Antifouling forward osmosis membranes by ε-polylysine mediated molecular grafting for printing and dyeing wastewater: Preparation, characterization, and performance

Abstract

Membrane fouling during forward osmosis (FO) seriously affects the service life of the membrane and increases the treatment cost. A facile strategy was developed to mitigate membrane surface fouling and simultaneously achieve high pollutants rejection. The amino group on ε-Polylysine (PL) reacted covalently with the active sites (acyl chloride and carboxyl group) on the polyamide (PA), thereby grafting the ε-PL onto the PA active layer of PAN/LiCl supported membrane. Effects of membrane orientation, concentration of draw solution (DS), and pH of feed solution (FS) on pollutants rejection were investigated. Results showed that rejection efficiencies of TOC, Ca, Mg, Sb, Cr, and aniline in wastewater by the 0.5 wt% PL-grafted PAN-1.5LiCl TFC-FO membrane (FO-0.5 PL) attained 93.3%, 96.7%, 99.3%, 98.3%, 99.9%, and 99.8%, respectively. The high rejection efficiencies were mainly attributed to the improvement of the surface hydrophilicity of the grafted membrane, the reduction of the roughness, and the improvement of membrane surface potential. The microbubble-assisted cleaning experiment showed that the flux recovery efficiency of the FO-0.5 PL membrane could reach 98.8%, which is 6% higher than that of the FO-P membrane. The PL-grafted FO membrane simultaneously improves the stability of permeation flux (15.2 L m−2 h−1) and fouling resistance performance of the membrane. This study revealed that the PL grafted method can improve the antifouling performance of the membrane and can be used as a feasible treatment method for printing and dyeing wastewater. The research results provided a new idea for facile preparation and application of FO membranes and had a certain reference value for the development of antifouling FO membrane.