Effect of Contaminant Hydrophobicity in the Treatment of Contaminated Soils by Catalyzed H₂O₂ Propagations (Modified Fenton’s Reagent)

Abstract

The effect of contaminant hydrophobicity on hydrogen peroxide dosage requirements in the treatment of contaminated soils using catalyzed H₂O₂ propagations (CHP) was investigated. Four chlorobenzenes of varied hydrophobicity, but equal reactivity with hydroxyl radical, were sorbed to a natural soil and treated with mineral, catalyzed CHP. The oxidation rates of 1,2,3-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene were measured and compared to desorption rates, and the effects of hydrogen peroxide concentration and slurry volume were evaluated using a central composite rotatable experimental design. Response surfaces were generated to determine optimum conditions for chlorobenzene degradation and reaction stoichiometry. All chlorobenzenes were degraded to below detection limits, but hydrogen peroxide requirements increased with a greater degree of chlorine substitution. Furthermore, significantly higher hydrogen peroxide concentrations were required for >99.9% degradation of hexachlorobenzene, resulting in a much higher hydrogen peroxide requirement compared to the other chlorobenzenes. The higher hydrogen peroxide requirement for hexachlorobenzene degradation was likely due to the need to overcome sorption limitations. The results of this research show that contaminant hydrophobicity may be the primary factor controlling hydrogen peroxide dosages in the treatment of contaminated soils by CHP.