High selectivity polyamide reverse osmosis membrane enhanced by aminosilane-modified silicalite-1 nanozeolites

Nanozeolites are proved to improve water permeability when they are incorporated into polyamide reverse osmosis membranes. But this incorporation also brings selectivity loss due to the non-selective defects derived from poor affinity of nanozeolites to polyamide matrix and aggregation of these nanoparticles. This work developed surface aminosilane modification involving anchoring 3-amino-propyltriethoxysilane onto nanosized silicalite-1 before integration with polyamide matrix via interfacial polymerization. Results of fourier transform infrared spectroscopy and X-ray photo electron spectroscopy showed that modified silicalite-1 particles formed a stronger covalent interaction with polyamide matrix than pristine ones, implying a better compatibility between these two materials. Characterization with dynamic lights cattering and transmission electron microscope manifested that modified nanozeolites formed much smaller nano-clusters both in preparing solution and resulting membrane than pristine ones, suggesting that aggregation was mitigated. Performance evaluation showed that the membrane incorporated with aminosilanized silicalite-1 zeolites (an optimum integrating concentration (0.05%, w/v)) exhibited superior NaCl rejection (98.6%) to that with pristine silicalite-1 (Rejection = 97.1%). A 67% increase in water flux (58.5 L/m(2).h) over the bare PA membrane was also achieved by applying the modified nanozeolites. The strategy of aminosilane-modification in this work is proved potential to prevent rejection loss for nanozeolites-enhanced RO membranes.