Ultrafiltration of Myoglobin using Surface-Sulfonated Polysulfone Hollow Fiber

The usage of ionic polysulfone (PSF) hollow fiber for the ultrafiltration of protein was investigated. The surface of polysulfone hollow fiber was sulfonated through the Blanc chloromethylation reaction to become anionic. Characterization of the modified hollow fiber was performed including ion exchange titration, pure water permeation, and molecular sieving measurement. The performance of ultrafiltration of protein was evaluated using myoglobin at various pH values. The results show that the water contact angles and hydraulic resistance are markedly decreased, indicating that the surface-modified PSF hollow fibers are more hydrophilic. In addition, the retention of myoglobin depends on the pH of the solution. At a pH higher than the isoelectric point of myoglobin, both hollow fiber and the protein have the same charge sign, and both the flux of the solution and the retention are the highest. The sulfonated PSF hollow fiber may be used as a biomaterial for protein separation and purification.     

Novel charged chitosan composite nanofiltration membranes containing chiral mesogenic group

To improve the performance of nanofiltration (NF) membranes, a chiral mesogenic compound, a positively charged compound, and a negatively charged compound were grafted to chitosan, respectively. Series of novel composite NF membranes were prepared by over‐coating the polysulfone ultrafiltration membrane with the mixture of chitosan and modified chitosan. The chiral mesogenic compound, the positively charged compound, the negatively compound and their chitosan derivatives were characterized by infrared spectrophotometer, differential scanning calorimetry, polarized optical microscope; the structure of the membrane was characterized by scanning electron microscopy. The performance of composite NF membranes was strictly related to the novel compounds grafted to chitosan and its composition. The rejection reached the maximum of 95.7% for CaCl₂ with P_2‐7 composite NF membrane, corresponding flux was 3155 Lm^?2h^?1. The rejection reached the maximum of 93% for Na₂SO₄ with P_3‐5 composite NF membrane, corresponding flux was 3879 Lm^?2h^?1. Comparing with conventional NF membranes, the membranes were used in low pressure with high flux, especially for the separation of high‐valence ions from solution. The membranes were typical charged NF membranes. POLYM. ENG. SCI., 57:22–30, 2017. © 2016 Society of Plastics Engineers     

Studies on cellulose acetate‐carboxylated polysulfone blend ultrafiltration membranes. III

Enhancement of the hydrophilicity in polymeric membrane materials results in membranes with higher flux and better membrane characteristics. Hence, polysulfone was carboxylated and ultrafiltration membranes were prepared from blends of cellulose acetate and carboxylated polysulfones having various degrees of carboxylation with a total polymer concentration of 20 wt % in casting solution and at different blend polymer compositions. The effects of degree of carboxylation on membrane characteristics such as compaction, pure water flux, and membrane hydraulic resistance (R_m) have been investigated. The influence of the polymer concentration in the blend solution on the performance of blend membranes at various blend polymer compositions has also been investigated and compared with that of blend membranes prepared from blends of cellulose acetate and polysulfone or carboxylated polysulfone with a total polymer concentration of 17.5 wt %. Further, the solute rejection performance of the membranes has also been investigated by subjecting the membranes to metal ion permeation studies using polyelectrolyte‐enhanced ultrafiltration. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 976–988, 2005     

Sulfonated polyethersulfone by heterogeneous method and its membrane performances

Polyethersulfone was sulfonated by heterogeneous method with chlorosulfonic acid. Ion exchange capacity was controlled to 0.68 meq/g to reduce fouling. Sulfonation was confirmed by Fourier transform infrared spectroscopy and ¹H‐nuclear magnetic resonance. Polyethersulfone and sulfonated polyethersulfone ultrafiltration membranes were prepared successively by the typical phase inversion method. Membrane performance of sulfonated polyethersulfone was compared with that of polyethersulfone. In the preparation of ultrafiltration membranes, the effect of the addition of dichloromethane and poly(vinyl pyrrolidone) in a casting solution was investigated on the membrane performance. It was observed that the addition of dichloromethane increased the solute rejection rate. By changing the ratio between polymer and poly(vinyl pyrrolidone), membrane performance could be controlled. Negatively charged sulfonated polyethersulfone could reduce fouling at higher or lower pH than isoelectric point of protein bovine serum albumin. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2046–2055, 1999     

Effects of Ionic Environments on Bovine Serum Albumin Fouling in a Cross‐Flow Ultrafiltration System

