Chromium removal from contaminated soils

The time-dependence of chromium extraction with HCL was studied from a chernozem and a humous alluvial soil contaminated with Cr-III and Cr-VI. In case of Cr-III, the extraction is a very slow process, the efficiency of removal is only 30% after three days. On the other hand, in case of Cr-VI, the extracted metal content increased sharply during the first few minutes and the efficiency of extraction reached 90%. After this time the chromium re-entered into the solid phase. We found that Cr-VI is partly reduced to Cr-III by organic matters present in the soil samples. The extraction of both chromium species is the result of overlapping reactions that needs further clarification.