Superior performance of ZnCoOx/peroxymonosulfate system for organic pollutants removal by enhancing singlet oxygen generation: The effect of oxygen vacancies

Combination of sulfate radical (SO4 center dot-) and singlet oxygen (O-1(2)) could enhance the removal of organic pollutants in PMS activation because of the high-selective oxidation of electmphilic compounds by O-1(2). Co oxides are highly active towards PMS activation, but improving the generation of O-1(2) in PMS activation with Co oxides as catalysts remains a great challenge. Herein, the Zn doped Co oxides (ZnCoOx) was prepared by calcining Zn doped ZIF-67 in air. The oxygen vacancies content of ZnCoOx could be adjusted by controlling Zn doping level and the presence of oxygen vacancies leads to the generation of O-1(2) in ZnCoOx/PMS system. The optimized ZnCoOx-2 presents the kinetic constant of 0.538 min(-1) for Rhodamine B removal, which is 14.2 times higher than that of undoped sample and 38.4 times higher than that of commercial Co3O4. O-1(2) and SO4 center dot- exist in ZnCoOx/PMS system while O-1(2) plays the dominant role for pollutants removal. The oxygen vacancies of ZnCoOx are demonstrated to be responsible for the generation of O-1(2) and the mechanism is further investigated. This study provided an efficient catalyst to combine the advantages of O-1(2) and SO4 center dot- for pollutants removal by PMS activation, and the results could open a new avenue for development of heterogeneous catalysts for PMS activation.

Automated summary

This study successfully prepared Zn-doped Co oxides for efficient generation of O-1(2) in PMS activation. The presence of oxygen vacancies in ZnCoOx was found to play a crucial role in the generation of O-1(2). The optimized ZnCoOx showed significantly improved removal efficiency for Rhodamine B compared to undoped samples and commercial Co3O4.