Simultaneous elution of heavy metals and organic compounds from soil by cyclodextrin

A major factor complicating the cleanup of many sites is the co-occurrence of organic compounds and heavy metals, so-called mixed wastes. We investigated the ability of cyclodextrin to simultaneously remove heavy metals and low-polarity organic compounds from contaminated soil. The results of the experiments showed that cyclodextrin could greatly enhance the simultaneous desorption and elution of the model organic compound (phenanthrene) and the model heavy metal (cadmium) from the three soils examined. The soils consisted of a sandy aquifer material containing minimal organic carbon and clay, a soil with a relatively high clay content (10.2%), and a soil with a relatively high organic carbon content (1.4%). Elution of phenanthrene that was in contact with soil for 38 days exhibited greater tailing than the unaged phenanthrene when water was the flushing solution, indicating greater resistance to desorption and removal. Conversely, the elution curves for the aged and unaged phenanthrene were essentially identical for the cyclodextrin solution. