Peroxymonosulfate Activation by Co3O4 Coatings for Imidacloprid Degradation in a Continuous Flow-Cell Reactor under Simulated Solar Irradiation

In this work, a Co3O4 coating prepared by precipitation and vacuum filtration was applied to photoactivate peroxymonosulfate (PMS), for the degradation of imidacloprid (IMD) under continuous-flow conditions. The effects of PMS concentration, flow rate, and type of irradiation were evaluated. Under optimal conditions (0.2 gPMS L-1, 0.1 mL min-1, and simulated solar irradiation), 99% IMD photodegradation was achieved after 2 h of operation. The outstanding performance of the Co3O4/PMS/solar irradiation process was attributed to the synergistic activation of PMS by Co2+ and Co3+ species in the Co3O4 catalyst and the UV component of solar irradiation, in either the homogeneous phase or following the adsorption of PMS onto Co3O4. Quenching ex-periments revealed that sulfate and superoxide radicals, as well as singlet oxygen, were the main active species responsible for IMD oxidation. Measurements using HPLC-high resolution mass spectrometry enabled the identification of eight intermediate products, allowing the proposal of a degradation pathway. The combination of solar light, Co3O4, and PMS is a simple and low-cost approach with the potential to treat effluents containing harmful pollutants.