Photochemical degradation of polyhalogenated carbazoles in hexane by sunlight

Shanshan Zhou, Xiaoxue Pan, Qiaozhi Tang, Hongbin Zhu, Jiayi Zhou, Lu Zhao, Jiehong Guo, Zunyao Wang, Weiping Liu, An Li

Research output: Contribution to journalArticlepeer-review

Abstract

Polyhalogenated carbazoles (PHCZs) are a class of halogenated dibenzopyrrole, which have been increasingly detected in the environment and found to be bioaccumulative and potentially toxic. However, their environmental transformation potential is largely unknown. In this study, UV absorption spectra of carbazole (CZ) and 10 PHCZs were obtained with wavelength range 290–400 nm, and three peaks were identified in most cases with the highest occurring around 300 nm. Hexane solutions of CZ, 10 individual PHCZs, and a sediment extract containing nine other PHCZs were separately irradiated under natural sunlight in order to investigate their photodegradation kinetics and pathways. The pseudo-first-order reaction rate constants (k) of these PHCZs varied from 0.183 h −1 to 2.394 h −1 , and increased exponentially with increasing numbers of chlorines and bromines in PHCZ molecules. Contribution to ln k from each bromine atom is more than doubling of that from each chlorine atom. Stepwise reduction debromination was confirmed to be one of the photodegradation mechanisms for both brominated and mixed halogenated (containing both bromine and chlorine) carbazoles. Only sporadic dechlorinated products were found during the photolysis of chlorinated carbazoles. By adopting a simplified kinetic approach, we estimated that dehalogenation contributed approximately 20% to 51% of the total loss of the parent PHCZs.

Original languageEnglish (US)
Pages (from-to)622-631
Number of pages10
JournalScience of the Total Environment
Volume671
DOIs
StatePublished - Jun 25 2019
Externally publishedYes

Bibliographical note

Funding Information:
This research was supported by the National Natural Science Foundation of China (No. 41877494), the Natural Science Foundation of Zhejiang Province (No. LY18B070012), and Shanghai Pujiang Program (No. 16PJD026).

Funding Information:
This research was supported by the National Natural Science Foundation of China (No. 41877494 ), the Natural Science Foundation of Zhejiang Province (No. LY18B070012 ), and Shanghai Pujiang Program (No. 16PJD026 ).

Publisher Copyright:
© 2019

Keywords

  • Hexane
  • Natural light
  • Photolysis
  • Polyhalogenated carbazoles

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