Document Type : Research Paper
Research and Development Department, DeltaMem AG, Sandweg 52, 4123 Allschwil, Switzerland
Although research on silicone rubber membranes focuses on the removal of volatile organic compounds (VOC) from water, here we report the use of silicone rubber as a protective layer in the fabrication of hydrophilic membranes. By combining the high water vapor permeability of silicone rubber with the high water selectivity of polyvinyl alcohol (PVA), we have developed a new multilayer pervaporation membrane. Firstly, a thinner and less cross-linked PVA membrane with enhanced water flux was developed (without compromising dramatically the selectivity). Secondly, the thin PVA membrane was protected by a silicone layer to hinder the swelling and dissolution of the polymer in hot aqueous solutions. The aim of protecting the PVA membrane is to improve the stability and lifetime of the thinner and less cross-linked membrane. Pervaporation tests showed that the additional silicone (hydrophobic) layer does not reduce the water permeate flux or the selectivity of the thin PVA membrane and confirms its role in protecting the selective layer. Long-term stability tests with ethanol/water and glycol ether/water mixtures demonstrated that the new multilayer membrane is stable under different operating conditions (e.g., feed water concentration from 0.5 to 100 wt.% and operating temperature up to 110°C). The multilayer membrane also showed promising performance for the emerging application of desalination by pervaporation. Therefore, this new membrane formulation produces a robust pervaporation membrane with high water flux.