Preparation of multi-layer silicone/PVDF composite membranes for pervaporation of ethanol aqueous solutions

Composite membrane of silicone/PVDF was prepared by curing a copolymer of polysiloxane and phosphate ester cast on porous PVDF substrate. The substrate was previously plasma-grafted with a thin layer of silicone compatible material. The formed composite membrane was employed in pervaporation separation processes to separate ethanol–water solutions. It was found that the synthesized composite membrane exhibited excellent ethanol-permselectivity, particularly in the low ethanol concentration range. The separation factor of the composite membrane increased with increasing the thickness of the active silicone layer whereas the permeation flux follows a reversed order. In addition, multiple-layer composite membranes with an alternating silicone/PVDF/silicone configuration were prepared and tested for their separation capabilities. The results indicated that the membrane with four silicone layers gave the best performance with a separation factor of 31, permeation rate of 0.9 kg/m2 h and PSI of 27,900 at a 10 wt.% ethanol feed concentration.