The influence of electrostatic interactions on membrane fouling during the separation of bovine serum albumin (BSA) from solution was studied in a cross‐flow ultrafiltration system. Experiments were carried out at different pH values between 3.78 and 7.46; and for different ionic strengths between 0.001 M and 0.1 M. The changes in permeate flux, cake layer resistance, zeta potentials of BSA and polyether sulfone (PES) membranes, and electrostatic interaction energies, were evaluated. At all of the ionic conditions studied, PES membranes are negatively charged. However, BSA molecules are either negatively or positively charged depending on the ionic environment. Whereas the cake layer resistance decreased with increasing pH and ionic strength, the permeate fluxes increased. The calculated electrostatic energy was a minimum at the isoelectric point (IEP) of BSA. However, at this point, the cake resistances corresponding to fouling at each ionic strength, were not minimized. Below the IEP of BSA, the electrostatic forces were attractive, while above the IEP, repulsive electrostatic forces were dominant.     

Relation between salt rejection and electrokinetic properties on Shirasu porous glass (SPG) membranes with nano-order uniform pores

The salt rejection by Shirasu porous glass (SPG) membranes having nano-order uniform pores was investigated for understanding the electrokinetic mechanism resulting from the surface charge developed on the membrane when in contact with salt solutions. Due to the dissociation of the hydroxyl groups such as silanol groups on the membrane surface, the membrane was negatively charged over a pH range of 3–10 from electrophoretic measurements. Cross-flow filtration experiments showed that up to 63% of NaCl was rejected by an SPG membrane having a mean pore diameters of 33 nm in a 1 mol m⁻³ NaCl solution at pH 7 under a transmembrane pressure of 74 kPa, even though the pore diameter is much larger than the ion diameter. This is a consequence of the electrostatic repulsive interaction between the co-ions (Cl⁻ ions) and the membrane surface. At the same pH, the rejection factor of NaCl decreased with increasing salt concentration due to an increase in the ionic strength. More negative charge on the membrane surface at higher pH resulted in higher rejection factors of NaCl for a fixed salt concentration. Higher rejection factors of NaCl by SPG membranes with smaller pore sizes for a fixed concentration are due to the higher ratio of the thickness of the electric double layer (Debye length) to the pore radius. The SPG membrane showed a salt rejection sequence: Na₂SO₄, NaCl and CaCl₂ at the same pH. This is because divalent anions (SO₄²⁻) are more strongly repelled by the negatively charged membrane, while divalent cations (Ca²⁺) adsorb specifically onto the membrane surface than monovalent cations (Na⁺). The salt rejection factor increased with increasing permeate volume flux. Due to the stronger acidity of the membrane materials, SPG membranes had a higher rejection factor and a lower isoelectric point (IEP < 3) than ceramic membranes.     

Charged membranes for ultrafiltration treatment of synthetic waste water containing peptone

Continuous ultrafiltration of synthetic waste water containing peptone was carried out by using positively and negatively charged polyacrylonitrile membranes. The filtration experiments were operated in cross-flow mode under 10 kPa of applied pressure. The filtration properties of the charged membranes were compared with those of uncharged polyacrylonitrile ultrafiltration membranes having similar molecular sieve characteristics and membrane structure to the charged ultrafiltration membranes. During the continuous filtration, the filtration rate decreased and the operation pressure increased because of the formation of a peptone gel layer on the membrane surface. It was found that, for the positively charged membrane, the decrease in the filtration rate of the charged membranes was smaller than that of the uncharged membrane. In addition, the positively charged membrane maintained the initial operation pressure during the filtration. The reduction of fouling in the positively charged membrane was discussed by analyzing the gel components on the membrane surface.     

