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.     

Preparation and properties of negatively charged ultrafiltration membrane: Photografted sodium styrene sulfonate onto brominated polyacrylonitrile membrane

Charged ultrafiltration membranes were prepared by photografting sodium styrene sulfonate onto photosensitive polyacrylonitrile membrane containing bromine atoms. The degree of the photografting was characterized by contact angles of air or n-octane in water and FTIR spectra for the negatively charged membrane. Permeations of dextran and dextransulfate through the negatively charged membranes were studied by ultrafiltration in the aqueous solutions of both solutes. With an increase of photoirradiation, the permeability of the solutes decreased. Also, an electrostatic repulsion of the solute and the membrane was confirmed by direct comparison between the permeability of the solutes, dextran, and dextransulfate, each having similar molecular size.     

Acrylonitrile-based copolymers: Synthesis,characterization, and formation of ultrafiltration membranes utilized for the immobilization of proteins

Various high molecular weight copolymers of acrylonitrile and a vinyl comonomer containing an aryl amine, a pyridine, or an aliphatic hydroxyl group were synthesized via slurry polymerization techniques so as to contain from 1 to 15 mol % functional comonomer. The comonomer content was quantitated by ultraviolet absorbance, base titration of acid polymer salts, and/or relative chemical reactivity with trichloro-s-triazine. Thin films were cast from copolymer solutions, coagulated into unsupported ultrafiltration membrances, and characterized with respect to both water permeability and pore size distribution. Analysis by size exclusion chromatography of the membrane permeate of a pool of dextran fractions yielded a continuous distribution curve for membrane pore size over the range 1.5 to 70 nm. The ultrafiltration membranes were used for protein immobilization after appropriate chemical activation. The three distinct types of functional copolymers gave comparable results for α-chymotrypsin, with protein weight loadings of 6–12% and 40–65% retention of enzymatic specific activity.     

Preparation and antimicrobial activity of Konjac Glucomannan modified with quaternary ammonium compound

Seven kind of graft copolymerization Konjac Glucomannan with quaternary ammonium group have been prepared, using Konjac Glucomannan (KGM) and methacryloxylethyl alkyl dimethyl ammonium bromide with c₈–c₁₈ alkyl and benzyl in water, ceric ammonium nitrate as initiator, the reaction temperature of 348 K, and the reaction period of 3 h. The structures were confirmed by FTIR. The 15 min inhibitory rates of all the graft copolymerization KGM against Escherichia coli and Staphylococcus aureus reached 99.99%, against Candida albicans somewhat lower, but 30 min inhibitory rate still reached 99.02% for graft copolymerization KGM with quaternary ammonium group having 14 alkyl. The antibacterial mechanism of the graft copolymerization KGM has been investigated by adsorption ability to E. coli, measure of 260 nm absorbing materials and SEM micrographs. Firstly, the bacteria were fastly adsorbed by graft copolymerization KGM. Interactions between bacterial membranes and antibacterial product cause fundamental changes in both membrane structure and function, induced leakage of cytoplasmic contents is a classic indication of damage to the bacterial cytoplasmic membrane. The loss of the connection between the outer membrane and the underlying peptidoglycan induces the abnormality of nodular structures and bleb formation of the cell envelope of E. coli. The antibacterial mechanism is in accordance with microbiologic findings identifying surface blebbing as the first morphologic change occurring in the permeability barrier of gram‐negative bacteria under mild heat stress and laser irradiation, etc. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyacrylonitrile ultrafiltration membranes containing negatively charged groups for permeation and separation of dextran and dextransulfate

Ultrafiltration membranes of poly(acrylonitrile-co-sodium styrenesulfonate) [P(AN-co-SSS)] were prepared by casting the copolymer solution into water. The ultrafiltration rate of P(AN-co-SSS) membranes was controlled by adding poly(ethylene glycol) (PEG) of various molecular weights to the casting solution. The effect of the PEG addition on the membrane properties was examined. By using the P(AN-co-SSS) membranes, which possess various molecular weight cutoff (MWCO) properties, the permeation behaviors of dextran (D) and dextransulfate (DS) were compared. The P(AN-co-SSS) membranes markedly restricted the permeation of DS, owing to electrostatic barrier of the negatively charged groups in the membrane. The electrostatic sieve separation of DS and D, each having similar molecular size, with the membranes was also investigated. The membrane having negatively charged groups effectively rejected to DS with a high permselectivity. © 1994 John Wiley & Sons, Inc.     

