Remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil with double dielectric barrier discharge plasma technology: influencing parameters

Abstract A double dielectric barrier discharge (DDBD) plasma reactor was used for the remediation of simulated contaminated soil by a mixture of two, three and four rings PAHs i.e. naphthalene (Nap), phenanthrene (Phe) and pyrene (Pyr). Various influencing parameters such as peak-to-peak applied voltage, soil moisture, oxygen to nitrogen ratio (O2:N2) of carrier gas and soil depth in the reactor were investigated. The results illustrate that with an initial PAH concentration of 100 mgkg-1the remediation efficiency increased by 27-30% when the applied voltage was increased from 28 to 40 kV. When the moisture content had been raised from 1.7% to 4% the remediation efficiency of Nap, Phe and Pyr increased from 89.55, 84.51 and 83.36% to 96.32, 89.08 and 88.59% respectively. However, further increase in moisture content decreased the PAHs remediation efficiency. With increasing oxygen to nitrogen ratio, the remediation efficiency of PAHs increased up to 20%. Higher oxygen concentrations in DDBD reactor has beneficial effect due to the generation of increased oxygenated species such as ozone, atomic oxygen and nitrogen oxides in discharge zone. When the soil thickness in the reactor was increased from 1 mm to 3 mm - due to decreased penetration of active species into the deeper zone of the soil - the remediation efficiencies decreased by 10%. Compared to ozonation the treatment of PAHs in the DDBD reactor resulted in higher remediation efficiencies. This is due to the generation of more active species in case of DDBD plasma treatment. The study demonstrates that DDBD plasma is a promising technology for remediation of heavily contaminated sites of PAHs due to its high remediation efficiency and robustness.