Abstract
Ribavirin (RBV) is an antiviral drug used for treating COVID-19 infection. Its release into natural waters would threaten the health of aquatic ecosystem. This study reports an effective approach to degrade RBV by the trace N-oxyl compounds (2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and N-Hydroxyphthalimide (NHPI)) enhanced UV activated free chlorine (UV/Chlorine) process. The results indicated that TEMPO and NHPI at low concentrations (0.1 μM and 1 μM, respectively) could strongly enhance RBV degradation in both deionized water with different pHs and practical surface water. The enhancement was verified to be attributed to the transformation of TEMPO and NHPI into their reactive forms (i.e., TEMPO(+) and PINO), which generations deeply relied on radicals. The two N-oxyl compounds inhibit ClO• yield by hindering the reaction of free chlorine vs. HO• and Cl•. The analyses on acute toxicities of RBV degradation products indicate that UV/Chlorine/N-oxyl compounds process can detoxify RBV more efficiently than UV/Chlorine process.