USE OF IRON MINERALS IN OPTIMIZING THE PEROXIDE TREATMENT OF CONTAMINATED SOILS

The treatment of silica sand contaminated with pentachlorophenol (PCP) using the standard Fenton's reagent procedure, sequential addition of iron (II) and H2O2, and a goethite (alpha-FeOOH)-H2O2 system was investigated. The standard Fenton's procedure oxidized 10 mg/L soluble PCP, but was ineffective in degrading 10 mg/kg or 250 mg/kg particulate and sorbed PCP in silica sand. Sequential addition of excess reagents(480 mg/L iron (II) and 7% H2O2) degraded particulate and sorbed PCP, but with high stoichiometric H2O2 requirements. The most efficient system for PCP degradation was the H2O2-goethite system. Although the experimental system used in this research lacks the complexity of natural soils, the data suggest that under proper conditions, the iron oxyhydroxide fractions of the soil matrix catalyze Fenton-like reactions, and that these mineral-catalyzed reactions may be the most efficient mechanism for the catalyzed hydrogen peroxide treatment of contaminated soils.