Studies on Performance of Cellulose Acetate and Poly(Ethelene Glycol) Blend Ultrafiltration Membranes Using Mixture Design Concept of Design of Experiments

Cellulose acetate (CA) membranes have several advantages over other membranes due to their moderate flux, high salt rejection properties, renewable source of raw material, etc. Membrane compositions containing different concentrations of CA, polyethylene glycol (PEG 600) as additive and N,N–dimethyl formamide (DMF) as solvent have been prepared using phase inversion technique based on the mixture design concept of design of experiments. The prepared membranes have been characterized for permeate flux, membrane hydraulic resistance, and separation of proteins such as pepsin, egg albumin (EA), and bovine serum albumin (BSA). Using statistical techniques, the experimental data have been analyzed and a suitable model was suggested for predicting the optimal level of response as a function of the input variable. The influence of variation of the CA, DMF, and PEG 600 on the asymmetric membrane properties has also been reported.     

Surface-modified polysulfone hollow fibers. IV. Chloromethylated fibers and their derivatives

A chloromethylated reaction was performed on the surfaces of polysulfone ultrafiltration hollow fibers and their derivative membranes, i.e., triethylaminated, ethylenediaminated, and acethylated fibers, were prepared. The modified fibers have a 30–60% insoluble region in chloroform, whereas nonmodified fibers can be dissolved in the chloroform. It is suggested that the insoluble parts of the fibers are highly cross-linked due to the high degree of chloromethylation. The modified fibers showed a 50–98% rejection of polyethylene glycol 6000 at a feed concentration of 0.5 wt %, except for the triethylaminated fibers, which gave a negative rejection from ?91 to ?96%. It was found that the modified segments significantly influenced the rejection behavior of the solutes. Absorption of bovine serum albumin on the ethylenediaminated fibers at pH 7.1 was estimated from permeation measurements to be less than that of the other modified and nonmodified fibers. This effect is attributed to the hydrophilic surface of the ethylenediaminated fibers.     

Effects of polymer molecular weight,concentration, and role of polyethylene glycol as additive on polyacrylonitrile homopolymer membranes

Polyacrylonitrile (PAN), is an important base polymer to cast porous membranes. In this work, a detailed study of the effects of molecular weight of PAN homopolymer and its concentration on the cast membrane has been undertaken. The effects of molecular weight of additive polyethylene glycol (PEG) and its concentration have also been investigated. The membranes are cast using dimethyl formamide as solvent using phase inversion technique. They are characterized in terms of porosity, water permeability, molecular weight cut off, average pore diameter, contact angle, and tensile strength at breaking point. Fourier transform infrared spectroscopy and scanning electron microscopy are used to characterize the chemical and morphological changes of the membrane surface. Further studies have been considered to evaluate the antifouling property of various membranes using filtration of bovine serum albumin solution. Membrane modified by PEG 400 membrane shows an improved separation performance and antifouling characteristics. POLYM. ENG. SCI., 54:2375–2391, 2014. © 2013 Society of Plastics Engineers     

Preparation and characterization of PVDF-PFSA flat sheet ultrafiltration membranes

High performance polyvinylidene fluoride (PVDF) flat sheet ultrafiltration (UF) membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid (PFSA) as a pore former and as a hydrophilic component of the membranes and polyethylene glycol (M_w = 400) (PEG400) as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin (BSA) protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane (5 wt-% PEG400+ 5 wt-% PFSA) had a pure water flux of 141.7 L/m²·h, a BSA rejection of 90.1% and a relative pure water flux reduction (RFR) of 15.28%. These properties were greatly superior to those of the native PVDF membrane (pure water flux of 5.6 L/m²·h, BSA rejection of 96.3% and RFR of 42.86%).     

