Blend Ultrafiltration Membranes Research Articles

A new high performance polyamide as an effective additive for modification of antifouling properties and morphology of asymmetric PES blend ultrafiltration membranes

Polyethersulfone (PES) ultrafiltration membrane with enhanced simultaneous permeability and fouling–resistance property was prepared using a new synthesized aromatic polyamide (PA-6) as an additive. A series of asymmetric membranes were prepared by adding different amounts of PA-6 to the casting solution using the phase inversion induced by immersion precipitation method. Attenuated total reflection-Fourier transform infrared spectra (ATR-FTIR) and water contact angle measurement confirmed the PA-6 enrichment at the membrane surface and increased the membrane hydrophilicity and wettability. The SEM images elucidated the effect of PA-6 addition on the PES membrane morphology by increasing the pore density. The results of filtration performance, which carried out by dead-end filtration of bovine serum albumin (BSA) solution showed that the permeability and fouling resistance property was improved by optimizing the PA-6 content. When the PA-6 content was 2 wt%, the permeability reached approximately 10 times over the pure PES membrane. In comparison to the blend membrane of PES and 2 wt% of polyvinyl pyrrolidone (PVP), the blend membrane of 2 wt% of PA-6 showed significant flux recovery ability. The rejection of all the blended membranes was approximately at high point over 95%. In addition, the results were compared with those obtained using PVP as a usual additive. Although the PVP blended membranes exhibited higher permeability, they showed lower antifouling properties. Finally, a membrane with 1 wt% PVP and 1 wt% PA-6 was prepared and showed the best performance regarding improved permeability and antifouling properties.

High-performance cellulose acetate/polysulfone blend ultrafiltration membranes for removal of heavy metals from water.

Neat cellulose acetate (CA) and CA/polysulfone (PSf) blend ultrafiltration membranes in the presence of polyvinylpyrrolidone as a pore former were prepared via a phase inversion technique. The prepared membranes were characterized by Fourier transform infrared, scanning electron microscopy, mechanical strength, water content, porosity, permeate flux and heavy metals (Pb2+, Cd2+, Zn2+ and Ni2+) rejection to comprehend the impact of polymer blend composition and additive on the properties of the modified membranes. The water flux expanded by increasing of PSf content in the polymer composition. CA/PSf (60/40) had the highest flux among prepared membranes. Prepared blend membranes were able to remove heavy metals from water in the following order: Pb2+ > Cd2+ > Zn2+ > Ni2+. The CA/PSf (80/20) blend membrane had great performance among prepared membranes due to the high heavy metals removal and permeate flux.

Ultrafiltration membranes with tunable morphology and performance prepared by blending quaternized cardo poly(arylene ether sulfone)s ionomers with polysulfone

Abstract The original quaternized cardo poly(arylene ether sulfone)s (QPES-I) ionomers was employed as the virgin polyelectrolyte and its counterions (I−) were exchanged with F− and PF6− to prepare QPES with different anions(QPES-X, X = F, PF6), then QPES-X/PSF blended ultrafiltration membranes was prepared by the nonsolvent induced phase inversion process. Scanning electron microscopy (SEM) was used to characterize the cross section morphology and surface morphology of blended membranes, and atom force microscopy (AFM) was employed for obtaining the three-dimensional images of QPES-X/PSF blended membranes, respectively. The surface chemical composition of the asymmetric membrane was investigated by X-ray photoelectron spectroscopy (XPS). Under similar preparation conditions, the water contact angle on membrane surface increased in the order of QPES-F

Preparation and characterization of PVC/PAN blend ultrafiltration membranes: Effect of PAN concentration and PEG with different molecular weight

