ABSTRACT
The role of triplet excited state compounds (TESC) in contaminants degradation by advanced reduction processes (ARPs) is rarely reported. In this study, Salicylic acid derivatives (SAD, e.g. Salicylic Acid (SA) and Sulfosalicylic acid (SSA)) were applied in ultraviolet activated sulfite process (UV/Sulfite) to generate TESC and enhance the decomposition of chloroquine derivatives (CQD, antiviral drugs being used for treating COVID-19 infection, e.g. chloroquine phosphate (CP)). The results indicated that the pseudo 1st order rate constant of CP (kobs-CP) increased by 2.76 and 6.26 fold, which increased from 9.10 × 10–4 s–1 in UV/Sulfite process to 2.51 × 10–3 s–1, 5.72 × 10–3 s–1 in UV/Sulfite/SA and UV/Sulfite/SSA process respectively. Similar phenomena were observed in other CQDs. Transient absorption spectra demonstrated that both triplet excited state SAD (3SAD*) and hydrated electron (eaq–) were the reactive intermediates in UV/Sulfite/SAD process, and contribute to the abatement of CP. The enhancement of SAD on contaminants degradation in UV/Sulfite/SAD process could attribute to the strong acceleration of eaq– toward the formation of 3SAD* in its photosensitive process, where SAD with intramoleuclar hydrogen bond would not undergo a directly photoionization process after absorbing a photon but undergo intersystem crossing to transform into 3SAD* which was then ionized to eaq– by biphotonic process, and constitute a hydrated electrons mediated photosensitization cycle with the supplement of eaq– from UV/Sulfite process. The higher CP degradation rate in UV/Sulfite/SSA process than that in UV/Sulfite/SA process was ascribed to a higher second order rate constant of 3SSA* toward CP and a higher yield of 3SSA*, which resulted from its higher intramolecular hydrogen bond energy enhancing photosensitization and photoionization.
ABSTRACT
Chloroquine Phosphate (CP) is an antiviral drug used for treatment of COVID-19. It is released into wastewater and eventually contaminates natural water. This study reports an effective homogeneous catalysis way for CP degradation by the 2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO) enhanced persulfate (PDS) activation under UVB-LEDs irradiation at 305 nm. TEMPO at a low concentration (0.1 µM) enhanced CP degradation in UV305/PDS process in deionized water at different pHs, in different anions and different molecular weight dissolved organic matter solutions and in real surface water. The enhancement was verified to be attributed to the electron shuttle role of TEMPO, which promoted the yield of SO4 â¢- by enhancing electron donating capacity of the reacting system. The degradation products of CP and their acute toxicities suggested that UV305/PDS/TEMPO process has better performance on CP detoxification than UV305/PDS process. This study provides a new way to tackle the challenge of pharmaceutical pollutions in homogeneous photocatalysis process for natural water and sewage restoration.
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 Clâ¢. 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.