Preparation of bridged silica RO membranes from copolymerization of bis(triethoxysilyl)ethene/(hydroxymethyl)triethoxysilane. Effects of ethenylene-bridge enhancing water permeability

Copolymerization of bis(triethoxysilyl)ethene (BTESE2) and hydroxymethyl(triethoxy)silane (HMTES) was carried out to prepare new bridged silica membranes containing C-O-Si linkages. The membranes were examined for reverse osmosis (RO) to evaluate the water desalination properties. It was found that the hydrolysis of C-O-Si bonds occurred during the RO experiments to generate hydrophilic alcohol (C-OH) and silanol (Si-OH) units, thereby increasing the water permeability of the bridged silica membranes. Similar phenomenon was already reported for copolymer membranes prepared from bis(triethoxysilyl)ethane (BTESE1) and HMTES. However, the present membranes showed improved performance with higher water permeance by 4-14 times when compared to the previous BTESE1/HMTES-based membranes, although NaCl rejection was slightly lowered.