Improvement of antifouling performance of poly(l‐lactic acid) membranes through incorporating polyaniline nanoparticles

Poly(l ‐lactic acid) (PLLA) composite membranes were fabricated by nonsolvent induced phase separation method using polyaniline (PANI) as an additive. Membrane structure was characterized by attenuated total reflectance Fourier transform‐infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, porosity, and pore size analysis. Membrane performance was assessed by goniometer, pure water flux, molecular weight cut‐off, static adsorption and dynamic filtration. The incorporation of PANI significantly improved the hydrophilicity and permeability of PLLA composite membrane, and eventually enhanced the antifouling performance of composite membrane compared with pure PLLA membrane. It was demonstrated that PLLA composite membrane with 1 wt % PANI had better separation and antifouling performance compared with other composite membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44452.     

Fabrication and characterization of silane-functionalized Na-bentonite polysulfone/polyethylenimine nanocomposite membranes for dye removal

In this study, tetraethoxysilane (TEOS)-functionalized Na-bentonite incorporated into polysulfone/polyethylenimine (PSF/PEI) membranes were fabricated by phase inversion method for the efficient removal of methylene blue dye. For the preparation of PSF/PEI nanocomposite membranes, silane-functionalized Na-bentonite and pure Na-bentonite were used at three different concentrations (0.5, 1, and 2 wt%). The prepared membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, porosity, hydrophilicity, and water permeability measurements. Antifouling behaviors and methylene blue dye rejections of the PSF/PEI nanocomposite membranes were also tested. The obtained results showed that the addition of pure Na-bentonite and silane-functionalized Na-bentonite both increased the water permeability of the membranes. The PSF/PEI membrane containing 2 wt% silane-functionalized Na-bentonite showed the highest water flux of 105 L m⁻² h⁻¹, while the lowest water flux of 1.2 L m⁻² h⁻¹ was recorded for pure PSF membrane. Filtration results demonstrated that the antifouling capacity was significantly increased due to the negatively charged surface of the newly generated silane-functionalized Na-bentonite PSF/PEI membranes. In summary, TEOS-functionalized Na-bentonite can be used to fabricate PSF/PEI nanocomposite membranes with effective filtration ability, antifouling capacity with lower decay ratio, higher flux recovery ratio, and 99% methylene blue dye removal performance.     

PVPK30和Tween80对中空纤维超滤膜结构和性能的影响

通过考察添加剂-聚乙烯吡咯烷酮（PVPK30）和Tween80对杂萘联苯聚醚砜酮（PPESK）中空纤维超滤膜结构和分离性能的影响，发现：随高分子添加剂聚乙烯吡咯烷酮K30浓度的升高，膜水通量减小，截留率基本无变化，膜结构逐渐由指状结构转变成海绵状结构。有机大分子添加剂Tween80可以提高膜的水通量，但膜结构不随添加剂浓度而改变，均为指状结构。当Tween80浓度小于5wt％时，随Tween80浓度的增加，膜水通量升高，截留率下降。比较不同凝胶浴温度下的膜分离性能可以看到，凝胶浴温度提高可以显著提升膜的纯水通量。     

Effects of operation conditions,solvent and gelation bath on morphology and performance of PPESK asymmetric ultrafiltration membrane

The effect of gelation temperature, evaporation time, solvent and gelation bath on the structure and performance of poly(phthalazinone ether sulfone ketone) (PPESK) asymmetric ultrafiltration membrane via phase inversion are investigated; the relationship between gelation thickness of dope solutions (X) and time for several polymer solutions with different solvents and gelation bath by online optical microscope–CCD camera experimental system (OM–CC system) are obtained. The results show that gelation temperature has much stronger influence on aperture opening ratio of membrane surface (AOR) and average diameter of membrane surface (AD) than evaporation time, whereas evaporation time has greater effect on the structure factor of membrane cross-section (S). Bovine serum albumin rejection (R) is mainly determined by surface structure; however, pure water flux (J) is controlled not only by the structure of surface and cross-section, but also the connectivity of the pores. PPESK membranes with fine performance can be fabricated under appropriate gelation temperature and evaporation time. In addition, the membrane structure and performance vary widely when various solvents and gelation bath are employed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Separation of heavy metal and protein from wastewater by sulfonated polyphenylsulfone ultrafiltration membrane process prepared by glycine betaine enriched coagulation bath

