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

The efficiency of chromium and arsenic removal using electromigration was i nvestigated with three different soils. The removal of the pollutants was p erformed in alkaline conditions using the generation of hydroxide ions at t he cathode. The influence of adding an oxidizing agent is shown. The optimi sation of the experimental conditions was conducted in laboratory tests. Th e experiments were performed with different soils : a kaolinite, a soil art ificially polluted with trivalent chromium and an industrial site soil cont aminated with arsenic. Tt was found to be possible to obtain a quantitative removal of chromium and arsenic with the electrokinetic process, but the s uccess 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 a lkaline and oxidizing environment allowed the elimination of all of this po llutant after 18 days in the case of a spiked kaolinite, 27 days being nece ssary to remove 74 % of chromium in the spiked soil. For arsenic, the elimi nation of As(V) could be realized from the soil in alkaline conditions. Exp eriments with the industrial site soil showed that the use of an oxidizing agent accelerates arsenic electromigration. Electromigration in alkaline an d oxidizing conditions allowed the complete remediation of the tested soils and represents an original technique for the removal of chromium and arsen ic.