Mechanism and Toxicity Evaluation of Antibiotics Degradation by a Z-Scheme Heterojunction Photocatalyst Composed of Bi₄O₅I₂/Glucose-Modified Bi₂O₂CO₃

The accumulation of potential antibiotics in water is potentially harmful to human beings and the environment. In this paper, a novel composite catalyst, Bi₄O₅I₂/glucose-modified Bi₂O₂CO₃ (BGBCO) with a high ciprofloxacin (CIP) removal rate, was rapidly synthesized by a low-temperature hydrothermal method. BGBCO demonstrated the best photocatalytic activity after 100 min irradiation by a 65 W energy-saving lamp. The apparent kinetic constants of BGBCO are 7.20, 2.28, and 1.41 times of Bi₂O₂CO₃, Bi₄O₅I₂, and glucose-modified Bi₂O₂CO₃, respectively. Experimental results and characterization show that the significant improvement of photocatalytic performance can be attributed to more active sites, a wider visible light absorption range, and improved photogenerated carrier separation rate. Free radical capture experiments confirmed that •O₂^- and h⁺ are primary active species responsible for the degradation of CIP. The toxicity prediction results showed that the toxicity of CIP degradation products decreased significantly. Based on various characterization results, the possible mechanism and pathway of photocatalytic degradation of CIP were proposed. This study provides valuable insights for the modification of Bi₂O₂CO₃-based heterojunction photocatalytic materials and their application in the purification of antibiotics in water.