Construction and actual application of In2O3/BiOBr heterojunction for effective removal of ciprofloxacin under visible light: Photocatalytic mechanism, DFT calculation，degradation pathway and toxicity evaluation

To effectively degrade antibiotics remained in surface water, a type-II heterojunction photocatalyst In2O3/BiOBr was constructed by the solvothermal method. The composite photocatalyst greatly improves the efficiency of photocatalytic degradation towards antibiotic ciprofloxacin through enhancing the response to visible light and accelerating the separation rate of electron-hole pairs. The optimal degradation rate of ciprofloxacin reaches 93.5% within 90 min, much higher than those of monomeric In2O3 (only 5.5%) and BiOBr (34.3%) under visible light. The hole radicals contribute a dominant role, while superoxide radicals have a certain contribution. The transfer pathway of carriers follows the type-II process, which is demonstrated by various characterizations and Density Functional Theory. The catalyst In2O3/BiOBr has a good performance for all three actual water samples, including lake water, tap water and domestic sewage. The degradation mechanism, pathways and toxicity evaluation of intermediates all reveal that the produced type-II heterojunction In2O3/BiOBr has a very high practical value in reducing residual antibiotics in water.