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...     

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

In 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%).     

凝固浴组成和温度对PVDF疏水微孔膜结构与性能的影响

利用非溶剂相转化法(NIPS),以聚偏氟乙烯(PVDF)/磷酸三乙酯(TEP)-N,N-二甲基乙酰胺(DMAc)为铸膜液体系,乙醇水溶液为凝固浴制备高性能的PVDF疏水微孔膜。考察了凝固浴中乙醇(EtOH)含量及凝固浴温度对PVDF成膜分相速率、膜结构和膜疏水性的影响。实验结果表明,在20℃的凝固浴温度下,凝固浴中乙醇含量的升高减慢了铸膜液体系的分相速率,提高了PVDF膜的孔隙率;在凝固浴中添加60%(wt)的乙醇,可形成表面荷叶状结构和截面对称的海绵状结构,膜表面的接触角为130.3°,呈很强的疏水性,并具有较优的膜强度。     

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     

Construction of membrane formation system with low critical solution temperature for preparing hydrophilic polysulfone membrane via modified reverse thermally induced phase separation process

This paper presents a novel method to construct a membrane formation system featuring a low critical solution temperature (LCST) by incorporating hydroxy terminated hyperbranched polyester (HBPE) into polysulfone (PSF) casting solution. PSF membranes were developed by modified reverse thermally induced phase separation (m-RTIPS) process while the introduction of HBPE improved the hydrophilicity of the membrane. The critical properties of the flat-sheet PSF membranes were discussed in detail. The cloud point decreased as the HBPE concentration was increased. When membranes were prepared via m-RTIPS, the region of bicontinuous finger-like pores in the sublayer gradually broadened. The membranes showed better permeation properties, larger pore size, and better mechanical properties than those of the membranes prepared via non-solvent-induced phase separation (NIPS) process. Furthermore, no matter the enhanced hydrophilicity of membrane or m-RTIPS membrane-forming mechanism was beneficial to the anti-fouling properties. In general, the membrane MPSF-8-b had relatively high flux, good hydrophilicity and excellent mechanical properties at 0.8 wt.% HBPE content, and the pure water flux recovery of the membrane was increased to 55.2%.     

Influence of hydroxyl‐terminated polybutadiene additives on the poly(ether sulfone) ultra‐filtration membranes

Hydroxyl‐terminated polybutadiene (HTPB) was blended into a poly(ether sulfone) (PES) casting solution used to prepare ultra‐filtration (UF) membranes via the phase inversion technique. The membranes were then characterized by contact angle (CA) measurements and UF experiments. The CA was increased with the addition of HTPB in the PES membrane and also by lowering the gelation bath temperature. It was observed that the CA was lower for membranes prepared with N‐methyl‐2‐pyrrolidinone (NMP) as the solvent than those using N,N‐dimethylacetamide (DMAc) as solvent. The flux values were higher for membranes made using a 4°C gelation bath when compared with the ambient temperature ((25 ± 1)°C) irrespective of the cast solvents, NMP or DMAc. The flux values were much higher and the solute separations were lower for the HTPB‐based PES membranes than for the pure PES membrane, when the membranes were cast with DMAc as a solvent. On the other hand, both flux and separation values were much lower for the HTPB‐based PES membranes than for the pure PES membrane, when the membranes were cast using NMP. Atomic force microscopy and scanning electron microscopy were used for morphological characterization and the correlation of topography/photography with the performance data was also examined. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2292–2303, 2006     

Fabrication and characterization of maleic anhydride grafted polypropylene membranes with high antifouling properties

In this study, maleic anhydride grafted polypropylene microporous flat‐sheet membranes were prepared via a thermally induced phase separation method with a mixture of dibutyl phthalate and dioctyl phthalate as a diluent. The effects of the polymer composition and coagulation bath temperature on the morphology and performance of the fabricated membranes were investigated. The hydrophilicity results of the membranes demonstrated that membrane modification reduced the water contact angle by about 45°, whereas the pure water flux was enhanced about four times. The antifouling behavior of the fabricated membranes was also investigated in a membrane bioreactor. The results show that the pure water flux, membrane pore size, and porosity decreased, whereas the antifouling performance was improved with increasing polymer concentration and decreasing bath temperature. Finally, the results reveal that the removal efficiency of contaminates was independent on the membrane characterization and was done exclusively through biological removal. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43857.     

