Assessment of IrO2-Ta2O5|Ti electrodes for the electrokinetic treatment of hydrocarbon-contaminated soil using different electrode arrays

Abstract

In recent years, physicochemical processes such as the electrokinetic treatment (EKT) have gained acceptance as suitable alternatives to restore hydrocarbon (HC)-contaminated sites. EKT entails relatively short times, moderate operation costs and high removal efficiencies, being usually applied in heterogeneous soils with low permeability. In this work, 1D and 2D configurations, which require one sole pair of electrodes (facing each other) or six anodes around a central cathode (radial array), respectively, have been tested by employing Ti cathodes and anodes, as well as purpose-made IrO2-Ta2O5|Ti as dimensionally-stable anodes (DSA). The electrodes were partially introduced into a real Vertisol soil contaminated with heavy and intermediate fractions of HC. The distance between the cathode and each anode was of 6 cm at laboratory scale employing a 276 cm3 container with 2.2 kg of polluted soil and a 115 cm3 container with 87.8 g of polluted soil for the 2D and 1D arrays, respectively. From GC-MS analysis of fat and oil content, it has been found that the radial 2D array with one central Ti cathode and six IrO2-Ta2O5|Ti anodes performed better, reaching 58% HC removal near the anode applying 30 V and an electric field of 2.4 A cm-1. The effect of the treatment on the morphology of the anodes has been analyzed by SEM-EDX.