Mechanistic investigation of visible light driven photocatalytic degradation of polyphenolic contaminant using a recyclable magnetic biochar/Bi4O5Br2 heterojunction

The development of a recoverable photocatalyst with exceptional photocatalytic activity is an idea strategy for wastewater purification. In this study, a novel recoverable magnetic biochar/Bi 4 O 5 Br 2 heterojunction with high-efficient removal efficiency for polyphenolic compounds was successfully prepared. Under 30 min visible light irradiation, approximately 98 % of polyphenolic compounds (catechin) was effectively eliminated, which is ∼2.77-folds and 4-folds to that of pure Bi 4 O 5 Br 2 and magnetic biochar, respectively. The influence of catalyst dosage, solution pH and initial concentration of catechin on the removal efficiency of magnetic biochar/Bi 4 O 5 Br 2 heterojunction were systematically investigated. Furthermore, the degradation pathway of polyphenolic compounds was studied using a LC–MS. The mechanism investigations revealed that h + , ·O 2 − , and ·OH are the primary active substances responsible for polyphenolic compounds degradation. The enhanced removal rate of magnetic biochar/Bi 4 O 5 Br 2 heterojunction can be attributed to the synergistic effects of adsorption and photocatalytic reaction. Additionally, a n-p transfer pathway at the interface of the magnetic biochar/Bi 4 O 5 Br 2 heterojunction was proposed, which improved the efficiency of charge separation and transfer, resulting in the enhanced photocatalytic activity. This work provides a valuable insight into designing a recoverable and high-efficient biochar-based photocatalyst for pharmaceutical wastewater purification.