In-situ enhanced heavy metal ion removal efficiency based on branched amino groups in the forward osmosis process

ABSTRACT Modification of the active layer is an effective method to improve the separation performance of the thin-film composite forward osmosis (FO) membranes. In this paper, the dendrimer polyamidoamine (PAMAM) was in-situ integrated into the polyamide (PA) active layer via the interfacial polymerization. The separation performance results showed that the addition of PAMAM significantly improved the separation water flux of the modified FO membrane by 1.7 times, and the reverse salt flux was almost unchanged. In addition, the removal efficiency of the modified FO membrane for heavy metal ions was enhanced, with the rejection rates of various heavy metal ions all higher than 99.6%, and the corresponding water flux was also significantly enhanced. The PAMAM integrated with the active layer contained a large number of hydrophilic segments and terminal amine groups, which in situ enhanced the hydrophilicity and permeability of the active layer, and further improved the removal of heavy metal ions based on the coordination and electrostatic repulsion effects. The purpose of this paper is to provide a feasible way to improve the practical application performance of the FO membranes.