overall permeability and selectivity were better than those of commercial and other previously reported UF membranes. This work provides insight toward a simple and cost-effective technique to address the trade-off between pure water permeance and solute rejection of UF membranes.

Fabrication of an antifouling PES ultrafiltration membrane via blending SPSF

Sulfonated polysulfone (SPSF) with different sulfonation degrees (10%, 30%, and 50%) was added to polyethersulfone (PES) to improve the separation and antifouling performance of polyethersulfone ultrafiltration membranes. The PES/SPSF blend ultrafiltration membrane was prepared by the non-solvent induced phase inversion method (NIPS), and the effect of sulfonation degree on the ultrafiltration performance was studied. The compatibility of SPSF and PES was calculated by the group contribution method, and confirmed by differential scanning calorimetry (DSC). The morphology and surface roughness of the membrane were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), the chemical composition of the membrane was analyzed by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR), and the permeability and anti-fouling performance of the blend membrane were studied through filtration experiments. The research shows that the flux and anti-fouling performance of the blend membrane have been improved after adding SPSF. When the sulfonation degree of the SPSF is 30%, the pure water flux of the blend membrane can reach 530 L m⁻² h⁻¹, the rejection rate of humic acid (HA) is 93%, the flux recovery rate of HA increases from 69.23% to 79.17%, and the flux recovery rate of BSA increases from 72.56% to 83%.

The chemical structures of (a) PES and (b) SPSF.

Multi-ionic electrolytes and E.coli removal from wastewater using chitosan-based in-situ mediated thin film composite nanofiltration membrane

This work presents the experimental investigation of flat sheet composite nanofiltration membrane synthesized with chitosan nanoparticles through interfacial polymerization of piperazine with trimesoyl chloride on polyethersulfone/sulfonated polysulfone substrates. The synthesized membrane was tested in wastewater treatment containing inorganic salts and E.Coli. Single binary electrolyte solution of KCl, MgCl₂, MgSO_4, and Na₂SO₄, ternary electrolyte solution, containing a combination of MgCl₂ and MgSO₄, KCl and MgCl₂ and quaternary electrolyte solution of KCl, MgCl_2, and MgSO₄ as feed were treated in crossflow membrane cell for the water flux and species rejection in the permeate under operating pressure up to 0.5 MPa. The rejection of Na¹⁺, K¹⁺, Mg²⁺, Cl^1-, and SO₄^2- was observed to be 81, 28, 87, 96, and 98%, respectively with an average water flux up to 214 ± 10 L m⁻².hr⁻¹ in the permeate for the binary electrolyte solution. Similarly, the rejection for K¹⁺, Mg²⁺, Cl^1- and SO₄^2- was noted to be 33, 94, 97, and 99%, respectively, for ternary electrolyte solution with an average water flux up to 211 ± 10 L m^-2.hr^-1. The quaternary ion system in the feed resulted in an average water flux up to 198 ± 12 L m⁻².hr⁻¹ with the rejection of K⁺, Mg⁺², Cl^- and SO₄^-2 as 35, 87, 96, and 99%, respectively. The model feed solution of E. coli after passing through the membrane achieved an E. coli rejection (99%) with water flux up to 220 L m^-2.hr^-1.

Surface water treatment for production of potable water by coagulation/filtration/nanofiltration membranes hybrid system

Providing potable water will be a challenge for humanity over the next years. In this research, water samples from the Gamasiab River (Iran) were purified to achieve drinking water by applying coagulation, conventional filtration in combination with the nanofiltration process. By using poly aluminum chloride as a coagulant, the turbidity decreased by 96.4%. The turbidity and COD decreased by 98.82% and 32.7%, respectively, via passing the effluent through the activated carbon. Membranes were made of polyethersulfone (PES). Cesium hydrogen phosphotungstic acid (Cs_0.5 H_2.5 PW₁₂ O₄₀ as CsPW) nanoparticles were incorporated into the polymer matrix to improve the hydrophilicity. The morphology of membranes was studied using the FE-SEM and AFM. The pure water flux and contact angle for the sulfonated PES with 1.5 wt.% CsPW were 51.9 kg/m²  h and 55.49 °, respectively. The percentage of the turbidity, conductivity, TDS, and COD removal was found to be 99.9, 89.3, 89.3, and 86.6%, respectively, after the hybrid process. The removal of calcium, magnesium, nitrate, chloride, sodium, sulfate, and bicarbonate ions was 90.5, 83.4, 87.9, 60.7, 49, 86, and 80.5%, respectively. Based on these results, the river water meets the standards for drinking water after being purified by applying the aforementioned coagulation/filtration and nanofiltration processes. PRACTITIONER POINTS: The treatment of the Gamasiab River (Iran) was selected for this study to produce potable water. A hybrid systematic coagulation/filtration/nanofiltration (NF) was considered. Water quality parameters were measured and compared with the standard values. The cesium hydrogen phosphotungstic acid was incorporated into the NF to increase the hydrophilicity and water flux. Polyethersulfone was sulfonated to add the sulfonyl group to the polymer.

