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.
Development of porous materials with excellent capture performance of radioactive iodides (mainly molecular I2 and organic CH3I) remains an ongoing challenge in nuclear industry. Currently, numerous efforts have been devoted to exploring novel adsorbents with good textural properties like high specific surface and large pore volume. However, some nonporous materials exhibited outstanding iodine adsorption capability. Therefore, it is not yet clear what factors determine the iodine uptake capacity. Herein, a novel paradigm of iodine capture that overturns previous cognition is proposed by exploring some 2D electron-donating nitrogen-containing covalent organic frameworks (COFs). As validated by different pores of 2D COFs shaping from rhombic to hexagonal and ranging from micropores to mesopores, their adsorption capabilities of either molecular I2 or CH3I are more likely to depend on the number of adsorption binding sites, rather than their textural properties. This novel paradigm of iodine capture is of great importance to design of porous materials for disposing of exhaust gases from nuclear power plants.
For two-dimensional covalent organic frameworks that have same topological structure and electron-donating nitrogen-containing fragments with similar adsorption affinity to iodine molecules, their adsorption capabilities, for either molecular I2 or organic CH3I, are more likely to depend on the number of adsorption binding sites, rather than their textural properties like specific surface areas and pore volumes.
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