The current study investigates the effect of polyacrylonitrile (PAN) addition on morphology and antifouling properties of poly(vinyl chloride) (PVC) asymmetric flat ultrafiltration (UF) membranes. The membranes are prepared via phase inversion method induced by immersion precipitation at different PVC/PAN blending ratio up to 40 wt% PAN. Also, membranes with blending ratio of PVC/ PAN:70/30, which showed the highest water flux and flux recovery ratio, were used for membrane preparation with 4 wt% of Polyethylene glycol (PEG) addition in four different molecular weight, 600 Da, 1,000 Da, 6,000 Da and 20,000 Da, which was used as pore former and hydrophilic polymeric additive. The performance of the membranes was studied by using pure water and bovine serum albumin (BSA) as feed at operating pressure of 3 bar. The cross-sections of the fabricated membranes were studied using SEM, and the images showed remarkable changes in morphology and structure of the prepared membranes after PAN and PEG addition. PAN addition led to increment in water flux up to 30 wt% and then decreased. The similar trend was observed in the case of flux recovery ratio. Also, viscosity of polymeric solution, contact angle and porosity of the membranes, antifouling and flux recovery of the membranes were studied.

Effect of lignin–cellulose nanofibrils on the hydrophilicity and mechanical properties of polyethersulfone ultrafiltration membranes

In the present research, novel polyethersulfone (PES)/lignin–cellulose nanofibril (LCN) blend ultrafiltration membranes with high hydrophilicity and noticeable mechanical properties were prepared via immersion precipitation method. LCN was employed to improve the hydrophilicity and mechanical properties of pure PES ultrafiltration membranes. Transmission electron microscopy and Fourier transform infrared spectroscopy (FTIR) were used to characterize the structure of the LCN. The performance of blend ultrafiltration membranes were characterized in terms of FTIR, thermogravimetric analysis, scanning electron microscopy, pure water flux (PWF), bovine serum albumin retention, water contact angle, surface energy, and mechanical properties. With the increase in content of LCN from 0 wt% to 1.2 wt%, the PWF improved from 322.8 L m−2 h−1 to 692.3 L m−2 h−1 and the tensile strength increased from 4.8 MPa to 7.2 MPa. It was revealed that the addition of LCN could improve the hydrophilicity and mechanical properties of pure PES ultrafiltration membrane.

Polyethersulfone/polyacrylonitrile blended ultrafiltration membranes: preparation, morphology and filtration properties.

Polyethersulfone (PES)/polyacrylonitrile (PAN) membranes have been paid attention among membrane research subjects. However, very few studies are included in the literature. In our study, asymmetric ultrafiltration (UF) membranes were prepared from blends of PES/PAN with phase inversion method using water as coagulation bath. Polyvinylpyrrolidone (PVP) with Mw of 10,000 Da was used as pore former agent. N,N-dimethylformamide was used as solvent. The effects of different percentage of PVP and PES/PAN composition on morphology and water filtration properties were investigated. Membrane performances were examined using pure water and lake water filtration studies. Performances of pure water were less with the addition of PAN into the PES polymer casting solutions. However, long-term water filtration tests showed that PES/PAN blend membranes anti-fouling properties were much higher than the neat PES membranes. The contact angles of PES/PAN membranes were lower than neat PES membranes because of PAN addition in PES polymer casting solutions. Furthermore, it was found that PES/PAN blend UF membranes' dynamic mechanical analysis properties in terms of Young's modules were less than neat PES membrane because of decreasing amount of PES polymer.

Preparation and performance of poly (vinyl chloride)/aminated poly (vinyl chloride) blend ultrafiltration membranes

AbstractPolyvinyl chloride (PVC) was treated with aqueous solution of ethylenediamine to obtain aminated polyvinyl chloride (APVC). PVC/APVC blends ultrafiltration membranes, by phase inversion technique. Different polymer blend compositions with and without an additive, like Poly (ethylene glycol) of molecular weight 600 Da were also prepared. The blend membranes were characterized and evaluated by scanning electron microscopy (SEM), Fourier Transform Infrared spectroscopy (FTIR), water contact angle, water content, pure water flux, and membrane porosity to investigate the influence of APVC on the final properties of the membranes. The presence of amine functional group was confirmed by FTIR spectrum. SEM analysis showed that the blend PVC membranes have thinner top layer and higher porosity in the sublayer. The blend membranes showed an increase in overall porosity, hydrophilicity, and water content, with increase in APVC content and in the presence of additive. The fouling resistant capability of the m...

