Covalent heparin modification of a polysulfone flat sheet membrane for selective removal of low-density lipoproteins: a simple and versatile method

A simple, convenient and economical method for the heparinization of PSf membranes is described, with the aim of preparing an LDL adsorber for simultaneous LDL apheresis and hemodialysis. An atmospheric pressure glow discharge generator is used to activate the PSf membrane surface, with subsequent chemical binding of heparin in the presence of EDC and NHS. ATR-FTIR spectroscopy and XPS measurements confirm successful surface modification. The PSf-Hep membrane shows good blood compatibility, with a relatively low amount and normal morphology of adherent platelets. ELISA results indicate that the PSf-Hep membrane exhibits excellent selective affinity for LDL in single and binary protein solutions, suggesting potential applications in hemodialysis with simultaneous LDL removal.     

木质素磺酸钠改性聚砜膜的制备及其在正渗透膜中的应用

采用木质素磺酸钠作为亲水添加剂,通过浸没沉淀相转化法制备了木质素磺酸钠共混改性聚砜膜,以改善聚砜膜的亲水性,并用作正渗透膜的支撑层,以降低内浓差极化效应.利用扫描电子显微镜、衰减全反射傅里叶变换红外光谱仪、水接触角仪等研究了不同木质素磺酸钠添加量对聚砜膜的结构和表面性质的影响.结果表明,添加木质素磺酸钠后,聚砜膜的指状孔变得规整且狭长.水接触角实验证实添加木质素磺酸钠能改善聚砜膜的亲水性,当木质素磺酸钠含量为0.4 wt%时,聚砜膜的表面水接触角可降低至65°.正/反渗透测试装置分别用于表征正渗透膜的传质性质和结构参数.结果表明,以0.4 wt%木质素磺酸钠改性聚砜膜为支撑层的正渗透膜的水渗透性能(A=3.12×10~(-5) LMH×Pa~(-1))优于纯聚砜基底正渗透膜(0.76×10~(-5)LMH×Pa~(-1)),而且前者的结构参数(S=2010mm)远小于后者(3450mm),说明木质素磺酸钠改性聚砜膜有效弱化了正渗透膜的内浓差极化效应.     

Mixed matrix membranes of polysulfone/polyimide reinforced with modified zeolite based filler: Preparation,properties and application

In this work,polysulfone/polyimide (PSf/PI) mixed matrix membranes were fabricated by reinforcement of modified zeolite (MZ) particles through solution casting method for investigation of antibacterial activity against two gram negative bacteria (Salmonella typhi,Klebsellapneumonia) and two gram positive bacteria (Staphylococcus aureus,Bacillus subtilis).The modified zeolite particles were incorporated to PSf and PI matrix and the influence of these particles on thermal,mechanical and structural properties was evaluated.The morphological evolution was investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis,which revealed good compatibility between organic polymer matrix and inorganic filler.Mechanical stability was investigated by tensile testing while thermal analysis was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).This revealed improvement in thermal properties with increasing filler concentration from 1 wt％ to 10 wt％.Structural analysis was successfully done using X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR) spectroscopy.Solvent content of fabricated mixed matrix membranes was observed to decrease while moving from more hydrophilic to less hydrophilic solvent.However,addition of filler content enhanced the porosity of fabricated membranes.The synthesized mixed matrix membranes exhibited good antibacterial activity and the highest activity was shown by PSf/PI/MZ mixed matrix membrane.Therefore,the combination effect of PSf,PI and MZ sufficiently enhanced the antibacterial activity of mixed matrix membranes.     

Surface structure and phase separation mechanism of polysulfone membranes by atomic force microscopy

Atomic force microscopy (AFM) was used to investigate the surface of polysulfone (PSf) membranes. The AFM method provides information on both size and shape of pores or cavities on the surface as well as the roughness of the skin. The pore sizes obtained from AFM observation were found to be more accurate than those obtained from scanning electron microscopy (SEM) since the potential of altering the pore structure of the membrane during sample preparation was eliminated. It was observed that two different modes of phase separation existed during the formation of PSf membrane when the coagulation conditions were varied.     

