Acid Enhanced Electrokinetic Remediation of a Contaminated Soil using Constant Current Density: Strong vs. Weak Acid

Abstract

The most typical enhancement for electrokinetic remediation (EKR) involves the neutralization of the alkaline front generated at the cathode by the addition of an acid to the catholyte. Although the use of strong and weak acids can be found in the literature, there is still a clear lack of reliable comparisons between them. This paper presents a comparison of the results obtained for a real lead contaminated soil treated by EKR enhanced with nitric or with acetic acid. The divergences that are usually observed in those experimental results obtained when using constant voltage drop are avoided here by the use of EKR with constant current intensity and the disposition in series of the soil lab columns. Important differences are observed in the behavior of the system when the acid was changed. The time needed to achieve the same metal recovery is more than 3 times longer for the nitric acid. A standard sequential extraction procedure was used to fractionate the lead concentration in the soil according to its mobility in a before- and after-treatment way. Regardless of these important differences observed in the remediation time, the fractionation results after the experiments were almost the same for the two acid enhanced EKRs.