Study on remediation of phenanthrene contaminated soil by pulsed dielectric barrier discharge plasma: The role of active species

Abstract

Polycyclic aromatic hydrocarbons (PAHs), which are detrimental to the environment and human health, are frequently found in soils. A pulsed dielectric barrier discharge (DBD) plasma system was employed for the remediation of phenanthrene (PHE)-contaminated soil. The role of active species was investigated by evaluating the effects of air flow rate and discharge voltage on the removal efficiency for their influence on the formation and transfer of these active species produced during plasma treatment. At an air flow rate of 0.6L/min and a voltage of 110V, the removal rate could reach 87.3% in 20min with an energy efficiency of 0.01mg/kJ. Radicals including O3, O, OH, OH+, N2∗, N2O+, and NO were identified by optical emission spectroscopy (OES). The contribution of ozone towards degradation was investigated by comparing ozone treatment with plasma treatment: ozone treatment was observed to account for 82.8% of the whole oxidation process. Theoretical calculations by Gaussian were employed to understand the degradation processes in combination of FTIR, GC–MS, and IC analysis and a possible degradation pathway of PHE was also proposed. Plasma technology was observed to be able to improve the biodegradability of PHE-contaminated soils. It was suggested that plasma treatment could be followed up by bio-remediation by taking advantage of the fast and effective plasma treatment (83.7% of PHE was removed in 20min) for heavily polluted organic soils.