Peroxymonosulfate activation by Co3O4 coatings for imidacloprid degradation in a continuous flow-cell reactor under simulated solar irradiation

Abstract

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 experiments 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.