Performance of polysulfone/carboxylated polysulfone membranes

Membranes were made from miscible blends of polysulfone (PSf) and carboxylated polysulfone (CPSf) having an average of 0.45 and 0.87 ? COOH groups per repeated unit. Membranes made from PSf and CPSf alone showed low separation for NaCl, glucose, polyethylene glycol (PEG) of various molecular weights and bovine albumin, from aqueous solutions under an applied pressure of 50 psig and higher. Membranes made from PSf/CPSf of varied blend composition showed higher separation factors for the above solutes. Highest separation was observed in membranes made from an 80/20 wt% PSf/CPSf 0.45 blend, which yielded a separation factor of 0.60 for NaCl, 0.97 for glucose, 0.98 for PEG and 0.99 for bovine albumin under an applied pressure in the range 50–150 psig. This higher performance is believed to be a result of a synergism between PSf and CPSf 0.45 to give a membrane morphology unique among the PSf/CPSf membranes.     

Development of membranes by radiation grafting of acrylamide into polyethylene films: Characterization and thermal investigations

Polyethylene-g-polyacrylamide membranes were prepared by graft polymerization of acrylamide into polyethylene films by preirradiation technique. The characterization and thermal behavior of membranes with different degrees of grafting were evaluated by density, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry measurements. Grafting led to considerable changes in the structure of polyethylene membranes. The density of the polyethylene film increased wtih the increase in the degree of grafting, although the increase beyond 100% grafting was less pronounced than at lower graft levels. The heat of fusion and the crystallinity of polyethylene decreased with the increase in the degree of grafting. The decrease in crystallinity is because of the cumulative effect of the dilution of inherent crystallinity by the incorporation of amorphous polyacrylamide grafts within the noncrystalline region of polyethylene (dilution effect) and partial disruption of the crystallites (crystal defects). X-ray diffraction measurements also revealed a decrease in the crystallinity in grafted films. Membranes behaved as a two-component system where polyethylene and polyacrylamide components underwent independent degradation irrespective of the graft levels. In general, the thermal stability of polyethylene in membranes was markedly improved by the grafting of acrylamide monomer as evident from the initial decomposition temperature increasing from 311°C for virgin PE to 390°C in grafted membranes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2629–2635, 2001     

聚间苯二甲酰间苯二胺平板膜的制备及其性能研究

以聚间苯二甲酰间苯二胺（PMIA）为制膜原料,氯化锂（LiCl）、聚乙二醇（PEG-400）和聚乙烯吡咯烷酮（PVP）为添加剂,通过非溶剂诱导相转化法制备了PMIA平板膜,系统考察了聚合物浓度、添加剂种类和含量对PMIA膜结构和性能的影响。结果表明,聚合物浓度和LiCl含量增加,铸膜液黏度增大,导致膜孔径减小,纯水通量降低。而PEG含量的增加,使得聚合物链呈现舒展状态,膜孔径增大,纯水通量升高,亲水性增强。随着PVP含量的增加,膜的纯水通量先升高后降低,膜的亲水性变差。当PMIA的质量分数为9%,LiCl的质量分数为2.8%,PVP的质量分数为1.2%时,膜的纯水通量高达1421.55 L·m^-2·h^-1·bar^-1,对牛血清蛋白（BSA）的截留率为80%,展现出较高的渗透性,为制备高性能膜材料提供了新的思路。     

聚间苯二甲酰间苯二胺平板膜的制备及其性能研究

以聚间苯二甲酰间苯二胺（PMIA）为制膜原料,氯化锂（LiCl）、聚乙二醇（PEG-400）和聚乙烯吡咯烷酮（PVP）为添加剂,通过非溶剂诱导相转化法制备了PMIA平板膜,系统考察了聚合物浓度、添加剂种类和含量对PMIA膜结构和性能的影响。结果表明,聚合物浓度和LiCl含量增加,铸膜液黏度增大,导致膜孔径减小,纯水通量降低。而PEG含量的增加,使得聚合物链呈现舒展状态,膜孔径增大,纯水通量升高,亲水性增强。随着PVP含量的增加,膜的纯水通量先升高后降低,膜的亲水性变差。当PMIA的质量分数为9%,LiCl的质量分数为2.8%,PVP的质量分数为1.2%时,膜的纯水通量高达1421.55 L·m^-2·h^-1·bar^-1,对牛血清蛋白（BSA）的截留率为80%,展现出较高的渗透性,为制备高性能膜材料提供了新的思路。     

