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.     

The effect of heat-treatment on the ultrafiltration performance of polyethersulfone (PES) hollow-fiber membranes

Polyethersulfone (PES) hollow-fiber membranes were prepared by the dry-wet spinning method and then heated in an oven at different temperatures to investigate the effect of heat-treatment on their ultrafiltration performance. It was found that the hollow-fiber membranes shrank by heat treatment, as evidenced by a decrease in flux and an increase in solute separation, although there was no visible change in the hollow-fiber dimension. The best results were obtained when the hollow fibers were heated at 150°C. A further investigation was made on the effect of the heating period, while the temperature was fixed to 150°C. It was found that the best combination of the temperature and the heating period was 150°C and 5 min.     

Comparative performance study of polyethersulfone and polysulfone membranes for trypsin isolation from goat pancreas using affinity ultrafiltration

The comparative performance of polysulfone and polyethersulfone membranes (of 30 kDa MWCO) in isolation of trypsin from goat pancreas by affinity ultrafiltration is examined using cross-linked soybean trypsin inhibitor (STI) as affinity ligand, 0.1 M Tris–HCl as wash buffer and 0.5 M KCl–HCl as elution buffer in an unstirred, dead-ended module at 392.28 kPa (4 kg/cm²) transmembrane pressure and room temperature (ca. 30 °C) with 1:1 (v/v) ratio of pancreatic extract and wash buffer. No active trypsin was found to be detectably present in the washing phase permeate in any of the experiments, indicating good binding efficiency of the target enzyme with the ligand employed. The total protein recovery obtained with the polyethersulfone membrane (70%) is 1.5 times higher than that with the polysulfone (46%). Yields of active trypsin for the two membranes are, however, similar (74% for polyethersulfone and 70% for polysulfone) although comparable with earlier reported trypsin yield (from porcine pancreas). In both the washing and elution phases of affinity ultrafiltration, the polyethersulfone membrane facilitates consistently and substantially higher volumetric flux as well as permeated protein throughput than the polysulfone.     

Towards superior permeability and antifouling performance of sulfonated polyethersulfone ultrafiltration membranes modified with sulfopropyl methacrylate functionalized SBA-15

A non-solvent induced phase separation (NIPS) process was used to fabricate a series of sulfonated polyethersulfone (SPES) membranes blending with different concentrations of SBA-15-g-PSPA with the applications in the ultrafiltration (UF) process. SBA-15 was modified with 3-methacrylate-propyltrimethoxysilane (MPS) to form SBA-15-g-MPS. It was further modified with the charge tailorable polymer chains by reacting with 3-sulfopropyl methacrylate potassium salt. The nanoparticles were uniformly dispersed and finger-like channels were developed within the membrane. The adding of surface modified SBA-15-g-PSPA nanoparticles has significantly improved membrane water permeability, hydrophilicity, and antifouling properties. The pure water fluxes of the composite SPES membranes were significantly higher than the pristine SPES membrane. For the membrane containing 5% (mass) of SBA-15-g-PSPA (MSSPA5), the pure water flux was increased dramatically to 402.15 L·m^-2·h^-1, which is ~1.5 times that of MSSPA0 (268.0 L·m^-2·h^-1). The high flux rate was achieved with 3% (mass) of SBA-15 nanoparticles with retained high rejection ratio 98% for natural organic matter. The results indicate that the fashioned composite membrane comprising SBA-15-g-PSPA nanoparticles have a promising future in ultrafiltration applications.     

Ethanol‐responsive characteristics of polyethersulfone composite membranes blended with poly(N‐isopropylacrylamide) nanogels

Ethanol‐responsive smart membranes with different microstructures are prepared from blends of polyethersulfone (PES) and poly(N‐isopropylacrylamide) (PNIPAM) nanogels by immersion precipitation phase inversion method in a convenient and controllable manner. The introduction of PNIPAM nanogels forms the microporous structures on the surface of the top skin layer and on the pore walls of the finger‐like porous sublayer of membranes. The ethanol‐responsive characteristics of the proposed PES composite membranes are systematically investigated. With increasing ethanol concentration in the range from 0 to 15 wt %, the trans‐membrane flux of ethanol solution increases. The microstructures and the resultant ethanol‐responsive characteristics of the composite membranes can be regulated by the content of PNIPAM nanogels blended in the membranes. The more the content of PNIPAM nanogels blended in the membranes, the more the number of the submicron pores is, and thus the better the ethanol‐responsive characteristics of the composite membranes. The proposed ethanol‐responsive smart membranes are expected to be combined with the traditional pervaporation membranes as a smart vavle to achieve continuous and highly efficient ethanol production during the biological fermentation. The preparation technique and results in this study provide valuable guidance for further design and the industrial‐scale fabrication of novel composite membranes for application in ethanol separation systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41032.     

