Enhanced degradation of Iron/extracellular polymeric substances/catalase engineered biochar on dibutyl phthalate: Insights into immobilization affinity and advanced free radicals/enzyme pathways

Engineered biochar gain increasing research interests on persistent organic pollutants remediation due to various degradation pathways. In this study, Fe-loaded biochar immobilized catalase (CAT) composite modified with bacterial extracellular polymeric substances (EPS) (CAT-EPS-FeBC) or glutaraldehyde (GA) were synthesized, and their efficiency and mechanisms on dibutyl phthalate (DBP) removal were evaluated. The characterization results showed the advanced association affinity of EPS with both of biochar and CAT, and the formation of Iron oxide (FeO n ) during biochar pyrolysis which enhanced the association between biochar and EPS through electrostatic attraction and nucleophilic. The total DBP removal efficiencies were in order of: CAT-EPS-FeBC (70.76%) > CAT-GA-FeBC (56.02%) > FeBC (36.60%) > BC (28.45%). EPS modification exhibited higher CAT activity than glutaraldehyde (GA) with degradation enzyme, CAT-EPS-FeBC produced stronger free radicals with •OH generated from FeO n and biochar, and 1 O 2 generated from EPS and CAT. The contribution of electrochemical degradation by biochar composites was insignificant. CAT-EPS-FeBC showed lower ecotoxicity on Chlorella vulgaris than did CAT-GA-FeBC. Overall, the findings in this study demonstrated the high DBP degradation efficiency of Fe loaded biochar immobized CAT with EPS modification through pathways including sorption, CAT catalysis, and free radicals. This study can provide new ideas for the development of biochar-immobilized enzyme and the remediation of persistent organic pollutants.