Light- and H2O2-Mediated Redox Transformation of Thallium in Acidic Solutions Containing Iron: Kinetics and Mechanistic Insights
Citations Over TimeTop 15% of 2022 papers
Abstract
The redox transformation between the oxidation states of thallium (Tl(I) and Tl(III)) is the key to influencing its toxicity, reactivity, and mobility. Dissolved iron (Fe) is widely distributed in the environment and coexists at a high level with Tl in acidic mine drainages (AMDs). While ultraviolet (UV) light and H2O2 can directly (by inducing Tl(III) reduction) and indirectly (by inducing Fe(III) to form reactive intermediates) impact the redox cycles of Tl in Fe(III)-containing solutions, the kinetics and mechanism remain largely unclear. This study is the first to investigate the UV light- and H2O2-mediated Tl redox kinetics in acidic Fe(III) solutions. The results demonstrate that UV light and H2O2 could directly reduce Tl(III) to Tl(I), with the extent of reduction dependent on the presence of Fe(III) and the solution pH. At pH 3.0, Tl(I) was completely oxidized to Tl(III), which can be ascribed to the generation of hydroxyl radicals (•OH) from the Fe(III) photoreduction or Fe(III) reaction with H2O2. The kinetics of Tl(I) oxidation were strongly affected by the Fe(III) concentration, pH, light source, and water matrix. Kinetic models incorporating Tl redox kinetics with Fe redox kinetics were developed and satisfactorily interpreted Tl(III) reduction and Tl(I) oxidation under the examined conditions. These findings emphasize the roles of the UV light- and H2O2-driven Fe cycles in influencing the redox state of Tl, with implications for determining its mobility and fate in the environment.
Related Papers
- → pH-dependent redox potential: how to use it correctly in the activation energy analysis(2003)64 cited
- → A spectroscopic and gravimetric study of the soot-NO2N2O4 reaction at various temperatures(1990)30 cited
- → Redox catalysis. Theory for a Nernstian reaction coupled to an irreversible reaction(1989)15 cited
- → Redox Reactions in Non‐Aqueous Solvents(2002)8 cited
- → A note on the use of the impedance to investigate parallel redox reactions and indicator redox reactions during gas evolution(1984)6 cited