Synthesis of a novel sulfonated poly(amide‐imide) and its application in preparation of ultrafiltration PES membranes as a modifier

Sulfonated poly(amide‐imide) (SPAI) copolymer was synthesized, characterized, and blended into poly(ether sulfone) (PES)/dimethylacetamide casting solutions to prepare ultrafiltration membranes. Different weight ratios of the copolymer (0–10 wt %) were mixed in the PES casting solution. The analyses of contact angle and attenuated total reflection‐Fourier transform infrared spectra were used to study hydrophilicity and physicochemical properties of the membrane surface, respectively. The membranes were further characterized by scanning electron microscopy images, ultrafiltration performance, and fouling analyses. The outcomes showed that addition of the SPAI in the PES matrix improved considerably the membranes hydrophilicity. Moreover, with increasing SPAI concentration, the porosity, flux recovery ratio, and pure water permeability of the modified membranes were improved. The pure water flux was increased from 3.6 to 12.4 kg/m² h by increasing 2 wt % SPAI. The antifouling property of the modified PES membranes against bovine serum albumin, tested by a dead‐end filtration setup revealed that bovine serum albumin rejection of the obtained membrane was also enhanced and the antifouling properties of the blending membranes were improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46477.     

多孔纳米材料改性水处理超滤膜的研究进展

基于压力驱动的超滤膜面临渗透性和选择性的制衡及膜污染问题。多孔纳米材料是高性能超滤膜改性制备中一类重要的添加剂,是新型水处理功能膜的研究热点之一。多孔纳米材料的添加为膜提供了额外水通道,其可调的孔尺寸又为在膜内构建出具有高度选择性的纳米通道提供了潜在有利条件,进而突破膜渗透性和选择性的Trade-off效应。同时,亲水性多孔纳米材料的添加有利于提升膜的抗污染性能。本文综述了近年来多孔纳米材料对超滤膜的改性方法,总结了微孔沸石分子筛、介孔炭、介孔二氧化硅、金属有机骨架材料和共价有机骨架材料对超滤膜的改性研究进展,着重评价了不同改性材料对超滤膜在亲水性、渗透性、污染物截留和抗污染能力等方面的影响。最后对未来多孔纳米材料改性超滤膜的研究及应用的发展趋势进行了展望。     

Permeabilities of coagulated cellulose acetate dialysis membranes

The diffusive flux of NaCl and the hydraulic flux of pure water through coagulated cellulose acetate membranes are examined. Coagulated cellulose acetate membranes (without densification by heat treatment or drying) possess higher permeability than what may be expected from the permeabilities of the dry polymer. Their overall hydraulic permeability (ultrafiltration rate of water) is greatly dependent upon the membrane casting conditions and the resulting asymmetry of the membrane. On the other hand, the asymmetry of a membrane does not play as great a role in the diffusive permeability of a solute. With homogeneous membranes, higher diffusive flux is always accompanied by higher hydraulic permeability. With asymmetric membranes, this is not always true. The diffusive permeability of NaCl and the hydraulic permeability of water through coagulated cellulose acetate membranes can be controlled nearly independently. Consequently, high diffusive (NaCl) permeability with low hydraulic water permeability and vice versa can be obtained by varying the casting conditions and also by partially saponifying the denser portion of the membrane.     