Positively charged hollow‐fiber composite nanofiltration membrane prepared by quaternization crosslinking

Poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) can be crosslinked by interfacial polymerization to develop a positively charged dense network structure. According to this mechanism, a positively charged hollow‐fiber composite nanofiltration (NF) membrane was prepared by quaternization to achieve a crosslinked PDMAEMA gel layer on the outer surface of polysulfone hollow‐fiber ultrafiltration (UF) membranes with a PDMAEMA aqueous solution as a coating solution and p‐xylylene dichloride as an agent. The preparation conditions, including the PDMAEMA concentration, content of additive in the coating solution, catalyzer, alkali, crosslinking temperature, and hollow‐fiber substrate membrane, were studied. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the structure of the membranes. This membrane had a rejection to inorganic salts in aqueous solution. The rejection of MgSO₄ (2 g/L aqueous solution at 0.7 MPa and 25°C) was above 98%, and the flux was about 19.5 L m^?2 h^?1. Moreover, the composite NF membranes showed good stability in the water‐phase filtration process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Initial flux and rejection characteristics of partially permeable ultrafiltration membranes

Solutions of bovine serum albumin (BSA) were ultrafiltered with and without stirring through membranes partially permeable to the solute, over a range of pH values. At the isoelectric point, flux was a minimum and rejection was a maximum. For all conditions, the flux for stirred ultrafiltration was greater than without stirring, as expected from conventional theory, and in contrast to recently reported “anomalous” behavior measured at the isoelectric point. Some evidence of unusual behavior at the isoelectric point was obtained when the flux of a freshly ultrafiltered solution of BSA was compared to that when the permeate and retentate were recombined, and when the retentate concentration was adjusted to the original concentration. For pH values other than the isoelectric point, the fluxes were similar for each set of experiments. At the isoelectric point, it was also found that flux was insensitive to changes in stirring speed. The unusual behavior at the isoelectric point is attributed to protein aggregation and precipitation causing loss of membrane permeability.     

Self-sharpening phenomenon arisen by ion-exchange membranes in multi-compartment free-flow isoelectric focusing (IEM-FFIEF)

In this article, the self-sharpening phenomenon arisen by ion-exchange membranes is studied. In order to reduce the overlapped components in a single chamber, aminated poly(2,6-dimethyl-1,4-phenylene oxide) (APPO) based anion-exchange membranes are applied in free-flow isoelectric focusing (FFIEF) instead of conventional immobiline membranes as the selective mass transfer media. The APPO polymers with different amination rates are blended with polysulfone and cast on non-woven clothes by the phase inversion technology. Characterizations of XPS scanning, streaming potential and ion-exchange capacity (IEC) demonstrate that the self-prepared membranes posses different extent of amination and IEC values. The performances of the three prepared APPO membranes with different IEC values are compared. Nine pieces identical solid phase porous APPO membranes are employed in FFIEF instead of pH imbedded gel-like immobiline membrane with a protein mixture comprising bovine serum albumin, myoglobin and lysozyme as a separation model. Experimental results show that membranes with the higher charge density perform not only the higher mass transfer rate, but also the stronger “self-sharpening” function. Therefore, the highly charged porous membranes are favorable in reducing components’ overlaps in individual chamber for multi-component protein separations.     

Simple design of cast myoglobin/polyethyleneimine modified electrodes

Negatively charged myoglobin (at pH values above its isoelectric point) was immobilized with the positively charged polyion polyethyleneimine (PEI) on pyrolytic graphite electrodes. A modified form of the common layer-by-layer technique was proposed, which consisted in forming non-ordered cast polyion films. The modified Mb electrodes obtained by both techniques were compared by cyclic voltammetry. The cast polyion technique gave less reproducible results but enable the immobilization of higher percentages of the total quantity of protein required to prepare the electrodes. The electrochemical properties of the negatively charged myoglobin were determined, and its capability to catalyze the electrochemical reduction of oxygen and the dechlorination of trichloroacetic acid was demonstrated. The mechanisms are discussed, and the modified pathway that has been proposed to take into account the influence of pH in the Mb-catalyzed reduction of oxygen was confirmed here.     

Preparation of polysulfonebenzylthiourea-reactive ultrafiltration plate membranes and their rejection properties for heavy toxic metal cations

The asymmetric membranes were prepared via phase inversion method, by using chloromethyl polysulfone as membrane materials, polyethylene glycol (PEG) as pore forming agent to improve the morphology and function of resultant membranes, N,N-dimethylacetamide as solvent, and water as the extraction solvent. Then the highly qualified polysulfonebenzylthiourea-reactive ultrafiltration plate membrane was prepared successively through the reactions between the chloromethyl polysulfone matrix membrane and thiourea. The thiourea-functionalized polysulfone plate reactive ultrafiltration membrane was used for the rejection of heavy toxic metal cations such as Cd²⁺ and Zn²⁺ through the coordination of the thiourea group and heavy toxic metal cations, in which the effects of the morphological and the structure of the membrane on the rejection properties were investigated. The rejection conditions, including the concentration of heavy toxic metal cations, temperature and pH of the solution had significant effects on the rejection capacity of polysulfonebenzylthiourea-reactive ultrafiltration membrane. The reactive ultrafiltration membrane containing thiourea group can be conveniently recovered by dilute hydrochloric acid for coordination of heavy toxic metal cations, which would have wide application for the treatment of waste-water-containing heavy toxic metal cations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Modified Polyethersulfone (PES) Ultrafiltration Membranes for Enhanced Filtration of Whey Proteins

