Construction of novel biochar/g-C3N4/BiOBr heterojunction with S-scheme mechanism for efficient photocatalytic degradation of tetracycline

In this work, a novel biochar/g-C3N4/BiOBr (BCN/BiOBr) S-scheme heterojunction was synthesized for the removal of tetracycline (TC) under visible light. The 0.75-BCN/BiOBr heterojunction exhibited a significantly higher degradation efficiency of TC in wastewater under visible light excitation, achieving about 86.5 % degradation in 72 minutes, which is 2.5 times higher than that of pure g-C3N4. Furthermore, the influence of factors such as pH, dosage of tetracycline and photocatalyst on TC degradation were investigated. Photochemical characterization experiments revealed that the enhanced degradation performance of the BCN/BiOBr heterojunction stemmed from the synergistic effects of adsorption and photocatalysis, providing more active sites to promote the photocatalytic reaction, and accelerating accelerate charge separation and light absorption ability. Meanwhile, the results from the active species indicated that h+, ·OH, and ·O2- play major roles in the degradation process. Additionally, the mechanism research revealed that the photogenerated carriers followed an S-scheme step transfer pathway at the interface of BiOBr and g-C3N4, and the two possible pathways for TC degradation. This provides guidance for improving wastewater treatment using biochar-modified high-efficiency S-scheme photocatalysts.