Identification of the reactive oxygen species responsible for carbon tetrachloride degradation in modified Fenton's systems.

TLDR: The results indicate that even dilute concentrations of solvents, including H202, can increase the reactivity of O2- in water, probably by changing its solvation sphere.

Abstract: The reactive oxygen species responsible for the transformation of carbon tetrachloride (tetrachloromethane, CT) by modified Fenton's reagent using hydrogen peroxide (H2O2) concentrations >0.1 M was investigated. Addition of the hydroxyl radical scavenger 2-propanol to modified Fenton's reactions did not significantly lower CT transformation rates. Scavenging by 2-propanol not only confirmed that hydroxyl radicals are not responsible for CT destruction, but also suggested that a major product of an iron (III)-driven initiation reaction, superoxide radical anion (O2•-), is the species responsible for CT transformation. To investigate this hypothesis, CT degradation was studied in aqueous KO2 reactions. Minimal CT degradation was found in CT−KO2 reactions; however, when H2O2 was added to the KO2 reactions at concentrations similar to those in the modified Fenton's reactions (0.1, 0.5, and 1 M), CT degradation increased significantly. Similar results were obtained when 1 M concentrations of other solvents wer...