Removal of N‐butanol from aqueous solutions by ion–exchange membranes containing organic counterions

The pervaporation of aqueous butanol solutions was investigated using thin‐film composite membranes composed of a poly(vinylidene fluoride) substrate coated with a sulfonated poly(2,6‐dimethyl‐1,4‐phenelene oxide) polymer. The polymer was ion‐exchanged with quaternary ammonium cations having aliphatic substituents of various chain lengths. The pervaporation of aqueous n‐butanol solutions using these membranes gave a permeate more concentrated in n‐butanol; therefore, they were alcohol‐selective. The separation factor increased and the permeate flux decreased as the chain lengths of the aliphatic substituents were increased. Hence, the mass‐transport properties of such membranes can be controlled or altered to yield some desired permselectivity by the introduction of a proper counterion. It was observed that the n‐butanol flux was small relative to the total flux and, therefore, the water flux dominated the total permeate flux. The degree of swelling of the membranes and its effect on membrane performance was investigated as well. As the n‐butanol content was increased, the swelling of the membranes increased greatly. High membrane swelling caused a reduction in the separation factor. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 47–58, 1999     

Matrix optimisation for hazardous organic waste sorption

Organophilic clays have proven to be interesting intermediates for the definitive stabilization of hazardous organic waste in cement matrix. In the present work, the influence of quaternary ammonium salt structure on the organophilic clay load capacity and the interaction type with the organic waste were investigated. Commercial organophilic montmorillonite clays, containing an ammonium quaternary salt with methyl and long chain aliphatic groups or both aliphatic and aromatic (benzyl) groups, were selected for the experiments. X-ray diffraction (XRD) and FT-IR spectroscopy were used to investigate the pollutant–organoclay interactions. An aromatic amine, i.e. 2-chloroaniline, was chosen as a model pollutant. Sorption isotherms, on organoclays exchanged with ammonium quaternary salts containing the aromatic group, showed a significant increase of the sorbed waste quantity in comparison with those obtained from ammonium quaternary salts with aliphatic groups. The distribution coefficient K_d, estimated on the basis of experimental data, could be explained with dispersive interactions, partially reversible, as resulted from the leaching experiments carried out after sorption process.     

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.     

Synthesis of a poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] block copolymer and its effects on the surface charges and pH‐responsive properties of poly(vinylidene fluoride) blend membranes

A poly(methyl methacrylate) (PMMA)‐b‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] (PDMAEMA) block copolymer was successfully synthesized by a reversible addition–fragmentation chain‐transfer method. The resulting copolymer was used to prepare poly(vinylidene fluoride) blend membranes via a phase‐inversion technique. The polymorphism, structure, and properties of the blend membranes were investigated by Fourier transform infrared spectrometry, scanning electron microscopy (SEM), ζ potential analysis, and filtration. The results indicate that PMMA‐b‐PDMAEMA could migrate onto the surface of the membrane during the coagulation process, and more of the β‐crystal phase appeared with the increase of the block copolymer in the membranes. The surface morphology and cross section of the membranes were also affected by the copolymer, as shown by SEM. The ζ‐potential results show that the surface charges of the membrane could be changed from positive to negative at an isoelectric point as the pH increased. The blend membrane also exhibited good pH sensitivity, and its water flux showed a great dependence on pH. The filtration experiment also indicated that the blend membrane had good hydrophilicity and antifouling properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40685.     

Preparation and characterization of modified ultrafiltration nylon 6 membrane modified by poly (acrylamide-co-maleic anhydride)

In attempt to prepare modified ultrafiltration (UF) Nylon 6 membrane and improve its hydrophilicity and anti-fouling performance, poly (acrylamide-co-maleic anhydride)(AM-MA) was utilized as hydrophilic copolymer additive in the dope solution. The UF Nylon 6/AM-MA membranes were synthesized through blending Nylon 6 with poly(AM-MA) using a phase inversion process. Characterization of the prepared membranes for morphological studies and thermal behavior was carried out by SEM and DSC instruments respectively. The SEM photos demonstrated that by increasing the copolymer density in the dope solution, the morphology was changed from spongy to bi-continuous, composed of small interlocked and stick-like crystallites. FTIR/ATR and water contact angle data also confirmed the existence of AM-MA copolymer on the blend membranes surface. Furthermore, the effect of different molecular weights and concentration of hydrophilic copolymer on filtration performance and antifouling properties were experimentally studied. The results exhibited that the blend UF membranes possessed better water flux permeability than pure Nylon 6 membrane due to the increased surface hydrophilicity and porosity. Fouling resistance experiments revealed that the surface anti-fouling ability of the blend membranes was improved via the addition of AM-MA copolymer with lower MW (co1) to the cast solution, while this parameter was weakened in higher MW of copolymer (co2).     

