Study on antiviral drugs degradation by UV/NH2Cl: Combination of experiments and quantum chemical calculation

The widespread use of antiviral drugs (AVDs) has introduced novel challenges to water treatment processes in recent years. Therefore, it is urgently required to develop an efficient and sustainable technology for AVDs elimination. This study examines the effectiveness of UV-activated monochloramine (UV/NH 2 Cl) as a potent treatment modality for degrading AVDs. Results showed that the degradation rate constants ( k ) of ganciclovir, acyclovir, and stavudine were 0.381, 0.339, and 0.395 min −1 , respectively, under UV/NH 2 Cl conditions (NH 2 Cl/AVDs molar ratio = 40). Both •OH and reactive chlorine species are crucial for AVDs degradation. The degradation pathways of AVDs in the UV/NH 2 Cl system are primarily characterized by C-N bond cleavage, oxidation, hydroxylation, and chlorination. A comprehensive evaluation on the degradation kinetics of ten AVDs UV/NH 2 Cl revealed a correlation between the AVDs molecular structures and the degradation efficiency. The k of AVDs was positively correlated with the polarizability. This phenomenon can be attributed to the spatial electron distribution of AVDs with a high polarizability, which is more susceptible to alteration. Conversely, the k was inversely correlated with the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap, as a smaller HOMO-LUMO gap makes the AVDs more conducive to electron exchange and subsequent participation in redox reactions. This study confirms the efficient abatement performance of the UV/NH 2 Cl system for AVDs, and simultaneously provides critical technical references and novel theoretical insights for the AVDs removal in real water matrices.