Formation of polyamide 12 membranes via thermal–nonsolvent induced phase separation

The thermal–nonsolvent induced phase separation method was used for the fabrication of porous membranes from polyamide 12 (PA12), an attractive engineering polymer; the water/formic acid (FA)/PA12 ternary system is explored in detail. Scanning electron microscopy, differential scanning calorimetry, X‐ray diffractometry, tensile strength analysis, and water flux were used to characterize the structure and properties of the fabricated membranes. The morphology of the membranes was found to depend on the FA content in the bath. The top surface of the membrane becomes less dense with increasing FA content in the bath. The cross section and bottom surface of all membranes exhibited a cellular morphology, except for the case of the novel procedure of dope precipitation in a cold neat solvent (FA) bath. In all cases membranes exhibited a crystallinity of ca. 38% with a melting point of ca. 179°C; tensile strengths in excess of 10 MPa were found possible in some cases. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Role of poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) in the modification of polysulfone membranes for ultrafiltration

In this study polysulfone membranes with antifouling and hydrophilic properties were synthesized using poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (AMPS) as an additive for the first time. Different wt % of AMPS was used to prepare polysulfone membranes by phase inversion method. The role of AMPS on the porosity, pore size distribution, hydrophilicity, and antifouling nature was investigated and analyzed in detail. Characterization techniques like field emission scanning electron microscope, atomic force microscopy, and imageJ software were used to characterize the morphology of prepared membranes. There is positive effect of the additive addition on all the membrane parameters like Pure water flux [101.76 L/(m² h)] (MR0) to 464.06 L/(m² h) (MR4)], hydraulic permeability [0.65 (MR0) to 2.01 (MR4)], equilibrium water content [21.74 (MR0) to 71.45 (MR4)], and porosity [0.024 (MR0) to 0.58 (MR4)]. Response surface methodology was used for the optimization of bovine serum albumin (BSA) flux and rejection. The results of the morphological as well as permeation studies depicted that permeate flux and antifouling nature were increased with the amount of AMPS present in the membrane matrix. The antifouling study of the prepared membranes was undertaken by using BSA solution of 1000 mg/L. Positive results were seen with the increase in amount of AMPS, since, the total membrane resistance has been decreased from 0.95 (MR0) to 0.74 (MR4). Separation of humic acid from aqueous medium was also performed with the best performing membrane (MR4, having the highest amount of AMPS). Separation efficiency of 100% and 94% were obtained using 10 mg/L and 50 mg/L of HA, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45290.     

Gas permeation performance of cellulose hollow fiber membranes made from the cellulose/N‐methylmorpholine‐N‐oxide/H2O system

Cellulose hollow fiber membranes (CHFM) were prepared using a spinning solution containing N‐methylmorpholine‐N‐oxide as solvent and water as a nonsolvent additive. Water was also used as both the internal and external coagulant. It was demonstrated that the phase separation mechanism of this system was delayed demixing. The CHFM was revealed to be homogeneously dense structure after desiccation. The gas permeation properties of CO₂, N₂, CH₄, and H₂ through CHFM were investigated as a function of membrane water content and operation pressure. The water content of CHFM had crucial influence on gas permeation performance, and the permeation rates of all gases increased sharply with the increase of membrane water content. The permeation rate of CO₂ increased with the increase of operation pressure, which has no significant effect on N₂, H₂, and CH₄. At the end of this article a detailed comparison of gas permeation performance and mechanism between the CHFM and cellulose acetate flat membrane was given. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1873–1880, 2004     

Formation of porous poly(ethylene‐co‐vinyl alcohol) membrane via thermally induced phase separation

