Construction of CoFe2O4/Fe2O3 S-type heterojunctions on biochar for activating peroxymonosulfate towards simultaneous removal of TC and Cr(VI)

The construction of S-type heterojunctions for restraining the rapid recombination of photogenerated charges is considered an efficient approach to boost redox capacity. Herein, the growth of CoFe2O4/Fe2O3 S-type heterojunctions on biochar (BC) was accomplished by thermal polymerization-hydrothermal. BC/CoFe2O4/Fe2O3 displayed a wide range of light absorption from 200 to 800 nm and enhanced photocurrent (0.41 μA cm−2). Furthermore, BC/CoFe2O4/Fe2O3 can remove tetracycline (TC) (98.84 %) and Cr(VI) (88.43 %) more efficiently compared to the CoFe2O4 (40.32 % of TC, 68.52 % of Cr(VI)) and Fe2O3 (29.81 % of TC, 53.67 % of Cr(VI)) single counterparts upon 45 min visible light irradiation in the presence of peroxymonosulfate (PMS). Free radical capture experiments revealed that •OH, •O2−, and SO4−• are the primary activated species for the removal of TC and e− is the major activated species for the removal of Cr(VI). Meanwhile, the degradation pathway of TC was monitored via LC-MS and Fukui index calculations. Combining density functional calculations (DFT) with UPS and radical capture tests, the possible mechanism of photocatalytic degradation was proposed. The findings demonstrated the remarkable photocatalytic activity and stability of the photocatalyst, evidencing the potential of BC/CoFe2O4/Fe2O3 for practical wastewater treatment.