Multiple sprayed composite membranes with high flux for alcohol permselective pervaporation

Abstract

Alcohol permselective pervaporation is a promising technology for bio-alcohol production. In this study, a multiple spray technique has been developed to prepare hydrophobic composite membranes for alcohol permselective pervaporation. A defect-free permselective layer was successfully obtained by repeated alternate spraying of dihydroxypolydimethylsiloxane (PDMS) and tetraethylorthosilicate with the addition of dibutyltin dilaurate on to a polysulfone ultrafiltration membrane using an automatic spray system. The effects of PDMS molecular weight and concentration, number of spraying cycles, spraying time and standing interval on the membrane performance were intensively investigated. Experiments proved that, compared with the dip-coated membrane, the membrane flux obtained in this way showed a dramatically increase while the selectivity remained at a comparable level. It was found that the multiple spray technique can ensure that there are no defects in the separation layer, by repeated adjustment of the number of spraying cycles, and can also greatly reduce the thickness of a selective layer. In addition, the automatic spray technology removes the inherent unreliability of manual techniques, so is beneficial for large-scale rapid preparation of composite membranes.