This work deals with a simple and eco-friendly approach for the development of ultrafiltration membranes for the separation of environmentally hazardous substances from the water source. Polysulfone and sulfonated polyphenylsulfone blend ultrafiltration membranes were fabricated by the non-solvent induced phase inversion technique. Prepared membranes were characterized for their morphology, hydrophilicity, porosity, filtration and antifouling properties. The blend membranes with 15 wt% of sPPSU demonstrated the best performance with water flux of 190.33 Lm^?2h^?1 and flux recovery ratio of 86.56%. The effect of aq. glycine betaine (GB) coagulation bath on the membrane property and performance was studied and compared with commonly used additives such as NaCl and NMP. The GB in coagulation bath exhibited better flux and performance with protein rejection of 66.3%, 74.0% and 91.2% for trypsin, pepsin, and bovine serum albumin, respectively, and heavy metal rejection of 75.2% and 87.6% for polymer enhanced ultrafiltration of Cd²⁺ and Pb²⁺ ions, respectively.     

Enhancing antifouling performance of poly(l‐lactide) membranes by TiO2 nanoparticles

Poly(l ‐lactide) (PLLA)/TiO₂ composite membranes were fabricated by immersion precipitation method. The resulting membranes were characterized using various methods including XRD, ATR‐FTIR, TGA, DSC, SEM, goniometer, and molecular weight cut‐off. The antifouling performance of the membrane was investigated through the filtration experiments of the oil/water emulsion. XRD, SEM, and ATR‐FTIR results indicated that TiO₂ was successfully introduced into the membrane, while DSC and TGA indicated the enhancement of thermal stability of membrane. The improvement of membrane hydrophilicity was confirmed by goniometer. In addition, the pore size and porosity on the membrane surface varied obviously with increasing the TiO₂ loading. It was concluded that PLLA/TiO₂ composite membranes had better antifouling and recycling performance compared with the pure PLLA membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43542.     

Fabrication and properties of PVDF and PVDF‐HFP microfiltration membranes

Poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride)‐co‐hexafluoropropylene (PVDF‐HFP) were used to fabricate porous microfiltration membranes via a thermally induced phase separation (TIPS) method, and dibutyl phthalate (DBP) was used as diluent. The effects of polymer concentration on structure and performance were studied in detail. In addition, the effect of incorporation of hexafluoropropylene (HFP) groups on the membrane was also investigated. The formation mechanism was proposed with the assistance of a phase diagram. The results showed that the incorporation of HFP groups resulted in a lower crystallization temperature (T_c) of the polymer/DBP system. In addition, the porosity, pure water flux, and ink solution flux decreased with increasing polymer concentration. In contrast, the water contact angle, ink rejection ratio, and mechanical properties had an increasing tendency. When the polymer concentration was 30 wt %, the obtained membrane was most suitable for microfiltration. Furthermore, the incorporation of HFP groups improved the properties of the obtained membrane, including better hydrophobicity, mechanical properties, antifouling property, and chemical resistance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46711.     

Preparation and characterization of PES/CA microporous membranes via reverse thermally induced phase separation process

The blend polyethersulfone (PES)/cellulose acetate (CA) flat‐sheet microporous membranes were prepared by reverse thermally induced phase separation (RTIPS) process. The effects of CA content and coagulation bath temperature on membrane structures and properties were investigated in terms of membrane morphology, water contact angle, permeation performance, and mechanical properties. The cloud point results indicated that the cloud point decreased with the increasing content of CA. When the coagulation bath temperature was lower than the cloud point, the membrane formation process underwent nonsolvent induced phase separation (NIPS) process and dense skin layer and finger‐like structure were formed in membranes. These membranes had lower pure water flux and poor mechanical properties. But when the coagulation bath temperature was higher than the cloud point, the membrane formation process underwent RTIPS process. The porous top surface as well as porous cross‐section of the membranes were formed. Therefore, high pure water flux and good mechanical properties were obtained. The contact angles results indicated that the hydrophilicity of the prepared membranes improved obviously with the addition of CA. When the content of CA was 0.5 wt% and the membrane formation temperature was 323K, the PES/CA microporous membrane which was prepared via the RTIPS process displayed a optimal permeability of the pure water flux of 816 L m^?2 h^?1 and the BSA rejection rate of 49.5%, which showed an increase of 48.9% and 23.6% than that of pure PES membrane, respectively. Moreover, the mechanical strengths of the membranes obtained by RTIPS process were better than those membranes prepared by NIPS process. POLYM. ENG. SCI., 58:180–191, 2018. © 2017 Society of Plastics Engineers     

