KEROSENE CONTAMINATED SOIL TREATMENT BY NONTHERMAL ATMOSPHERIC PLASMA DISCHARGE
OGNIER Stéphanie, REDOLFI Michael, MAKLHOUFI Camel and CAVADIAS Siméon
UPMC Univ Paris 06, Laboratoire de Génie des Procédés Plasmas et Traitement de
Surfaces, 11 rue Pierre et Marie Curie, 75231 Paris Cedex France
Stephanie-ognier@enscp.fr
Abstract
A great number of techniques have been developed to treat soils polluted by nonaqueous phase liquids (NAPLs). Among the various methods, the combination of chemical
oxidation and biodegradation appears as a promising route for soil remediation. Actually, the
partial oxidation of pollutants enhances their solubility (bioavailability) and their
biodegradability allowing bio-remediation, considered as the least damaging and most
environmentally acceptable technique, to proceed faster and more efficiently. However, the
environmental and energetic cost of the oxidation step is still too high. In fact, the
conventional oxidation techniques (ozonation, use of chemical reagent such as H2O2, Fenton
reagent, permanganate ion…) suffer from major drawbacks that are a high consumption of
chemical reagents and/or a high energetic cost. There is therefore a need to develop new
environment friendly oxidation technologies. Non-Thermal Plasma (NTP) atmospheric
pressure discharges could be a new efficient oxidation technique. Electrical discharges
generated in air allow the creation of a chemically reactive medium by producing active
species (ions, radicals, excited molecules, etc…) able to oxidise the pollutants. Compared to
the other oxidation processes, this technique presents a great interest because the gaseous
oxidant species (O3, singlet oxygen, O°…) are generated directly in the bulk of the soil to be
treated, preventing the use of liquid chemical reagents with poor diffusion.
In the present work, the applicability of a non-thermal atmospheric plasma discharge
technique for the treatment of soils contaminated by hydrocarbon pollutants was investigated.
A soil polluted by kerosene (74 mg.kg-1) was treated in a dielectric barrier discharge reactor at
atmospheric pressure using air as sweep gas flow. The soil was deposited as a thin layer
between the two electrodes where the discharge takes place. The average discharge power
was 10 W. The concentrations of kerosene components in the soil were determined by GCFID analyses of soil extracts. The removal percentages varied from 25 to 88% for treatment
times ranging from 4 to 12 minutes. The analyses of soils showed also that the decrease of
kerosene components was accompanied by the formation of new organic compounds in the
soil in non negligible quantities. Some of them could be identified by gas chromatography
coupled to mass spectrometry as oxidised hydrocarbon compounds containing alcohol and/or
acid functional groups. During the soil treatment experiments, analyses of the exhaust gas
phase were also performed. They showed that CO, CO2, and total hydrocarbons represented
less than 6 % of carbon balance, indicating that the transfer of organic contaminants from
solid phase to gas phase was negligible.
Finally, this study showed that the treatment of a polluted soil by plasma discharge
resulted in the partial oxidation of kerosene in the soil matrix. Plasma technology appears
therefore as a promising oxidation technique to be used in coupling with bioremediation.