Selectivity for modified Fenton's oxidation of crude oil in soils

Abstract

ABSTRACTModified Fenton’s (MF) operations affect the selectivity for MF oxidation of crude oil vs. soil organic matter (SOM) in contaminated soils; however, the mechanisms are not known. MF oxidation was tested in the lab to treat two crude oil-contaminated soils using three MF operations: (1) increasing hydrogen peroxide (H2O2) concentration, (2) enhancing iron (Fe(II)) levels, and (3) stepwise addition of H2O2 rather than a single exposure. The experiments demonstrated that the selectivity for MF oxidation of crude oil in the two soils significantly decreased with a rise in H2O2 and Fe(II) concentrations. The total petroleum hydrocarbon (TPH) removal efficiency in the two soils was between 40% and 50% when the concentration of H2O2 was greater than 1100 mM. The limited oxidation of crude oil might possibly be attributed to poor selectivity for MF oxidation of crude oil in soils when the concentration of H2O2 exceeded 1100 mM. The results indicated that sufficient Fe(II) is important for selectively removing TPH. Notably, a 25% higher removal of TPH (51%–58%) was observed in the two soils after stepwise dosing with H2O2 compared with a one-step addition. Data indicated a distinct selectivity for MF oxidation of crude oil vs. SOM by stepwise addition of H2O2. In addition, the findings demonstrated a distinct selectivity for MF oxidation of SOM vs. crude oil when rapid decomposition of H2O2 was present.