Mineralization of a sorbed polycyclic aromatic hydrocarbon in two soils using catalyzed hydrogen peroxide

• Published in: Water research (Oxford) 2002-10, Vol.36 (17), p.4283-4292
• Main Authors: Watts, Richard J., Stanton, Patrick C., Howsawkeng, Jimmy, Teel, Amy L.
• Format: Article
• Language: English
• Subjects: Applied sciences; Benzo[ a]pyrene; Catalyzed hydrogen peroxide; Crystallization; Decontamination. Miscellaneous; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Fenton's reagent; Hydrocarbons; hydrogen peroxide; Hydrogen Peroxide - chemistry; Hydroxyl radicals; Iron - chemistry; Oxidants - chemistry; Oxidation-Reduction; Oxidations; Pollution; Pollution, environment geology; Polycyclic Aromatic Hydrocarbons - chemistry; Soil - analysis; Soil and sediments pollution; Soil Pollutants; Soil remediation
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(02)00142-2

Hydrogen peroxide (H 2O 2) catalyzed by soluble iron or naturally occurring soil minerals, (i.e., modified Fenton's reagent) was investigated as a basis for mineralizing sorbed and NAPL-phase benzo[ a]pyrene (BaP), a hydrophobic and toxic polycyclic aromatic hydrocarbon, in two soils of different complexity. 14C-Benzo[ a]pyrene was added to silica sand and a silt loam soil, and mineralization was investigated using three-level central composite rotatable experimental designs. The effects of H 2O 2 concentration, slurry volume, and iron(II) amendment were investigated in the silica sand systems. In a Palouse loess silt loam soil, the variables included H 2O 2 concentration, slurry volume, and pH, with H 2O 2 catalyzed by naturally occurring iron oxyhydroxides. Regression equations generated from the data were used to develop three-dimensional response surfaces describing BaP mineralization. Based on the recovery of 14C-CO 2, 70% BaP mineralization was achieved in the sand within 24 h using 15 M H 2O 2 and an iron(II) concentration of 6.6 mM with a slurry volume of 0.3×the field capacity of the sand. For the silt loam soil, 85% mineralization of BaP was observed using 15 M H 2O 2, no iron amendment, and a slurry volume of 20×the soil field capacity. The balance of the radiolabeled carbon remained as unreacted BaP in the soil fraction. Gas-purge measurements over 5 d confirmed negligible desorption under nontreatment conditions. However, oxidation reactions were complete within 24 h and promoted up to 85% BaP mineralization, documenting that the natural rate of desorption/dissolution did not control the rate of oxidation and mineralization of the BaP. The results show that catalyzed H 2O 2 has the ability to rapidly mineralize sorbed/NAPL-phase BaP and that partitioning, which is often the rate-limiting factor in soil remediation, does not appear to limit the rate of vigorous Fenton-like treatment.