Surface modified polysulfone membranes: Separation of mixed proteins and optical resolution of tryptophan

Ultrafiltration separation experiments on mixed solution of bovine serum albumin and gamma globulin were performed in a stirred batch cell through nonmodified and surface modified polysulfone membranes. Gamma globulin permeated through the surface modified membrane to some extent, but the bovine serum albumin was 100% rejected towards the end of the concentration process at pH 7.2 and 9.0, although the molecular weight of gamma globulin is higher than that of bovine serum albumin. It is suggested that the separation of mixed proteins is caused not by a sieving effect or by charge repulsion between membranes and proteins but by the balance of hydrophilic and hydrophobic segments on the surface of the modified membranes. Ultrafiltration separation experiments on a racemic tryptophan solution were also performed by using the binding site of bovine serum albumin to L-tryptophan. It was found that immobilized bovine serum albumin membranes efficiently demonstrated optical resolution of racemic tryptophan.     

Modification of polyolefin films by photochlorination

Composite polyolefin membranes with graded chlorination gradient were obtained by photochlorination of polyethylene, polypropylene, and polystyrene films using ultraviolet and visible light. The maximum chlorine contents of these membranes were 12%, 8.5%, and 6.5%, respectively. As for polyethylene, the surface photochlorination reduced gas permeation of carbon dioxide and oxygen down to 1/30 and 1/21 of the original polyethylene; it also improved the wettability without changing substantially other favorable physical properties such as tensile strength, elongation, and water vapor permeation. The water contact angle of chlorinated polyethylene was comparable to that of poly(vinyl chloride). The infrared spectra suggest the presence of the chlorine of the ? CHCl? CHCl? type rather than of the ? CCl₂? type in the photochlorination of polyethylene. In an effort to obtain useful membranes with a photocrosslinking functional group as a side chain, surface-photochlorinated polyethylene was allowed to react with sodium N,N-dimethyldithiocarbamate or sodium N-methyl-N-carboxymethyldithiocarbamate in dimethylformamide at 50°C for 48 hr according to the procedure by which poly(vinyl chloride) was previously reacted. The polymer thus obtained has 4.1 mole-% ? SCS? NMe₂ and 3.4 mole-% ? SCS? N(CH₃)CH₂COONa groups.     

Ultrafiltration of Albumin-Ethanol Solutions on Mineral Membranes

Abstract

This paper investigates the ultrafiltration of albumin-ethanol solutions on ZrO₂ mineral membranes for the preparation of human albumin from plasma. The classical process consists of a preconcentration phase of a 20% ethanol-albumin 7.5 g/L solution to raise albumin concentration to 80 g/L, then a diafiltration to reduce ethanol concentration to less than 0.3 g/L, and a final concentration to adjust albumin concentration to its final value of 210 g/L. The potential advantages of mineral membranes relative to the polysulfone membranes presently used are a longer membrane life and higher permeate fluxes in the presence of ethanol. In addition, they lend themselves to the use of back flushing or pulsatile flows for reducing membrane fouling. Using 2.7 mm i.d. Carbosep membranes with a 10 kd cut-off and velocities of 7 m/s, permeate fluxes of 40 L/hμm² at 4[ddot]C were obtained with 50 g/L albumin, 20% ethanol solutions representative of the preconcentration phase, while 45 to 50 L/hμm² were obtained at albumin concentrations of 100 g/L without ethanol at 8[ddot]C, representative of the final concentration phase. These fluxes compare favorably with fluxes obtained previously in our laboratory with polysulfone membranes which were respectively of 22 and 40 L/hμm² for the same solutions. This study confirms the expectation of a smaller reduction in the presence of ethanol of the permeate flux for the mineral membranes while albumin concentration in the permeate remained generally under 0.4 g/L irrespective of retentate concentration. The superposition of pressure and flow pulsations on the filter inlet by a piston-in-cylinder system decreases concentration polarization and increases permeate flux by 50 to 60% as compared with steady flows under the same conditions.     

