GO-ZnO-PNIPAM temperature response smart nanofiltration membrane with self-cleaning capability for wastewater treatment

Abstract

Membrane separation is a very reliable technology for water purification. Based on the performance of graphene oxide (GO) nanofiltration membranes, this paper uses a physical intercalation composite process to create a GO-ZnO-PNIPAM nanofiltration membrane. This membrane has temperature-responsive and photocatalytic self-cleaning functions. It combines temperature-sensitive PNIPAM with ZnO, which is grown on the surface of GO. The membrane exhibited excellent separation performance with maximum retention rates of 99.77 %, 99.46 %, 99.98 %, 98.10 %, and 83.43 % for five dyes and 87.2 % for sodium nitrite (NaNO₂). This performance was significantly better than that of a GO nanofiltration membrane. Meanwhile, the PNIPAM's temperature-sensitive property allowed for variation in water flux at different temperatures, reaching a maximum of 59.63 L m⁻² h⁻¹ bar⁻¹, which was 3.38 times higher than that of GO nanofiltration membrane (17.62 L m⁻² h⁻¹ bar⁻¹). Additionally, the GO-ZnO membrane has a UV-catalyzed self-cleaning ability. The GO-ZnO-PNIPAM nanofiltration membrane can degrade surface-adsorbed pollutants under UV light with a maximum recovery rate of 99.06 %. This dual-function design strategy, combining temperature response and self-cleaning, provides an innovative solution for developing energy-efficient water treatment technology.