Industrial site soils contaminated with arsenic or chromium:: Evaluation of the electrokinetic method

The efficiency of chromium and arsenic removal using electromigration was investigated with three different soils. The removal of the pollutants was performed in alkaline conditions using the generation of hydroxide ions at the cathode. The influence of adding an oxidizing agent is shown. The optimisation of the experimental conditions was conducted in laboratory tests. The experiments were performed with different soils : a kaolinite, a soil artificially polluted with trivalent chromium and an industrial site soil contaminated with arsenic. Tt was found to be possible to obtain a quantitative removal of chromium and arsenic with the electrokinetic process, but the success of the process is governed by the control of alkaline pH and by the injection of hypochlorite in the soil sample. For chromium, the use of an alkaline and oxidizing environment allowed the elimination of all of this pollutant after 18 days in the case of a spiked kaolinite, 27 days being necessary to remove 74 % of chromium in the spiked soil. For arsenic, the elimination of As(V) could be realized from the soil in alkaline conditions. Experiments with the industrial site soil showed that the use of an oxidizing agent accelerates arsenic electromigration. Electromigration in alkaline and oxidizing conditions allowed the complete remediation of the tested soils and represents an original technique for the removal of chromium and arsenic.