Preparation and improvement anti-fouling property and biocompatibility of polyethersulfone membrane by blending comb-like amphiphilic copolymer

Comb-like amphiphilic copolymer was synthesized by esterification reaction of styrene maleic anhydride and methoxy polyethylene glycol. The synthesized copolymer was characterized by H-Nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopy. Finally, the copolymer was used to improve the hydrophilicity and biocompatibility of ultrafiltration polyethersulfone membranes. The properties of modified membranes were characterized by attenuated total reflection Fourier transform infrared spectrometer, scanning electron microscope and water contact angle. The ultrafiltration performance of the membranes was investigated by dynamic filtration bovine serum albumin and extracellular polymeric secretions solution. The membrane modified with 2 wt% copolymer displayed the best permeation and antifouling properties. The biocompatibility of the membranes was also evaluated by protein adsorption, platelet adhesion and hemolysis test. The results revealed that the modified membranes had good biocompatibility featured by the lower platelet adhesion, protein adsorption and a little hemolysis.     

Preparation of carboxylated graphene oxide nanosheets/polysulphone hollow fibre separation membranes with improved separation and dye adsorption properties

Novel hollow fibre polysulphone (PSF) separation membranes were prepared via the incorporation of carboxylated graphene oxide (cGO) in membrane matrix during the dry‐wet spinning process to improve the membrane performance of water flux and dye adsorption. The surface composition and morphology of the prepared cGO‐incorporated hollow fibre membranes were characterised by means of Fourier Transform–infrared spectra and scanning electron microscopy. The effects of different cGO contents on membrane surface hydrophilicity, separation performance, anti‐compaction and adsorption properties were investigated through measurements of the water contact angle, cross‐flow filtration and methylene blue (MB) adsorption experiments. The results demonstrated that the cGO‐incorporated membranes had more hydrophilic surfaces, higher permeation flux, better anti‐compaction properties and a higher adsorption rate of MB than that of the PSF control membrane. When cGO content was 0.45 wt.%, the pure water flux of the modified membrane increased from 90.56 to 148.26 l m^?2 h^?1 at 0.1 MPa; also, rejections of bovine serum albumin and polyethylene glycol (PEG‐20000) maintained relatively high values of 98.81 and 93.89%, respectively. The incorporation of cGO nanosheets could effectively improve membrane anti‐compaction properties and the adsorption rate of MB.     

Recognition of amino acids by membrane potential and circular dichroism of immobilized albumin membranes

The shifts in membrane potential, caused by the injection of some amino acids into a permeation cell, were measured using immobilized serum albumin membranes at isoelectric points of the amino acids. The effective fixed charge density was estimated to decrease after the injection of alamine, phenylalanine, and tryptophan and to increase after the injection of serine. The change in the fixed charge density originated from the conformational change of the immobilized albumin membranes induced by the binding between the albumin and amino acids in the membranes, since the conformational change of the immobilized albumin membranes induced by the binding of the amino acids to the serum albumin was observed from circular dichroism measurements. There was found, however, some discrepancy between the conformational change of the serum albumin in the albumin membranes detected by the membrane potential measurements and the circular dichroism measurements. This is explained by the fact that the circular dichroism measurements detect the increase or decrease in the α-helix, β sheet, and random coil contents; however, they do not always contribute to the detection of the change in the charge density due to the presence of the amino acid in the albumin membranes. © 1995 John Wiley & Sons, Inc.     

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.     

Effects of solubility parameter differences among PEG,PVP and CA on the preparation of ultrafiltration membranes: Impacts of solvents and additives on morphology,permeability and fouling performances

The effects of two different hydrophilic additives and two solvents on the membrane morphological structure,permeability property and anti-fouling performances of cellulose acetate (CA) ultrafiltration membranes were investigated.During the phase-inversion process,cellulose acetate was selected as a membrane forming polymer;polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) were used as additives;acetone (Ac):N,N-Dimethylacetamide (DMAc) andN,N-Dimethylformamide (DMF) were used as solvents;and deionized (DI) water was used in the coagulation bath.All the prepared membranes were characterized in terms of hydraulic permeability (Pm),membrane resistance,average pore radius,and hydrophilicity.The top surface and crosssectional view of the prepared membranes were also observed by using field emission scanning electron microscopy.Membrane fouling and rejection experimentations were done using a stirred batch-cell filtration set-up.The experimental studies of fouling/rinsing cycles,rejection,and permeate fluxes were used to investigate the effect of PEG and PVP additives and effect of the two solvents on the fabricated membranes using bovine serum albumin (BSA) as a model protein.     