Preparation and characterization of novel microporous ultrafiltration PES membranes using synthesized hydrophilic polysulfide-amide copolymer as an additive in the casting solution

Novel asymmetric microporous polyethersulfone (PES)/polysulfide-amide (PSA) blended ultrafiltration membranes with superior properties were prepared using the phase inversion induced by immersion precipitation method. The hydrophilic PSA copolymer with nitro groups, thiazole rings, and thioether linkages was synthesized via phosphorylation polycondensation. Different concentrations of the copolymer were used in the PES casting solutions for improving membrane properties and the results were compared with polyvinyl pyrrolidone (PVP)/PES membrane. The presence of amide band, correlated with the stretching vibration of the carbonyl group and bending vibration of NH group on the ATR-FTIR spectra of the modified membranes confirmed the existence of PSA in the PES membrane structure. The cross-section SEM images showed that the membranes with lower skin layer thickness were formed by addition of PSA in the casting solution. Not only the pure water and BSA solution flux of the blended membranes were increased by enlarging PSA concentrations in the casting solutions up to 2% PSA, but also antifouling properties were improved. Comparing PSA with PVP additive showed that the PSA could improve membrane hydrophilicity, porosity, permeability and antifouling properties. However, the PVP has better performance in case of the porosity and the permeability improvement. Therefore, for coupling of the effect of these two additives, the membrane with 1 wt% PVP and 1 wt% PSA was prepared. The results showed that the prepared membrane had good solution flux with good antifouling properties.

Upgrading polysulfone ultrafiltration membranes by blending with amphiphilic block copolymers: Beyond surface segregation

Surface segregation of amphiphilic copolymers in the phase inversion process has long been used to improve membrane hydrophilicity. Typically, the copolymer is sparsely dosed into the casting solutions as additives. Herein we substantially increase the dosages of amphiphilic copolymers, and obtain blend ultrafiltration membranes with synergetically upgraded performances because of extra permeability-enhancing effect of the copolymer in addition to the surface segregation effect. We blend amphiphilic block copolymer, polysulfone-block-polyethylene glycol (PSf-b-PEG), with polysulfone base polymer at various percentages up to 70%. There is no compatible issue between the PSf and PSf-b-PEG as they are miscible at any blend ratio. Infrared spectroscopy and X-ray photoelectron spectroscopy confirm the surface segregation of PEG blocks. Moreover, PSf-b-PEG evidently influences the phase separation process by slowing down the precipitation rate of the polymer solutions, thus producing membranes with thicker skin layers. Interestingly, increasing copolymer percentages result in more water-permeable PEG microdomains in the blend membranes and consequently enhanced water permeance. The blend membranes exhibit simultaneously upgraded permeance, hydrophilicity, fouling resistance, and also performance stability. The highest permeance reaches nearly 400L/(m2hbar) at a copolymer percentage of 40%, which is much higher than those of PSf membranes prepared in other works. By comparing with PEG homopolymer, we identify that the superior performances are originated also from the additional water permeability through PEG microdomains in addition to the effect of surface segregation of PSf-b-PEG copolymers.

Modeling and optimizing the performance of PVC/PVB ultrafiltration membranes using supervised learning approaches

A systematic data analytics framework is developed based on supervised learning (SL), which is used to optimize poly(vinyl chloride) (PVC) and polyvinyl butyral (PVB) blend ultrafiltration membranes fabricated via dry/wet phase inversion.

Preparation and characterization of xanthated cotton fiber modified cellulose triacetate ultrafiltration membrane

Cellulose triacetate (CTA)/xanthated cotton fiber (XCF) blend ultrafiltration (UF) membranes were prepared via phase inversion in the absence and presence of 2.5 wt.% additive, namely polyethylene glycol 6000 (PEG 6000). The XCF which can adsorb heavy metal ions was chosen as the modifier. The prepared membranes were characterized using pure water flux, contact angle, rejection of the metal ion solution, flux recovery ratio, and mechanical analysis techniques to investigate the influence of XCF and PEG 6000 on the final properties of the membranes. Membrane cross-sectional structures and surface morphology were characterized by scanning electron microscopy and atomic force microscopy, respectively. The results showed that the permeability, ion adsorption, surface hydrophilicity, and mechanical properties of the ultrafiltration membranes were enhanced greatly. According to molecular weight, the interception rate of heavy metal ions followed this order: Cu(II) > Zn(II) > Ni(II) > Cd(II). Compared with the membranes prepared from pure CTA, the CTA/XCF blend UF membranes possessed better performances.