Preparation of blend polyethersulfone/cellulose acetate/polyethylene glycol asymmetric membranes for oil–water separation

Blend PES/CA hydrophilic membranes were prepared via a phase-inversion process for oil–water separation. PEG-400 was introduced into the polymer solution in order to enhance phase-inversion and produce high permeability membranes. A gas permeation test was conducted to estimate mean pore size and surface porosity of the membranes. The membranes were characterized in terms of morphology, overall porosity, water contact angle, water flux and hydraulic resistance. A cross-flow separation system was used to evaluate oil–water separation performance of the membranes. From FESEM examination, the prepared PES/CA membrane presented thinner outer skin layer, higher surface porosity with larger pore sizes. The outer surface water contact angle of the prepared membrane significantly decreased when CA was added into the polymer solution. The higher water flux of the PES/CA membrane was related to the higher hydrophilicity and larger pore sizes of the membrane. From oil–water separation test, the PES/CA membrane showed stable oil rejection of 88 % and water flux of 27 l/m² s after 150 min of the operation. In conclusion, by controlling fabrication parameters a developed membrane structure with high hydrophilicity, high surface porosity and low resistance can be achieved to improve oil rejection and water productivity.     

Effect of additives concentration on performance of cellulose acetate and polyethersulfone blend membranes

Asymmetric micro porous membranes have been prepared successfully from blending of cellulose acetate (CA) and polyethersulfone (PES) by the phase inversion method with N, N-dimethylformamide (DMF) as solvent. Two additives were selected in this study, including polyethylene glycol 600 (PEG 600) and polyvinylpyrrolidone (PVP). The effects of concentration of additives on CA/PES blend membrane performance and cross-section morphology were investigated in detail. CA/PES membranes were compared with CA/PES/PEG and CA/PES/PVP membranes in the performance such as pure water flux, membrane resistance, porosity and cross-section morphology. The resulting blend membranes were also carried out the rejection and permeate flux of Egg Albumin (EA) proteins with molecular weight of 45 Da. The membranes thus obtained with an additive concentration of 5 wt% of both PEG and PVP exhibited superior properties than the 80/20% blend composition of CA and PES membranes. The permeate flux of protein was increased from 44 to 134 lm² h with increase in concentrations of both PVP and PEG in 80/20% blend composition of CA and PES membranes. Cross-sectional images from scanning electron microscopy showed larger macropores in the bottom layer of the membranes with increasing additives content. Observations from scanning electron microscopy provided qualitative evidence for the trends obtained for permeability and porosity results.     

Effects of coagulation bath temperature on performances of polyethersulfone membranes modified by nanosilver particles in situ reduction

In this work, an in situ reduction method was used to prepare nanosilver‐modified polyethersulfone (PES‐Ag) ultrafiltration membranes by mixing up the reducing agent ethylene glycol and the protective agent polyvinylpyrrolidone to reduce AgNO₃ in the casting solution. The effects of coagulation bath temperature (CBT) on the separation performances, antifouling property, tensile strength, and stability of the nanosilver particles were researched. The results indicated that when the PES‐Ag membranes were prepared in 40°C coagulation bath, the loss rate of nanosilver particles during preparation was minimum, only 18.5%. With the CBT increasing from 20 to 60°C, the water flux of the PES and PES‐Ag membranes increased, whereas the rejection rate decreased. The largest flux reached 471 L·m^?2·h^?1 for PES‐Ag membranes prepared at 60°C and the rejection was over 90%. The results of contact angle and flux recovery ratio showed that PES‐Ag membranes had better hydrophilicity and antifouling property. Furthermore, the PES‐Ag membranes could inhibit Escherichia coli from growing. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

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。     

Preparation of mesh-reinforced cellulose acetate forward osmosis membrane with very low surface roughness

Mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting compositions such as CA percent and 1, 4-dioxane/acetone ratio and also preparation conditions such as evaporation time, coagulation bath and annealing temperatures were tested for membranes’ performance. The results were compared with commercially CTA membranes. The best membrane (17.9% polymer and 1, 4-dioxane/acetone ratio of 1.89) showed water flux of 9.3 L/m²h (LMH) and RSF of 0.536 mol NaCl/m²h. Moreover, the membrane structure was reinforced by a polyester mesh, which created micro pores in the back of the membrane. This caused higher water flux and RSF compared to membranes without mesh. FO membrane prepared under best conditions, had a smoother surface than commercial ones. This feature enhances the fouling properties of the membrane, which can be appropriate for wastewater treatment applications.     

