Preparation and characterization of TiO2/Pebax/(PSf‐PES) thin film nanocomposite membrane for humic acid removal from water

New thin film composite (TFC) membrane was prepared via coating of Pebax on PSf‐PES blend membrane as support, and its application in wastewater treatment was investigated. To modify this membrane, hydrophilic TiO₂ nanoparticles were coated on its surface at different loadings via dip coating technique. The as‐prepared membrane was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), field emission SEM, and contact angle analysis. The Fourier transform infrared spectroscopy analysis and surface SEM images indicated that TiO₂ was successfully coated on the membrane surface. In addition, the results stated that the hydrophilicity and roughness of membrane surface increased by addition of TiO₂ nanoparticles. Performance of TFC and modified TFC membranes was evaluated through humic acid removal from aqueous solution. Maximum permeate flux and humic acid rejection were obtained at 0.03 and 0.01 wt% TiO₂ loadings, respectively. Rejection was enhanced from 96.38% to 98.92% by the increase of feed concentration from 10 to 30 ppm. Additionally, membrane antifouling parameters at different pressures and feed concentration were determined. The results indicated that surface modification of membranes could be an effective method for improvement of membrane antifouling property.     

Nanostructured polyethersulfone membranes for dye and protein separation: Exploring antifouling role of holmium (III) molybdate nanosheets

Nanostructured polymer membranes are nowadays of crucial importance in achieving antifouling properties. Nanomaterials with tunable composition, size, and morphology, surface modification and functionality offer unprecedented opportunities for efficient wastewater treatment. In this work, the effect of holmium (III) molybdate (Ho₂MoO₆) nanomaterial as a new nanofiller on preparation of nanostructured polyethersulfone (PES) mixed matrix membranes was examined in terms of hydrophilicity, membrane morphology, permeability, dye and protein separation and antifouling property. The Ho₂MoO₆ nanosheets were synthesized and characterized by FTIR, XRD, and FESEM and used in different amounts in PES matrix. The pore size and the membrane porosity increased with Ho₂MoO₆ loading. The nanocomposite membranes showed enhancement in hydrophilicity, antifouling properties, dye rejection and permeability. The remarkably pure water flux (195 L/m²h at 3 bar) and 92.3% flux recovery after bovine serum albumin (BSA) filtration were obtained for the membrane mixed with 2 wt% Ho₂MoO₆ compared to 95 L/m²h and 75.2% obtained for the bare PES, respectively. Moreover, significantly high rejection of Acid Red 125 (95 ± 1%) was achieved. Thus, the experimental results established the potential efficiency of the novel nanocomposite membrane for the separation applications.     

Thermo-responsive and antifouling PVDF nanocomposited membranes based on PNIPAAm modified TiO2 nanoparticles

A novel hydrophilic nanocomposite additive(TiO2-g-PNIPAAm) was synthesized by the surface modification of titanium dioxide(TiO2) with N-isopropylacrylamide(NIPAAm) via "graft-from" technique. And the nanocomposite membrane of poly(vinylidene fluoride)(PVDF)/TiO2-g-PNIPAAm was fabricated by wet phase inversion. The graft degree was obtained by thermo-gravimetric analysis(TGA). Fourier transform infrared attenuated reflection spectroscopy(FTIR-ATR) and X-ray photoelectronic spectroscopy(XPS) characterization results suggested that TiO2-g-PNIPAAm nanoparticles segregated on membrane surface during the phase separation process. Scanning electron microscopy(SEM) was conducted to investigate the surface and cross-section of the modified membranes. The water contact angle measurements confirmed that TiO2-g-PNIPAAm nanoparticles endowed PVDF membranes better hydrophlilicity and thermo-responsive properties compared with those of the pristine PVDF membrane. The water contact angle decreased from 92.8° of the PVDF membrane to 61.2° of the nanocompostie membrane. Bovine serum albumin(BSA) static and dynamic adsorption experiments suggested that excellent antifouling properties of membranes was acquired after adding TiO2-gPNIPAAm. The maximum BSA adsorption at 40 °C was about 3 times than that at 23 °C. The permeation experiments indicated the water flux recover ratio and BSA rejection ratio were improved at different temperatures.     

