Hydrogen peroxide decomposition in model subsurface systems

Rates of hydrogen peroxide decomposition, hydroxyl radical production, and oxygen evolution were investigated in silica sand-goethite slurries using u nstabilized and stabilized hydrogen peroxide formulations. The goethite-cat alyzed decomposition of unstabilized hydrogen peroxide formulations resulte d in more rapid hydrogen peroxide loss and oxygen evolution relative to sys tems containing a highly stabilized hydrogen peroxide formulation. Systems at neutral pH and those containing higher goethite concentrations were char acterized by higher rates of hydrogen peroxide decomposition and by more ox ygen evolution. The stabilized hydrogen peroxide formulation showed greater hydroxyl radical production relative to the unstabilized formulations. Fur thermore, hydroxyl radical production rates were greater at neutral pH than at the acidic pH regimes. The results suggest that when stabilized hydroge n peroxide is injected into the subsurface during in situ bioremediation, n aturally occurring minerals such as goethite may initiate Fenton-like react ions. While these reactions may prove to be toxic to microorganisms, they h ave the potential to chemically oxidize contaminants in soils and groundwat er. (C) 1999 Elsevier Science B.V. All rights reserved.