Anchoring Bi4O5I2 and CDs on brown TiO2−x: S-scheme heterojunction mechanism for impressive degradation of several antibiotics under visible light

Fully aware of the global water pollution caused by more consumption of antibiotics, we successfully prepared novel brown TiO2−x/Bi4O5I2/carbon dots (B-TiO2−x/Bi4O5I2/CDs) photocatalysts through a facile strategy. The as-prepared samples were specified via XRD, FESEM, UV–vis DRS, XPS, EDS, TEM, HRTEM, FTIR, BET, BJH, EIS, photocurrent, and PL analyses. The ternary photocatalysts were utilized for the degradation of several antibiotics, including cephalexin (CEX), metronidazole (MNZ), and tetracycline (TC), under visible-light exposure provided by a 50 W LED. The B-TiO2−x/Bi4O5I2/CDs (1 mL) nanocomposite presented impressive activity in the photodegradation of CEX, MNZ, and TC antibiotics, which was 14.4, 39.8, and 49.7-folds of TiO2, and 4.71, 11.1, and 12.3 times as high as B-TiO2−x, respectively. The enhanced photo-degradation proficiency of optimal nanocomposite was assigned to the higher visible-light absorbance, reduced recombination of photo-induced carriers, and higher redox capability owing to the construction of S-scheme heterojunction amongst the components. In particular, ∙O2− and h+ showed a major role in the degradation of TC antibiotic. Moreover, the TC degradation mechanism was studied using LC-MS analysis. Finally, the optimized B-TiO2−x/Bi4O5I2/CDs (1 mL) nanocomposite displayed significant stability after four cycles, and it was displayed that the resultant solution after the degradation process has considerable biocompatibility through the growth of wheat seeds.