Aromatic solvent-assisted interfacial polymerization to prepare high performance thin film composite reverse osmosis membranes based on hydrophilic supports

We report an aromatic solvent-assisted interfacial polymerization (IP) method to prepare high performance thin film composite reverse osmosis (RO) membranes based on a polyacrylonitrile support. The use of toluene and xylene as an organic solvent phase led to excellent water flux and unprecedentedly high NaCl rejection (∼99.9%), exceeding both the control membrane prepared using a conventional aliphatic solvent (n-hexane) and commercial RO membranes. The membrane prepared using n-hexane had a thick and moderately dense PA layer, due to the limited amine monomer diffusion, accounting for its relatively low performance. In contrast, the membranes fabricated using toluene/xylene had roof-like structures covering a thin and highly dense basal PA layer, which was formed by increased amine diffusion and an expanded miscible interface zone resulting from the enhanced miscibility of toluene/xylene with water. The excellent membrane performance achieved using toluene/xylene can be attributed to the thin and highly cross-linked basal PA layer.