The activation of peroxymonosulfate via oxygen/cobalt-modified carbon nitride for decomposition of acid orange 7: role of high-value cobalt and superoxide radical

Abstract

We prepared Co@O-gCN as a means of activating peroxomonosulfate (PMS) to remove acid orange 7 (AO7). The effects of a series of considerations including catalyst amount, PMS dosage, pH and temperature on the degradation of AO7 were evaluated, and we discovered that the time needed to remove AO7 completely decreased as pH increased, and as the pH was adjusted to 11, the addition of 10 mg Co@O-gCN and 375 mg/L PMS resulted in the complete removal of 20 mg/L of AO7 within 10 min. The effects of coexisting anions and the actual water matrix in the process of removing AO7 by the Co@O-gCN /PMS system were investigated. Electron paramagnetic resonance (EPR) and quenching experiments revealed that under acidic as well as neutral conditions, Co (IV) was the main reactive species, whereas under alkaline conditions, the main reactive species changed to superoxide radicals (O₂^·−), followed by monoclinic oxygen (¹O₂).