A loose NF membrane by grafting TiO2-HMDI nanoparticles on PES/β-CD substrate for dye/salt separation

In this study, a high flux loose nanofiltration (NF) membrane was fabricated for the desalination of dye wastewater through a facile method which combined doping and surface grafting. First, PES ultrafiltration substrate was prepared via non-solvent induced phase separation by introducing multi-hydroxyl beta-cyclodextrin (beta-CD) into the casting solution as hydrophilic additive. Then, titanium dioxide (TiO2) nanoparticles were grafted uniformly on membrane surface with the assistance of 1, 6-hexamethylene diisocyanate (HMDI), resulting in the enhancement of surface hydrophilicity and separation performance of the resultant membranes. Remarkably, the membrane prepared at optimized conditions achieved a high pure water flux (52.0 L.m(-2).h(-1) at 0.2 MPa) and high permeate flux for dyes (e.g. 30.5 L.m(-2).h(-1) for Congo Red at 0.2 MPa). It also exhibited high rejection for dyes (e.g. 97.4% for Congo Red) and high transmittance of salts (e.g. 94.0% for Na2SO4). Moreover, the membrane possessed good antifouling performance with a high flux recovery ratio of 93.7% after fouled by humic acid (HA). The results indicated that the novel loose NF membrane had an impressive potential application for dye wastewater treatment.