Preparation of Robust Hybrid Silica Membranes for Reverse Osmosis

Membrane-based reverse osmosis (RO) is now the leading technology for production of pure water from seawater and brackish water. However, commercially dominant polyamide RO membranes suffer from poor tolerance to chlorine, which is the most widely used biocide in water treatment. Here, we developed a new type of hybrid silica membrane and were the first to apply this membrane to water purification by reverse osmosis. Sol-gel derived hybrid silica membranes were prepared using (C₂H₅O)₃Si–CH₂CH₂–Si(OH₅C₂)₃ (bis(triethoxysilyl) ethane, BTESE) in the design of the molecular sieve organic-inorganic silica network. Use of the organically bridging groups between two silicon atoms affords precise control of the pore size for the silica membranes according to the separation requirements. Our studies demonstrated that the hybrid silica membranes possessed an impressive hydrothermal stability, even under an elevated temperature of 90 °C. Furthermore, the prepared membranes exhibited an excellent chlorine resistance over a wide range of chlorine concentrations. After a total chlorine exposure of up to 35,000 ppm×h, there was no obvious change in membrane performance. We believe that the hybrid silica membranes with robust performance (high chlorine-resistance and excellent hydrothermal stability) will open a new realm of applications of reverse osmosis.