The treatment of soil contaminated with pentachlorophenol, trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl) benzenamine], hexadecine, and dieldrin (3,4,5,6,9,9-hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-dimethanonaphth[2,3-b]oxirene) using catalyzed hydrogen peroxide [H2O2 and iron(II)] was investigated in a soil of low development with organic C ranging from 2000 mg kg-1 to 16000 mg kg-1. Soil treatment was conducted at pH 3 with 240 and 400 mg L-1 iron additions and 120000 mg L-1 H2O2. Pentachlorophenol and trifluralin degradation rates decreased as a function of soil organic C content. However, soil organic C had no effect on the degradation rates of dieldrin and hexadecane. In addition, the four contaminants degraded at equal rates with soil containing organic C > 10000 mg kg-1. The ratio of first-order rate constants for contaminant degradation to hydrogen peroxide consumption (k(contaminant/k(H2O2) was used as an empirical measure of treatment efficiency. These ratios were sensitive to both the soil organic C content and to the concentration of iron added during treatment. The efficiency ratios were highest for treatment with no iron addition; these data suggest that iron minerals and H2O2 provide a system in which Fenton-like oxidations are catalyzed. The ability of iron minerals and H2O2 to oxidize pentachlorophenol was evaluated in goethite-, hematite-, and magnetite-silica sand at pH 3. Pentachlorophenol was degraded in the mineral-silica sand systems, which was verified by the loss of organic C and the stoichiometric recovery of chloride.