Hydrophilic goethite nanoparticle as a novel antifouling agent in fabrication of nanocomposite polyethersulfone membrane

The goethite nanoparticle was used as a multifunctional additive to fabricate antifouling polyethersulfone (PES) nanofiltration membranes. The goethite/PES membranes were synthesized via the phase inversion method. The scanning electron microscopy (SEM) photographs showed an increase in pore size and porosity of the prepared membranes with blending of the goethite. The static water contact angle measurements confirmed a hydrophilic modification of the prepared membranes. With increase in the goethite content from 0 to 0.1 wt %, the pure water flux increased up to 12.7 kg/m² h. However, the water permeability decreased using high amount of this nanoparticle. Evaluation of the nanofiltration performance was performed using the retention of Direct Red 16. It was observed that the goethite/PES membranes have higher dye removal capacity (99% rejection) than those obtained from the unfilled PES (89%) and the commercial CSM NE 4040 NF membrane (92%). In addition, the goethite/PES blend membranes showed good selectivity and antifouling properties during long‐term nanofiltration experiments with a protein solution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43592.     

Polyamide/polyacrylonitrile thin film composites as forward osmosis membranes

Thin film composites (TFCs) as forward osmosis (FO) membranes for seawater desalination application were prepared. For this purpose, polyacrylonitrile (PAN) as a moderately hydrophilic polymer was used to fabricate support membranes via nonsolvent‐induced phase inversion. A selective thin polyamide (PA) film was then formed on the top of PAN membranes via interfacial polymerization reaction of m‐phenylenediamine and trimesoyl chloride (TMC). The effects of PAN solution concentration, solvent mixture, and coagulation bath temperature on the morphology, water permeability, and FO performance of the membranes and composites were studied. Support membranes based on low PAN concentrations (7 wt %), NMP as solvent and low coagulation bath temperature (0 °C) demonstrated lower thickness, thinner skin layer, more porosity, and higher water permeability. Meanwhile, decreasing the PAN solution concentration lead to higher water permeance and flux and lower reverse salt flux, structural parameter, and tortuosity for the final TFCs. Composites made in N,N‐dimethylformamide presented lower permeance and flux for water and salt and higher salt rejection, structural parameter, and tortuosity. FO assay of the composites showed lower water permeance values in saline medium comparing to pure water. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44130.     

Effects of coagulation bath temperature and polyvinylpyrrolidone content on flat sheet asymmetric polyethersulfone membranes

In this study, effects of coagulation bath temperature (CBT) and polyvinylpyrrolidone (PVP K15) concentration as a pore former hydrophilic additive on morphology and performance of asymmetric polyethersulfone (PES) membranes were investigated. The membranes were prepared from a PES/ethanol/NMP system via phase inversion induced by immersion precipitation in a water coagulation bath. The morphology of prepared membranes was studied by scanning electron microscopy (SEM), contact angle measurements, and mechanical property measurements. Permeation performance of the prepared membranes was studied by separation experiments using pure water and bovine serum albumin (BSA) solution as feed. The obtained results indicate that addition of PVP in the casting solution enhances pure water permeation flux and BSA solution permeation flux while reducing protein rejection. Increasing CBT results in macrovoid formation in the membrane structure and increases the membrane permeability and decreases the protein rejection. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Polypropylene composite hollow fiber ultrafiltration membranes with an acrylic hydrogel surface by in situ ultrasonic wave-assisted polymerization for dye removal

In this study, polypropylene composite hollow fiber membrane with an acrylic hydrogel layer was fabricated successfully by in situ ultrasonic wave-assisted polymerization. The ultrasonic irradiation can significantly improve the grafting efficiency of acrylic acid on the membrane surface. The modified membranes were characterized on the basis of physicochemical characteristics, permeation performance and antifouling property. The results revealed that the pure water flux of modified membranes was significantly increased when the graft density was lower than 0.82 mg cm⁻², due to the improvement of hydrophilicity. Interestingly, the optimized membrane PPM1.49 could efficiently remove organic dyes from aqueous solution, showing retentions of 99.5 and 98.7% to Congo red and methylthionine chloride, respectively. Meanwhile, its flux recovery ratio was elevated from 68.0 to 92.0% using bovine serum albumin aqueous solution as a foulant compared with the pristine membrane. These promising results indicate that modified membranes developed in this study are potentially applicable for dye removal from wastewater. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47099.     

