Facile synthesis of nanofiltration membrane with asymmetric selectivity towards enhanced water recovery for groundwater remediation

Abstract

<p>Groundwater remediation by nanofiltration (NF) membrane is still hindered by low water recovery due to membrane scaling. In this study, a simple NaOH-promoted interfacial polymerization strategy was proposed to tailor the membrane asymmetric selectivity of calcium over sulfate ions to reduce scaling potential towards high water recovery. A 0.5 wt% NaOH was introduced during the interfacial polymerization of piperazine (PIP) and trimesoyl chloride on a polysulfone support. The promoted interfacial polymerization reduced polyamide defects for better rejection and enabled the use of lower PIP concentrations. Enhanced hydrolysis of the polyamide layer created a more negatively charged surface with larger pore sizes to achieve asymmetrical selectivity together with enhanced permeance. The water permeance of fabricated TFC-0.1 membrane with the aid of NaOH was 2.1 times that of commercial NF270 membrane, while exhibiting comparable perfluorooctanesulfonic acid rejections (>95%). This membrane also achieved similar to 50% more water recovery than that of NF270 membrane under simulated gypsum scaling condition, owing to the selective passage of calcium (low rejection of 11.4 +/- 0.6%). The exemplified strategy of NaOH-promoted interfacial polymerization is facile and readily scalable, which demonstrated strong potential towards high water recovery in groundwater remediation contaminated by emerging pollutants.</p>