Enhanced heterogeneous photo-Fenton-like degradation of tetracycline over CuFeO/biochar catalyst through accelerating electron transfer under visible light.

The visible-light induced heterogeneous photo-Fenton-like (HPF-like) process is regarded as a promising technique for organic pollutants degradation due to its efficient utilization of solar energy and high HO activation activity. This study prepared the CuFeO/biochar catalysts via hydrothermal technique at no extra reductant and systematically investigated their band structure and photoelectric properties. The dispersed distribution of CuFeO particles in CuFeO/biochar composites narrowed bandgap of CuFeO and promoted electron transport of CuFeO. Compared with CuFeO, the CuFeO/biochar containing 1.0 g biochar in the preparation (CuFeO/biochar-1.0) possessed higher carrier density and longer photoelectron lifetime, which is beneficial to higher catalytic performance. The apparent rate constant for tetracycline as target pollutant degradation by CuFeO/biochar-1.0 was 2.0 times higher than that by CuFeO. The acquired optimum conditions for tetracycline degradation were 220 mg L CuFeO/BC-1.0, 22 mM HO and pH 6.4 using response surface methodology. The quenching experiments and ESR analysis revealed that OH was the predominant active species, and photoelectron and O were auxiliary species. The photoelectron could promote in-situ recycling of Cu to Cu and Fe to Fe, which significantly improved HO activation by CuFeO. The possible pathway of tetracycline was proposed according to intermediates identified by HPLC/MS. The toxicity analysis demonstrated that the overall toxicity of the identified intermediates was reduced in HPF-like system.