Stimuli responsive and low fouling ultrafiltration membranes from blends of polyvinylidene fluoride and designed library of amphiphilic poly(methyl methacrylate) containing copolymers

Amphiphilic copolymers have the ability to improve membrane flux and antifouling property. Copolymers are also able to induce responsive properties in membranes. It is highly desirable to provide a protocol to obtain a library of copolymer modified membranes. Herein, we report a general and convenient approach for the preparation of pH or temperature or simultaneous pH and temperature responsive high flux and low fouling polyvinylidene fluoride (PVDF)/copolymer blend ultrafiltration membranes by conventional phase inversion process. The approach was based on blending PVDF with library of amphiphilic random copolymers containing a common hydrophobic polymer component which is compatible with PVDF. Poly(methyl methacrylate) (PMMA)-co-X copolymers [where X=poly(dimethylaminoethyl methacrylate) (PDMA), poly(acrylic acid) (PAA), poly(N-isopropyl acrylamide) (PNIPAM), poly(N,N-dimethyl acrylamide) (PDMAA), poly(N-vinyl pyrrolidone) (PVP), PDMA-co-PNIPAM, PAA-co-PNIPAM and PDMA-co-PDMAA] are such versatile blending agents for PVDF, easily synthesized by conventional free radical polymerization. The structural effects of X on the membrane pore radius, porosity, permeate flux, responsive behaviour and fouling resistance ability was systematically studied. The beneficial effect of PMMA as a common polymer component in the amphiphilic copolymers for the preparation of blend membranes is attributed to the compatibility of PMMA with PVDF which lowers the phase separation in casting solutions for further phase inversion and enhances the stability of the copolymers in the membrane matrix owing to the enhancement of interfacial adhesion between copolymer and PVDF. This approach is promising for the preparation of library of PVDF/copolymers blend membranes and screening of membranes thereof for further applications.

Preparation and evaluation of heavy metal rejection properties of polysulfone/chitosan, polysulfone/N-succinyl chitosan and polysulfone/N-propylphosphonyl chitosan blend ultrafiltration membranes

Heavy metal rejection properties of chitosan based polysulfone/chitosan (PSf/CS), polysulfonef/N-succinyl chitosan (PSf/NSCS) and polysulfone/N-propylphosphonyl chitosan (PSf/NPPCS) ultrfiltration (UF) membranes were evaluated. The rejection of membranes towards the copper, cadmium and nickel ions was studied during ultrafiltration (UF) by polymer enhanced ultrafiltration (PEUF) processes. The flux change during the UF process and the effect of pH on the rejection were determined. The membrane recycling property was studied during PEUF process by filtering chelated CuSO4 solution. A maximum of 78% of Cu, 73% of Ni and 68% of Cd rejection for M-5 membrane, 75% of Cu, 71% of Ni and 66% of Cd rejection for M-8 membrane and 76% of Cu, 69% of Ni and 66% of Cd rejection for M-2 membrane with reasonably good flux was observed. Further improvement in heavy metal ion rejection was achieved by PEUF process. Membrane M-5 showed a maximum of 98%, 95% and 92% rejection for Cu, Ni and Cd respectively with steady state flux of 117L/m2h. An increase in membrane recycling property after the metal ion rejection was mainly attributed to the hydrophilicity of CS, NSCS and NPPCS.