Hydrophilic nanofiltration membranes with self-polymerized and strongly-adhered polydopamine as separating layer

Inspired by the self-polymerization and strong adhesion characteristics of dopamine in aqueous conditions,a novel hydrophilic nanofiltration（NF） membrane was fabricated by simply dipping polysulfone（PSf） ultrafiltration（UF） substrate in dopamine solution.The changes in surface chemical composition and morphology of membranes were determined by Fourier transform infrared spectroscopy（FTIR-ATR）,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM） and atomic force microscopy（AFM）.The experimental results indicated that the self-polymerized dopamine formed an ultrathin and defect-free barrier layer on the PSf UF membrane.The surface hydrophilicity of membranes was evaluated through water contact angle measurements.It was found that membrane hydrophilicity was significantly improved after coating a polydopamine（pDA） layer,especially after double coating.The dyes filtration experiments showed that the double-coated membranes were able to reject completely the dyes of brilliant blue,congo red and methyl orange with a pure water flux of 83.7 L/（m²·h） under 0.6 MPa.The zeta potential determination revealed the positively-charged characteristics of PSf/pDA composite membrane in NF process.The salt rejection of the membranes was characterized by 0.01 mmol/L of salts filtration experiment.It was demonstrated that the salts rejections followed the sequence:NaCl2SO₄422,and the rejection to CaCl₂ reached 68.7%.Moreover,the composite NF membranes showed a good stability in water-phase filtration process.     

A comparison between polysulfone,zirconia and organo-mineral membranes for use in ultrafiltration

In this paper, representative polymeric (a PSf/PVP membrane), ceramic (a ZrO₂ membrane) and organo-mineral (a ZrO₂/PSf membrane) ultrafiltration membranes, all in the tubular configuration, are being compared for their basic membrane properties, and for the typical ultrafiltration application of protein recovery of cheese whey. These three different membranes with a quite similar pore size (the cut-off values for each of the three membranes were comprised between 25 000 and 50 000 Dalton) showed pure water permeability coefficients between 135 and 1250 l/h m² bar. The highest pure water flux was found for the organo-mineral membrane, the lowest for the polymeric membrane. By FESEM analysis of the top-surfaces (skin) of both the PSf/PVP and the ZrO₂/PSf membrane a strong difference in surface-porosity was found. These results were claimed to partially explain the difference in pure water flux. From SEM pictures of the cross-section of the ZrO₂/PSf membrane it could also be seen that the skin layer thickness is smaller, at these places where particles are present near the skin-surface, compared to the rest of the membrane as well as to the skin of the PSf/PVP membrane. These latter observations were also used to further explain the flux difference between the PSf/PVP and the ZrO₂/PSf membrane.     

Effect of γ irradiation on the surface properties of wet polysulfone films containing poly(vinylpyrrolidone)

In Japan, hemodialyzers are usually sterilized by γ irradiation. However, the polymer materials used in the dialysis membrane, such as polysulfone (PSf) and poly(vinylpyrrolidone) (PVP), undergo crosslinking or degradation on exposure to γ radiation. In the present study, we prepared PSf/PVP films (PVP content, 0–50 wt%) and used atomic force microscopy (AFM) to perform nanoscale evaluations of the effect of γ irradiation (25 and 50 kGy) on the surface properties of wet PSf/PVP surfaces. Force‐curve measurements were used to evaluate the hardness of and fibrinogen adsorbability on the wet PSf/PVP surface; fibrinogen adsorbability on the wet PSf/PVP surface was evaluated using AFM probes with fibrinogen immobilized on the tips of the probes. At PVP levels greater than 5 wt%, the wet PSf/PVP film surface was completely covered with hydrated and swollen PVP particles. The surface hardness of the wet PSf/PVP films exposed to 25‐kGy γ irradiation greatly decreased with increasing PVP content, whereas the surface hardness of the wet PSf/PVP films exposed to 50‐kGy γ irradiation did not decrease significantly. At higher PVP levels, the reduction in the fibrinogen adsorbability on a wet PSf/PVP film exposed to 25‐kGy γ irradiation was more significant than that on a wet PSf/PVP film exposed to 50‐kGy γ irradiation. PVP particles on the wet PSf/PVP film surface exposed to 50‐kGy γ irradiation did not show significant hydration and swelling because the polymer materials PVP–PSf and PVP‐PVP in these membranes has undergone excessive crosslinking due to γ irradiation. Copyright © 2010 John Wiley & Sons, Ltd.     