聚丙烯腈超滤膜的制备

为了得到高性能的超滤膜,采用相转化法,以聚丙烯腈(PAN)为原料,N-甲基-吡咯烷酮(NMP)为溶剂,制备了聚丙烯腈超滤膜.采用纯水通量以及膜对牛血清蛋白(BSA)的截留率作为评价标准,并使用扫描电镜对膜结构进行表征.研究了聚合物质量分数、添加剂种类、凝胶浴温度、凝胶浴种类对膜性能的影响.研究发现:在一定范围内提高聚合...     

Synthesis and characterization of polyethersulfone membranes

Phase inversion method was used to prepare polyethersulfone (PES) ultrafiltration (UF) membranes. Polyethylene glycol (PEG); N, N-dimethyl formamide (DMF) and water were utilized as pore-forming additive, solvent and non-solvent, respectively. Effects of PES and PEG concentrations in the casting solution, PEG molecular weight (MW) and coagulation bath temperature (CBT) on morphology of the prepared membranes were investigated. Taguchi experimental design was applied to run a minimum number of experiments. 18 membranes were synthesized and their permeation and rejection properties to pure water and human serum albumin (HSA) solution were studied. It was found out that increasing PEG concentration, PEG MW and CBT, accelerates diffusional exchange rate of solvent (DMF) and non-solvent (water) and consequently facilitates formation of macrovoids in the membrane structure. The results showed that, increasing PES concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. A trade-off between water permeation and HSA rejection was involved, with membranes having higher water permeation exhibited lower HSA rejection, and vice versa. Hence, optimizing preparation variables to achieve high pure water permeation flux along with reasonable HSA rejection was inevitable. Analysis of variance (ANOVA) showed that all parameters have significant effects on the response (water flux and HSA rejection). However, CBT and PES concentration were more influential factors than PEG concentration and MW on the responses.     

Influence of the coagulation‐bath temperature on the phase‐separation process of poly(vinylidene fluoride)‐graft‐poly(N‐isopropylacrylamide) solutions and membrane structures

A poly(vinylidene fluoride)‐graft‐poly(N‐isopropylacrylamide) (PVDF‐g‐PNIPAAm) copolymer was synthesized, and flat‐sheet membranes were prepared via the phase‐inversion method with N,N‐dimethylformamide (DMF) as the solvent and water as the coagulation bath. The effects of the coagulation‐bath temperature on poly(vinylidene fluoride) (PVDF)/DMF/water and PVDF‐g‐PNIPAAm/DMF/water ternary systems were studied with phase diagrams. The results showed that the phase‐separation process could be due to the hydrophilicity/hydrophobicity of poly(N‐isopropylacrylamide) at low temperatures, and the phase‐separation process was attributed to crystallization at high temperatures. The structures and properties of the membranes prepared at different coagulation‐bath temperatures were researched with scanning electron microscopy, porosity measurements, and flux measurements of pure water. The PVDF‐g‐PNIPAAm membranes, prepared at different temperatures, formed fingerlike pores and showed higher water flux and porosity than PVDF membranes. In particular, a membrane prepared at 30°C had the largest fingerlike pores and greatest porosity. The water flux of a membrane prepared in a 25°C coagulation bath showed a sharp increase with the temperature increasing to about 30°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of PEG on Morphology and Permeation Properties of Polyethersulfone Membranes

Abstract

Flat sheet asymmetric polyethersulfone (PES) ultrafiltration (UF) membranes were prepared from a homogenous solution of PES via immersion precipitation in a water coagulation bath. The effect of the solvents (N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF)) in preparation of the casting solution was studied. The effects of the molecular weight of polyethylene glycol (PEG) (400, 1500, and 6000 Da) on the morphology and the permeation properties of PES membranes were also investigated. Surface and cross-sectional morphology of the prepared membranes were studied by Scanning electron microscopy (SEM). The permeation performance of the prepared membranes was evaluated in terms of pure water flux (J_w), water content, porosity, hydraulic permeability, protein solution flux, and protein rejection. A solution of human serum albumin (HSA, Mw = 66,000 Da) was used as feed to study the permeation properties of the prepared membranes. Increasing molecular weight of PEG additives from 400 to 6000 Da enhances pure water permeation flux and HSA solution permeation flux while it reduces the protein rejection.     

