Simultaneous removal of Cr (VI) and norfloxacin over BiOBr nanosheet with regulated oxygen vacancies: Intermediates and toxicity evaluation

Developing highly efficient photocatalysts toward simultaneous removal of chromium (Cr (VI)) and norfloxacin (Nor) in refractory wastewater was still an arduous challenge. Herein, the concentration of oxygen vacancies (OVs) in BiOBr was adjusted by a temperature control method, which could facilitate the photocatalytic Nor removal and Cr (VI) reduction. The removal capacity over V_o-BOB-90 of the photocatalytic Cr (Ⅵ) reduction and Nor degradation were 95.44 and 32.47 times higher than those of pure BiOBr, respectively. In the mixed wastewater, the V_o-BOB-90 could degrade 90.15 % of Nor within 90 min and almost all of Cr (VI) within 20 min, which was 2.71 and 1.48 times higher than single Nor and Cr (VI) solution, respectively. The improved activity could be attributed to the improved light absorption capacity and enhanced the photogenerated charges separation efficiency. Additionally, SPV, PL, and TRPL tests exhibited that the existence of OVs could regulate the electronic structure to accelerate charge transfer. Furthermore, according to the experimental data of LC-MS test and the experiment on growth of Mung bean seeds, the toxicity of the mixed solution was reduced during the degradation process. This study put forward an in-depth understanding of the removal of pollutants in complex water environments using OVs regulation.