Role of clay-based membrane for removal of copper from aqueous solution

The present study focuses on the fabrication of polysulfone (PSf)-clay minerals impregnated hybrid membrane for treatment of Cu (II) ions. Blending and phase inversion methods have been employed to develop clay-based membranes by the mixing of bentonite, sepiolite and zeolite in the matrix of PSf. Moreover, characterization of fabricated membranes was carried out using SEM, FTIR, zeta potential, pore size and water contact angle measurement. Adsorption and filtration experiments were conducted to evaluate the permeation performance of the membrane. Obtained results of permeation study reveal that the presence of clay minerals in the matrix of modified membrane not only increases the adsorption and rejection efficiency for Cu (II) but, it also improves the flux of pure water. Among all developed membranes, the membrane prepared by the mixing of zeolite demonstrates the highest adsorption (2.82 mg/g) and rejection value (97%) towards Cu (II) at low pressure (0.5 bar). Regeneration performance results confirm the reusability of membrane up to 3–5 cycles along with 82.5–90% metal recovery. Based on significant metal recovery, clay-based low-cost zeolite/PSf membrane could be used to remove Cu (II) from water at low pressure to replace current conventional membrane.     

Membrane formation mechanism and permeation properties of a novel porous polyimide membrane

The transport properties of a novel porous fluorinated polyimide membrane fabricated by a wet phase inversion process were studied with a stirred dead‐end filtration cell. The porous membrane‐forming solvents were tetrahydrofuran (THF), acetone, N,N‐dimethylacetamide (DMAc), N‐methylpyrrolidone (NMP), N,N‐dimethylformamide (DMF), and dimethylsulfoxide (DMSO). The phase separation phenomena in a ternary system of polyimide/solvent/water were investigated from cloud point curves by a titration method and binary interaction parameters. Solvent–water demixing in the system has been found to play very important roles in determining the structure and surface morphology of the polyimide membrane. The porous fluorinated polyimide membranes showed pore sizes from 4 to 500 nm and permeation properties from ultrafiltration to a microfiltration range. In this study, we particularly focused on fouling of the polyimide membranes, because fouling decreases the flux and increases the resistance. Interestingly, the porous polyimide membrane showed excellent water flux recovery after water cleaning compared with that of the polyethersulfone (PSf) membrane, which suggest that for a 6FDA‐6FAP membrane, the protein–membrane and protein–protein interaction was not so strong compared with those in a PSf membrane. Copyright © 2002 John Wiley & Sons, Ltd.     

Determination of molybdenum in environmental samples

Molecular imprinted membrane of indole-3-ethanol (IE) was prepared by hybridization of IE imprinted polymer powder and polysulfone (PSf) membrane. The IE imprinted polymer by covalent imprinting method was synthesized with copolymerization of indole-3-ethyl methacrylate (IEMA) and divinylbenzene (DVB). The cross-linked P(IEMA-co-DVB) was ground to be powders having less than 63 μm size and then hybridized within PSf membrane by using phase inversion process. The resultant imprinted powder showed binding capacities of 1.8, 7.2, 0 and 0 μmol g⁻¹ for IE, indole, 8-hydroxyquinoline and pyrrole in aqueous solution, respectively, and after hybridization with the PSf membrane, the value was 46, 26, 0 and 0 μmol g⁻¹. As a result, it was found that the IE imprinted powder alone showed non-selectively binding to the IE, but, the hybridized powder within the PSf membrane bound selectively the IE. Evidence was presented that hydrophobic interaction of the PSf matrix caused the selective and efficient binding. We also showed separation behavior of the hybrid membranes and discussed on the binding selectivity of the IE molecule. In view point of hybrid effect of the PSf membrane and the cross-linked imprinted powder, the results of the separation of these substrates were considered.     

Light scattering and membrane formation studies on polysulfone solutions in NMP and in mixed solvents of NMP and ethyl acetate

The relationship between the characteristics of the polymer dope solution and the skin formation mechanism as well as the performance of the asymmetric membrane has been investigated. The solution characteristics have been studied on the polysulfone (PSf) dope solution as a function of the concentrations of both polymer and the cosolvent, ethyl acetate (EA), by dynamic light scattering. An anomalous light scattering was observed at small angles in both PSf/NMP and PSf/NMP:EA (6:4 by weight) solutions, indicating the inhomogeneity of the dope solutions. In the case of the PSf/NMP:EA (6:4) solution, an integrally skinned asymmetric membrane without defects having high gas selectivity was obtained while the membrane from the PSf/NMP solution had a defective skin. The scattered light intensity of the dope solution of PSf/NMP:EA (6:4) increased with the aging time while no notable change was observed in the PSf/NMP solution. The characteristics of the solution affect the final morphology of the membrane, particularly when phase separation occurred significantly before the immersion into the gelation medium.     

