TY - JOUR

T1 - Mechanistic investigation of humic substances assisted photodegradation of imipramine under simulated sunlight

AU - Pozdnyakov, Ivan P.

AU - Tyutereva, Yuliya E.

AU - Parkhats, Marina V.

AU - Grivin, Vyacheslav P.

AU - Fang, Yuan

AU - Liu, Lu

AU - Wan, Dong

AU - Luo, Fan

AU - Chen, Yong

N1 - Publisher Copyright: © 2020 Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/10/10

Y1 - 2020/10/10

N2 - 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.

AB - 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.

KW - Electron transfer interaction

KW - Humic substances

KW - Imipramine

KW - Photoproducts

KW - Photosensitization

KW - AQUEOUS-SOLUTIONS

KW - ACID

KW - PHARMACEUTICALS

KW - OXYGEN

KW - WASTE-WATER

KW - DRUGS

KW - LASER FLASH

KW - PHOTOCHEMISTRY

KW - DISSOLVED ORGANIC-MATTER

KW - PHOTOLYSIS

KW - Water Pollutants, Chemical

KW - Humic Substances/analysis

KW - Photolysis

KW - Sunlight

UR - http://www.scopus.com/inward/record.url?scp=85086758024&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2020.140298

DO - 10.1016/j.scitotenv.2020.140298

M3 - Article

C2 - 32806347

AN - SCOPUS:85086758024

VL - 738

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 140298

ER -