Development of new pervaporation composite membranes for desalination: Theoretical and experimental investigations

Pervaporation (PV) has mainly been used for dehydration in industrial applications as well as for the recovery of some organic components from various organic or water mixtures. Nevertheless, to date, pervaporation has never been seen as a potential industrial solution to get drinkable water by water permeation, contrarily to membrane distillation (MD). Nevertheless, at the lab scale, some studies with hydrophilic PV membranes have been reported. This work intends to underline the potential industrial interest of hydrophobic PV composite membranes for desalination. Indeed, even in hypersaline solutions, the water activity remains very high (>0.9), and it is wise to use membranes with stable properties in water to guarantee steady performance. Therefore, this study investigates the interest of hydrophobic polymers as coating selective layers for desalination. To guide our choice, a rational approach was used based on the prediction of the membrane resistance to water transfer. Polymethylpentene, poly(1-trimethylsilyl-1-propyne) and Teflon™ AF2400 were tested as the top layer to obtain hydrophobic composite PV membranes. Several feed NaCl solutions with or without a surfactant were used to investigate the mass transfer properties of these PV membranes for water treatment comparatively to more conventional porous membranes (e.g. PVDF) currently studied in membrane distillation.