Remediation of soil contaminated by NAPLs using modified Fenton reagent: application to gasoline type compounds

BACKGROUND A modified Fenton reaction was used for the remediation of a soil polluted with ethylbenzene (EB), a toxic compound in gasoline. Fe(III) and trisodium citrate were used as catalyst and chelating agent, respectively. pH remained near‐neutral during the process. Contaminant, chelating agent, oxidant and iron in solution were monitored at all times. A comparison between slurry (aqueous‐organic and soil phases) and liquid systems (aqueous‐organic phases) was carried out. RESULTS EB conversion increased as H2O2/EB ratios rose, for a given EB concentration. Furthermore, the contaminant conversion was decreased as the EB concentration increased, at a fixed H2O2/EB ratio. This indicates that the reaction takes place in the aqueous phase, with the oxidation rate limited by the EB concentration in this phase. The presence of soil produces a better contact between phases, enhancing EB transport from the organic to the aqueous phase. As EB was oxidized in the aqueous phase, the toxicity of this phase decreased, because non‐toxic oxidation byproducts were obtained. The chelant was oxidized, but not totally mineralized. This chelant oxidation produces precipitation of the catalyst from the aqueous phase. CONCLUSIONS The results suggest the suitability of modified Fenton reaction to remediate contaminated soils with non‐aqueous phase liquids. © 2014 Society of Chemical Industry