Oxygen Vacancy-Dominated Activation of Chlorite and Oxidative Degradation of Sulfamethoxazole

Oxygen vacancy-rich bismuth oxyhalides (BiOX, where X = Cl, Br, I) were successfully synthesized as heterogeneous catalysts for efficiently activating chlorite to produce chlorine dioxide (ClO2) as the prevailing reactive oxidized species (ROS) for sulfamethoxazole (SMX) degradation. Material characterization and density functional theory (DFT) calculations show that BiOI possesses the highest oxygen vacancies, which act as highly active sites. Oxygen vacancies (OVs) not only absorb chlorite but also improve the internal electron conduction efficiency between chlorite and metal ions. The best removal of SMX (84.3%) was achieved under neutral conditions using 70 mg of BiOI and 0.1 mM chlorite. It was discovered that ClO2 is the primary ROS, which was generated via two reactions that involved the formation of HOCl and Bi(IV). The minimal change in acute toxicity and the well-maintained performance in degrading pollutants indicated the potential practical applications of the BiOI/chlorite system. This work reveals a unique mechanism for the OV-mediated activation of chlorite, which highlights the potential advantages of activation via heterogeneous metal oxides BiOX and supplies a new viewpoint for the activation of chlorite for contaminant degradation.