Membranes constructed by metal–ligand complexation for efficient phosphorus removal and fouling resistance in forward osmosis

Abstract

Low permeation flux and rapid flux decline are challenging membrane technology in wastewater treatment. Here we used a metal–ligand complexation protocol to construct novel forward osmosis (FO) membrane for efficient and sustainable phosphorus removal. Disodium and tetrasodium salts of ethylenediaminetetraacetic acid (EDTA-2Na, EDTA-4Na) were separately grafted onto the conventional polyamide (PA) membranes via chemical complexation using Fe3+ as a bridge. These EDTA salts substantially improved the membrane properties. Consequently, the water fluxes produced by the EDTA-2Na and EDTA-4Na modified membranes increased by 109% (11.1 LMH) and 140% (12.7 LMH), respectively, relative to that of the pristine membrane (5.3 LMH) with 0.5 M NaCl as the draw solution. Meanwhile, the EDTA-4Na modified membrane surpassed the naked PA membrane in performance with higher water recovery efficiencies and solute rejections after long-term experiments against a mixture of bovine serum albumin and HPO42−. Moreover, the water flux recovery ratio of the naked PA membrane was only 51%, while that of the EDTA-4Na modified membrane reached over 93% after three cycles of fouling experiments. This study provides a new paradigm to develop FO membrane via a metal–ligand complexation protocol for efficient and sustainable wastewater treatment. Novel FO membranes synthesized through a complexation protocol are used for phosphorus removal and fouling resistance in forward osmosis.