Positively Charged Nanofiltration Membrane with Dendritic Surface for Toxic Element Removal

Abstract

A novel positively charged nanofiltration membrane has been prepared by the reaction of carboxylic acids on the surface of a polyamide thin film composite with poly(amidoamine) dendrimer in the presence of 2-chloro-1-methylpyridinium iodide as an activating agent. The membrane was prepared with excellent grafting efficiency and showed a high isoelectric point of pH 9.9. Because of the high density of free protonated amino groups, the membrane showed excellent rejections toward various toxic elements including Cu2+, Ni2+ and Pb2+. The rejection order also followed the size of the ions in terms of their hydrated radius. Furthermore, the membrane obtained by the surface grafting method exhibited outstanding alkaline stability compared to the membrane prepared by the conventional coating process. These results clearly indicate that grafting the poly(amidoamine) dendrimer onto the surface of the polyamide thin film composite membrane is a promising approach to improve the rejection of toxic containments.