APTMS‐Modified Silica as a Thin‐Film Nanocomposite Forward Osmosis Membranes: Towards Enhanced Selectivity and Dye Rejection Stability for Congo Red and Rhodamine B

Abstract Fumed silica (SiO 2 ) is often applied in the modification of thin‐film composite (TFC) forward osmosis (FO) membranes due to its hydrophilicity. However, a key challenge to be solved is to improve its compatibility with organic matrices and dispersion in the material. In this study, we synthesized well‐designed nanoparticles of (3‐aminopropyl)trimethoxysilane‐modified SiO 2 (APTMS‐SiO 2 ) and applied them for the first time in the preparation of FO membranes. Furthermore, we systematically investigated the effects of different pretreated SiO 2 , SiO 2 dosages, draw solution types, and concentrations on FO membranes. The results showed that APTMS‐SiO 2 thin‐film nanocomposite with a silica dosage of 0.1 wt.% has the highest water permeate flux (J w ) (26.25 LMH, 370.43 % higher than the control TFC of 5.58 LMH) and the minimum specific reverse solute flux (SRSF) of 0.17 g/L with 1 M NaCl as the draw. The incorporation of APTMS effectively prevented mutual agglomeration of SiO 2 and improved its dispersion. The J w of 13.36 LMH after seven cycles and the rejection of above 96.6 % for Congo Red and 95.8 % for Rhodamine B indicated potential reusability and dye rejection. This work presents an alternative approach to prepare FO membranes with enhanced water flux and increased selectivity, and it also offers insights for the treatment of printing and dyeing wastewater using FO.