Preparation and characterization of novel PES‐(SiO2‐g‐PMAA) membranes with antifouling and hydrophilic properties for separation of oil‐in‐water emulsions

In the present study, modification of nanoparticles (NPs) was investigated to mitigate aggregation of SiO₂ nanoparticles and improve the polymeric membrane's performance. For this purpose, the surface of SiO₂ nanoparticles was activated with amine groups, and polymethacrylic acid (PMAA) was grafted on the surface of NPs by atom transfer radical polymerization. Modified NPs were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) tests. Polyethersulfone (PES) membranes were fabricated with both SiO₂ and SiO₂‐g‐PMAA NPs via nonsolvent‐induced phase separation method. The fabricated membranes were characterized regarding their permeability, hydrophilicity, and porosity properties, and their separation efficiency was tested using the synthetic oil‐in‐water emulsion. The surface and cross‐sectional morphologies of membranes were observed by field emission scanning electron microscopy (FESEM). The experimental trials showed that modified NPs dispersed more uniformly in the structure of membranes and hydroxyl groups on the surface of NPs acted more effectively. Modification of NPs enhance the membrane performance in terms of permeate flux, hydrophilicity, and porosity. NPs modification improved the permeate flux about 46%. Oil rejection for all tested membranes was more than 98%, and modification of NPs did not reduce the rejection of membranes. The optimum concentration was obtained as 1 wt.% and 1.5 wt.% for SiO₂ and SiO₂‐g‐PMAA, respectively. Aggregation effect dominated at concentrations beyond the optimum values that decreased the permeate flux, consequently.     

Formation of appropriate sites on nanofiltration membrane surface for binding TiO2 photo-catalyst: Performance, characterization and fouling-resistant capability

Titanium dioxide (TiO₂) nanoparticles were assembled on the surface of nanofiltration blend membrane. For settling TiO₂ on the membrane surface, two membrane categories were used: (i) unmodified polyethersulfone (PES)/polyimide (PI) blend membrane, and (ii) –OH functionalized PES/PI blend membrane with different concentrations of diethanolamine (DEA). These membranes were radiated by UV light after TiO₂ depositing with different concentrations. 15 min immersion in colloidal suspension and 15 min UV irradiation with 160 W lamps were used for modification. The modification resulted in the formation of a photo-catalytic property with enhanced membrane hydrophilicity. The self-assembly of TiO₂ nanoparticles was established through coordinance bonds with –OH functional groups on the membrane surface. A comparison between the UV irradiated TiO₂ deposited blend membrane and deposited-functionalized blend membranes showed that –OH groups originate excellent adhesion of TiO₂ nanoparticles on the membrane surface, increase reversible deposition, and diminish irreversible fouling. The membranes were characterized using SEM, FTIR, EDX, contact angle, cross flow filtration, and antifouling measurements. SEM images show that the presence of –OH groups on the DEA-modified membrane surface is the main parameter for extra uniformly settlement of TiO₂ nanoparticles on the membrane surface. This procedure is a superior technique for modification of PES/PI nanofiltration membranes to enhance water flux and minimization membrane fouling.     

Improving surface structure of photocatalytic self‐cleaning membrane by WO3/PANI nanoparticles

