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−) and singlet oxygen (1O2) could enhance the removal of organic pollutants in PMS activation because of the high-selective oxidation of electrophilic compounds by 1O2. Co oxides are highly active towards PMS activation, but improving the generation of 1O2 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 1O2 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. 1O2 and SO4− exist in ZnCoOx/PMS system while 1O2 plays the dominant role for pollutants removal. The oxygen vacancies of ZnCoOx are demonstrated to be responsible for the generation of 1O2 and the mechanism is further investigated. This study provided an efficient catalyst to combine the advantages of 1O2 and SO4− for pollutants removal by PMS activation, and the results could open a new avenue for development of heterogeneous catalysts for PMS activation.