The hydroxyl radical, ●OH, is one of the most powerful free radicals and plays significant roles in the oxidative degradation of organic pollutants and the electron-transfer with inorganic ions in natural and engineered environmental processes. To quantitatively determine the contribution of ●OH to oxidative reactions, a specific scavenger, such as tert-butyl alcohol (TBA), is usually added to eliminate ●OH effects. Although TBA is commonly assumed to transform ●OH into oxidatively inert products, this study demonstrates utilizing TBA as an ●OH scavenger generates the secondary peroxyl radical (ROO●), influencing the oxidation of transition metals, such as Mn. Compared with short-lived ●OH, ROO● has a half-life of seconds, which enables more redox reactions, such as the oxidation of Mn2+ (aq) to MnIV oxide solids. In addition to promoting Mn2+ (aq) oxidation kinetics, the concentrations of TBA have influences on the crystalline phases, oxidation states, and morphologies of Mn oxide solids. Thus, the roles of ●OH in inorganic redox reactions cannot be examined simply by adding TBA: the effects of secondary ROO● must also be considered. This study urges a closer look at the potential formation of secondary radicals during scavenged oxidative reactions in the environment.

Does tert-butyl alcohol really terminate the oxidative activity of hydroxyl radical in inorganic redox chemistry?

ACS Fall 2021

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