To create a self‐cleaning feature and improve antifouling property, polysulfone (PSf) membranes were modified with WO₃ and polyaniline (PANI) nanoparticles (0–2 wt%) via phase inversion method for ultrafiltration of landfill leachate. The mass ratio of WO₃ nanoparticles was varied between 0, 40 and 60 wt% in different loadings. All synthesized membranes were tested with and without UV irradiation to evaluate the self‐cleaning feature. The synthesized PANI was analyzed with scanning electron morphology (SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). The surface hydrophilicity of the modified membranes increases with increasing the nanoparticle loadings (0–2 wt%). The membrane morphology indicated higher porosity and more finger like pores for the modified membranes. The porosity of 86.8% was achieved for the membrane containing 2 wt% PANI. The flux recovery ratio (FR) of membranes without UV radiation was increased by increasing the ratio of PANI to WO₃ nanoparticles, while the antifouling ability of membranes including WO₃ nanoparticles improved and reached to 98.87% after UV radiation. The highest COD removal before (76.65 %) and after (78.42%) UV radiation was obtained for the membrane containing 2 wt% nanoparticle loading. Copyright © 2016 John Wiley & Sons, Ltd.     

微乳液聚合耦合共混法构建聚偏氟乙烯共混杂化膜

以苯乙烯和甲基丙烯酸甲酯混合物作为油相, 采用反相微乳液法制备了AgCl纳米粒子; 通过微乳液原位聚合油相单体得到包含AgCl纳米粒子的聚合乳液; 将聚合乳液与聚偏氟乙烯(PVDF)通过共混法构建了包含AgCl纳米粒子的PVDF共混杂化膜. 紫外-可见光谱、 透射电子显微镜(TEM)及扫描电子显微镜(SEM)等表征结果和超滤实验结果表明, 聚合乳液加入的同时引入了亲水性聚合物和表面亲水的AgCl纳米粒子, 不仅改善了PVDF共混杂化膜的孔隙率和平均孔径, 还显著增强了PVDF共混杂化膜的极性和亲水性, 最终提升了膜的水通量和抗污染性能; 过量聚合乳液加入后不能与PVDF材料均匀共混, 而且AgCl纳米粒子也会在膜中形成团聚物堵塞膜孔隙, 从而削弱了膜的水通量和抗污染性能.     

Impact of TiO2 nanoparticles on morphology and performance of crosslinked polyimide organic solvent nanofiltration (OSN) membranes

Chemically crosslinked polyimide organic–inorganic composite nanofiltration membranes suitable for application in harsh organic solvents were successfully prepared by phase inversion of dope solutions. TiO₂ nanoparticles were dispersed in these dope solutions, comprising polyimide (PI) in N,N-dimethylformamide/1,4-dioxane. The impact of TiO₂ on the resulting PI membranes was investigated using SEM, TGA, water contact angle, dope viscosity measurements and mechanical strength. The presence of TiO₂ nanoparticles within the membrane matrix was proved by the detection of a peak characteristic of TiO₂ in the WAXS pattern. SEM pictures of the cross-section of the PI/TiO₂ membranes showed dramatically changed morphology compared to reference membranes with no TiO₂ addition. Macrovoids present in reference membranes were suppressed by increasing loading of TiO₂ nanoparticles, and eventually disappeared completely at a TiO₂ loading above 3 wt.%. Decreasing water contact angle and an increase in ethanol flux indicated that hydrophilicity increased as nanoparticle loading increased. The effect of TiO₂ on the functional performance of the membranes was evaluated by measuring flux and rejection using cross-flow filtration. Perhaps surprisingly, the presence of TiO₂ improved the compaction resistance of the membranes, whereas rejection and steady flux were almost unaltered.     

Cellulose acetate nanocomposite ultrafiltration membranes tailored with hydrous manganese dioxide nanoparticles for water treatment applications

Hydrous manganese dioxide (HMO) nanoparticles incorporated cellulose acetate (CA) composite ultrafiltration (UF) membranes are prepared with the aim of improving the water permeation and BSA contaminant removal. The HMO nanoparticles are synthesized from manganese ion and characterized by FT‐IR, XRD, and FESEM. The effect of variation of HMO on CA membranes is probed using FT‐IR, EDAX, contact angle, SEM, and AFM analysis to demonstrate their chemical functionality, hydrophilicity, and morphology. CA/HMO membranes are showing the enhancement in pure water flux (PWF), water uptake, porosity, hydrophilicity, fouling resistance, BSA rejection, and flux recovery ratio (FRR). CA‐1 membrane displayed higher PWF (143.6 Lm²h^?1), BSA rejection (95.9%), irreversible fouling (93.3%), and FRR (93.3%). Overall results confirmed that the CA/HMO nanocomposite UF membranes overcome the bottlenecks and shows potential for water treatment applications.     