逆向热致相分离法(RTIPS)制备PES/DMAc/DEG体系微孔膜及其性能表征

以PES/DMAc/DEG低临界共溶温度(LCST)体系为铸膜液,利用低临界共溶温度(LCST)的热致相分离(LCST-TIPS,简称RTIPS)法制备PES微孔膜.探究影响PES微孔膜理化性能及其结构的2个主要因素:凝胶浴温度、非溶剂(DEG)/溶剂(DMAc)的质量比.运用扫描电镜(SEM)﹑纯水通量﹑BSA截留率...     

Fabrication of fullerenol-incorporated thin-film nanocomposite forward osmosis membranes for improved desalination performances

Development and use of novel membranes for forward osmosis (FO) applications have gained popularity throughout the world. To enhance FO membrane performance, a novel thin-film nanocomposite membrane was fabricated by interfacial polymerization incorporating Fullerenol (C₆₀(OH)_n) nanomaterial, having n in the range of 24–28 into the active layer. Different concentrations of fullerenol loading (100, 200, 400, and 800 ppm) were added to the top skin layer. The structural and surface properties of the pure thin-film composite membrane (TFC) and fullerenol-incorporated thin-film nanocomposite (FTFC) membranes, were characterized by ATR-FTIR, SEM, and AFM. FO performance and separation properties were evaluated in terms of water flux, reverse salt flux, antifouling propensity, water permeability and salt permeability for all TFC and FTFC membranes. Osmotic performance tests showed that FTFC membranes achieved higher water flux and reverse salt flux selectivity compared with those of TFC membranes. The FTFC membrane with a fullerenol loading of 400 ppm exhibited a water flux of 26.1 L m^?2 h^?1 (LMH), which is 83.03% higher than that of the TFC membrane with a specific reverse salt flux of 0.18 g/L using 1 M sodium chloride draw solution against deionized water in FO mode. The fullerenol incorporation in FTFC membranes also contributed to a decreased fouling propensity.     

Effects of bath temperature on the morphology and performance of EVOH membranes prepared by the cold‐solvent induced phase separation (CIPS) method

The development and characteristics of porous EVOH membranes by cold‐solvent induced phase separation (CIPS) process were investigated. Binary dopes of 1,3‐propandiol/EVOH prepared at 80 °C were immersed in 1,3‐propandiol at a lower temperature to engender polymer precipitation. The quench temperature affects phase separation modes, and hence structure and performance of resulting CIPS membranes. When the bath temperature was set below the crystallization line and above the binodal (e.g. 45 °C), the formed membrane was dominated by a packing of semicrystalline EVOH globules. When the bath was set at a temperature just below the spinodal (e.g. 20 °C), spinodal decomposition (SD) dominated the precipitation process to give a lacy‐like bicontinuous structure; yet there is also a clear imprint from polymer crystallization. When the bath temperature was set deeply within the spinodal dome (e.g. 5 °C), polymer crystallization affected only little the SD‐derived bicontinuous morphology. Water permeation flux, wettability, tensile strength, and ultra‐filtration experiments of the membranes were conducted. The results indicated that those properties were closely correlated with the porosity level, pore size, and membrane morphology. Moreover, X‐ray diffraction and DSC analyses indicated that the formed membranes had a crystallinity of 38 to 42%, consistent with the literature data. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44553.     

Separation of Humic Substances by Porous Ion-Exchange Membranes from Sulfonated Polysulfone

Abstract

Ultrafiltration involving sulfonated polysulfone membranes provides high efficiency for humic matter removal from water. The increase in ion-exchange capacity of the polymer matrix from 0.24 to 0.96 mmol SO₃H groups per 1 g of dry membrane increases the membrane pore diameter and its hydrophilicity, and thus the permeate flux from 0.05 to 3.69 m³/m²·d. In order to decrease the manufacturing cost, membranes from polysulfone and sulfonated polysulfone blends were investigated. It was shown that a one-to-one blend resulted in a membrane having similar antifouling properties to pure sulfonated polysulfone. Both membranes reject humic matter in the 91–98% range and show a flux decline of 5–30% as a result of surface fouling.     

