Development of high-performance mixed matrix reverse osmosis membranes by incorporating aminosilane-modified hydrotalcite

Thin film nanocomposite (TFN) reverse osmosis (RO) membranes were prepared by dispersing 3-aminopropyltriethoxysilane (APTES) modified hydrotalcite (HT), designated as A-HT, in aqueous solution and incorporating the nanoparticles in polyamide layers during the interfacial polymerization process. Results of Fourier transform infrared spectroscopy and zeta potential characterization showed the successful modification of nanoparticles by APTES. In addition, Fourier transform infrared spectroscopy suggested that amidation would take place between the aminosilane on APTES and trimesoyl chloride in organic solution, providing firm covalent interaction between the nanoparticles and polyamide matrix. Dynamic light scattering and transmission electron microscopy indicated that aminosilane modification improved dispersibility of the nanoparticles in aqueous solution and obtained membranes, which suppressed the aggregation. Both the covalent interaction and aggregation suppression were beneficial to compatibility between nanoparticles and the polyamide matrix. TFN RO membranes incorporated with A-HT demonstrated excellent performance. Compared with the pristine RO membrane, the water flux of A-HT-0.050 prepared with an optimum A-HT concentration of 0.050 wt% was enhanced by 18.6% without sacrificing the salt rejection. Moreover, the selectivity of A-HT-0.050 was superior to that of HT-0.050 prepared with HT of 0.050 wt%, which proved aminosilane modification of hydrotalcite was beneficial to high membrane performance especially to selectivity.