Effects of Additives on the Morphology and Performance of PPTA/PVDF in Situ Blend UF Membrane

Poly(p-phenylene terephtalamide) (PPTA), a high-performance polymer with high modulus and good hydrophilicity, is often used as a reinforced material. However, due to its high crystallity, micro-phase separation often occurs in the blends. In this paper, PPTA/poly(vinylidene fluoride) (PVDF) compatible blend solution was synthesized by in situ polycondensation. Blend ultra-filtration membrane was prepared through the immersion phase inversion process. In order to obtain desired pore structure, the effects of different additives including hydrophilic polymer (polyethylene glycol (PEG)), inorganic salt (lithium chloride (LiCl)) and the surfactant (Tween-80) on the morphology and performance of PPTA/PVDF blend membranes were studied. The membrane formation process was investigated through ternary phase diagram (thermodynamics) and viscosities (kinetics) analysis. It was found that, with the increasing of LiCl content, a porous membrane structure with long finger-like pores was formed due to the accelerated demixing process which resulted in the increase of porosity and pore diameter as well as the enhancement of water flux and the decline of PEG rejection. When Tween content increased to over 3 wt%, dynamic viscosity became the main factor resulting in a decreased phase separation rate. The transfer of PEG and LiCl molecules onto membrane surface increased the surface hydrophilicity. The effect of Tween content on membrane hydrophilicity was also correlated with the compatibility of blend components.

Improved oil/water emulsion separation performance of PVC/CPVC blend ultrafiltration membranes by fluorination treatment

The introduction of perfluoroalkyl groups played an important role in enhanced antifouling ability in oil/water emulsion membrane separation. Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) blend membranes were used to prepare the novel fluorinated membranes. Amination treatment of PVC/CPVC blend membranes was first carried out through chemical grafting with ethylenediamine (EDA). Fluorination treatment was then achieved through chemical reaction between the redundant amino group of EDA and the carboxyl group of pentadecafluorooctanoica acid. The component of the fluorinated membrane surfaces was measured by X-ray photoelectron spectroscopy. The structure change was observed by scanning electron microscope. The fluorinated membranes were fully wetted by water in short time according to water contact angle measurement. The fluorinated membranes had higher permeate fluxes and higher flux recovery than PVC/CPVC blend membranes in oil/water emulsion membrane separation.

Fabrication of polyvinyl chloride ultrafiltration membranes with stable antifouling property by exploring the pore formation and surface modification capabilities of polyvinyl formal

Polyvinyl chloride (PVC) and polyvinyl formal (PVF) blend ultrafiltration membranes were fabricated by non-solvent induced phase separation (NIPS) method with different casting solution composition. The PVC/PVF membranes were characterized and evaluated by scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), water contact angle measurement and performance measurement. The results showed that PVF played the role of pore formation agent during the NIPS process, and both of porosity and the mean pore size of the membranes were increased with the increased dosage of PVF. Simultaneously, PVF was enriched to membrane surface via spontaneous surface segregation and the membrane surface hydrophilicity was greatly elevated, which implied the remarkably enhanced antifouling property. The robust residence of PVF on the membrane surface was confirmed by a long-term test of incubating membranes in deionized water, which revealed the stable antifouling property of PVC/PVF membranes. Therefore, PVF could be explored as a potential versatile modifier for fabricating high performance ultrafiltration membranes.

Sulfonated polyethersulfone-based membranes for metal ion removal via a hybrid process

Membranes are being increasingly used as an economic alternative for wastewater treatment compared to conventional methods. Ultrafiltration membranes are widely used in metal ions’ rejection. Sulfonated Polyethersulfone (SPES)/polysulfone (PSf) blend flat sheet membranes are prepared using polar solvent N-methyl-2-pyrrolidone (NMP) by the dry–wet phase inversion technique. Polyethylene glycol (PEG-200) is used as a non-solvent additive in the casting solution. The effect of PSf/SPES blend ratio on the morphology, hydrophilicity, water content, porosity, hydraulic resistance, pure water flux, compaction, and molecular weight cut-off (MWCO) of the prepared membranes was studied and found to be improved significantly by the incorporation of SPES in the dope solution. Scanning electron microscopy (SEM) studies revealed that the membranes formed had an asymmetric structure with a thin skin layer and porous sublayer. The prepared membranes were used for rejection of Cu(II) and Zn(II) which are complexed with water-soluble chelating polymer polyethyleneimine. The results show that the order of rejection is Cu(II) ion > Zn(II) ion. Thus, it is worth mentioning that the PSf/SPES blend ultrafiltration membranes prepared in this study would offer immense potential in removal of toxic metal ion from industrial effluents.

