Application of advanced oxidation processes and electrooxidation for the remediation of river sediments contaminated by PAHs.

This study was performed to assess and compare the effectiveness of electrochemical oxidation and chemical oxidation with hydrogen peroxide and modified Fenton's reagent for the remediation of sorbed polycyclic aromatic hydrocarbons (PAHs) in river sediments. The initial total PAH concentration in the sediment samples ranged from about 1032.8 mg/kg(DW) to 2816.4 mg/kg(DW) and a 90% degradation was required to meet the remediation goals. Several tests were performed at laboratory scale, the removal efficiency being evaluated in terms of contaminant removal and of ecotoxicity. The chemical oxidation tests resulted in about 95% total PAH degradation, when a sufficient oxidant dose was used (i.e. about 50-100 mmol of H2O2 per 30 g sediment samples), but proved to increase the ecotoxitity of the treated sediments significantly. Electrooxidation showed degradation efficiencies above 90%, with a negligible residual toxic effect, after 4-week treatments at constant voltage gradients of 1-2 V/cm. This technique seems to be effectively applicable either for the in situ or for the ex situ recovery of the target sediments.