Non-radical pathway dominated degradation of organic pollutants by nitrogen-doped microtube porous graphitic carbon derived from biomass for activating peroxymonosulfate: Performance, mechanism and environmental application.

The agricultural waste-derived biochar can be used as an effective green catalyst for peroxymonosulfate (PMS) activation to utilize the biomass resource. Herein, nitrogen-doped microtubes porous graphitic carbon (N-MPGC) derived from loofah sponge was facilely prepared via the impregnation-calcination method. The amount of N doping was positively correlated with the catalytic performance of N-MPGC. The obtained N-MPGC-2 as a metal-free carbon catalyst showed excellent ability for rhodamine B (RhB) degradation via PMS activation with the pseudo-first-order reaction rate constant (k) of 0.293 min, which was 22.5-fold as high as that over microtube porous carbon (MPC). Besides, N-MPGC-2 showed still outstanding stability and reusability for RhB degradation after ten successive cycles. Excitingly, the N-MPGC-2 membrane exhibited good catalytic activity after the N-MPGC-2 had been immobilized in the polytetrafluoroethylene (PTFE) membrane. Non-radical pathways including singlet oxygen and electron transfer played a major role in RhB degradation for the N-MPGC-2/PMS/RhB system. The carbonyl (CO) group and graphitic N of N-MPGC-2 were the main active sites for PMS activation. This work opened a new idea for synthesizing N-doped biochar as a low-cost and high-efficiency catalyst and provided theoretical support for the mechanism of biochar-based carbonaceous materials activation of PMS for practical applications.