Generation mechanism of singlet oxygen from the interaction of peroxymonosulfate and chloride in aqueous systems. (15th May 2023) - Wang, Anna
Highlights: The interaction of PMS and Cl − efficiently produces 1 O2 and free chlorine. A reaction of Cl2 molecule and PMS forms 1 O2 with the rate constant of 10 5 M -1 s -1 . Carbamazepine is degraded by major 1 O2 and minor Cl2 at pH 4.1–6.7 in PMS/Cl − . 1 O2 formed in PMS/Cl − enhances the practical application in water purification. Abstract: Peroxymonosulfate (PMS, HSO5 − ) is a widely-used disinfectant and oxidant in environmental remediation. It was deemed that PMS reacted with chloride (Cl − ) to form free chlorine during water purification. Here, we demonstrated that singlet oxygen ( 1 O2 ) was efficiently generated from PMS and Cl − interaction. Mechanism of 1 O2 formation was uniquely verified by the reaction of HSO5 − and chlorine molecule (Cl2 ) and the oxygen atoms in 1 O2 deriving from the peroxide group of HSO5 − were revealed. Density functional theory calculations determined that the reaction of HSO5 − and Cl2 was thermodynamically favorable and exergonic at 37.8 kcal/mol. Quite intriguingly, 1 O2 was generated at a higher yield (1.5 × 10 5 M − 1 s − 1 ) than in the well-known reaction of H2 O2 with Cl2 (35 M − 1 s − 1 ). Besides chlorine, 1 O2 formed in PMS-Cl − interaction dominated the degradation of micropollutants, also it substantially enhanced the damage of deoxynucleoside in DNA, which were beneficial to micropollutant oxidation and pathogen disinfection. The contribution of 1 O2 for carbamazepine degradation was enhanced at higher Cl − level and lower pH, and reached 96.3% at pH 4.1 and 5 min. Natural organic matter (NOM) was a sink for chlorine, thereby impeding 1 O2 formation to retard carbamazepine degradation. 1 O2 also played important roles (48.3 − 63.5%) on the abatement of deoxyguanosine and deoxythymidine at pH 4.1 and 10 min in PMS/Cl − . On the other hand, this discovery also alerted the harm of 1 O2 for human health as it can be formed during the interaction of residual PMS in drinking water/swimming pools and the high-level Cl − in human bodies. Graphic abstract: Image, graphical abstract