Study on the degradation performance of tetracycline in water by chitin-based biochar-Bi2O3

Abstract

To enhance the photocatalytic degradation performance of Bi₂O₃ against tetracycline (TC) pollutants, a Biochar/Bi₂O₃ (BC/Bi₂O₃) composite photocatalyst was synthesized using chitin as a carbon source through a one-step calcination method. The tetracycline degradation efficiency of the photocatalytic material (m_{BC: Bi2O3} = 2:1) synthesized at 500 °C for 4 h was reached 83.43 %, as well as 5.5 and 1.5 times higher than that of the BC and Bi₂O₃ monomers, respectively, while the degradation rate constant of BC/Bi₂O₃ (2:1) was 0.0052 min⁻¹, which was 13 and 1.7 times higher than that of BC (0.0004 min⁻¹) and Bi₂O₃ (0.0030 min⁻¹). Extensive property analysis shows that BC and Bi₂O₃ interact through Bi-O-C bonds after synthesize, which improves the electron transport efficiency and provides more active sites for the composite. The interaction between these two materials allows the composite to provide more active sites while improving the electron transfer efficiency. UV–vis spectroscopy and free radical quenching experiments further corroborated the direct degradation ability of the BC/Bi₂O₃ composite photocatalyst towards TC. As the reaction progressed, TC undergoes degradation mineralization via two distinct pathways, faciliatetd by the action of h⁺ and •O₂⁻ radicals. Overall, the functional BC/Bi₂O₃ with high photocatalytic activity provides worthwhile insights of photocatalytic materials application in the wasterwater treatment field.