Enhanced visible-light-driven photocatalytic degradation to 2,4,6-trichlorophenol with magnetic sulfur doping constructed nitrogen vacancies in g-C3N4: Spectrum broaden, photogenerated electron acceleration and degradation pathway shorten

2,4,6-Trichlorophenol (2,4,6-TCP) is commonly used in the production of insecticides and preservatives with the characteristics of accumulation and toxicity due to the complex chemical structure with a halogenated aromatic ring. In order to effectively degrade and mineralize 2,4,6-TCP from water, a stack-coral-like catalyst of magnetic sulfur doping constructed nitrogen vacancies in graphitic carbon nitrides (Fe 3 O 4 /S-g-C 3 N 4 , FSCN-T) was designed and prepared through polymerization combined with precipitation. This visible-light-driven photocatalytic degradation to 5 mg/L 2,4,6-TCP was 95 % within 60 min with 0.1 g/L FSCN-T amendment. The degradation and carbonization rate constant were 0.118 and 0.089 min −1 respectively. This high removal was attributed to nitrogen vacancies, which broaden the visible light absorption range and shorten the electron transfer path with narrow CN bandgap (from 2.94 eV to 2.49 eV). Moreover, the introduction of iron accelerated electron cycling and enhanced magnetic recovery performance with above 95 % recovery and catalytic stability after 5 cycles of use. The degradation contribution from the active species were h + (41 %)> •OH (28.9 %) > •O 2 - (16.1 %)> 1 O 2 (8.7 %). This degradation underwent three pathways of substitution, elimination, and hydroxyl oxidation. Further, the intermediates were oxidized with ring opening and mineralization according to density functional theory (DFT) calculations and LC-Qtof-MS identification. The oxidative degradation process reduced the toxicity of 2,4,6-TCP and its intermediates. This study provided an efficient catalyst and low-energy consumption approach for toxic wastewater treatment.