Laboratory studies on remediation of chromium-contaminated soils

Soil washing processes and in-situ immobilization techniques have been often-suggested technologies for remediation of soils contaminated with heavy metals such as chromium. Laboratory batch extraction studies were conducted with synthetically contaminated soils [with Cr(VI)I to determine the ability 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 chromium present in the synthetically contaminated soil was removed by 0.12 M Na4P2O7. The synthetically contaminated soils were also treated with FeSO4 and NaOH solutions to immobilize chromium and investigated for leachability of Cr by Cr-free water. Up to 80% of the chromium could be retained in the soil following the immobilization process. The presence of soil organic matter and clay content enhanced the immobilization of chromium in both chromium flushing and immobilization experiments.