Nitrogen-doped biochar fiber with graphitization from Boehmeria nivea for promoted peroxymonosulfate activation and non-radical degradation pathways with enhancing electron transfer

Advanced oxidation has great promise in the degradation of organic pollutants, but the high preparation requirements, adjustment difficulty, high cost, potential hazard, and low repeatability of catalysts limit the practical applications of this technology. In this study, a metal-free biochar-based catalyst derived from biomass fiber was prepared assisted by graphitization and nitrogen incorporation (PGBF-N). The heterogeneous catalysis of peroxymonosulfate (PMS) was triggered by PGBF-N with degradation rate 7 times higher than that of pristine biochar. The high catalytic efficiency was attributed to the accelerated electron transfer originated from the high degree of graphitization and nitrogen functionalization of PGBF-N, in which the non-radical pathways containing carbon-bridge and singlet oxygen-mediated oxidation were elucidated as the predominant pathways for tetracycline degradation, instead of the dominant role of radical pathway in pristine biochar. Vacancies and defective edges formed on sp(2)-hybridized carbon framework as well as the nitrogen doping sites and ketonic group of PGNF-N were considered as possible active sites. The excellent degradation rate in actual water indicated that the PGBF-N/PMS system dominated by non-radical pathway exhibited a high anti-interference ability to surrounding organic or inorganic compounds. This study provides a facile protocol for converting biomass fiber into functional catalyst and enables underlying insight in mediating dominated degradation mechanism of heterogeneous catalysis by biochar fiber.