Preparation of modified MFI-type/PDMS composite membranes for the separation of dichlorobenzene isomers pervaporation.

Zeolite-polymer composite membranes have become promising and effective materials for the pervaporative separation of liquids, especially for isomeric mixtures. In this paper, silicalite-1/PDMS composite membranes have been used to investigate the separation of dichlorobenzene (DCB) isomers pervaporation for the first time. Silicalite-1 zeolites modified by the silane coupling agent, NH-CH-Si(OCH), have been incorporated into polydimethylsiloxane (PDMS). Then, the silicalite-1/PDMS composite membranes have been successfully prepared on porous polyvinylidene fluoride (PVDF) supports. The morphology and structure of the silicalite-1 zeolites and silicalite-1/PDMS composite membranes have been characterized by XRD, FTIR, SEM and BET techniques. The results show that the modified silicalite-1 zeolite particles have smaller pore sizes dispersed more uniformly in the active layers of the silicalite-1/PDMS composite membranes and present fewer aggregation and pinholes formed by the accumulation of zeolite particles. The silicalite-1/PDMS composite membranes are all dense and continuous with good homogeneity. To evaluate the pervaporative separation performance of the DCB isomers, the unmodified and modified silicalite-1/PDMS composite membranes have been further tested in single-isomer and binary-isomer systems at 60 °C. The modified silicalite-1/PDMS composite membranes present higher DCB isomer separation factors. The separation factors of the modified silicalite-1/PDMS composite membranes in the binary-isomer systems for -/-DCB and -/-DCB are 3.53 and 5.63, respectively. The permeate flux of -DCB through the modified silicalite-1/PDMS composite membranes in the -/-DCB binary-isomer system is 116.7 g m h and in the -/-DCB binary-isomer system, it is 93.5 g m h. The result provides a new approach towards the pervaporative separation of DCB isomers from their mixture for future industrialization applications.