Electrokinetic removal of petroleum hydrocarbon from residual clayey soil following a washing process

This study investigates total petroleum hydrocarbon (TPH) removal from residual clayey soil, after a washing procedure, using an electrokinetic process. Eight electrokinetic experiments were carried out to investigate the characteristics of TPH removal. When 0.1 M MgSO₄ or 0.1 M NaOH was used as an electrolyte, the electric current rapidly increased within the first 100 or 200 h, respectively. A negatively charged soil surface resulted in a more negative zeta potential and greater electroosmotic flow toward the cathode. Therefore, the accumulated electroosmotic flow (EOF) when using 0.1 M NaOH as the anolyte-purging solution was higher than when using 0.1 M MgSO₄. Although the energy consumption for the two purging solutions was similar, the efficiencies of TPH removal when 0.1 M MgSO₄ and 0.1 M NaOH with surfactant were used were 0 and 39, respectively, because the electroosmotic flow rate increased with TPH removal efficiency. When 5 isopropyl alcohol (IPA) was used as a circulation solution, the electric current increased but the TPH removal was similar to that using water. In terms of energy consumption, the use of a surfactant-enhanced electrokinetic process with NaOH as electrolyte was effective in removing TPHs from low-permeability soil.