The use of Fenton's reagent for completely oxidizing hexadecane and benzo[a]pyrene (BAP) to their thermodynamic endpoints, carbon dioxide and water, was investigated. Confirmation of oxidation was determined by using 14C-labeled compounds and recovering the evolved 14CO2. Experimental design procedures incorporating factorial matrices were used to determine optimal treatment conditions based on three variables at five levels. Oxidative treatments were conducted in silica sand and a Palouse Loess soil. Silica sand experiments investigated the effects of slurry volume, hydrogen peroxide concentration, and iron (II) concentrations. In the Palouse soil systems, the variables investigated included slurry volume, hydrogen peroxide concentration, and pH.
Aggressive conditions were required for oxidizing hexadecane and benzo[a]pyrene in silica sand, which were related to their slow rates of desorption. Under optimal conditions, 74% of the hexadecane and 73% of the benzo[a]pyrene were oxidized to CO2 and H2O. In both cases, optimal treatment conditions entailed the use of 14,700 mM hydrogen peroxide. Treatment conditions differed in that slurry volumes of 4.0 x F.C. and an iron (II) concentration of 25 mM were required for hexadecane oxidation while slurry volume of 0.25 x F.C. and an iron (II) concentration of 5 mM were required for the oxidation of benzo[a]pyrene.
In soils, the presence of organic matter and other species that compete for and quench hydroxyl radicals require additional reagents to promote oxidative treatment. Under optimal conditions, 67% of the hexadecane and 78% of the benzo[a]pyrene were oxidized to CO2 and H2O. The optimal conditions, 67% of the two compounds was found at the same treatment conditions. These conditions consisted of 14,700 mM hydrogen peroxide, a slurry volume of 20 x field capacity and a pH of 8.0. More importantly, the ability of mineral catalyzed hydrogen peroxide for oxidizing contaminants at a neutral pH was documented.
The results show that hydrocarbons common to diesel, motor oil, and other refractory petroleum products may be oxidized to CO2 and H2O using Fenton's reagent.