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.