Search

Abstract: The morphology and swelling performance of poly(methyl methacrylate) (PMMA) and polyurethane (PU) membranes containing pristine multi-walled carbon nanotubes (P-MWCNTs) was investigated. Next, amino (NH2) groups were introduced into the MWCNTs by chemical modification for improving their affinity to the membranes, thereby resulting in a better distribution of the MWCNTs in the membranes. The performance of the hybrid membranes was evaluated by swelling and pervaporation experiments. The Fourier transform infrared and transmission electron microscopy analyses showed that the addition of both the pristine and functionalized MWCNTs to the membranes improved their permeation performance. The dispersion of the P-MWCNTs and MWCNTs-NH2 in the PU hybrid membranes was better than that in the corresponding PMMA hybrid membranes because of the rapid polymerization rate of the monomers and the elasticity of the membranes. Thus, the P-MWCNTs/PU and MWCNTs-NH2/PU hybrid membranes performed better than the corresponding P-MWCNTs/PMMA and MWCNTS-NH2/PMMA hybrid membranes. The surface functionalization promoted the affinity of the MWCNTs to the monomer solution and the polymer membranes. Compared to the P-MWCNTs, the MWCNTs-NH2 showed an improved distribution in the PU and PMMA hybrid membranes, and the membranes containing the MWCNTs-NH2 performed better than those containing the P-MWCNTs. [Copyright &y& Elsevier]

Abstract: Functionalized multiwalled carbon nanotubes (MWNTs) were incorporated into a chitosan membrane for separation of benzene/cyclohexane mixtures by pervaporation. The pristine MWNTs were treated by mixed acid (H2SO4/HNO3=3/1) and then functionalized with isonicotinic acid. Ag+ was grafted to the pyridine ring on the MWNTs by a complexation reaction. Membranes made of chitosan and Ag+/carbon nanotubes were prepared with polysulfone membranes as support. The surface structure of modified MWNTs was examined by FT-IR, TEM, EDS and XPS to assess its morphology. The swelling and pervaporation characteristics of the membranes for separation of benzene/cyclohexane mixtures were investigated. The swelling degree of the membranes in benzene was more than 2.5 times that of the pristine chitosan membrane. The swelling degree was found to increase with the content of the MWNTs–Ag+ in the membrane and the benzene content in the feed. Pervaporation results also showed that the MWNTs–Ag+/chitosan hybrid membrane separation performance is better than MWNTs/chitosan hybrid membrane and pristine chitosan membrane. The permeation flux of the membrane increased, the selectivity increased firstly and then decreased with the increase in the content of MWNTs–Ag+. The selectivity reached 7.89 and the permeate flux was 357.96g/m2 h (the mass ratio of benzene was 50%, the temperature was 20°C) when the percentage by weight of the MWNTs–Ag+ to chitosan was 1.5%. The Arrhenius activation parameter of 1.5% MWNTs–Ag+/chitosan (CS) hybrid membrane is 4.28kJ/mol while 1.5% MWNTs/CS membrane is 10.6kJ/mol in 50% benzene concentration in feed. [Copyright &y& Elsevier]

Abstract: Ultrafiltration (UF) has become an accepted process for drinking water treatment, but membrane fouling remains a significant problem. Polyethersulfone (PES)/SiO2 composite membranes were prepared by phase inversion method with nano-SiO2 as additive. Water contact angle measurement was conducted to investigate the hydrophilicity and surface wettability of the membranes. The effect of SiO2 nanoparticles on the membrane permeation properties, anti-fouling performances, and membrane morphologies and structures was examined and discussed. The influence of SiO2 on the water permeability, anti-fouling of the PES membranes were evaluated by raw water UF experiments. The results showed that the membrane structure was not obviously affected by addition of SiO2, and the membrane performances such as hydrophilicity and anti-fouling ability were enhanced by adding SiO2 nanoparticles. [Copyright &y& Elsevier]

The article presents information on a study which described the preparation of novel pervaporation (PV) membranes for ethanol dehydration by blend poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMCS). A review of the related literature is provided. It describes the crosslinking procedure with glutaraldehyde. Fourier transform infrared and X-ray diffraction were used to investigate the structure and miscibility of the blend membranes. It discusses the findings of the research.

Abstract: Asymmetric and charged ultrafiltration membranes were prepared from blends with synthesized polyacrylonitrile (PAN) and hydrophilically modified polyacrylonitrile by the classical phase inversion technique in water. As hydrophilically modified polyacrylonitrile was added, the membranes were more hydrophilic and better anti-fouling performance. Collagen extract was separated by the resulted ultrafiltration membranes. The results showed that, compared to the pure PAN ultrafiltration membrane, the blend membrane possessed higher hydrophilicity and better anti-fouling property. Fouling of collagen particles on the blend membranes was able to reduce as the composition of hydrophilic polyacrylonitrile increased. And the resulted membrane can be used to purify and concentrate collagen extract effectively. The pH of the collagen extract and the hydrophilic polyacrylonitrile content in the blend membrane could influence the membrane separation performance during separating the collagen extract. [Copyright &y& Elsevier]

Abstract: A copolymer with a water-soluble polymer was synthesized from acrylic acid (AA) and 2-(dimethylamino) ethyl methacrylate (DMAEMA) by radical polymerization. The composite membrane was prepared with the DMAEMA-AA copolymer as the top layer and a PS ultrafiltration membrane as the support. The permeation of pure CO2 and CH4 through the composite membrane was measured. The effects of feed gas pressure, separation layer thickness, temperature and heat treatment on the composite membrane performance were studied. The results show that the composite membranes possess good CO2 permeance and selectivity of CO2 over CH4. The membrane displays a CO2 permeation rate of 6.12×10−7 cm3(STP) cm−2 s−1 Pa−1 and CO2/CH4 selectivity of 253.1 at 26°C, 1140 Pa of gas pressure. [Copyright &y& Elsevier]