Crystalline poly(ethylene‐co‐vinyl alcohol) (EVOH) membranes were prepared by a thermally induced phase separation (TIPS) process. The diluents used were 1,3‐propanediol and 1,3‐butanediol. The dynamic crystallization temperature was determined by DSC measurement. No structure was detected by an optical microscope in the temperature region higher than the crystallization temperature. This means that porous membrane structures were formed by solid–liquid phase separation (polymer crystallization) rather than by liquid–liquid phase separation. The EVOH/butanediol system showed a higher dynamic crystallization temperature and equilibrium melting temperature than those of the EVOH/propanediol system. SEM observation showed that the sizes of the crystalline particles in the membranes depended on the polymer concentration, cooling rate, and kinds of diluents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2449–2455, 2001     

Strong effects of Tween 20 additive on the morphology and performance of poly(vinylidene fluoride) hollow‐fiber membranes

Poly(vinylidene fluoride) (PVDF) hollow‐fiber membranes were prepared from a Tween 20/water/triethyl phosphate/PVDF system. The effects of Tween 20 on the morphology and properties of the membranes were explored. Field emission scanning electron microscopy imaging indicated the presence of skinlike layers on both surfaces of the membranes. In the cross section, a bicontinuous morphology comprised of interlocked crystallites was observed. As the dosage of Tween 20 was raised, the size and quantity of nanopores on the surfaces increased, and the morphology of the crystallites in the cross section changed from sheaflike to sticklike. Tween 20 was removed almost completely during the membrane‐formation process, as validated by Fourier transform infrared–attenuated total reflection and ¹H‐NMR spectrometry. Dextran filtrations were preformed to demonstrate the potential applications of these membranes in separation processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44600.     

Superior effect of TEMPO-oxidized cellulose nanofibrils (TOCNs) on the performance of cellulose triacetate (CTA) ultrafiltration membrane

Cellulose triacetate (CTA) ultrafiltration membranes were prepared via phase inversion technique using hydrophilic TEMPO-oxidized cellulose nanofibrils (TOCNs) as modifying agents. The permeation performance of the prepared membranes was evaluated in terms of pure water flux (Ji), protein rejection (Rm) and flux recovery ratio (FRR). Membrane surface morphology and cross-sectional structures were characterized by atomic-force microscopy (AFM) and scanning electron microscopy (SEM), respectively. XRD was performed in order to investigate the interactions between membrane components. Meanwhile, the effects of TOCN concentration on hydrophilicity of the membrane surface and mechanical properties were also examined. The experimental results indicated that CTA/TOCN composite membranes exhibit significant differences in surface properties and intrinsic properties due to the addition of TOCNs.     

Improving the charged and antifouling properties of PVDF ultrafiltration membranes by blending with polymerized ionic liquid copolymer P(MMA‐b‐MEBIm‐Br)

This study describes the fabrication and properties of poly(vinylidene fluoride) (PVDF) filtration membranes modified by blending with ionic liquid block copolymer P(MMA‐b‐MEBIm‐Br), which is synthesized via reversible addition‐fragmentation chain transfer polymerization method. The attenuated total reflectance‐Fourier transform infrared spectroscopy and X‐ray photoelectron analyses reveal that the ionic liquid block copolymers are immobilized on PVDF membrane surface. The modified PVDF membrane exhibits excellent charged and antifouling properties because of the charged and hydrophilic properties of the copolymer. Scanning electron microscopy and atomic force microscopy also indicate the morphological characteristics of the membrane and demonstrate that the surface porous structure becomes denser after adding the copolymer. The data of filtration and the zeta potential of the membranes suggest that the charged properties of the ionic liquid block copolymers are mainly responsible for the improvement of the reversible fouling ratio and the decrease in the total fouling ratio of the membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44751.     

Preparation and properties of soluble copolysulfoneimide and performance of solvent‐resistant ultrafiltration membrane

Soluble copolysulfoneimides were synthesized by thermal two‐step method in solution of N‐methyl‐2‐pyrrolidone. The used aromatic diamines were bis[4‐(3‐aminophenoxy)phenyl]sulfone (BAPS‐m) and 3,3′‐diaminosulfone, and dianhydrides were pyromellitic dianhydride, 4,4′‐oxyphthalic anhydride, and 3,3′,4,4′‐diphenylsulfone tetracarboxylic dianhydride. The molar ratio of diamines was changed to reduce the content of BAPS‐m. The thermal and mechanical properties of polyimides were investigated. The polyimide ultrafiltration membrane with molecular weight cut‐off of 10 kDa could be successfully prepared by phase‐inversion method. Various solvent (water, alcohols, acetone, and hexane) fluxes were measured to investigate solvent‐resistance and membrane behavior during solvent permeation. The activation energy relationship between hexane flux and viscosity with temperature was also studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1024–1030, 2002     