Excellent hydrophilic and anti-bacterial fouling PVDF membrane based on ag nanoparticle self-assembled PCBMA polymer brush

A silver nanoparticles-poly(carboxybetaine methacrylate)(AgNPs-PCBMA) nanocomposite was prepared on poly(vinylidene fluoride)(PVDF) membrane surface to improve its hydrophilicity and antifouling properties. Firstly, the PVDF membranes were grafted by PCBMA via physisorbed free radical grafting technique. Then Ag+ coordinated to the carbonyl group on PCBMA andsubsequently was reduced to silver nanoparticles. The hydrophilicity of the PVDF-gPCBMA/Ag membrane wasenhanced with the increasing fixed degree(FD) of AgNPs, and the original water contact angle of membrane was reduced to 33.97°. Additionally, water flux recovery ratio(FRR) andbovine serum albumin(BSA) rejection ratio of PVDF-g-PCBMA/AgNPs membrane wereimproved from 52% to 93.32% and 28.12% to 91.12%, respectively. Further, the PVDF-g-PCBMA/AgNPs membranes exhibited the more pronounced inhibition zone. The study demonstrated that compared with pure AgNPs or the PCBMA polymer brush, the synergistic effect of PCBMA and AgNPs made PVDF membranes havebetter hydrophilicity and anti-bacterialperformances.     

Versatility of hydrophilic and antifouling PVDF ultrafiltration membranes tailored with polyhexanide coated copper oxide nanoparticles

Hydrophilic poly(vinylidene fluoride) (PVDF) nanocomposite ultrafiltration (UF) membranes with excellent antifouling and antibiofouling characteristics are fabricated by employing polyhexanide coated copper oxide nanoparticles (P–CuO NPs). The presence of P–CuO NPs is played a significant role in altering the PVDF membrane matrix and probed by XRD, FTIR, FESEM and contact angle analysis. The PVDF/P–CuO nanocomposite membranes exhibited an outstanding antifouling performance indicated by the superior pure water flux, effective foulant separation and maximum flux recovery ratio during UF experiments as a result of the formation of the hydrophilic and more porous membrane due to the uniform distribution of P–CuO NPs. Particularly, the PVDF/P–CuO-3 membrane showed higher PWF of 152.5 ± 2.4 lm⁻²h⁻¹ and porosity of 64.5% whereas the lower contact angle of 52.5°. Further, it showed the higher rejection of 99.5 and 98.4% and the flux recovery ratio of 99.5 and 98.5% respectively for BSA and HA foulants, demonstrated its increased water permeation, foulant separation and antifouling behavior. Further, the decent antibacterial activity is showed by the PVDF/P–CuO nanocomposite membranes with the formation of halo-zone around the membrane when exposed to the bacterial medium demonstrated that, by this process an antibacterial water treatment membrane can be developed by simple phase inversion technique with good membrane stability.     

Exploring the characteristics,performance, and modification of Matrimid for development of thin‐film composite and thin‐film nanocomposite reverse osmosis membranes

