Reactive oxygen species (ROS) play important roles in natural and engineered aquatic systems by participating in various redox reactions. Among all radicals produced in natural photochemical processes, the hydroxyl radical ●OH) is one of the most reactive free radicals, contributing to the oxidative destruction of organic pollutants and the electron transfer of inorganic ions. To eliminate the role of ●OH in the oxidation processes, tert-butyl alcohol (TBA) is often utilized as a scavenger of ●OH because of its high reaction rate constant with ●OH. It is commonly assumed that ●OH can be fully scavenged by TBA, and that TBA will terminate the redox reaction. However, we found when TBA is utilized as a ●OH scavenger it generates a secondary peroxyl radical (ROO●). Although ROO● is less reactive than ●OH, it has an extended half-life and diffusion distance that allow ROO● to participate in more redox reactions, such as photochemical oxidation of Mn2+ (aq) to Mn oxide solids. In addition, the presence of TBA affected the crystalline phases, oxidation states, and morphologies of the formed Mn oxide solids. Thus, the role of ●OH in aqueous redox reactions cannot be determined simply by adding ●OH scavenger without considering the effect of secondary radicals on the system’s oxidation.

Underestimated role of tert-butyl alcohol, a scavenger of ●OH, in photochemical inorganic redox reactions

ACS Spring Meeting 2021

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