Preparation and characterization of TiO2/Pebax/(PSf‐PES) thin film nanocomposite membrane for humic acid removal from water

New thin film composite (TFC) membrane was prepared via coating of Pebax on PSf‐PES blend membrane as support, and its application in wastewater treatment was investigated. To modify this membrane, hydrophilic TiO₂ nanoparticles were coated on its surface at different loadings via dip coating technique. The as‐prepared membrane was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), field emission SEM, and contact angle analysis. The Fourier transform infrared spectroscopy analysis and surface SEM images indicated that TiO₂ was successfully coated on the membrane surface. In addition, the results stated that the hydrophilicity and roughness of membrane surface increased by addition of TiO₂ nanoparticles. Performance of TFC and modified TFC membranes was evaluated through humic acid removal from aqueous solution. Maximum permeate flux and humic acid rejection were obtained at 0.03 and 0.01 wt% TiO₂ loadings, respectively. Rejection was enhanced from 96.38% to 98.92% by the increase of feed concentration from 10 to 30 ppm. Additionally, membrane antifouling parameters at different pressures and feed concentration were determined. The results indicated that surface modification of membranes could be an effective method for improvement of membrane antifouling property.     

Synthesis and characterization of hybrid molecularly imprinted polymer (MIP) membranes for removal of methylene blue (MB)

This work reports the synthesis and characterization of a hybrid molecularly imprinted polymer (MIP) membrane for removal of methylene blue (MB) in an aqueous environment. MB-MIP powders were hybridized into a polymer membrane (cellulose acetate (CA) and polysulfone (PSf)) after it was ground and sieved (using 90 μm sieve). MB-MIP membranes were prepared using a phase inversion process. The MB-MIP membranes were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Parameters investigated for the removal of MB by using membrane MB-MIP include pH, effect of time, concentration of MB, and selectivity studies. Maximum sorption of MB by PSf-MB-MIP membranes and CA-MB-MIP membranes occurred at pH 10 and pH 12, respectively. The kinetic study showed that the sorption of MB by MB-MIP membranes (PSf-MB-MIP and CA-MB-MIP) followed a pseudo-second-order-model and the MB sorption isotherm can be described by a Freundlich isotherm model.     

Comparative study of effect of low and medium dose rate of γ irradiation on microporous polysulfone membrane using spectroscopic and imaging techniques

The effect of low (LDR) and medium dose rate (MDR) of γ irradiation at low doses (0-100 kGy) on the structural and chemical changes of microporous polysulfone (PSf) membrane has been studied using UV-vis, FTIR, SEM and dead-end filtration techniques. PSf membrane was cast by phase inversion method. Irradiation was done at room temperature in air media. The doses chosen were 0-100 kGy for LDR and 0-50 kGy for MDR; they were below and above sterilization dose. Analysis of UV-vis and IR spectra and SEM images obtained suggested that chain scissions and crosslink had occurred simultaneously in the irradiated membranes in both cases. This radio-oxidation effects observed start at a very low dose i.e. 1.66 kGy and increase with increase in dose. It is supported by the flux values obtained; it is increased with increase in dose. The results indicate that a very low dose γ irradiation was able to change the physicochemical characteristics of microporous PSf membrane which depend on dose rate of exposure.     

Immobilization of bovine serum albumin onto porous polyethylene membranes using strongly attached polydopamine as a spacer

Based on the self-polymerization and strong adhesion characteristics of dopamine in aqueous solution, a novel and convenient approach was developed to immobilize protein onto porous polyethylene (PE) membranes. A thin polydopamine (pDA) layer was formed and tightly coated onto PE membrane by dipping simply the membrane into dopamine aqueous solution for a period of time. Subsequently, bovine serum albumin (BSA) was bound onto the obtained PE/pDA composite membranes via the coupling between BSA and the reactive polydopamine layer. The firm immobilization of polydopamine layer and BSA was verified by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results of water contact angle measurement showed that the hydrophilicity of PE membrane was significantly improved after coating polydopamine and binding BSA. The experiments of blood platelet adhesion indicated that BSA-immobilized PE membrane had better blood compatibility than the unmodified PE and the PE/pDA composite membranes. The investigations on hepatocyte cultures and cell viability revealed that the polydopamine coating endowed PE membrane with significantly improved cell compatibility. Compared to BSA surface, polydopamine surface is more favorable for cell adhesion, growth, and proliferation.     

PEG-grafted PVA Membrane and Its Blood Compatibility

Preparation and blood compatibility of different shape polyvinyl alcohol(PVA) membrane were investigated. Firstly, the tabular and tubular[polytetrafluoroethylene(PTFE) capillary as supporter] PVA membranes were prepared; then, methoxy polyethylene glycol(mPEG) was grafted onto the surface of the PVA membranes. The effects of the shape, structure and properties of the membrane surface on blood compatibility were studied in detail. The experiment results show that mPEG modified PVA membranes, especially mPEG modified tubular membrane, could availably repel the adhesion of the platelets. In addition, the anticoagulant mechanism of mPEG with a steric repulsion effectiveness was confirmed further via different grafting methods.     

