Kinetics and mechanisms of diniconazole degradation by α-MnO2 activated peroxymonosulfate

Abstract As one of the high-efficiency triazole fungicides, diniconazole (DIN) has been used on a large scale in agricultural production. Due to its high stability and toxicity, DIN is usually persisted in soil and water and has been demonstrated to be a potential threat to environment and humans. In this study, the degradation kinetics, mechanisms, and degradation products of DIN by peroxymonosulfate (PMS) activated with α-MnO2 were systematically studied. The results showed that DIN was rapidly degraded in α-MnO2 activated PMS system, and the degradation kinetics of DIN in this reaction system could be described by the pseudo-first-order kinetic model. The degradation of DIN was affected by environmental conditions. Acidic condition was beneficial to the degradation of DIN, whereas co-existing anions (HPO42-, Cl- and HCO3–) and humic acid inhibited the degradation of DIN in MnO2 activated PMS system. SO4 - and HO generating from PMS activated by α-MnO2 were confirmed as the major active species in degradation of DIN. The potential sites attacked in the DIN structure might be 11Cl, 10Cl, 14C and 17C based on the DFT calculation. Moreover, the degradation pathways of DIN were proposed, including hydroxylation, hydroxyl addition, cleavage of 14C-15N and intramolecular cyclization.