Development of polyethersulfone phase‐inversion membranes for membrane distillation using oleophobic coatings

Highly porous macrovoid‐free polyethersulfone membranes have been prepared using the phase‐inversion process with water as the non‐solvent. These membranes are of great interest for membrane distillation (MD) after application of a hydrophobic/oleophobic coating. The membrane structure was controlled by optimizing the process conditions and dope composition. Counter intuitively, increasing the polymer concentration favors the formation of larger surface pores under similar process conditions. A symmetric membrane is obtained when a sufficient amount of high‐molecular‐weight polyvinylpyrrolidone was added to the dope solution, which appears to play an important role in the structure formation process. The final membrane shows similar performance compared to commercial MD membranes. However, the membranes developed in this study show an oleophobic character, broadening the applications of MD. Moreover, the compressibility of these membranes is severely reduced compared to stretched membranes, which is expected to result in an improved MD performance at full scale. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45516.     

Polyether‐segmented nylon hemodialysis membrane. VII. Studies on surface structures of various poly(ethylene oxide)‐segmented nylon membranes

The relationships of the surface morphologies to the surface chemical compositions in poly(ethylene oxide)‐segmented nylon (PEO–Ny) membranes prepared by the phase‐inversion method were studied using scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and static secondary ion mass spectrometry (SSIMS). The PEO–Ny's used were high semicrystalline PEO‐segmented polyiminosebacoyliminohexamethylene (PEO–Ny610), low semicrystalline PEO‐segmented poly(iminosebacoylimino‐m‐xylylene) (PEO–NyM10), and amorphous PEO‐ segmented poly(iminoisophthaloyliminomethylene‐1,3‐cyclohexylenemethylene) (PEO–NyBI). SEM observation showed that the surfaces of the PEO–Ny610 and PEO–NyM10 membranes were composed of crystalline spherulite and that the PEO–NyBI membrane surface had a nodular structure. ESCA analysis exhibited the enrichment of the PEO segment at the surfaces of the PEO–Ny610 and PEO–NyM10 membranes. On the other hand, the enrichment of the Ny segment was observed in the case of the PEO–NyBI membrane. SSIMS analysis revealed that the outermost surfaces of the PEO–Ny membranes except the PEO–NyBI membrane were almost covered with the PEO segment. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 517–528, 2000     

Preparation and characterization of poly(ethylene‐co‐vinyl alcohol) membranes via thermally induced liquid–liquid phase separation

Porous membranes were prepared through the thermally induced phase separation of poly(ethylene‐co‐vinyl alcohol) (EVOH)/glycerol mixtures. The binodal temperature and dynamic crystallization temperature were determined by optical microscopy and differential scanning calorimetry measurements, respectively. It was determined experimentally that the liquid–liquid phase boundaries were shifted to higher temperatures when the ethylene content in EVOH increased. For EVOHs with ethylene contents of 32–44 mol %, liquid–liquid phase separation occurred before crystallization. Cellular pores were formed in these membranes. However, only polymer crystallization (solid–liquid phase separation) occurred for EVOH with a 27 mol % ethylene content, and the membrane morphology was the particulate structure. Scanning electron microscopy showed that the sizes of the cellular pores and crystalline particles in the membranes depended on the ethylene content in EVOH, the polymer concentration, and the cooling rate. Furthermore, the tendency of the pore and particle sizes was examined in terms of the solution thermodynamics of the binary mixture and the crystallization kinetics. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 853–860, 2003     

Fabrication of membranes of polyethersulfone and poly(N‐vinyl pyrrolidone): influence of glycerol on processing and transport properties

In this study, we focus on membranes of polyethersulfone and poly(N‐vinyl pyrrolidone) and elucidate the influence of composition on the rheological, diffusion and precipitation properties of solutions which are used for membrane preparation via a non‐solvent‐induced phase separation process. The low‐molar‐mass component of the solution is a mixture of the solvent N‐methyl‐2‐pyrrolidone and the non‐solvent glycerol. Cloud point, viscosity and diffusion measurements as well as precipitation experiments were performed in order to achieve a comprehensive understanding of the time dependence of the precipitation process. The addition of glycerol yields an increase of viscosity and a stronger tendency for demixing. The enhanced tendency for demixing causes a more rapid precipitation process. The average relaxation time of the solution as a function of glycerol concentration follows a similar trend to its viscosity. The increase of viscosity is associated with the increase of the monomeric friction coefficient. Two diffusive processes with clearly separated time scales appear in dynamic light scattering experiments in the presence of glycerol. This phenomenon is discussed taking into account the phase behaviour of the solution and the quality of the solvent. The addition of glycerol yields a lower pure water permeance whereas the molecular weight cut‐off is not altered in the ultrafiltration range. © 2020 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

