Preparation of Co₃O₄/BiOCl composite material for photocatalytic degradation of trinitrotoluene wastewater

The aim of this paper is to improve the photocatalytic ability of pure BiOCl by a composite approach to solve the problem of degradation of trinitrotoluene (TNT) wastewater, which is difficult to degrade. Co₃O₄/BiOCl composite photocatalysts were successfully and efficiently synthesized using a combination of hydrothermal and calcination methods. The Co₃O₄/BiOCl composites were characterized, tested, and investigated by various complex techniques. Then, the high photocatalytic performance of the material was determined by its efficiency in degrading simulated TNT wastewater under visible light. From the above data, the possible degradation mechanism of the material in the photocatalytic system was deduced. The experimental results showed that the composite of Co₃O₄ significantly enhanced the photocatalytic performance of BiOCl and improved the efficiency of the composites in degrading TNT wastewater under visible light. In particular, the 0.05CoBi composite exhibited optimal degradation performance, reaching a 92% degradation efficiency of the TNT wastewater within 3 h. The composite was also found to be highly efficient in the degradation of TNT wastewater. After three consecutive photocatalytic degradation cycles, the 0.05CoBi composite maintained 80% degradation efficiency. In addition, radical trapping experiments showed that O₂⁻ plays a major role, followed by h⁺, in the degradation of TNT wastewater by 0.05CoBi. From our experiments, we propose a photocatalytic mechanism for this material.