Prediction of the phenol removal capacity from water by adsorption on activated carbon

High-performance sulfonated polysulfone (SPSf) mixed-matrix membranes (MMMs) were fabricated via a nonsolvent-induced phase separation (NIPS) method using zeolitic imidazolate frameworks-67 (ZIF-67) as a crosslinker. Acid-base crosslinking occurred between the sulfonic acid groups of SPSf and the tertiary amine groups of the embedded ZIF-67, which improved the dispersion of ZIF-67 and simultaneously improved the membrane strzcture and permselectivity. The dispersion of ZIF-67 in the MMMs and the acid-base crosslinking reaction were verified by energy-dispersive X-ray spectroscopy (EDX), X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The pore structure analysis of MMMs indicated that filling ZIF-67 into SPSf enhanced the average surface pore sizes, surface porosities and more micropore in cross-sections. The crossflow filtrations showed the MMMs have higher pure water fluxes (57 to 111 L m^-2 h^-1) than the SPSf membrane (55 L m^-2 h^-1) but also higher bovine serum albumin (BSA) rejection rate of 93.9-95.8%, a model protein foulant. The MMMs showed a higher water contact angle than the SPSf membrane due to the addition of hydrophobic ZIF-67 and acid-base crosslinking, and also maintained high thermal stability evidenced by the thermogravimetric analysis (TGA) results. At the optimal ZIF-67 concentration of 0.3 wt%, the water flux of the SPSf-Z67-0.3 membrane was 82 L m^-2 h^-1 with a high BSA rejection rate of 95.3% at 0.1 MPa and better antifouling performance (FRR = 70%).

Applied organic-inorganic nanocomposite of PLA-TiO2 for preparing polysulfone membrane: structure, performance and UV-assisted cleaning strategy

Blended organic copolymer (or homopolymer) and inorganic nanoparticles have been widely used (separately or simultaneously) for optimizing membrane pore structure and surface functionality. However, the prepared membranes suffer from degraded stability and insufficient integrity due to the high solubility or incompatibility of the blending additives. In this work, an organic-inorganic nanocomposite (i.e., PLA-TiO₂) was designed, and employed for PSF membrane preparation. The Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis confirmed that bidentate chelating dominated the bonding mechanism between PLA and TiO₂. The resultant PSF/PLA-TiO₂ membranes possessed a highly porous surface with narrowed pore size distribution, demonstrating the strong pore forming ability of PLA-TiO₂ for membrane preparations. Moreover, owing to the distinct inorganic-organic molecular conformation, the PLA-TiO₂ exhibited enhanced stability and dispersibility within the PSF substance, which endowed the membrane with long-acting hydrophilicity and UV responsiveness. Given the UV responsiveness that is introduced by PLA-TiO₂, UV-assisted strategies (UV-F and UV-C) were designed to further mitigate membrane fouling. The fouling analysis indicated that both reversible fouling and irreversible fouling were reduced in the UV-C process, signifying the synergistic effect between photocatalysis and hydraulics in membrane fouling mitigation. The enhanced membrane performance and the efficient preparation process highlight the potential of PLA-TiO₂ in membrane modifications.

Strategies in Forward Osmosis Membrane Substrate Fabrication and Modification: A Review

Forward osmosis (FO) has been recognized as the preferred alternative membrane-based separation technology for conventional water treatment technologies due to its high energy efficiency and promising separation performances. FO has been widely explored in the fields of wastewater treatment, desalination, food industry and bio-products, and energy generation. The substrate of the typically used FO thin film composite membranes serves as a support for selective layer formation and can significantly affect the structural and physicochemical properties of the resultant selective layer. This signifies the importance of substrate exploration to fine-tune proper fabrication and modification in obtaining optimized substrate structure with regards to thickness, tortuosity, and porosity on the two sides. The ultimate goal of substrate modification is to obtain a thin and highly selective membrane with enhanced hydrophilicity, antifouling propensity, as well as long duration stability. This review focuses on the various strategies used for FO membrane substrate fabrication and modification. An overview of FO membranes is first presented. The extant strategies applied in FO membrane substrate fabrications and modifications in addition to efforts made to mitigate membrane fouling are extensively reviewed. Lastly, the future perspective regarding the strategies on different FO substrate layers in water treatment are highlighted.

