Solvent-Assisted Insertion of Molecular Supports for Enhanced Separation Performance and Stability of Thin Film Composite Reverse Osmosis Membranes

Abstract

This study presents an innovative approach to enhance the separation performance and stability of thin-film composite (TFC) reverse osmosis (RO) membranes through post-treatment by inserting 15-crown-5 (CE15) as molecular supports, assisted by methanol. By varying the CE15 concentration (0–4 wt%), the physicochemical properties of the membranes can be regulated with significantly improved separation performance. Comprehensive characterizations reveal that an optimal CE15 concentration of 1 wt% increases the water permeance by 148% (from 1.86 to 4.61 LMH bar−1) while maintaining a high salt rejection of 98.9%. Additionally, chelation of CE15 with Li+ or Na+ further enhances the membrane’s structural robustness, ensuring long-term stability. Over a 72-hour period, the treated membranes exhibit only a 3.4% reduction in water permeance, compared to a 15.8% decline observed for the untreated membranes. This facile post-treatment method offers a scalable and effective solution to improve the permeability, selectivity and durability of TFC membranes, presenting a promising advancement for desalination and water treatment applications.

Keywords: Thin-film composite membranes, Reverse osmosis, 15-crown-5, solvent activation, Desalination