EVALUATING ACIDS AND CHELATING-AGENTS FOR REMOVING HEAVY-METALS FROM CONTAMINATED SOILS

the prevalence of heavy metal soil contamination at Army facilities po ses a serious threat to human health and the environment. To address t his problem, the US Army Engineer Waterways Experiment Station in Vick sburg. MS is developing a mobile pilot-scale soil washing treatment fa cility that can be used to remove metals from the contaminated soils. To support this project, laboratory studies were conducted on both aci ds and chelating agents to evaluate their ability in extracting heavy metals from contaminated soils. Eight soils contaminated with lead, ca dmium, and chromium were selected for use in this study. Contaminant c oncentrations in the various soils ranged from 4,000-30,000 mg/kg lead , 40-1,000 mg/kg cadmium, and 500-2,000 mg/kg chromium. The results in dicated that, before a full-scale clean-up in initiated, a preliminary investigation is needed to determine principal contaminants of concer n, their concentrations, and soil type followed by treatability studie s to determine optimal reagent and concentrations of reagents for clea nup. Specific results from this study also indicated that Cd was the e asiest metal to remove from soils followed by Pb and Cr. The results a lso suggested that the strong acids and chelating agents were both eff ective extracting agents, and the latter group of compounds may be mor e useful in soil washing because they are less harmful to the soil env ironment. Finally, higher initial concentrations of metal contaminants in the soil resulted in greater metal removal efficiencies using the reagents.