Novel thin-film composite nanofiltration membranes consisting of a zwitterionic co-polymer for selenium and arsenic removal

Selenium (Se) and arsenic (As) ions in water would cause severe risks in aqueous environments. In order to remove them efficiently, a water-soluble zwitterionic co-polymer, P[MPC-co-AEMA], was designed and synthesized via a single-step free-radical polymerization between 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-aminoethyl methacrylate hydrochloride (AEMA). The P[MPC-co-AEMA] co-polymer was incorporated into the polyamide selective layer of thin-film composite (TFC) membranes via interfacial polymerization to remove Se and As concurrently. Comparing to the pristine TFC (TFC-0) membrane, the novel co-polymer modified TFC membranes show improved pure water permeability (PWP) and rejections for both pollutants due to their reduced pore sizes, higher hydrophilicity. Additionally, the newly developed TFC membrane containing 50 wt% of P[MPC-co-AEMA] exhibits the highest PWP of 8.5 LMH/bar and impressive rejections of 98.2%, 99.1% and 99.8% toward SeO32-, SeO42- and HAsO42-, respectively. Higher rejections are also obtained in the simultaneous removal of Se and As. The modified TFC membrane demonstrates robust durability under 180-h testing. To our best knowledge, this is the pioneering work to study the effects of incorporating the P[MPC-coAEMA] zwitterionic co-polymer into the polyamide selective layer of TFC membranes. This study may provide useful insights to design next generation NF membranes for heavy metal removal in water treatment.