Reverse osmosis (RO) membrane technology is widely employed to address the demands for freshwater. In this study, fabrication and performance evaluation of customized RO membranes comprised of Matrimid and polyacrylonitrile (PAN) is carried out. While exploring adoption of slip coating procedure, the effects of various modification techniques including incorporation of TiO₂ nanoparticles and polyethylene glycol (PEG) into the skin layer as well as cross‐linking were investigated. The individual and combined effects of parameters on membrane morphology, surface characteristics and performance were also examined. Despite the distinctive characteristics of involved materials, delamination‐free composite membranes were successfully formed with an intimate contact at the interface of two layers. The results also indicated that increasing concentration of Matrimid in dope solution led to increase in membrane thickness and consequently decline in water flux. In the best case, membrane prepared using 1 wt.% Matrimid in dope exhibited water flux of 0.98 LMH and NaCl rejection of 95.7%. Also, incorporation of 3 wt.% TiO₂ nanoparticles offered membranes with improved water flux of 1.37 LMH and salt rejection of 95.8%. On the other hand, water flux and salt rejection in membranes containing 5 wt.% PEG were 1.18 LMH and 96.2%, respectively. The co‐presence of both nanoparticles and PEG provided more insights about the contributing factors in tuned membranes. Modification of skin layer by cross‐linking significantly improved salt rejection at the expense of water flux. The results are scientifically interpreted and compared to the values reported in literature.     

Chitosan‐modified graphene oxide as a modifier for improving the structure and performance of forward osmosis membranes

Chitosan (CS) with good hydrophilicity and charged property was used to modify graphene oxide (GO), the obtained GO‐CS was used as a novel modifier to fabricate thin film composite forward osmosis (FO) membranes. The results revealed that the amino groups on CS reacted with carboxyl groups on GO, and the lamellar structure of the GO nanosheets was peeled off by CS, resulting in the reducing of their thicknesses. The GO‐CS improved the hydrophilicity of polyethersulfone (PES) substrate, and their contact angles decreased to 64° with the addition of GO‐CS in the substrate. GO‐CS also increased the porosity of the substrate and surface roughness of FO membrane, thereby optimizing the water flux and reverse salt flux of FO membrane. The average water flux of the FO membrane reached the optimal flux of 21.34 L/(m² h) when GO‐CS addition was 0.5 wt%, and further addition of GO‐CS to the substrate would decrease the water flux of FO membrane, and the reverse salt flux also decreased to the lowest value of 2.26 g/(m² h). However, the salt rejection of the membrane increased from 91.4% to 95.1% when GO‐CS addition increased from 0.5 to 1.0 wt% under FO mode using 1 mol/L sodium chloride (NaCl) solution as draw solution (DS). In addition, high osmotic pressure favored water permeation, and at the same concentration of DS, magnesium chloride (MgCl₂) exhibited better properties than NaCl. These results all suggested that GO‐CS was a good modifier to fabricate FO membrane, and MgCl₂ was a good DS candidate.     

Pervaporation separation of water + isopropanol mixtures using novel nanocomposite membranes of poly(vinyl alcohol) and polyaniline

Novel nanocomposite polymeric membranes containing nanosized (30–100 nm) polyaniline (PANI) particles dispersed in poly(vinyl alcohol) (PVA) were prepared and used in the pervaporation separation of water–isopropanol feed mixtures ranging from 10 to 50 mass% of water at 30 °C. Of the three nanocomposite membranes prepared, the membrane containing 40:60 surface atomic concentration ratio of PANI:PVA produced the highest selectivity of 564 compared to a value of 77 observed for the plain PVA membrane. Flux of the nanocomposite membranes was lower than those observed for the plain PVA membrane, but selectivity improved considerably. Membranes were characterized by differential scanning calorimetry, dynamic mechanical thermal analyzer, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The highest selectivity with the lowest flux was observed for 10 mass% water containing feed mixture. Flux increased with increasing amount of water in the feed, but selectivity decreased considerably. These results were attributed to the acid-doped PANI particles in the PVA membrane as a result of change in the micromorphology of the nanocomposite membranes. In addition, molar mass between cross-links and fractional free volume of the membranes are responsible for the varying membrane performance. Temperature effect on permeability was investigated for 10 mass% water containing feed with the membrane containing higher concentration of PANI particles, the presence of which could be responsible for varied effect of water permeation through the membrane. Membranes of this study could remove as much as 98% of water from the feed.     