Morphological controlling of CTA forward osmosis membrane using different solvent-nonsolvent compositions in first coagulation bath

Cellulose triacetate (CTA) membranes were fabricated via a modified nonsolvent induced phase separation (NIPS) method. Different solvent-nonsolvent compositions in first coagulation bath (FCB) were introduced to optimize CTA membrane structures. The effects of FCB compositions, immersion time and mass ratio of solvent (N-methyl-2-pyrrolidone, NMP) and nonsolvent (water, ethanol, ethylene glycol and glycerol) on membrane morphology and performance were systematically investigated. Prospective membranes with a dense bottom layer and a scaffold-like top layer were obtained under room temperature, owing to the low relative energy difference (RED) between nonsolvent and polymer as well as the high viscosity of FCBs. A high water flux J_v (12.6 L m^?2 h^?1) and a low reserve salt flux J_s (1.32 g m^?2 h^?1) were obtained in the optimized membrane, with a structural parameter S of 119 μm. Compared with membranes prepared via conventional NIPS method and commercial CTA forward osmosis (FO) membranes, a remarkable improvement of J_s/J_v value and S value was achieved, indicating membranes with single dense-layer structure might suffer less from internal concentration polymerization (ICP) which is the main obstacle for the development of FO process. This study might help us pave the way to design superior CTA membrane structures for forward osmosis application.     

Effect of solvents on performance of polyethersulfone ultrafiltration membranes: Investigation of metal ion separations

The new polyethersulfone (PES) based ultrafiltration membranes were formed using a two stage process of dry and wet phase inversion in non solvent coagulation bath. The effects of three different solvents such as, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and Dimethyl sulphoxide (DMSO) of 82.5% and 85% concentrations on the performance of final membranes were extensively investigated. Scanning electron microscopy (SEM) image results proved that PES membranes with an asymmetric structure were successfully formed. The number of pores formed on the top layer of PES membranes using above-mentioned three solvents was the result of the combined effect of the thermodynamic properties of the system (composition, concentrations, and phase behaviour) and membrane formation kinetics, whereas, the formation of the macroporous sub layer of those membranes was controlled by the diffusion rate of solvent–nonsolvent. The flux of pure water, membrane resistance, mechanical stability, molecular weight cut-off (MWCO) and separation performance of the PES membranes were studied. Separation of metal ions from aqueous solutions was studied for Ni(II), Cu(II) and Cr(III) using two complexing polymer ligands: polyvinyl alcohol (PVA) and poly(diallyldimethylammonium chloride) (PDDA).The separation and permeate rate (flux) efficiencies of the new membranes are compared using different solvents and different PES/solvent compositions.     

Development of novel surface modified phase inversion membranes having hydrophobic surface-modifying macromolecule (nSMM) for vacuum membrane distillation

Eleven PES membranes, into which newly synthesized surface-modifying macromolecule (nSMM) was incorporated, were prepared by using the ‘phase inversion technique’ with different preparation conditions to find the effects of membrane casting parameters on the characteristics and performances of the surface modified PES membranes. The membranes so prepared were characterized by solute separation data from ultrafiltration experiments. The results showed that the mean pore size as well as the surface hydrophobicity increased with an increase in evaporation time for the casting solution blended with nSMM (without PVP). When PVP was added into the casting solution, the mean pore size as well as the contact angle decreased while the pure water permeation flux increased. The surface hydrophobicity decreased with an increase in gelation bath temperature.Four membranes were further prepared and subjected to vacuum membrane distillation (VMD). They were characterized by different analytical instruments and pure water permeation test before being used to VMD. The results showed that a distinctive surface layer was formed in nSMM blended PES membranes. It was also found that nSMM blended PES membranes were sufficiently hydrophobic and porous to be used for the separation of an ethanol/water mixture.     

Effects of Tween 80 concentration as a surfactant additive on morphology and permeability of flat sheet polyethersulfone (PES) membranes

In this study, effects of Tween 80 (polyoxyethylene sorbitan monooleate) as a variable hydrophilic surfactant additive on morphology and permeability of flat sheet polyethersulfone (PES) membranes prepared from PES/polyethylene glycol (PEG)/n-methyl-2-pyrrolidone (NMP) system via phase inversion induced by immersion precipitation in water coagulation bath were investigated. Cross-sectional morphology of the prepared membranes was studied by scanning electron microscopy (SEM). Permeation performance of the prepared membranes was evaluated in terms of pure water permeability (L_P), water content, porosity, hydraulic permeability and thickness of the prepared membranes. It was found out that little addition of Tween 80 to the casting solution increases water content and porosity of the membrane support layer and enhances pure water permeability through the membranes.