Degradation of glucocorticoids in water by a synergistic system of peroxymonosulfate, microbubble and dielectric barrier discharges

Abstract Glucocorticoids (GCs) in the environment have been an increasing concern. Most recently, GCs have been shown to be an effective remedy to manage septic shock in patients infected with COVID-19. In this study, a self-made dielectric barrier discharge reactor integrating microbubbles and peroxymonosulfate (DBD/MB/PMS) was used to degrade the GCs in water. At neutral pH and ambient temperature, hydrocortisone (HC), betamethasone (BT) and fluocinolone acetonide (FA) were degraded effectively by the DBD/MB/PMS system with the 90-min degradation efficiencies of 77%, 80% and 82%, respectively (discharge power: 83.5 W; PMS:GC ratio: 20:1). In comparison, the 90-min degradation efficiencies for HC, BT and FA by DBD/MB system (discharge power: 83.5 W, pH unadjusted, flow rate 40 mg/L) were only 49%, 54% and 60% respectively; and the efficiencies by heat activated PMS (90 °C) were only 24%, 12%, and 16%, respectively. Hence, DBD/MB is an efficient approach for PMS activation, which resulted in increased removal efficiencies and energy yields for GCs degradation. The rate constants for GCs degradation also increased with the increase of PMS dosage and initial solution pH. Both SO4− and OH were prominent species for GCs degradation. Based on the results of scavenging experiment, the contributions of SO4− for HC, BT and FA degradation were roughly estimated to be 51%, 59% and 60%, respectively, and the contributions of OH were 30%, 29% and 27%, respectively. This work not only provides a novel approach in dealing with GCs contaminated water, but also highlights the synergistic effect of plasma, MB and PMS.