Visible-light enhanced peroxymonosulfate activation on Co3O4/MnO2 for the degradation of tetracycline: Cooperation of radical and non-radical mechanisms

Advanced oxidation processes (AOPs) dominated by SO4·- species have drawn mainly attentions for the removal of persistent pollutions. Nevertheless, single radical underutilizes the oxidizing capacity of reactive oxygen species and possesses poor adaptability to the environment compared with the cooperation of radical and non-radical. Herein, a Co3O4/MnO2 heterojunction catalyst is synthesized and used to peroxymonosulfate (PMS) activation for the degradation of tetracycline (TC) via non-radical cooperates with radical under visible irradiation. The optimized 10-Co3O4/MnO2 (10-CMO) composite catalyst exhibits 99.4% TC degradation efficiency within 60 min, and the apparent rate constant is 0.1353 min−1, which is 6.77 and 45.10 times higher than that of in 10-CMO/PMS and 10-CMO/Vis systems, respectively. The PMS acts as an electron accepter and induces the non-radical pathways accelerating TC degradation. After 5 cycles, the 10-CMO catalyst can still remove 93.7% TC with low Co (0.06 mg/L) and Mn (0.20 mg/L) ions leakage. The reactive species trapping experiments and electron paramagnetic resonance analysis demonstrate that the 1O2, h+ and SO4·- species dominate the TC degradation. Theoretical calculation results further reveal the probable PMS activation mechanism and the superiority of heterojunction for the PMS activation. This work shows great potential for pollutions control with visible-light-assisted PMS activation in presence of catalyst.