Studies on sulfonated styrene acrylonitrile and cellulose acetate blend ultrafiltration membranes

ABSTRACTMembranes are increasingly used in the chemical and bioprocess industries replacing more conventional separation techniques. Blending of various polymers has stimulated great interest in membrane science to improve the performance of membranes, such as hydrophilicity and flux and to reduce the fouling behavior. This paper deals with the preparation of flat-sheet asymmetric blend ultrafiltration (UF) membranes by solution casting, followed by a phase separation method. Sulfonated styrene acrylonitrile (SSAN) was selected as the hydrophilic polymer in the blend. The blend membranes were prepared with different compositions of CA and SSAN. The prepared membranes were characterized for their UF performances, such as pure water flux, water content, porosity, membrane hydraulic resistance, and morphology. The average pore size and porosity of the membranes were revealed by pore statistics and molecular weight cut-off (MWCO) studies using different molecular weight of proteins. Observations from scanning...

Effect of poly(ether–ether–sulfone) concentration on the morphology, performance, thermal stability, mechanical strength, and antifouling of asymmetric cellulose acetate ultrafiltration membranes

The aim of the present work is to investigate the morphology, performance, thermal stability, mechanical strength, and antifouling of the poly(ether–ether–sulfone) (PEES)-incorporated asymmetric cellulose acetate (CA)-blended ultrafiltration membranes. High-performance CA/PEES blend ultrafiltration membranes were prepared by the phase inversion technique. The effects of PEES concentration (0–30 wt%) on pure water permeability (PWP), water content, porosity, molecular weight cutoff, mean pore size, morphology, hydrophilicity, and thermal and mechanical properties of the CA/PEES blend membranes were investigated. Morphological studies were carried out using scanning electron microscopy. scanning electron microscopic studies revealed that the incorporation of PEES resulted in the formation of a thin top layer, a porous sub-layer, and the open pores in the bottom layer. The thermal properties of these polymeric membranes were evaluated by thermogravimetric and differential thermogravimetric analyses measurements, whereas the glass transition temperature of the membranes was calculated by differential scanning calorimetry. With the increase in the concentration of PEES on the CA membranes, the PWP, hydrophilicity, water content, porosity, the thermal stability, glass transition temperature, tensile strength, tensile modulus, and elongation at break significantly improved in the blend membranes. The efficiency of these membranes in the separation of commercially important proteins such as bovine serum albumin (BSA), egg albumin, pepsin, and trypsin was studied and found to be enhanced as compared to CA membranes. In fouling experiments, BSA was used as the model protein, and flux recovery ratio (FRR) of the membranes was calculated. Attempts have been made to correlate the changes in membrane morphology with pure water flux, water content, porosity, thermal and mechanical stability, separation efficiency, and antifouling property of the CA/PEES membranes. It has been demonstrated that the fouling-resistant ability of CA/PEES membranes is enhanced due to the high FRR with the addition of PEES in the casting solution. Based on the findings, it can be concluded that the membranes prepared with 80/20 composition of CA/PEES blend membranes are promising candidates for industrial applications.

Concentration of Astragalus Polysaccharide by Polysulfone-Activated Carbon Modified with Nitric Acid Blend Ultrafiltration Membranes

In this study, Astragalus polysaccharides were concentrated by ultrafiltation membranes prepared by blending polysulfone (PSF) with activated carbon modified with nitric acid(HAC) by immersion precipitation phase inversion method. Water flux and retention to bovine serum albumin of the membranes were investigated. The morphology of membranes were also observed by scanning electron microscopy (SEM). In order to obtain best concentration performance, effects of operating pressure, feeding temperature, operating time, feeding concentration and pH value on concentration and extraction of astragalus polysaccharide were studied. The best conditions for concentration were as follows: operating pressure is 0.4 MPa, feeding temperature is 25 °C, feeding concentration is 1 g·L-1, pH value is neutral. Under these conditions, the ultrafiltration membrane flux was 62.6 L·m-2·h-1, the retention to astragalus polysaccharide was 91.2%, and the attenuation rate of water flux was 12.5% in one hour.