Facile synthesis of CoFe2O4@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 CoFe2O4@Biochar (CoFe2O4@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 CoFe2O4 and the electron transfer promote the production of reactive oxygen species (ROS) (OH, SO4- and O2-), efficiently removing p-NCB enriched by CoFe2O4@BC. Under optimum conditions, the CoFe2O4@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-, HCO3-, HPO42- and humic acid (HA) through quenching effect or occupation of CoFe2O4@BC surface active sites while HPO42- could also improve the efficiency by directly activating PMS. The CoFe2O4@BC/PMS system can be efficiently applied in the remediation of p-NCB pollution in water and soil.