The effectiveness of advanced oxidation processes is typically measured against the number of moles of reagent added and the yield of corresponding reactive oxygen species. Here we quantify the cooperative effect of autoxidation as a source of secondary oxidants that can also effect remediative goals. The autoxidation of 3,4,5-trihydroxybenzoic acid (gallic acid) was used to introduce reactive oxygen species into natural waters to elicit co-oxidation of environmental contaminants without the addition of high energy photons, ozone, or reduced transition metals. All reactions were monitored using ultra high-performance liquid chromatography and mass spectrometry (UPLC-ESI-MS/MS) for organic products and the Amplex Red method for hydrogen peroxide. Gallic acid was added to aerated, buffered waters (t = 0) and its spontaneous oxidation observed along with concomitant formation of hydrogen peroxide. Hydrogen peroxide formation was rapid upon addition of gallic acid to the solution at pH of 7 or higher with an approximate yield of 2.3 mole hydrogen peroxide/mole gallic acid consumed. The addition of superoxide dismutase reduced the rate of gallic acid oxidation by a factor of approximately 12 with a corresponding decrease in the rate of hydrogen peroxide formation, demonstrating the critical role of superoxide as a chain carrier for the process. Performance of this reaction in natural waters resulted in an increased rate of hydrogen peroxide production, correlating with the organic carbon content of the water (R<sup>2</sup> = 0.90). Reactive oxygen species generated during this process were capable of degrading anthropogenic chemicals, including the pesticide fipronil and its major degradation products. The potential of this system to drive natural attenuation of contaminants through co-oxidation of humic materials is demonstrated for removal of emerging contaminants.

Autoxidation of gallic acid to generate reactive oxygen species for removal of organic micropollutants

256th National Meeting (2018)

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