The role of trace N-Oxyl compounds as redox mediator in enhancing antiviral ribavirin elimination in UV/Chlorine process

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 concen-trations (0.1 mu M and 1 mu M, 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 rad-icals. The two N-oxyl compounds inhibit ClO center dot yield by hindering the reaction of free chlorine vs. HO center dot and Cl center dot. 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.

Automated summary

This study found that the degradation of ribavirin in water can be enhanced by TEMPO and NHPI, which rely on the generation of reactive forms that mainly depend on radicals. At the same time, the two N-oxyl compounds also inhibit the generation of harmful substances by hindering the reaction of free chlorine with other substances.