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Abatement of Sorbed Crude Oil by Heterogeneous Fenton Process Using A Contaminated Soil Pre-Impregnated with Dissolved Fe(II) and Humic Acid

Xu, Jinlan, Li, Xiumin, Huang, Tinglin
Soil & sediment contamination 2017 v.26 no.2 pp. 195-209
humic acids, hydrogen peroxide, hydroxyl radicals, iron, oxidation, oxygen production, pH, petroleum, polluted soils, response surface methodology
Dissolved Fe(II) and humic acid (HA) were pre-impregnated into contaminated soil to catalyze hydrogen peroxide to remove crude oil (CO). The effects of parameters such as initial Fe(II), HA and H ₂O ₂ concentrations on the oxidation of total petroleum hydrocarbon (TPH) were investigated using response surface methodology based on Box–Behnken design. The rate of hydrogen peroxide decomposition is decreased by pre-impregnating with dissolved Fe(II) + HA compared with only pre-impregnated Fe(II) and modified Fenton (MF). Oxygen evolution is the predominant route of hydrogen peroxide decomposition at natural pH. Unlike O ₂ evolution, the kinetics of hydroxyl radical (OH •) production are clearly uncoupled from H ₂O ₂ decay in these systems. The steady-state hydroxyl radical production rate is higher in the systems with pre-impregnated dissolved Fe(II) and HA, and more significance is the decrease in detectable TPH (70.84% removal efficiency) when soil is pre-impregnated with dissolved 25 mM Fe(II) + 0.7 mg/mL HA, and with the application of 700 mM H ₂O ₂, possibly due to hydrogen peroxide catalyzed by the iron of this complex (CO-HA–Fe(II)) producing hydroxyl radical in close proximity to the CO. Meanwhile, the removal efficiency of C ₂₁–C ₃₀ is up to 65.69%, which is 2.6 times higher than that of the MF (25.52%).