Removal of PAHs and pesticides from polluted soils by enhanced electrokinetic-Fenton treatment

• The electrokinetic-Fenton technology has been used for the removal of PAHs and pesticide form soil.
• The metal precipitation was demonstrated as the main drawback of the treatment.
• The addition of citric acid enhances the treatment efficiency increasing the reached removals.
• After the electrokinetic-Fenton using citric acid the treated soil showed low phytotoxicity levels.

In this study, electrokinetic-Fenton treatment was used to remediate a soil polluted with PAHs and the pesticide pyrimethanil. Recently, this treatment has emerged as an interesting alternative to conventional soil treatments due to its peculiar advantages, namely the capability of treating fine and low-permeability materials, as well as that of achieving a high yield in the removals of salt content and inorganic and organic pollutants.In a standard electrokinetic-Fenton treatment, the maximum degradation of the pollutant load achieved was 67%, due to the precipitation of the metals near the cathode chamber that reduces the electro-osmotic flow of the system and thus the efficiency of the treatment. To overcome this problem, different complexing agents and pH control in the cathode chamber were evaluated to increase the electro-osmotic flux as well as to render easier the solubilization of the metal species present in the soil. Four complexing agents (ascorbic acid, citric acid, oxalic acid and ethylenediaminetetraacetic acid) in the Fenton-like treatment were evaluated. Results revealed the citric acid as the most suitable complexing agent. Thereby its efficiency was tested as pH controller by flushing it in the cathode chamber (pH 2 and 5). For the latter treatments, near total degradation was achieved after 27 d.Finally, phytotoxicity tests for polluted and treated samples were carried out. The high germination levels of the soil treated under enhanced conditions concluded that nearly complete restoration was achieved.