The Preparation And Studies Of PDMS-PVDF Pervaporation Ethanol-permseletive Composite Membrane

Pervaporation is a new technology of membrane separation for the separation of liquid mixtures,which based on the membrane's different selectivity towards the various components in the mixture. It has special advantage in the use of the separation of homogenous mixtures such as azeotropic,closing-boiling and isomeric mixtures,which are difficult or impossible to separate by conventional methods.The purpose of this work is studying pervaporation membrane used in the seperation of dilute alcohol aqueous solution .It is one of the vital technologies of priducing fuel alcohol.In this paper,a plat Polydimethylsiloxane (PDMS) composite membrane was prepared by coating thin PDMS active layer on polyvinylidene fluoride(PVDF) which is singled out to act as supporting layer. The experiment of the separation of ethanol from dilute ethanol aqueous solution with the PDMS-PVDF composite membranes was carried out. The effect of the operating conditions temperature was studied. The PDMS-PVDF composite membranes have moderate selectivity towards ethanol,stable permeate flux and separation factor.An increase of the temperature results in an increase of the total flux and separation factor.The permeating flux conformed to Arrenhenius equation.Polydimethysiloxane (PDMS) membranes filled with ZMS-5 zeolite were prepared, the effect of the different Si/Al ratio on the separation of ethanol from dilute ethanol aqueous solution was studied The results showed that the bigger ratio of zeolite,the better separation results was got;And the best filled content of zeolit was 30%.Also the swelling characteristics of the zeolite filled PDMS membranes dipped in ethanol-water solutions were investigated by a series of experiments. Results are demonstrated that the swelling ratio of PDMS membrane increased quickly with the change of filled content of zeolit within the same temperature and ethanol aqueous solution.And the swelling ratio of PDMS membrane increased with the ethanol concentration. Swelling selectivity factor of zeolite filled PDMS membrane decreased with the increasing temperature.The effect of the temperature and feed concentration on the swelling selectivity factors and swelling ratios were studied.