Laboratory studies on remediation of chromium-contaminated soils

Soil washing processes and in-situ immobilization techniques have been ofte n-suggested technologies for remediation of soils contaminated with heavy m etals such as chromium. Laboratory batch extraction studies were conducted with synthetically contaminated soils [with Cr(VI)I to determine the abilit y of extractants such as 0.12 M Na4P2O7, 0.1 M NaF, and 1.0 M HCl to remove chromium from three types of soils with varying soil pH (5.8-8.1), organic matter (1.0-5.0%), and clay content (10-35%). Up to 73% of the total chrom ium present in the synthetically contaminated soil was removed by 0.12 M Na 4P2O7. The synthetically contaminated soils were also treated with FeSO4 an d NaOH solutions to immobilize chromium and investigated for leachability o f Cr by Cr-free water. Up to 80% of the chromium could be retained in the s oil following the immobilization process. The presence of soil organic matt er and clay content enhanced the immobilization of chromium in both chromiu m flushing and immobilization experiments.