Electrified Nitrogen-Doped MXene Membrane Electrode for Micropollutants Decontamination via Peroxymonosulfate Activation

Advanced oxidation processes based on peroxymonosulfate (PMS) activation have attracted tremendous attention as a promising approach for removing micropollutants. Herein, we designed a nitrogen-doped Ti3C2Tx MXene (N-Ti3C2Tx) electrocatalytic filtration system for the activation of PMS to efficiently and selectively degrade micropollutants. The system was configured for flow-through operation, which led to significant improvements in performance compared with a conventional batch reactor system because of the enhanced convective mass transfer. Specifically, a 90.8% removal of 0.04 mmol L-1 sulfamethoxazole (SMX) solution could be achieved in flow-through mode (k = 0.0173 +/- 0.0003 min(-1)) within 120 min under optimal conditions. This value was 4.7-fold higher than the conventional batch mode (k = 0.0037 +/- 0.0001 min(-1)). Radical quenching tests, electron paramagnetic resonance measurements, and electrochemical tests verified that SMX was degraded in the N-Ti3C2Tx/PMS filtration system primarily via nonradical pathways. Density functional theory calculations demonstrated that doping of N changed the PMS activation pathway and enhanced the ability of the N-Ti3C2Tx membrane electrode to transfer electrons. In the presence of inorganic anions or humic acids (15.0 mmol L-1), the SMX removal efficiency remained above 81.1%, illustrating that naturally occurring substances in water did not interfere with the system. This work demonstrates the capabilities of the N-Ti3C2Tx membrane electrode, which should provide beneficial improvements in systems targeting the serious issue of micropollutants in water.