A foundation for the risk-based treatment of gasoline-contaminated soils using modified Fenton's reactions

The relative oxidation of representative aromatic and aliphatic hydrocarbons found in gasoline was evaluated to provide the foundation for risk-based treatment of petroleum-contaminated soils and groundwater using modified Fenton's reagent (catalyzed hydrogen peroxide). Aromatic components of gasoline are considered more hazardous than the aliphatic fractions due to their higher mobility in the subsurface and their higher acute and chronic toxicities. Benzene, toluene, and mixed xylenes (BTX) were selected as aromatic compounds representative of unleaded gasoline, while nonane, decane, and dodecane (NDD) were used as model aliphatic compounds. The effects of hydrogen peroxide (H(2)O(2)) concentration, iron catalyst concentration, and pH on the degree of treatment of the model compounds were investigated using central composite rotatable experimental designs. Oxidation of the aromatic compounds required less iron and less H(2)O(2) than did oxidation of the aliphatic compounds, while proceeding more effectively at near-neutral pH. Greater than 95% of the BTX was treated at near-neutral pH using 2. 5% H(2)O(2) and 12.5 mM iron (III), while only 37% nonane, 7% decane, and 1% dodecane oxidation was achieved under the same conditions. The results show that the more toxic and mobile aromatic fraction was more effectively oxidized using less H(2)O(2) and more economical conditions, including near-neutral pH, compared to the aliphatic fraction. A process design based on treating only the aromatic fraction of petroleum may provide significantly lower costs when using modified Fenton's reagent for the treatment of contaminated soils and groundwater.