Rejection and adsorption of trace pharmaceuticals by coating a forward osmosis membrane with TiO2

Abstract

The active layer of a thin film composite polysulfonate forward osmosis (FO) membrane impregnated with nanoparticles of titanium dioxide (nano-TiO2) using polydopamine was developed. A mass balance and adsorption thermodynamic analysis of selected pharmaceuticals in the FO process was investigated. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy were used to examine the physical and chemical properties of the modified membrane. The contact angle and zeta potential decreased significantly after modification. A small increase in rejection capacity for the selected pharmaceuticals after modification was observed. The modified membrane also displayed less tendency to be fouled by humic acid than the virgin one. The pH of the feed solution had less impact on the rejection of pharmaceuticals by the modified membrane than the virgin membrane, which was likely due to changes in the zeta potential and functional groups of the modified membrane. We demonstrated that adsorption plays a significant role in TCS removal but not in the removal of MTP and SMX.