Electrokinetic treatment of soils contaminated by tannery waste

Electrokinetic remediation of metal contaminated soils is strongly affected by soil-type and chemical species of the contaminants. This paper investigates, at the laboratory scale, the feasibility of using electrokinetics for the in situ remediation of a metal-contaminated soil in relation to metal speciation. Existing soil contamination at the site was caused by the effluents from tannery shops that used metallic salts in their industrial processes and whose activity ceased decades ago. Chromium, zinc, lead and copper can still be found at considerable concentrations in the soil. Over time, washing by the rain and aging has changed the chemical distribution of the metals in the soil and nowadays they concentrate in the most stable fractions. Limited mobilization was achieved during normal electrodialysis tests. The use of oxidants (sodium persulfate) as electrolyte additives yields noticeable higher mobilization of the metals. Post treatment fractionation studies show that to some extent, metal is being transferred from the residual fraction to the rest and into solution.