Rational regulation of peroxymonosulfate activation over porous Co3O4 with carbon coating to boost utilization efficiency of peroxymonosulfate and achieve rapid removal of pollutants

It is of great significance to regulate rationally the activation mechanism of persulfate for promoting the development of sulfate radical-based advanced oxidation processes in wastewater treatment. Herein, carbon coated porous Co3O4 with hollow structure was synthesized. Notably, the formation of porous hollow structure improved specific surface area of Co3O4 and offered more redox couples of Co2+/Co3+, thereby reducing electron transfer resistance. Thus, the generation of reactive oxygen species and the role of high-valent transition metal complexes (namely Co3O4---Co4+) were improved. The formation of carbon layer on the Co3O4 surface can avoid the release of Co ion during reaction process. Benefiting from the role of carbon layer in electron transport, catalyst-mediated the direct electron transfer from pollutant to PMS was boosted. Radical and nonradical pathways worked in coordination each other and realized the rapid removal of various organic pollutants in the presence of a little PMS. In short, current work revealed that modulating rationally the microstructure of catalyst was an efficient strategy for achieving controllable regulation of PMS activation process. More significantly, whether the direct electron transfer process can occur or not depended on both catalyst structure and electronic density of pollutants.