Abstract

Application of membrane technology to whey protein separation is an interesting development that has seen growth in recent years. In particular, modification of existing membranes to impart charge properties on the membrane surface or in the pores has been shown to improve membrane selectivity, product purity, and throughput of protein solutions. This paper focuses on exploring the effects of membrane charge and solution pH on filtration of the major whey proteins α‐lactalbumin (14.1 kDa) and β‐lactoglobulin (18.4 kDa) using functionalized PES membranes. The membranes have an open pore structure containing charged sulfonated grafted polymer chains that allows for greater protein retention. The modified membranes were synthesized by polymerization of styrene in the membrane pores followed by sulfuric acid treatment of the resulting polystyrene grafts. The charged membrane gave a calculated selectivity of five times better than the raw membrane at pH 7.2 based on data from single protein transmission experiments. The enhanced selectivity of the tailor‐made membrane was due to increased retention of β‐lactoglobulin due to a reduction in molecular sieving combined with electrostatic repulsion between negatively charged β‐lactoglobulin and the negatively charged membrane.     

Electrokinetic measurements on porous polysulfone membranes

The surface properties of porous ultrafiltration membranes were determined by means of the streaming potential. The membranes were prepared from chemically modified polysulfone through a phase inversion process. The chemical reactions were carried out in such a way that the resulting polysulfone either was fitted out with chloromethyl substituents or with quaternary ammonia groups. Due to this, the surface of the membranes cast from these materials were either neutral or positively charged. In aqueous solution, ion adsorption as well as dissociation can occur at the surface of the membranes. This can be demonstrated by streaming potential measurements at different pH values, but constant ionic strength. From the calculated zeta potential using a recently developed model, evidence can be given on the dissociation constants of acidic and basic functional groups on the surface of the membranes and on the amount of charges within the shear plane adjacent to the membrane. Using solutions which contained surfactants, qualitative information on the amount of charges within the capillaries of the membrane can be obtained. In the range from 20 to 70°C no temperature dependency of the zeta potential could be observed.     

Solvent‐stable UV‐cured acrylic polysulfone membranes

A systematic investigation of the effect of the presence of acrylate resin on polysulfone‐based membranes was performed with the aim of obtaining chemically stable crosslinked membranes without affecting their flux performances. The membranes were prepared via UV curing of the polymer dope followed by a non‐solvent‐induced phase separation process. Two different acrylic monomers were investigated and their amount was varied in the polymer dope, to study the influence of concentration on final results. High crosslinking degrees were achieved by irradiating the solution for one minute. Morphological investigations of the active surface and of the cross‐sections of the fabricated membranes showed that the typical porosity of ultrafiltration membranes was obtained starting from solutions containing a low amount of crosslinker (10 wt%), which is consistent with the water flux values which were comparable to that of the pristine polysulfone membrane. High concentrations of crosslinker resin in the initial polymer dope produced denser membranes with lower permeability. High rejection of 27 nm particles (>90%) was measured for all samples having measurable flux. The addition of the crosslinker allowed one to obtain stability in various solvents without affecting the flux and rejection performance of the porous membranes. © 2016 Society of Chemical Industry     

Preparation and characterization of porous polysulfone membranes with spacer-bonded N-containing groups

Ultrafiltration membranes were prepared from epoxidized polysulfone by the conventional phase separation procedure. For epoxidizing, the polymer was first lithiated and a reaction followed with glycidyl-4-oxohexylether providing an eight atomic spacer. The reaction of the epoxy group with N-containing substituents was performed heterogeneously using the ready membranes. The stability of the substituted membranes is visible by the fact that they are reacted under reflux conditions for 24 h. The reagents were trimethyl amine, diethylamine, n-butyl amine, and tauric acid. Thus, positively charged, negatively charged, and neutral membranes were obtained. The membranes were characterized via ultrafiltation using dextran solution as well as human albumin solutions. In addition, the streaming potential was measured in the presence and absence of the protein. By these measurements the obviously neutral membranes were surprisingly identified to be positively charged. This is related to subsequent reactions of the spacer-bonded epoxy groups with the amino groups. © 1995 John Wiley & Sons, Inc.     

