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.
- Reaction mechanism
- S-TiO photocatalysis
- Visible and simulated solar light activity
- Water treatment
ASJC Scopus subject areas
- Process Chemistry and Technology
- Physical and Theoretical Chemistry