Optimum conditions for the Fenton's reagent treatment of pentachlorophenol in a simplified soil system

Abstract

The optimum conditions for the Fenton's reagent treatment of pentachlorophenol-contaminated silica sand was investigated as a basis for the in situ decontamination of surface soils. Fenton's reagent consists of hydrogen peroxide and ferrous iron which produces hydroxyl radical, a strong, nonspecific oxidant. In the presence of excess hydrogen peroxide, maximum pentachlorophenol degradation rates were observed at ferrous sulfate concentrations of 0.040% to 0.048% as Fe in the soil solution. The optimum iron concentration did not vary as a function of hydrogen peroxide dose or initial pentachlorophenol concentration. The hydrogen peroxide decomposition rate was directly proportional to the iron concentration, but was unaffected by initial pentachlorophenol concentration. The apparent first order rate constant for pentachlorophenol degradation decreased rapidly as a function of the initial pentachlorophenol concentration from 10 mg/kg to 10,000 mg/kg in the soil. A pilot study in which 250 mg/kg pentachlorophenol was treated suggests that Fenton's reagent treatment of contaminated soil may be cost competitive with other clean-up methods.