Facile synthesis of CoFeO@BC activated peroxymonosulfate for p-nitrochlorobenzene degradation: Matrix effect and toxicity evaluation.

p-Nitrochlorobenzene (p-NCB) is widely used in industry and poses a potential threat to the public health due to its persistence, carcinogenicity and mutagenicity. Herein, magnetic catalyst CoFeO@Biochar (CoFeO@BC) was synthesized by a facile sol-gel method, efficiently activating peroxymonosulfate (PMS) to degrade p-NCB. The synergistic effect of Fe and Co in well-dispersed CoFeO and the electron transfer promote the production of reactive oxygen species (ROS) (OH, SO and O), efficiently removing p-NCB enriched by CoFeO@BC. Under optimum conditions, the CoFeO@BC/PMS system could remove 89% of p-NCB from water, and the degradation efficiency could reach 80% in soil. Toxic chlorinated intermediates appeared during the degradation process and thus efficient dechlorination process can lower the toxicity of the reaction solution, which was also proved by the oxygen uptake inhibition experiment as well as zebrafish toxicity experiments. Furthermore, p-NCB degradation efficiency could be inhibited by Cl, HCO, HPO and humic acid (HA) through quenching effect or occupation of CoFeO@BC surface active sites while HPO could also improve the efficiency by directly activating PMS. The CoFeO@BC/PMS system can be efficiently applied in the remediation of p-NCB pollution in water and soil.