Strategies for powering electrokinetic soil remediation: A way to optimize performance of the environmental technology

The electro-kinetic remediation of soils using different powering strategies has been studied, in order to clarify which is the best strategy to couple solar powering with this remediation technology, in a context of developing more sustainable electrochemical remediation technologies. Direct powering from photovoltaic panels (Case a), application of constant electric fields with the same average value of Case a (Case b) and application of constant specific power with the same average value of Case a (Case c) have been compared. Results show an outstanding influence of the powering strategy on the removal efficiency of clopyralid (model of herbicide used in this work). The direct use of solar power profiles obtained the lowest removal efficiencies, which contrasts with the higher expected sustainability of this powering strategy. Reversion of pollutant transport overnight and extreme electric field values at noon help to explain the lower efficiency of this strategy. Evaporation mechanisms are promoted by operating at extreme large electric fields. In addition, harsher conditions lead to a higher negative soil affectation in terms of regions affected by extreme pHs, water contents and/or conductivities and to lower specific pollutant removals. Therefore, maximum efficiencies were found for Case b (constant electric potential gradient) with a total removal over 110 g kWh(-1) and only a slight affectation into the final soil properties.