Positively charged ultrafiltration membranes fabricated via graft polymerization combined with crosslinking and branching for textile wastewater treatment

2-methacryloyloxy ethyl trimethylammonium chloride (DMC) was successfully grafted with 2-hydroxyethyl methacrylate (HEMA) as branching agent and N, N'-methylenebisacrylamide (MBAA) as crosslinker onto the surface of hydrolyzed polyacrylonitrile (HPAN) ultrafiltration membrane with high density via ceric ion (Ce 4+ )-induced graft polymerization. The successful graft polymerizations were confirmed by characterization of attenuated total reflectance spectrophotometer, X-ray photoelectron spectroscopy, scanning electron microscope and atomic-force microscopy. The obtained membranes showed surface positive charges and favorable hydrophilicity, which resulted in an ultrahigh permeability, distinguished rejection for positively charged dyes (>99%) and almost no retention for divalent salts (<4%), as well as excellent stability in multiple cycles of filtration. This work provided an efficient and facile approach to tailor the structure and properties of ultrafiltration membranes.