Preparation and characterization of positively charged composite nanofiltration membranes by coating poly(ether ether ketone) containing quaternary ammonium groups on polysulfone ultrafiltration membranes

The novel positively charged poly(ether ether ketone)s (PEEKs) with pendant quaternary ammonium groups were synthesized by copolymerization of 3, 3′‐dimethylaminemethylene‐4,4′‐biphenol (DABP), 3,3′,4,4′‐tetramethylbiphenol, and 4,4′‐bisfluorobenzophenone followed by reaction with iodomethane. The resulting copolymers were used to prepare thin film composite (TFC) nanofiltration (NF) membranes via the dip‐coating method. The effects of different parameters such as copolymer concentration and curing time on the membrane performance (flux and rejection of inorganic salts) were investigated. The optimum parameters were that 1.5 wt % quaternary ammonium PEEK containing 1.8 quaternary ammonium groups per unit with 0.5 wt % DMSO coated on the polysulfone (PSf) support membrane and cured at 100°C. The results of the performance testing showed that the trend for rejection was R > R > R_NaCl > R (R = rejection), which was a typical positively charged membrane. The best performance of these composite nanofiltration membranes was 91.3% rejection for 500 ppm MgCl₂ and 62.5 L/m² h water permeability at 0.4 MPa. The MWCO of the membrane was 800 Da. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development of ultrafiltration membranes from acrylonitrile co-polymers

Summary Hydrophobic polymer surfaces show higher tendency to protein adsorption and bacteria attachment, thus hydrophobic polymeric membranes foul rapidly in water purification operations. A change in membrane surface properties can reduce fouling; this may be accomplished by increasing the hydrophilicity of the membrane surface, and by using a membrane with smaller pore size. The ultrafiltration membranes were prepared via phase inversion process in our laboratory. Negatively charged hydrophilic ultrafiltration membranes were prepared from acrylonitrile-vinyl acetate (CP16)/Acrylonitrile-vinyl acetate-sodium p-sulfophenyl methallyl ether (CP24). Scanning electron microscopy (SEM) revealed the asymmetric structure of these membranes. The roughness of the surface was measured by atomic force microscopy (AFM). The basic characteristics of these membranes like water permeability, water content and membrane selectivity were also measured. Received: 29 April 2001/Revised version: 14 September 2001/Accepted: 14 September 2001     

Preparation and characterization of layered membranes constructed by sequential redox‐initiated grafting onto polyacrylonitrile ultrafiltration membranes

Layered membranes were prepared by sequential grafting—by means of redox initiators—of water‐soluble monomers, with oppositely charged ionic groups, onto ultrafiltration (UF) polyacrylonitrile (PAN) membranes at room temperature. Grafting of a single layer of 2‐hydroxyethylmethacrylate (HEMA) onto a PAN membrane gave a highly grafted membrane with a relatively high water flux. Bilayered membranes with various properties containing poly‐2‐(dimethylamino)ethyl methacrylate (p‐2DMAEMA) as the bottom layer and polymethacrylic acid or polystyrenesulfonic acid (p‐SSA) as the upper layer were prepared and compared—by means of infrared spectroscopy and electron microscopy—with single‐layered membranes of grafted polyhydroxyethylmethacrylate. Layered membranes exhibited a significant decline in water flux in comparison with the initial UF membranes. The flux could, however, be manipulated by controlling the concentration of monomers, the time of grafting, and the number of layers. When four layers of p‐2DMAEMA and p‐SSA were sequentially grafted onto a PAN membrane, pure water fluxes were stable over a wide range of pH values and did not change over long storage times. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 509–520, 2005     

