Improving the water permeability and antifouling property of thin-film composite polyamide nanofiltration membrane by modifying the active layer with triethanolamine

Interfacially synthesized polyamide (PA) thin-film composite (TFC) membranes, as the state-of-the-art polymeric membranes for nanofiltration (NF), are prone to fouling in processing wastewaters and industrial fluids due to the inherent surface physicochemical properties of polyamide active layer. Here, we report the facile and effective modification of PA-TFC nanofiltration membranes for improved water permeability and antifouling property by surface grafting. Ttriethanolamine (TEOA) molecules were bonded onto the surface of PA-TFC NF membrane through esterification reaction between the hydroxyl groups of TEOA and the residual acyl chloride groups on the nascent PA-TFC membrane by pouring the TEOA aqueous solution on membrane surface. The covalent attachment of TEOA molecules was shown to tailor the surface chemistry of the composite membrane without altering the morphology of active layer. The PA-TFC membrane became more hydrophilic after modification and thus more permeable to water and antifouling against hydrophobic foulants, while maintaining its molecular weight cut-off. The results of tertiary treatment of industrial effluent also demonstrated that the modification performed in our study could effectively improve the water permeability and antifouling property of the PA-TFC NF membrane in processing wastewater.