Dialysis membranes from polyethylene films grafted with acrylic acid

Low‐density polyethylene‐g‐poly(acrylic acid) membranes were prepared by the direct radiation grafting of aqueous acrylic acid solutions (containing Mohr's salt) onto low‐density polyethylene films and were irradiated at two different irradiation doses (2 and 3 Mrad) at a dose rate of 0.02 Mrad/h. Two series of polyethylene‐g‐poly(acrylic acid) membranes with 100 and 150% grafting were obtained. The free carboxylic acid groups in the grafted films were converted into the corresponding acrylates by reactions with different metal salts. The swelling (water uptake) and dialysis permeability of glucose and urea through the grafted membranes in different metal‐ion forms were investigated. The prepared membranes showed good permeability to both solutes, which increased as the hydrophilicity of the membrane increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 10–14, 2004     

Surface modification of polyethersulfone hollow-fiber membranes by γ-ray irradiation

The fouling of ultrafiltration membrane is often caused by gel formation on the membrane surface. This gel layer arises due to concentration polarization or macromolecular adsorption on the membrane surface. The gel layer affects both the hydraulic permeability and the rejection properties of the membrane. In this report, the adsorption of porcine albumin and the concentration polarization effect on modified and unmodified polyethersulfone (PES) hollow-fiber membrane is studied. PES ultrafiltration hollow-fiber membranes were modified by the grafting of polyethylene glycol (PEG) polymer on the internal surface using γ-ray irradiation method. The modified hollow fibers were less susceptible to fouling than were the unmodified fiber. The performance of both modified and unmodified hollow fibers was tested as a function of feed flow rates and protein concentrations. © 1994 John Wiley & Sons, Inc.     

Membrane-based electrolyte sheets for facile fabrication of flexible dye-sensitized solar cells

New electrolyte sheets based on porous polyethylene membranes for flexible dye-sensitized solar cells have been developed. Ionic liquid electrolytes are accommodated in commercial polyethylene membranes to form the electrolyte sheets. The morphology of membranes and iodine concentrations in ionic liquid are varied. The electrochemical measurement results show that the morphology, pore structure, and iodine concentration affect mass transport in electrolyte sheet, as well as charge transfer between platinum electrode and electrolyte sheet greatly. Based on these electrolyte sheets, lamination method instead of conventional vacuum injection of electrolyte is used to fabricate flexible dye-sensitized solar cells. Optimal device with an open-circuit voltage (V_oc) of 0.63 V, a fill factor of 0.58, and a short-circuit current density (J_sc) of 6.17 mA cm⁻² at an incident light intensity of 100 mW cm⁻² is obtained, which yields a light-to-electricity conversion efficiency of 2.25%.     

黏性包覆原理用于制备iPP/PE-HD/iPP三层微孔膜

利用"黏性包覆"原理,通过毛细管流变仪详细研究了多相体系在流场中的分相机制和控制方法,基于单螺杆挤出流延机组制备了具有等规聚丙烯/高密度聚乙烯/等规聚丙烯(iPP/PE-HD/iPP)结构的三层膜。结果表明,将iPP、PE-HD预混,可以得到不同相结构的iPP/PE-HD共混膜;三层片材中PE-HD的实际面积为94%,三层膜的孔隙率可达51.82%,含有25%iPP的具有双连续相结构的共混膜的微孔分布更加均匀;研究发现牵引比为50时,大孔含量高达84%;探究了共混微孔膜的成孔机理,揭示了三层膜中iPP和PE-HD过渡层成孔的复杂性,论证了过渡层晶体结构和微孔形貌对三层膜性能的重要性。