Fabrication of PES-based nanofiltration membrane modified by composite PAA-co-PMMA-g-ZnA nanoparticles

In the current research, nanocomposite polyethersulfone-based nanofiltration membranes were prepared by composite PAA-co-PMMA-g-ZnA nanoparticles. NF membranes were fabricated by phase inversion through casting solution technique. The effect of composite PAA-co-PMMA-g-ZnA nanoparticles concentration into the casting solution on physicochemical characteristics of membrane was studied. Scanning optical microscopy images showed uniform particle distribution for the membranes. Scanning electron microscopy images also demonstrated that membrane porosity was enhanced by increase in nanoparticles content ratio. The membrane surface 3D images showed smooth surface for the membranes filled with 0.05, 0.1 and 0.5 wt% nanoparticles. The contact angle results exhibited that membrane hydrophilicity was improved significantly by using of NPs in membrane matrix. The contact angle was decreased from 65.38° for PES membrane to 48.33° for membrane filled with 0.5 wt% nanoparticles. The water permeability was reduced initially by addition of 0.05 wt% nanoparticles into the casting solution and then increased by more nanoparticles loading rate (0.1 wt%). The water permeability was decreased again by more increase in nanoparticles loading range from 0.5 to 1 wt%. The salt rejection was improved strongly from 68.4 % for PES to 88.58 % for membrane filled with 0.5 wt% nanoparticles. The membranes mechanical strength was increased sharply from 2835.5 to 3337.3 kPa with addition of nanoparticles into the casting solution.     

Fabrication of blend hydrophilic polyamide imide (Torlon®)-sulfonated poly (ether ether ketone) hollow fiber membranes for oily wastewater treatment

Blend hydrophilic polyamide imide (PAI)-sulfonated poly (ether ether keton) (SPEEK) hollow fiber membranes were fabricated for oil-water emulsion separation. The structure and performance of the membranes were examined by FESEM analysis, N₂ permeation, overall porosity, collapsing pressure, water contact angle, pure water flux, molecular weight cutoff (MWCO), and oil rejection tests. By studying ternary phase diagrams of polymer/solvent-additive/water system, the higher phase-inversion rate was confirmed for the solutions prepared at higher PAI/SPEEK ratio. A more open structure with larger finger-likes was observed by increasing PAI/SPEEK ratio. Mean pore size of 81 nm, overall porosity of 79% and water contact angle of 58° were obtained for the improved membrane prepared by PAI/SPEEK ratio of 85/15. Increasing SPEEK ratio resulted in lower mechanical stability in terms of collapsing pressure. Pure water flux of about 2.5 times of the plain PAI membrane was found for the improved membrane. MWCO of 460 kDa was found for the improved blend membrane. From oil rejection test, all the membranes demonstrated an oil rejection of over 95%. The improved membrane showed a lower rate of permeate flux reduction compared to the plain membrane which was related to the smaller fouling possibility. Less fouling resistance of the improved membrane was related to the higher flux recovery ratio (about 92%). For all the membranes, the dominant fouling mechanism was found to be the cake filtration. The improved PAI-SPEEK hollow fiber membranes was found to be practical for ultrafiltration of oily wastewaters.     

Investigation of structure‐performance properties of a special type of polysulfone blended membranes

Membranes require superior mechanical strength due to applied harsh conditions. The mechanical properties of membranes decrease with increasing hydrophilicity of its elements. In this study, mechanical properties were investigated for two special blended membranes which were made by blending polysulfone with (polysulfone‐g‐poly (n‐butylacrylate) and polysulfone‐g‐poly (tert‐butylacrylate) as components. All of the prepared membranes were characterized by differential scanning calorimeter, thermal gravimetric analysis, field emission scanning electron microscope, and atomic electron microscope and were investigated in terms of pure water flux, water contact angle, molecular weight cut off, and morphology. It was found that water contact angle decreased from 73.6° which belongs to neat membrane decreased to 46° for blended membranes containing higher amounts of copolymers; however, the pure water flux increased with increasing copolymer content considerably compared with the neat membrane. Also, molecular weight cut off increased aggressively. Furthermore, mechanical properties including tensile strength, Young modulus, and elongation at break were measured and compared with the neat polysulfone membrane. Results showed that the tensile strength and modulus decreased with an increase in the copolymers content, despite the increase in the elongation at break. The effect of applied pressure on the membrane structure and also bursting strength were studied, and it has been proved that not only the structure of the membranes but also their performance is strongly affected by the composition of the membranes.     

