MeSiCl3 functionalized polyamide thin film nanocomposite for low pressure RO membrane desalination

Most thin film nanocomposite (TFN) membranes with higher permeability are related to hydrophilic nanocomposites. Nevertheless, in nature, water permeates faster in hydrophobic pores (e.g. aquaporin) because of less affinity between water and wall of the pore. Here we show hydrophobic methyltrichlorosilane (MeSiCl3, MTS) functionalized polyamide TFN can be used to construct highly efficient desalination membranes. The TFN membranes were synthesized through the interfacial polymerization of aqueous amine and organic MTS/acyl chloride solutions. Both the water flux and water/salt selectivity increased. The water flux increased by more than a factor of 1.96, from 2.4 to 4.7 LMH/bar, as the fraction of MTS increased from 0 to 0.1 mM in the organic solution. Importantly, the water/salt selectivity ratio increased from 11.4 to 18.5 bar(-1). Thus, MeSiCl3 imparted narrow water channels to the polyamide matrix with higher flow rate and better selectivity. The enhanced compatibility and interactions between MTS and the polyamide polymers were attributed to their covalent (Si-N) and hydrogen (O center dot center dot center dot H) bonds. MTS modified TFN membranes also show high water flux and recovery ratio in the bovine serum albumin (BSA) solution. This facile in situ modification provides a new insight into the high performance of hydrophobic TFN membranes.