Treatment of Pb-contaminated soil by electrokinetics: Enhancements by varying voltage, chelant, and electrode material

Abstract

This work examines the removal of lead (Pb) from artificially contaminated soils (1000 mg/kg Pb) using the Electrokinetic Remediation (EKR) technique. Operating parameters, including periodic voltage gradient, electrolyte amendments with ethylenediaminetetraacetic acid (EDTA) and a non-ionic surfactant (Tween 80), and type of electrode material were investigated. Results indicated that a high voltage gradient (2.5 V/cm), in conjunction with EDTA as electrolyte, and stainless-steel electrodes favored the overall removal process. Pb removal by selected electrolytes was in order EDTA (65 %) > Distilled water (64.1 %) > Tween 80 (6.2 %). Visual Minteq v.3.1 software was employed to predict the chemical equilibrium of different chemical species of Pb against pH. Results confirmed that when EDTA was used as an electrolyte, the [Pb-EDTA]2− complex predominated over the Pb(OH)2 complex at an alkaline pH, resulting in more removal. Findings suggested that stainless steel was a better alternative to graphite with respect to removal efficiency and corrosion effect at the anode. Considering the maximum Pb removal with EDTA at higher voltage, the energy consumption was also maximum (78.3KWh/m3). Nevertheless, the economic evaluation suggested that the cost per gram removal of Pb was lowest in this experiment (8 US$/g Pb) and, thus, can be considered for practical applications to treat the Pb-contaminated soils.