Preparation and properties of polysulfone/TiO2 composite ultrafiltration membranes

The influence of inorganic filler TiO₂ nanoparticles on the morphology and properties of polysulfone (PS) ultrafiltration membranes was investigated. PS/TiO₂ composite membranes were prepared by a phase‐inversion method. TiO₂ nanoparticles modified by sodium dodecyl sulfate were uniformly dispersed in an 18 wt % PS casting solution. The addition of TiO₂ resulted in an increase in the pore density and porosity of the membrane skin layer. The pore size distribution changed from the log‐normal distribution to the bimodal distribution because of the presence of TiO₂ nanoparticles, and some large pores were observed when the concentration of the filler was over 3 wt %. The skin layer was gradually thickened; meanwhile, the morphology sublayer changed from macrovoids to spongelike pores, in comparison with PS membranes without the filler. The addition of TiO₂ also induced increases in the hydrophilicity, mechanical strength, and thermal stability. The ultrafiltration experiments showed when the concentration of TiO₂ was less than 2 wt %, the permeability and rejection of the membrane was enhanced and then decreased drastically with a higher filler concentration (>3%). © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 879–887, 2006     

Fabrication of Cu(OH)<Subscript>2</Subscript> Nanowires Blended Poly(vinylidene fluoride) Ultrafiltration Membranes for Oil-Water Separation

Cu(OH)2 nanowires were prepared and incorporated into poly(vinylidene fluoride) (PVDF) to fabricate Cu(OH)2-PVDF ultrafiltration (UF) membrane via immersion precipitation phase inversion process.The effect of Cu(OH)2 nanowires on the morphology of membranes was investigated by X-ray photoelectron spectroscopy (XPS),Fourier transform infrared (FTIR) spectroscopy,atomic force microscopy (AFM),scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements.The results showed that all the Cu(OH)2-PVDF membranes had wider fingerlike pore structure and better hydrophilicity,smoother surface than pristine PVDF membrane due to the incorporation of Cu(OH)2 nanowires.In addition,water flux and bovine serum albumin (BSA) rejection were also measured to investigate the filtration performance of membranes.The results indicated that all the Cu(OH)2-PVDF membranes had high water flux,outstanding BSA rejection and excellent antifouling properties.It is worth mentioning that the optimized performance could be obtained when the Cu(OH)2 nanowires content reached 1.2 wt％.Furthermore,the membrane with 1.2 wt％ Cu(OH)2 nanowires showed outstanding oil-water emulsion separation capability.     

Enhancing the antifouling property of polyethersulfone ultrafiltration membranes through surface adsorption-crosslinking of poly(vinyl alcohol)

An adsorption-crosslinking process of poly(vinyl alcohol) (PVA) was introduced to modify the surface of polyethersulfone (PES) ultrafiltration membranes for enhancement of their antifouling property. XPS and water contact angle measurement confirmed the obvious enhancement of surface hydrophilicity. Ultrafiltration results showed that the spreading of PVA chains over the hydrophobic membrane surface caused substantial but acceptable decrease on membrane flux. The fouling type analysis indicated that PVA adsorption effectively improved the antifouling property of PES membranes. With a PVA concentration of 0.5 wt% and three cycles of alternative adsorption-crosslinking, the total and irreversible fouling ratio of modified membranes were 0.38 and 0.22, respectively, much lower than those of control PES membrane (0.61 and 0.47), and the flux recovery ratio was increased accordingly. The long-term ultrafiltration experiment demonstrated the improvement of recycling property and the reliability of adsorption-crosslinking process.