Synthesis and Characterization of Polycarbonate/TiO2 Ultrafiltration Membranes: Critical Flux Determination

A novel polycarbonate (PC) membrane was modified with titanium dioxide via nonsolvent-induced phase separation method to improve its hydrophilicity and antifouling properties in a submerged membrane system for the removal of humic acid (HA) both with and without polyaluminum chloride (PAC) coagulant. The effect of TiO₂ additive on the morphology and performance of the nanocomposite membranes was studied by atomic force microscopy, field emission scanning electron microscopy, energy dispersive X-ray, mechanical properties, water contact angle, porosity, pure water flux, rejection tests, and antifouling parameters. The obtained results revealed that a higher critical flux was achieved by the PC/TiO₂ nanocomposite membrane. The flux recovery ratio of the neat PC membrane increased with the addition of TiO₂ nanoparticles and without PAC coagulant. HA removal for the PC nanocomposite membrane was higher than that of the neat PC membrane with and without PAC coagulant.     

Enhanced water flux through ultrafiltration polysulfone membrane via addition‐removal of silica nano‐particles: Synthesis and characterization

In the present paper, hierarchically structured ultrafiltration polysulfone (PSf) membrane was prepared to explore the effect of addition and subsequent removal of SiO₂ nano‐particles on the membrane morphology, hydrophilicity, and separation properties. The PSf based membranes namely PSf, PSf/SiO₂ and PSf/WSiO₂ (i.e. SiO₂ nano‐particles was acid‐washed and removed from PSf/SiO₂), were synthesized and characterized by different characterization methods. Pure water flux through the membranes was determined using a filtration unit operating at a continuous dead‐end flow mode. The modification enhanced the morphology, hydrophobicity, porosity and transport properties of the modified membranes, although the molecular weight cut‐off (MWCO) of the membranes was not changed considerably. In comparison, PSf/WSiO₂ membrane exhibited excellent pure water flux (about 4.5 times the flux of PSf, and 17 times the flux of PSf/SiO₂), although antifouling property of PSf/SiO₂ in separation of bovine serum albumin (BSA) was better than that of PSf and PSf/WSiO₂ membranes. The results suggested that the addition/removal of sacrificial solid fillers within/from a membrane matrix may provide a promising strategy to enhance PSf membrane transport property. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43556.     

High-density polyethylene membranes embedded with carboxylated and polyethylene glycol-grafted nanodiamond to be used in membrane bioreactors

In this work, neat and modified nanodiamond (ND) particles were embedded into high-density polyethylene (HDPE) membranes to improve hydrophilicity and antifouling properties. The membranes were prepared via thermally induced phase separation (TIPS) method and used for pharmaceutical wastewater treatment in membrane bioreactors (MBR) system. To prevent the agglomeration of ND, it was modified using two methods: thermal carboxylation (ND-COOH) and grafting with polyethylene glycol (ND-PEG). Membranes with different concentration of ND-COOH and ND-PEG nanoparticles ranging from 0.00 to 1.00 wt % were prepared and characterized using a set of analyses including water contact angle, pure water flux, tensile strength, differential scanning calorimeter, field emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. It was found that the optimum contents of ND-COOH and ND-PEG nanoparticles were 0.50 wt % and 0.75 wt %, respectively. The interfacial interaction between nanoparticles and HDPE matrix was studied based on Pukanzsky model. To examine the performance of membranes, critical flux, filtration experiment in the MBR, and fouling analysis of membranes were carried out. The results showed that among the fabricated membranes, 0.75 wt % HDPE/ND-PEG membrane had the highest water flux and the best antifouling properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47914.     

Development of a novel graphene oxide-blended polysulfone mixed matrix membrane with improved hydrophilicity and evaluation of nitrate removal from aqueous solutions

In this study, four types of mixed matrix membranes were fabricated using polysulfone (as the base polymer) and different contents of graphene oxide (GO) nanosheets (as modifier) through wet phase inversion method. Based on the amounts of GO (0, 0.5, 1, and 2?wt%), the synthesized membranes named as M1, M2, M3, and M4, respectively. The membranes characteristics were evaluated using FE-SEM, FT-IR, and water contact angle measurements. In addition, the performance of the prepared membranes was investigated in terms of basic parameters: filtrate water flux, nitrate removal efficiency, and antifouling properties. Results showed significant improvements of the characteristics of modified membranes with GO. Accordingly, the permeability and hydrophilicity were enhanced and water flux was considerably improved. At operating pressure of 4?bar and nitrate concentration of 110?mg/L, the removal efficiency for unmodified membrane (M1) was 15.5% and for modified M2, M3, and M4 membranes were 22.78%, 39.12%, and 41.37%, respectively. In addition, the results of flux recovery ratio (FRR) showed that the anti-fouling properties of the GO modified membranes were improved due to the increase in membrane surface hydrophilicity.