Electrokinetic Remediation of Soils Polluted With Pesticides: Flushing and Fence Technologies

This research aims to compare electrokinetic soil technologies for the removal of pesticides from spiked soils using four different electrodes arrangements: rows of facing electrodes (flushing), a central cathode surrounded by six anodes (1C/6A), a central anode surrounded by six cathodes (1A/6C) and alternate circular distribution of anodes and cathodes (fence). In all cases, long term experiments of soils polluted with 2,4-dichlorophenoxyacetic acid (polar pesticide) and oxyfluorfen (non-polar pesticide) have been carried out in a bench-scale set-up completely automatized and operating on potentiostatic mode. Results show that the four strategies lead to very different results in terms of flushing fluid and pesticide mobilization. Flushing and fence strategies lead to higher water mobilization to cathodic wells, but the volume of water drained by gravity and evaporated are comparable and seem to depend on the water demand, resulting current intensity and temperature. Regarding herbicide transport, both, 2,4-D and oxyfluorfen are dragged towards the cathode wells by electroosmotic fluxes and transported to the anode wells by electromigration, being this last process much more important in the electroremediation of 2,4-D polluted soils. In addition to electrokinetic transport, pesticides are also transferred to atmosphere in nonnegligible amounts (at least 25 % of the pesticide).