Efficient surface modification of thin-film composite membranes with self-catalyzed tris(2-aminoethyl)amine for forward osmosis separation

Abstract

Interfacially synthesized polyamide (PA) thin-film composite (TFC) membranes are widely employed in forward osmosis (FO) applications because of the easy fabrication and excellent separation performance. But they generally suffer from the relative low water permeability and high fouling tendency due to the inherent hydrophobic nature of the PA layer. In this study, an efficient surface modification of nascent TFC membranes is performed by grafting a self-catalyzed tripodal amine—tris(2-aminoethyl)amine (TAEA), in order to improve the membrane performance. This tertiary amine plays a dual role of the reactive amine monomer reacting with acyl chloride groups and the catalyst accelerating the amidation reaction between 1,3,5-trimesoyl chloride (TMC) and TAEA, therefore contributing to an efficient grafting effect to the greatest extent. State-of-the-art characterizations are applied to verify the modification mechanism. The effects of the pH and concentration of the TAEA solution on the overall properties of the resultant TFC membranes are systematically investigated, including the surface chemical composition, surface morphology, hydrophilicity, surface charge, separation performance, and fouling resistance. Compared with the control TFC membrane, TAEA-modified TFC membranes exhibit significantly improved water fluxes, higher antifouling propensity, and comparable reverse salt fluxes.