添加剂对聚砜膜结构和性能的影响

通过浸没沉淀相转化法制备聚砜超滤膜,分别以高分子聚乙烯基吡咯烷酮（PVP-K30,PVP-K90）、聚乙二醇（PEG-6000,PEG-20000）和小分子氯化锌（ZnCl2）、丙酸（AS）6种物质作为制备聚砜超滤膜的添加剂,含量均为10%。并对聚砜超滤膜的断面结构、纯水通量、牛血清蛋白（BSA）截留率、孔隙率及平衡水含量等5项性能进行了测试及表征。由断面结构可以看出,PVP-K90作为添加剂时,制得膜的断面完全为海绵状结构,其它添加剂制得膜断面中均有指状孔结构;PVP-K30作为添加剂时制得膜的纯水通量最大;丙酸作为添加剂制得膜的BSA截留率最高;聚乙烯基吡咯烷酮（PVP）和聚乙二醇（PEG）制得膜的平衡水含量及总孔隙率均较高,但闭孔也较多。     

Cellulose acetate and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization

Modification of polymeric membrane materials by incorporation of hydrophilicity results in membranes with low fouling behavior and high flux. Hence, Polysulfone was functionalized by sulfonation and ultrafiltration membranes were prepared based on sulfonated polysulfone and cellulose acetate in various blend compositions. Polyethyleneglycol 600 was employed as a nonsolvent additive in various concentrations to the casting solution to improve the ultrafiltration performance of the resulting membranes. The total polymer concentration, cellulose acetate, and sulfonated polysulfone polymer blend composition, additive concentration, and its compatibility with polymer blends were optimized. The membranes prepared were characterized in terms of compaction, pure water flux, membrane resistance, and water content. The compaction takes place within 3–4 h for all the membranes. The pure water flux is determined largely by the composition of sulfonated polysulfone and concentration of additive. Membrane resistance is inversely proportional to pure water flux, and water content is proportional to pure water flux for all the membranes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1749–1761, 2002     

Composite membranes formed by plasma-polymerized acrylic acid for ultrafiltration of bleach effluent

Composite membranes were formed by deposition of plasma-polymerized acrylic acid (PPAA) films onto porous commercial membranes to improve the rejection, especially of chlorinated compounds, in ultrafiltration of E-stage bleach effluent. Although increased rejections were accompanied by reduced flux, in most cases, the reductions were not significant considering the extent of increased rejections. A good composite membrane showed the AOX removal of 94% (76% before the modification) and the chemical oxygen demand (COD) removal of 84% (67% before the modification) with 33% reduction of the flux. The permeate was optically clean. The improved rejection is attributed to the tightly crosslinked network of a plasma polymer film and its negatively charged surface. Ultrathin film thickness and the hydrophilic property of a plasma polymer film minimize the reduction of flux. © 1993 John Wiley & Sons, Inc.     

Preparation,structure, and transport properties of ultrafiltration membranes of poly(vinyl chloride) (PVC), carboxylated poly(vinyl chloride) (CPVC), and PVC/CPVC blends

Ultrafiltration (UF) membranes were prepared from poly(vinyl chloride) (PVC), carboxylated poly(vinyl chloride) (CPVC), and PVC/CPVC blends by the phase-inversion method. The physical structure of the membranes was characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The fouling characteristics of all the three membranes and acrylamide (AA)-grafted PVC membranes were characterized by ultrafiltration of bovine serum albumin (BSA) solution over a range of pH and of salt concentrations. Maximum adsorption of the protein on the membrane occurred near the isoelectric point of BSA and in the presence of the salts. The charge on BSA appears to be a dominant factor in determining the fouling. The UF results are explained in terms of nature of the membrane polymer, and effect of different ionic environments on the conformational changes of the protein. The ultrafiltration fluxes are correlated by a model based on the membrane resistance and the time-dependent resistance of the concentration polarization layer of the protein. The values of a mass transfer coefficient and concentration polarization were determined. Zeta potential of the membranes were also determined before and after the UF. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1117–1130, 1999