PEEKWC ultrafiltration hollow‐fiber membranes: Preparation,morphology, and transport properties

A series of hollow‐fiber membranes was produced by the dry–wet spinning method from PEEKWC, a modified poly(ether ether ketone) with good mechanical, thermal, and chemical resistance. The fibers were prepared under different spinning conditions, varying the following spinning parameters: polymer concentration in the spinning solution, height of the air gap, and bore fluid composition. The effect of these parameters on the water permeability, the rejection of macromolecules (using dextrane with an average molecular weight of 68,800 g/mol), and the morphology of the membranes was studied. The results were also correlated to the viscosity of the spinning solution and to the ternary polymer/solvent/nonsolvent phase diagram. The morphology of the cross section and internal and external surfaces of the hollow fibers were analyzed using scanning electron microscopy (SEM). All membranes were shown to have a fingerlike void structure and a skin layer, depending on the spinning conditions, varying from (apparently) dense to porous. Pore size measurements by the bubble‐point method showed maximum pore sizes ranging from 0.3 to 2 μm. Permeability varied from 300 to 1000 L/(h^?1 m^?2 bar) and rejection to the dextrane from 10 to 78%. The viscosity of polymer solutions was in the range of 0.2 to 3.5 Pa s. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 841–853, 2004     

Fundamental understanding of the effect of air‐gap distance on the fabrication of hollow fiber membranes

The objectives of this work are, fundamentally, to understand hollow fiber membrane formation from an engineering aspect, to develop the governing equations to describe the velocity profile of nascent hollow fiber during formation in the air gap region, and to predict fiber dimension as a function of air‐gap distance. We have derived the basic equations to relate the velocity profile of a nascent hollow fiber in the air‐gap region as a function of gravity, mass transfer, surface tension, drag forces, spinning stress, and rheological parameters of spinning solutions. Two simplified equations were also derived to predict the inner and outer diameters of hollow fibers. To prove our hypotheses, hollow fiber membranes were spun from 20 : 80 polybezimidazole/polyetherimide dopes with 25.6 wt % solid in N,N‐dimethylacetamide using water as the external and internal coagulants. We found that inner and outer diameters of as‐spun fibers are in agreement with our prediction. The effects of air‐gap distance or spin‐line stress on nascent fiber morphology, gas performance, and mechanical and thermal properties can be qualitatively explained by our mathematical equations. In short, the spin‐line stresses have positive or negative effects on membrane formation and separation performance. A high elongational stress may pull molecular chains or phase‐separated domains apart in the early stage of phase separation and create porosity, whereas a medium stress may induce molecular orientation and reduce membrane porosity or free volume. Scanning electron microscopic photographs, coefficient of thermal expansion, and gas selectivity data confirm these conclusions. T_g of dry‐jet wet‐spun fibers is lower than that of wet‐spun fibers, and T_g decreases with an increase in air‐gap distance possibly because of the reduction in free volume induced by gravity and elongational stress. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 379–395, 1999     

Preparation and oxygen permeation of U‐shaped perovskite hollow‐fiber membranes

The oxygen permeation of dense U‐shaped perovskite hollow‐fiber membranes based on Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ prepared by a phase inversion spinning process is reported. The perovskite hollow fibers with totally dense wall were obtained with the outer diameter of 1.147 mm and the inner diameter of 0.691 mm. The dependences of the oxygen permeation on the air flow rate on the shell side, the helium flow rate on the core side, the oxygen partial pressures, and the operating temperatures were experimentally investigated. According to the Wagner theory, it follows that the oxygen transport through the U‐shaped hollow‐fiber membrane is controlled by both surface reaction and bulk diffusion at the temperature ranges of 750–950°C. High oxygen permeation flux of 3.0 ml/(min cm²) was kept for about 250 h at 950°C under the conditions of the air feed flow rate of 150 ml/min and the helium flow rate of 50 ml/min. © 2010 American Institute of Chemical Engineers AIChE J, 2011