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Abstract: Novel liquid membrane system, which is named polymeric pseudo-liquid membrane was constructed from polymethacrylate derivative bearing oligodimethylsiloxane (PDMSMA), showing rubbery state under operating conditions, as a membrane matrix. In the present study, dibenzo-18-crown-6 (DB18C6), dibenzo-21-crown-7 (DB21C7) or O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (AMCC) was adopted as a carrier for KCl transport, CsCl transport or optical resolution of racemic mixture of phenylglycine (Phegly), respectively. The results of KCl and CsCl transports revealed that the membrane transport was attained by carrier-diffusion mechanism like conventional liquid membranes. The present study led the conclusion that PDMSMA can be applicable not only to membrane transport of alkali metal ions, such as K+ and Cs+, but also to chiral separation. Keywords: Chiral separation, Crown ether, Liquid membrane, Optical resolution, Polymeric pseudo-liquid membrane. |
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Abstract: In this study, it is first time to obtain a complete separation of using β-cyclodextrin (β-CD) modified cellulose microfiltration membrane. Commercially cellulose membrane with the pore diameter of 0.22μm was functionalized with β-cyclodextrin (β-CD) by aldolization at the solid–liquid interface. Filtration experiments were carried out using a dead-end filtration cell holding a flat sheet membrane with effective area of 36 mm2. Aqueous solution of racemic tryptophan (0.05g/L, 150 mL) was forced to permeate through the cellulose membrane immobilized by β-CD at a flow rate of 0.1 ml/min through the membrane microdevice. Chiral ligand exchange chromatography was used to determine the concentration and ratio of D- and L-tryptophan in the filtrate. A complete separation of racemic tryptophan can be obtained by using this novel composite membrane-based separation system. In addition, a multi-stage filtration separation was applied in order to obtain higher permselectivity. The objective of this study is to obtain an easy prepared chiral membrane with good reproducibility and can be applied to a variety of chiral separations. Keywords: Cellulose membrane, Enantiomeric separation, Glutaraldehyde, Tryptophan, Multi-stage filtration.Download Full Article |
Abstract : Preparation and Performance of Catalytic Hollow Fibre Membranes for Hydrogenation Reduction of Nitrites in Water
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Abstract: Porous Al2O3 hollow fiber membranes have been fabricated via a phase inversion – sintering technique. Pd-loaded carbon nanotubes(CNTs) are formed inside the hollow fibre wall by the catalytic decomposition of methane over Fe particles, followed by impregnation and reduction with hydrogen to form catalytic hollow fibre membranes. Hydrophobic modification of the hollow fibres is conducted by gas permeable polymeric coating. The resultant hollow fibre membranes exhibit highly catalytic activity to the hydrogenation reduction of nitrites in aqueous solution. Hollow fibre membrane reactors are assembled for nitrite hydrogenation by pumping nitrite solution into the tube side and introducing hydrogen countercurrently to the shell side of the reactor. The nitrite removal in the hollow fibre membrane reactors increases with the operation temperature and the hydrogen feed concentration at lower hydrogen partial pressures, but less influenced by the hydrogen feed concentration when it is higher than 50%. A higher nitrite concentration favors the nitrite hydrogenation reaction but lowers the nitrite removal efficiency. Keywords: Hollow fibre,catalytic membrane reactor,nitrite removal,hydrogenation reduction.Download Full Article |
Abstract : Preparation and Characterization of Superhydrophobic Modification of Polyvinylidene Fluoride Membrane by Dip-Coating
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Abstract: The superhydrophobicity polyvinylidene fluoride (PVDF) membranes were modified via reducing surface energy by dip-coating perfluoroalkyl methacrylic copolymer (Zonyl 8740) onto the membranes prepared on mat glass. The chemical component of the unmodified and modified PVDF membranes surface was investigated by ATR-FTIR. Morphology and hydrophobicity of the unmodified and modified PVDF membranes were examined by scanning electronic microscopy and water contact angle, respectively. The effects of concentration of Zonyl 8740, coating time, conditions of heat treatment on hydrophobic capability of PVDF membranes were investigated. The results showed that the water contact angle increased from 141˚ to 151˚ by the dip-coating modification, therefore getting superhydrophobic PVDF membrane. Moreover, the porosity and the morphology of modified PVDF membrane were unchanged by the dip-coating modification. This results suggested that the hydrophobicty stability of the modified PVDF membrane was also good. Keywords: Polyvinylidene fluoride, Superhydrophobic, Coating modification, Perfluoroalkyl methacrylic copolymer, Membrane preparation. Download Full Article |
Abstract : Preparation of PVDF UF Membranes under an External Electric Field with PVP as Additive
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Abstract: In this study, PVDF UF membraneswere prepared with PVP as additive via a favorable method of applying high voltage external electric field (2kV) through the immersion precipitation phase inversion process. The influence of external electric field on the structure, surface functional groups, membrane potential, and surface hydrophilicity of the membranes were researched. In addition, anti-fouling property and separation performance of the membranes were also investigated. The results indicated that the protein adsorption amount on the electric treated membranes was distinctly reduced. Especially for the electric treated PVDF membrane with PVP K70 as additive, the value of water contact angle reached 75.4° and the protein adsorption amount decreased 76 %, reaching 20.39 µg·cm-2. The separation performance of the electric treated membrane was also superior to that of the un-treated membrane. All the experimental results indicatedthat this electric treated approach open a promising way for the modification of PVDF membrane because it combined membrane preparation and modification in only one physical step without additional chemical reagents. Keywords: Electric field, membrane potential, PVDF membrane, ultrafiltration, adsorption.Download Full Article |