Study Of Molecularly Imprinted Membranes For Efficient Chiral Resolution Of Phenylalanine Isomers In Aqueous Solution

Optical resolution is of obvious importance in both theory and reality, and of great challenge. Molecularly imprinted membranes (MIMs), which combine the advantages of molecular imprinting and membrane technology, will potentially become novel separation media for the recognition and separation of chiral substances. In this work, novel MIMs were prepared and efficient separation of L, D-amino acids in aqueous solution was realized.MIMs were prepared using L-phenylalanine (L-Phe) as template, chitosan (CS) with large numbers of amine groups and hydroxyl groups as a multifunctional polymer and bulk membrane matrix. Firstly, molecularly imprinted and control CS membranes were prepared by phase conversion method together with aqueous alkali or sulfuric acid treatment. The chemical composition, structure and morphology of the CS membranes were obtained by FT-IR and SEM. The effect of heat-treatment temperature, template content and ethanol concentration in feed on the ability of membranes for chiral resolution of D, L-Phe aqueous mixtures were investigated.Secondly, L-Phe molecularly imprinted and control chitosan/tetraethoxyortho- silane (CS/TEOS) hybrid membranes were prepared by a simple sol-gel process in aqueous system. The chemical composition, structure and morphology of CS/TEOS hybrid membranes were obtained by FT-IR and SEM. The effects of heat-treatment temperature and TEOS content on the chiral resolution ability of the membranes were investigated.Finally, L-Phe molecularly imprinted and control chitosan/γ-glycidoxypropyl- trimethoxysilane (CS/GPTMS) hybrid membranes were prepared by a similar sol-gel process as above-mentioned. The chemical composition, physical structure and thermal stability of the hybrid membranes were characterized by FT-IR, SEM, EDX, 29Si NMR, XRD and TG. The binding capacity and selectivity of the membranes were obtained by binding experiments. The effects of reaction time, heat-treatment temperature, GPTMS content and feed concentration on the chiral resolution ability of the membranes were investigated. The results indicated that molecularly imprinted CS/GPTMS hybrid membranes showed improved specific adsorption selectivity towards templates compared with control membranes. The transport of L- phenylanaline through MIMs fit the mechanism of"preferential sorption, retarded...