Efficient degradation of lindane by visible and simulated solar light-assisted S-TiO2/peroxymonosulfate process: Kinetics and mechanistic investigations

Sanaullah Khan, Changseok Han, Hasan M. Khan, Dominic L. Boccelli, Mallikarjuna N. Nadagouda, Dionysios D. Dionysiou

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Organochlorine pesticides (OCPs) are toxic and the most potent endocrine disrupting chemicals in the environment. Most OCPs are resistant towards oxidation by [rad]OH due to presence of electron-withdrawing chlorine group in their molecular structures. Here, we investigated a visible and simulated solar light-assisted sulfur doped TiO2 (S-TiO2)/peroxymonosulfate (HSO5) process to eliminate a selected OCP, lindane. Initially, visible and simulated solar light-assisted S-TiO2 photocatalysis resulted in 31.0 and 63.4% removal of lindane (C0 = 1.0 μM), respectively in 6 h. The photocatalytic activity of S-TiO2 was dramatically increased in the presence of 0.2 mM HSO5, leading to 68.2 and 99.9% lindane removal under visible and simulated solar light illumination, respectively in 6 h. The observed pseudo first-order rate constant for simulated solar light-assisted S-TiO2/HSO5 decreased with increasing initial concentration of lindane, corresponding to 8.98 × 10−1, 6.58 × 10−1 and 3.84 × 10−1 h−1 at [lindane]0 of 0.5, 1.0 and 2.0 μM, respectively. The degradation kinetics were significantly affected by solution pH, leading to 88.2, 99.9 and 71.4% removal of lindane in 6 h at pH 4.0, 5.8 and 8.0, respectively. S-TiO2 film exhibited a high mechanical strength with only 3.3% loss of efficiency after four repeated cycles. Based on the detected reaction intermediates, a possible reaction mechanism was proposed, suggesting dechlorination, dehydrogenation, and hydroxylation via [rad]OH, SO4[rad] and O2[rad] attack. The results suggest that visible and simulated solar light-assisted S-TiO2/HSO5 is a promising alternative for treatment of water contaminated with most OCPs.

Original languageEnglish (US)
Pages (from-to)9-16
Number of pages8
JournalMolecular Catalysis
Volume428
DOIs
StatePublished - 2017
Externally publishedYes

Keywords

  • Lindane
  • Peroxymonosulfate
  • Reaction mechanism
  • S-TiO photocatalysis
  • Visible and simulated solar light activity
  • Water treatment

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology
  • Physical and Theoretical Chemistry

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