Current Mechanism of Peroxymonosulfate Activation by Cobalt-Based Heterogeneous Catalysts in Degrading Organic Compounds

Persulfate based advanced oxidation processes (PS-AOPs) have been regarded as a mainstream degradation technology of organic compounds due to their high efficiency in wastewater treatment. In particular, peroxymonosulfate (PMS) has a unique structure and chemical properties, which can be efficiently activated by Co-based catalysts to produce active species with a high oxidation potential. These active species usually determine the subsequent degradation of organic compounds in an efficient process, while the intrinsic reaction mechanism behind this complex process remains unclear and therefore impedes the continual development in this scientific community. Recently, density functional theory (DFT) calculations have emerged as a powerful means to identify the electronic properties and distinguish energy changes in the PMS activation system. With the assistance of this quantum calculation, increasing investigations have been conducted focusing on explaining the phenomenon that occurred in experiments. However, these calculations mainly contributed in part to the reaction mechanism of PMS activation by Co-based catalysts and sometimes even differ from each other, lacking a comprehensive summary based on DFT calculation results. In this review, we introduce the main uses of DFT in the catalytic activation of PMS, provide recent application of calculation examples of Co-based heterogeneous catalysts with different structures, and then discuss the mechanism of PMS activation in detail. Finally, the research results of the DFT method in this field are summarized, and the future research focus and challenges are put forward, which is conducive to guiding the practical design of Co-based catalysts and further application of PS-AOPs in creating value products.