Rates of Trace Mineral-Catalyzed Decomposition of Hydrogen Peroxide

Rapid hydrogen peroxide (H2O2) decomposition is a significant limitation of catalyzed H2O2 propagations (i.e., modified Fenton’s reagent) for the remediation of contaminated soil and groundwater by in situ chemical oxidation. Rates of H2O2 decomposition mediated by seven trace minerals and four iron and manganese oxides were evaluated in batch reactors containing slurries of H2O2 and each of 11 minerals. At pH 3, the dominant catalysts in the decomposition of H2O2 on a per surface area basis were the manganese and iron oxides pyrolusite, goethite, and hematite, while decomposition rates in the presence of the manganese oxyhydroxide manganite and the trace mineral siderite were one to two orders of magnitude lower. At pH 7, the dominant catalysts were hematite and pyrolusite, and decomposition rates were one to two orders of magnitude lower in the presence of goethite, manganite, and siderite. The trace minerals anatase, bauxite, cuprite, ilmenite, magnesite, and willemite provided the least activity for decomposing H2O2 at both pH regimes. The results of this study document that the trace minerals anatase, bauxite, cuprite, ilmenite, magnesite, siderite, and willemite do not provide a significant pathway for H2O2 decomposition in the subsurface, and efforts to stabilize H2O2 for ISCO should focus on reactions occurring on the surfaces of iron and manganese oxides.