Synergistic photocatalytic-photothermal contribution enhanced by recovered Ag⁺ ions on MXene membrane for organic pollutant removal

The coordinated removal of pollutants in wastewater, especially metal ions and organic pollutants, is regarded as a tough challenge and has focused wide attentions. Synergistic photocatalytic-photothermal route is a powerful technology for the potential wastewater treatment. Herein, we designed a synergistic photocatalytic-photothermal system based on two-dimensional Ti3C2Tx MXene (TCM) membrane for simultaneous recovery of Ag+ ions and removal of aqueous rhodamine B (RhB). The photo-reduction of Ag+ ions into Ag nanoparticles with the conversion rate up to 100% was achieved on TCM membrane under visible-light irradiation. These Ag nanoparticles uniformly deposited on the surface and interlayers of TCM membrane. It facilitated the separation of photo-generated charges for forming more active species, including both center dot O-2(-) and center dot OH radicals, to oxide RhB molecular. At the same time, the surface plasma effect of Ag nanoparticles enhanced the light adsorption and photothermal conversion efficiency (similar to 81%) on the TCM membrane. Conversely, photothermal effect was beneficial for further enhancing the reaction rate of both reduction of Ag+ ions and photo-oxidation of RhB by concentrating the solution and promoting the electron transfer. The novelty of the synergistic photocatalytic-photothermal contribution is significant for simultaneous recovery of metal ions and removal of organic pollutants in wastewater.