Polyvinylidene Fluoride-Graphene Oxide Membranes for Dye Removal under Visible Light Irradiation

In this study, polyvinylidene fluoride (PVDF)-graphene oxide (GO) membranes were obtained by employing triethyl phosphate (TEP) as a solvent. GO nanosheets were prepared and characterized in terms of scanning and transmission electron microscopy (SEM and TEM, respectively), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), chemical analysis and inductively coupled plasma mass spectroscopy (ICP). Two different phase inversion techniques, Non-Solvent Induced Phase Separation (NIPS) and Vapour-Induced Phase Separation (VIPS)/NIPS, were applied to study the effect of fabrication procedure on the membrane structure and properties. Membranes were characterized by SEM, AFM, pore size, porosity, contact angle and mechanical tests, and finally tested for photocatalytic methylene blue (MB⁺) degradation under visible light irradiation. The effect of different pH values of dye aqueous solutions on the photocatalytic efficiency was investigated. Finally, the influence of NaCl salt on the MB+ photodegradation process was also evaluated.

Low pressure modified polyamide 6 membrane for effective fractionation of dyes and NaCl

A co-polymer (SPAA6) of 5-sulfoanthranilic acid (5SAA) and ε-caprolactam was used to prepare membrane through nonsolvent induced phase separation (NIPS) method. The micro-structure of membrane was adjusted by small molecules to improve mechanic strength and performance, involving 7 commercial ionic surfactant and a self-synthesized one, S20. S20 showed the best compatibility with SPAA6, which converted spherical phase into network of strip-like units in micro-structure of membrane. Meanwhile, average pore size of the membrane was narrowed from 4.271 nm to 3.391 nm, tested by BET method. Tensile strength of membrane was improved from 2.5 MPa to 2.9 MPa. Therefore, anionic dyes rejection and membrane stability were both improved. It actually demonstrated that molecular weight distribution of SPAA6 was crucial for micro-structure construction of membrane since S20 was the SPAA6 of low molecular weight. In blend solution filtration test, membrane MS2 (1:2 for S20:SPAA6) displayed 98.22% rejection to Congo Red (CR) acid and 96.18% NaCl permeation under 1 bar. It showed 80.18% rejection to chrome blue K (ABK) and 96.28% NaCl permeation. Both water permeance were higher than 3.5 L·m^-2·h^-1·bar. Membrane MS2 showed the potential of fractionation of dye and NaCl, which was promising in textile waste water treatment.

Modification of forward osmosis membrane with naturally-available humic acid: Towards simultaneously improved filtration performance and antifouling properties

In this work, a thin-film composite forward osmosis (FO) membrane was fabricated on polyethersulfone substrate by interfacial polymerization with naturally-available humic acid (HA) as a stable membrane additive in the support layer. Compared with the pristine polyethersulfone substrate, the incorporation of HA significantly altered the cross-section structure, increased average pore size and porosity of the substrate, leading to a thinner polyamide layer, further increasing the water flux (permeability). Specifically, the FO membrane showed a higher water flux (~20 L m^-2 h^-1) with the introduction of HA than the membrane synthesized without HA (~15 L m^-2 h^-1) in the FO mode with 2 M NaCl as draw solution. Moreover, the selectivity of the membrane was improved ~45% by dosing 0.8 wt% HA into the substrate, in comparation to the pristine membrane without HA doped. Besides, the average roughness of the polyamide layer was reduced by up to 68% when HA was present in the substrate, which mitigated the fouling potential. Thus, a slower flux decline ratio (~60%) was observed for the membrane modified with 0.8 wt% HA than the pristine membrane (~80%). Taken together, our findings shed light on using natural-available HA for effectively and efficiently modifying membrane substrate to simultaneously enhance the permeate-selectivity performance and the anti-fouling behavior in FO membrane process. The fundamental causes of these differences in membrane separation performance and fouling behavior are considered and related to the physical and chemical characteristics of support layer (i.e., porosity and pore size) and polyamide layer (i.e., active layer thickness and roughness) of membranes.

Amphiphilic Block Copolymer of Poly(dimethylsiloxane) and Methoxypolyethylene Glycols for High-Permeable Polysulfone Membrane Preparation

Poly(dimethylsiloxane)-block-methoxypolyethylene glycols (PDMS-b-mPEG) were synthesized by Steglich esterification. The high-permeable membrane (PSf/PDMS-b-mPEG) was prepared by using PDMS-b-mPEG as additives. The successful synthesis of PDMS-b-mPEG was confirmed by nuclear magnetic resonance. Field emission scanning electron microscopy images show that the distribution of finger-like macroporous and sponge-like macroporous can be modulated by controlling the ratio of the hydrophilic/hydrophobic components of additives. The distribution of additives and membrane wettability are validated with X-ray photoelectron spectroscopy and water contact angle test. The permeability of the blended membrane, especially for the membrane PSf/PDMS-b-mPEG1900 (M3), was remarkably improved. The water permeability of M3 (239.4 L/m²·h·bar) was 6.6 times that of the unblended membrane M0 (42.5 L/m²·h·bar). The findings of protein BSA filtration show that the flux recovery ratio of M3 is 89.2% at a BSA retention rate of about 80%, which demonstrates that the polysulfone membranes blended with PDMS-b-mPEG have excellent antifouling performance and extraordinary permeability.