Preparation and characterization of antifouling poly(vinylidene fluoride) blended membranes

Poly(vinylidene fluoride) (PVDF) membranes have been widely used in microfiltration and ultrafiltration because of their excellent chemical resistance and thermal properties. However, PVDF membranes have exhibited severe membrane fouling because of their hydrophobic properties. In this study, we investigated the antifouling properties of PVDF blended membranes. Antifouling PVDF blended membranes were prepared with a PVDF‐g‐poly(ethylene glycol) methyl ether methacrylate (POEM) graft copolymer. The PVDF‐g‐POEM graft copolymer was synthesized by the atom transfer radical polymerization (ATRP) method. The chemical structure and properties of the synthesized PVDF‐g‐POEM graft copolymer were determined by NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. To investigate the antifouling properties of the membranes, we prepared microfiltration membranes by using the phase‐inversion method, which uses various PVDF/PVDF‐g‐POEM concentrations in dope solutions. The pure water permeabilities were obtained at various pressures. The PVDF/PVDF‐g‐POEM blended membranes exhibited no irreversible fouling in the dead‐end filtration of foulants, including bovine serum albumin, sodium alginate, and Escherichia coli broth. However, the hydrophobic PVDF membrane exhibited severe fouling in comparison with the PVDF/PVDF‐g‐POEM blended membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Multilayer composite surfaces prepared by an electrostatic self‐assembly technique with quaternary ammonium salt and poly(acrylic acid) on poly(acrylonitrile‐co‐acrylic acid) membranes

An electrostatic self‐assembly technique was applied to prepare ion complex polymer layers on polyacrylonitrile with acrylic acid segments {poly(acrylonitrile‐co‐acrylic acid) [P(AN‐co‐AA)]}. For the ionic complex layers, quaternary ammonium salts, such as cetyl trimethyl ammonium chloride (CTAC) and tetramethyl ammonium chloride (TMAC), were used as cationic species, and also, poly(acrylic acid) (PAA) was used as an anionic species. These cationic and anionic species were self‐assembled alternately on the surface of the P(AN‐co‐AA) membrane. Fourier transform infrared spectroscopy, AFM, and water contact angle measurements of the membrane surface were used to confirm the formation of the multilayer composites on the P(AN‐co‐AA). The permeabilities of water and macromolecules of different molecular weights were evaluated by a membrane filtration technique. The values of permeability strongly depended on the formation layer by layer of these ion composites on the base P(AN‐co‐AA). Through the measurement of the values of the contact angle of water, it was clear that surface nature of the base membrane treated by CTAC or TMAC and PAA dramatically changed. We concluded that such an electrostatic self‐assembly technique is useful for the preparation of multicomposite layers to modify the surface of base P(AN‐co‐AA) membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and permeability of solutes through acrylic acid-g-methylcellulose copolymer membranes

Graft copolymer membranes from the methylcellulose and the acrylic acid were prepared and their properties and the permeability of four solutes were estimated. Acrylic acid-g-methylcellulose (AA-g-MC) copolymer dissolved in aqueous acetone solvent was cast to prepare membranes followed by the subsequent crosslinking either with aluminium potassium sulfate or by the thermal-curing method. The equilibrium water content in the membrane increased with the volume fraction of acetone in the aqueous acetone solvent system. Membrane, the ionically crosslinked with the aluminum potassium sulfate, showed the water content in the range of 38.5 and 58.4% and 0.25–0.33 kg/mm² of the tensile strength in the wet state. Compared with ionically crosslinked membranes, thermally dried membranes exhibited a more dense structure, resulting in lower water contents and higher mechanical strength. Experimental results on the permeation of four small and midsize solutes through the graft copolymer membranes revealed the molecular weight dependence of the permeability coefficient. The higher the degree of swelling, the greater the permeability coefficient. Ionically crosslinked membranes had higher solute permeability than the commercial Cuprophane membrane had. © 1993 John Wiley & Sons, Inc.