Enhancing water flux of thin-film nanocomposite (TFN) membrane by incorporation of bimodal silica nanoparticles

Abstract

Modern reverse osmosis (RO)/nanofiltration (NF) membranes are primarily made of thin-film composites (TFC) fabricated through interfacial polymerization of m-phenylene diamine (MPD) and trimesoyl chloride (TMC) on a polysulfone (PSF) supporting membrane. In this study, two types of bimodal silica nanoparticles (~80 nm) with different internal pore structures were synthesized and incorporated into the polyamide (PA) thin-film layer during interfacial polymerization at concentrations varying from 0 to 0.1 wt%. The as-prepared membranes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, and their performances were evaluated in terms of the water permeability and salt rejection. The results showed the water permeability increased with increasing BSN concentrations, reaching a maximum of 53.5 L m−2 h−1 at a bimodal silica nanoparticle (BSN) concentration of 0.5 wt% (pressure at 300 psi, NaCl concentration: 2000 ppm). This represented a flux increase of approximately 40%, while a near constant salt rejection of 95% was maintained. The study demonstrated that the internal micro-mesoporous structures of bimodal silica nanoparticles contributed significantly to the membrane performance, which is consistent with previous studies with relatively uniform internal pores.