Separation and Photodegradation of Dye-Containing Oil/Water Mixtures with a Photothermally Responsive PNIPAm-MXene/PAN-PNIPAm Nanofibrous Hydrogel Membrane

Abstract

Although several separation membranes for the purification of dye-containing oily wastewater have been reported, achieving continuous onestep separation and photodegradation of complex oil/water effluents containing dyes is still a significant challenge. In previous studies, the purification of oil/ water mixtures has typically involved a two-step process involving the initial separation of oil/water mixtures followed by the subsequent photodegradation of organic dyes. This is because one-step purification requires the membrane to concurrently possess an excellent separation efficiency and photodegradation ability to ensure efficient degradation of dyes as they rapidly pass through the separation membrane. Herein, we propose a photothermally responsive poly(Nisopropylacrylamide)-MXene/polyacrylonitrile-poly(N-isopropylacrylamide) nanofibrous hydrogel membrane (PNIPAm-MXene/PAN-PNIPAm, PMPP membrane). The PMPP membrane is composed of a PNIPAm-MXene hydrogel bonded to the surface of a PAN-PNIPAm nanofibrous membrane. The PNIPAm-MXene hydrogel layer imparts excellent photothermally responsive wettability, photodegradation activity, and antifouling properties to the membrane. The PAN-PNIPAm nanofibrous membrane provides a porous structure that ensures the highly efficient separation of complex oil/water mixtures. The PMPP membrane achieves simultaneous one-step separation and photodegradation of complex oil/water effluents under light irradiation, particularly in the case of multiphase heavy oil/water/light oil mixtures containing both oily and water-soluble organic dyes and oil−water emulsions. The degradation and separation efficiencies of the PMPP membrane exceed 99.5%. Even after 20 cycles, the degradation rates of Sudan IV and methyl blue (MB) remain above 95.7 and 99.9%, respectively.