Facile synthesis of activated biochar/BiVO4 heterojunction photocatalyst to enhance visible light efficient degradation for dye and antibiotics: applications and mechanisms

The applications of biochar in catalysis have become a research hotspot, but studies using activated biochar (ACB) and enhanced mechanisms are limited. To improve the photocatalytic performance of BiVO 4 , the nano-photocatalyst (ACB-BiVO 4 ) was synthesized via a facile hydrothermal reaction. Various characterization techniques were performed, and the adsorption-photodegradation of the organic pollutants rhodamine B (RhB), tetracycline (TC), norfloxacin (NOR), and chloramphenicol (CAP) under visible light were investigated. Meanwhile, the effects of loading ratios, initial concentrations, recycling tests, more enhancement strategies, actual wastewater treatment, and disinfection effects on photocatalysis of ACB-BiVO 4 were comprehensively evaluated. The results confirmed that the tetragonal phase BiVO 4 was successfully composited onto the support ACB forming heterojunction, which displayed the best performance at a mass ratio of 1:0.62. The degradation rate by ACB-BiVO 4 reached 84.52% for RhB at a kinetic constant of 0.0133 min −1 , which was 5.78 times higher than pure BiVO 4 . ACB-BiVO 4 completely removed RhB and TC from the investigated surface water and removed more than 73.50% of RhB and TC from industrial wastewater. ACB-BiVO 4 had excellent disinfection effects on E. coli and Staphylococcus aureus with a sterilization rate of over 99% at 12 h · OH and holes were dominant active species and the enhancement mechanism is associated with the heterojunction. ACB-BiVO 4 expanded the visible light (∼545 nm) absorption and reduced the band gap (2.26 eV), and effectively inhibited the photogenerated carriers recombination. The unique structure (defects) and surface properties (functional groups and environmentally persistent free radicals) of ACB were found to play a critical role.