Mechanistic investigation of humic substances assisted photodegradation of imipramine under simulated sunlight

Ivan P. Pozdnyakov, Yuliya E. Tyutereva, Marina V. Parkhats, Vyacheslav P. Grivin, Yuan Fang, Lu Liu, Dong Wan, Fan Luo, Yong Chen

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Imipramine (IMI) is a frequently prescribed tricyclic antidepressant and widely detected in the natural waters, while the environmental fate of IMI is yet poorly understood. Here, we investigated the photodegradation of IMI under simulated sunlight in the presence of humic substances (HS), typically including humic acid (HA) and fulvic acid (FA). The direct and indirect IMI photodegradation was found to increase both with increasing pH and with deoxygenation of the reaction solutions. The excited triplet state of HS (3HS) was mainly responsible for the photosensitized degradation of IMI according to the steady-state quenching and direct time-resolved experiments. The electron transfer interaction between 3HS and IMI was observed by laser flash photolysis (LFP) with bimolecular reaction rate constants of (4.9 ± 0.4) × 109 M−1 s−1. Evidence of electron transfer from IMI to 3HS was further demonstrated by the photoproduct analysis. The indirect photodegradation was triggered off in the side chain of IMI with the nonbonding nitrogen electron transferring to 3HS, followed by hydroxylation, demethylation and cleavage of the side chain. Very important that HS photosystem does not lose its efficiency with decreasing of IMI concentration, meaning that the studied photosystem still be used at environmentally relevant concentrations of IMI. These results suggest that photodegradation could be an important attenuation pathway for IMI in HS-rich and anaerobic natural waters.

Original languageEnglish
Article number140298
Number of pages7
JournalScience of the Total Environment
Volume738
DOIs
Publication statusPublished - 10 Oct 2020

Keywords

  • Electron transfer interaction
  • Humic substances
  • Imipramine
  • Photoproducts
  • Photosensitization
  • AQUEOUS-SOLUTIONS
  • ACID
  • PHARMACEUTICALS
  • OXYGEN
  • WASTE-WATER
  • DRUGS
  • LASER FLASH
  • PHOTOCHEMISTRY
  • DISSOLVED ORGANIC-MATTER
  • PHOTOLYSIS
  • Water Pollutants, Chemical
  • Humic Substances/analysis
  • Photolysis
  • Sunlight

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