Catalytic performance of wrapped CoO by MgO in oxidative degradation of chloroquine phosphate with peroxymonosulfate

Cobalt oxide could be used to activate peroxymonosulfate (PMS) for removal of contaminants, while its use was restricted due to low catalytic activity by limited active sites and the risk of cobalt ion leaching. This study investigated chloroquine phosphate (CQP) degradation by Co-Mg mixed metal oxides with highly dispersed minute quantities of CoO nanoparticles to activate PMS. It was demonstrated that the Co/Mg optimal molar ratio of catalyst was 1/200, and by characterization of catalysts and their effects on degradation of CQP, CoO nanoparticles could be widely dispersed and wrapped by MgO support. In the catalyst/PMS system, degradation of CQP could accelerate with the increase of catalyst dosage, PMS concentration and temperature and the addition of Cl-, HPO42- and H2PO4-, but decrease with the addition of Mg2+, NO3-, HCO3- and nature organic matter (NOM). By quenching experiments of active radicals, it was illustrated that SO4·- and O2·- made more significant contributions than HO· in this system for CQP degradation. The activation mechanism of PMS by the catalyst with good repeatability and stability was explained that MgO could effectively adsorb hydroxy groups, promoting the formation of Co-OH complex and accelerating the redox cycle of Co2+- Co3+- Co2+ in the catalyst. The strong interaction between CoO and MgO prevented cobalt ion leaching and enhanced catalyst activity over the wide pH range (5–10). And proposed intermediates and degradation pathways of CQP were analyzed.