(3-Aminopropyl)trimethoxysilane-Functionalized Titanium Dioxide Thin-Film Nanocomposite Membrane: Enhanced Rejection Performance for Unary and Binary High-Salt Wastewater

Titanium dioxide (TiO2) nanoparticles act as very good nanofillers to prepare the polymeric nanocomposite membranes to tackle the problem of heavy metal pollution in the water body. A key challenge to be solved is to improve their compatibility with organic matrices and dispersion in the material. Herein, (3-aminopropyl)trimethoxysilane-modified TiO2 (APTMS-TiO2) was prepared using coupling agent modification, and APTMS-TiO2 thin-film nanocomposite (TFN) membrane was successfully applied in the forward osmosis (FO) process. Moreover, the effects of different pretreated TiO2, TiO2 dosages, draw solution types, and concentrations on FO membranes were systematically studied. Results showed that APTMS-TiO2 TFN with a TiO2 dosage of 0.05 wt % has the maximal water permeate flux (Jw) (18.14 LMH, 225.09% higher than the control TFC of 5.58 LMH) and the minimum specific reverse solute flux of 0.40 g/L with 1 M NaCl as the draw. Unary (Cu2+ and Ni2+) and binary (Cu2+ + CR and Cu2+ + RhB) high-salt wastewater were applied as the feed to investigate the reusability and dye rejection of the APTMS-TiO2 TFN. The rejection rate of Cu2+ and Ni2+ by APTMS-TiO2 TFN was above 98.00 and 97.00%, respectively, while the rejection rate of Cu2+ + CR and Cu2+ + RhB was 96.87 and 95.83%, respectively, indicating excellent reusability and rejection. The present research finding concludes that the incorporation of APTMS-TiO2 nanosheets in the TFN layer enhances the flux and rejection of targeted mineral salts. Additionally, the APTMS-TiO2 TFN revealed outstanding rejection performance of unary and binary wastewaters, signifying that contact with heavy metals and colored solutes will not affect the performance.