Phosphorus doping-induced electron transfer promotes cobalt-iron biochar activation of peracetic acid: Selective reactive substance generation for pesticide degradation

This study employed phosphorus (P) doping to modify the intrinsic structure of cobalt-iron biochar derived from waste biomass, thereby enhancing its efficacy in activating peracetic acid (PAA). The degradation efficiencies of P-doped cobalt-iron biochar-activated PAA for various organochlorine pesticides were significantly improved, with enhancements ranging from approximately 1.53 to 5.98 times. In comparison to the cobalt-iron biochar/PAA system, the degradation of pesticide was primarily attributed to the formation of catalyst-PAA complexes, rather than intermetallic redox reactions. Based on both experimental analyses and theoretical calculations, the synergistic effects of Co, Fe, and P are identified and summarized as follows: i) the formation of a highly porous structure and P species enhances the adsorption of PAA and pesticides onto the catalyst surface; ii) P atoms enhance the reactivity of the carbon layer and further regulate the ability of Co sites to sequester PAA, thereby promoting the formation of ≡Co(III)–OO(O)CCH₃; iii) P doping facilitates electron transfer between the catalyst and PAA, enabling the sequential generation of catalyst-PAA complexes and high-valent metal–oxygen species. This study thoroughly elucidates the synergistic role of heteroatoms (P) in modulating the activation of PAA by typical transition metal–carbon-based catalysts.