Abstract: A copolymeric membrane material containing an amine group for CO2 facilitated transport was synthesized by radical polymerization of acrylamide and maleic anhydride. The relative molecular weight and chemical structure of the copolymer were analyzed by viscometric measurement, elemental analysis, and FTIR. The copolymeric membranes were prepared. The sorption behavior as well as the permeabilities of the membranes for pure CO2 and CH4 were investigated. The results show that the copolymeric membrane possesses a higher permeability of CO2 and a lower permeability of CH4. The membrane displays a CO2 permeability of 5×10−12 cm3(STP)/cm2.s.pa, and a CH4 permeability of 2×10−13 cm3(STP)/cm2.s.pa. CO2 sorption behavior of the copolymeric membrane, which can be classified as a dual-mode sorption model, and CH4 sorption behavior of the copolymeric membrane accord with the Fickian diffusion model. [Copyright &y& Elsevier]

A novel poly(amide-urethane@imide) reverse osmosis (RO) composite membrane with chlorine-tolerant property was prepared on a polysulfone supporting film through two-step interfacial polymerization. The crosslinking agent – 5-choroformyloxyisophaloyl chloride (CFIC) was first reacted with 4-methyl-phenylenediamine (MMPD) via interfacial polymerization to get the nascent poly(amide-urethane) base membrane (CFIC–MMPD) without curing treatment. Then the resultant base membrane contacted again with the second aqueous solution containing functional secondary amine – N,N′-dimethyl- m -phenylenediamine (DMMPD) to obtain the poly(amide-urethane@imide) TFC RO membrane (MMPD–CFIC@CFIC–DMMPD). X-ray photoelectronic spectroscopy (XPS) was combined with attenuated total reflectance infrared (ATR-IR) to verify that the ultrathin polyimide film (CFIC–DMMPD) has been successfully grafted on the surface of the MMPD–CFIC base membrane. The images of scanning electronic microscopy (SEM) and atomic force microscope (AFM) showed that the poly(amide-urethane@imide) membrane has much smoother, more hydrophilic surface than the poly(amide/imide-urethane) membrane (MMPD/DMMPD–CFIC) prepared by conventional one-step interfacial polymerization of CFIC and composite MMPD/DMMPD. However, the permeation experiment revealed that the poly(amide-urethane@imide) membrane has a slight loss in both salt rejection and water flux than the poly(amide/imide-urethane) membrane and conventional commercialized polyamide membrane (MPD–TMC), but exhibits better chlorine-tolerant property due to the introduction of ultrathin polyimide film (CFIC–DMMPD) on the outmost surface of the TFC RO membrane, and the combination of IR and XPS analyses shows a good agreement with the chlorine exposure results of membranes. [ABSTRACT FROM AUTHOR]

Ion exchange membranes are essential for electrodialysis. However, the presence of multivalent ions, such as Ca 2+ , Mg 2+ , or CO 3 2− , SO 4 2− , may result in a detrimental risk of membrane scaling. Mono-valent cation selective membranes may solve this problem. In this study, the surfactant N,N-dimethyl-N-2-propenyl-2-propene-1-ammonium chloride-2-propenamide (poly-quaternium-7, PQ7) is used to modificate the cation exchange membranes. Different concentrations of degraded polyquaternium-7 and sodium hydroxide are investigated to determine the optimal point. The composition and characteristics of the membranes were determined with Fourier transform infrared spectroscopy (FTIR), X-ray photo-electron spectroscopy (XPS), Scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM). Hydrophilic and functional groups of the membrane were determined by the water uptake, contact angle and ion exchange capacity. Current–voltage curves were measured to characterize the transport properties of membranes. The obtained results showed that the limiting current was reduced while the Ohmic and electro-convection resistances were increased. Diffusion dialysis experiments have demonstrated that leakage of modified membrane is lower. Furthermore, a series of electrodialysis experiments was conducted to evaluate the monovalent selectivity of the unmodified and modified CEMs. The leakage of Zn 2+ was decreased from 22.0% to 14.2% and the leakage of Ca 2+ and Mg 2+ were both decreased while the membranes are used in seawater concentration. The obtained results indicate that the membrane has an excellent performance, particularly with respect to selectivity. [ABSTRACT FROM AUTHOR]

A polyacrylonitrile/palygorskite composite chemically modified with amidoxime groups was prepared by free-radical graft polymerization of acrylonitrile onto 3-glycidyloxypropyl trimethoxy silane (KH-560)-modified palygorskite and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Adsorption of uranium(VI) from simulated seawater on the material was investigated. Batch experiments were carried out to study the effects of initial pH, contact time, initial feed concentration and ionic strength on uranium removal. The solution pH values had a major impact on uranium(VI) adsorption with optimal adsorption observed around pH 5. The kinetic data followed the pseudo second-order process. The equilibrium data fitted the Freundlich model well and the maximum adsorption capacity was found to be 78.13 mg/g. The ionic strength did not significantly affect uranium removal and chemisorption was assumed to describe the uranium adsorption. Desorption was performed using 0.1 M HCl solution, and the regenerated adsorbents could be reused with little loss of adsorption capacity after five cycles. [ABSTRACT FROM AUTHOR]