Reducing Agents Enhanced Electrokinetic Soil Remediation (EKSR) for Heavy Metal Contaminated Soil

Abstract

Reducing agents-Enhanced electrokinetic Soil Remediation (EKSR) was performed for the removal of chromium (Cr), cobalt (Co) and nickel (Ni) from contaminated soil. The reducing agents oxalic acid and ascorbic acid were investigated under constant voltage gradient (2.0 V/cm), current changes, pH, redox potential, concentration changes and removal performance of Heavy Metals (HMs). The results indicated that the reducing agents were effective in the desorption of metals at the cathode with catholyte conditioning pH. The removal performance of heavy metals in reducing agents-enhanced EKSR was about 2-2.5 times more than in unenhanced treatment. The amount of HMs migrated to the catholyte was more than in the anolyte, which might be evidenced that the negatively charged metal-oxalate/ascorbate complexes migrated via electroosmosis. However, positively charged HM-oxalate/ascorbate complexes and free HM cations moved to the catholyte by electromigration action. Furthermore, the mass balance and cost analysis were performed for all EKSR experiments after 20 days of operation. The energy consumption per cubic meter of treated soil was 1104-18496 kWh/m3 and the total cost was about US$ 110.4-2095, including the cost of the enhancing agents. The study demonstrated that reducing agents-enhanced EKSR is cost-effective and efficient in the removal of HMs from contaminated soil.