Pervaporation separation and mass transport of ethylbutanoate solution by polyether block amide (PEBA) membranes

Dense and composite membranes were developed from polyether block amide (PEBA). Polyacrylonitrile (PAN) and polysulfone (PSf) were used as the porous supports for the composite membranes. The membranes were tested for pervaporation separation of ethylbutanoate (ETB) solutions. Sorption and desorption experiments were also performed to provide data for analysis of mass transport based on resistance-in-series model.

The composite membranes with polyether block amide (PEBA) casted on PSf (PEBA/PSf) showed superior pervaporation performance than that casted on PAN (PEBA/PAN). The analysis of transport resistances revealed that: (1) the resistances in liquid boundary of ETB were highest and, therefore, were the controlling resistances; and (2) the transport resistances in the porous supports were much lower than those in the membrane top layers.

The results on plasticizing coefficients showed that ETB plasticized the membranes (positive, k_ii) but water did not (negative, k_jj). Negative coupling coefficients (k_ij) indicated that water reduced diffusivity of ETB in the membranes and the presence of ETB enhanced water diffusion in the membranes due to positive k_ji.     

Ultrafiltration of stable oil-in-water emulsion by polysulfone membrane

This paper focuses on treatment of oily wastewater coming out from the post-treatment unit of petroleum industries where finely divided oil droplets are uniformly dispersed in large volumes of water. Polysulfone (PSf) membranes which had been modified for higher porosity and hydrophilicity through the use of additives such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) were used for removal of oil from the oily wastewater. The performances of different PSf membranes were evaluated by treating with pure water as well as with laboratory made oil-in-water (o/w) emulsion. Experiments were carried out with 12 such membranes in a semi-batch filtration cell made of Teflon and the influence of operating conditions such as transmembrane pressure and feed properties such as initial oil concentration and pH of feed solution on membrane performance were investigated. Results show that all the parameters play a key role in permeate flux as well as percent oil separation. Also change in morphological properties of membranes due to addition of different molecular weight PVP and PEG are found to have a significant influence on the permeate flow rate and hence subsequent oil removal. The experimental results showed that oil retentions of almost all the membranes were over 90% and oil concentration in the permeate was below 10 mg/L, which met the requirement for discharge. It was concluded that the ultrafiltration (UF) membranes developed in the study were reasonably resistant to fouling and hence the developed PSf membranes may be considered feasible in treating oily wastewater.     

聚丙烯微孔膜表面肝素化及其对低密度脂蛋白的吸附特性

为了赋予聚丙烯微孔膜(PPMM)选择性吸附低密度脂蛋白(LDL)的能力,发展了一种有效的PPMM表面共价固定肝素的方法.基于紫外引发丙烯酸的接枝聚合,通过碳二亚胺活化,以乙二胺为间隔臂,将肝素共价固定于PPMM表面,获得表面肝素化的PPMM.ATR-FTIR和XPS分析确证了修饰过程中膜表面基团及化学成分的变化.采用静...     

Membrane thickness and preparation temperature as key parameters for controlling the macrovoid structure of chiral activated membranes (CAM)

A macrovoid structure is formed in polysulfone (PSf) polymeric membranes prepared by the immersion technique using N-dimethylformamide (DMF)/water as a solvent/non-solvent pair. It is actually important controlling the macrovoid formation process, because macrovoids can cause unwanted mechanical failure during high-pressure applications. In order to control the formation of these structures, the influence of different parameters like membrane thickness, solvent additives (isopropyl myristate, IPM or N-hexadecyl-l-hydroxypriline, HHP), temperature of the coagulation bath, and solvent/non-solvent pair has been studied for chiral activated membranes. With the same purpose, corresponding membranes where physically characterized by scanning electron microscopy (SEM) measurements of their cross-section images. Those SEM images have been treated by the software IFME^®, which provides the parameters of asymmetry and irregularity of the membranes. The surface of the membranes has been analyzed by atomic force microscopy (AFM) and brightness analysis in order to calculate their roughness. A comparison of the same PSf membranes, but prepared by evaporation precipitation, or by using chloroform/methanol as solvent/non-solvent pair during the immersion precipitation step, has been also checked. That paper helps us to understand and predict which will be the best conditions to prepare the optimum membranes.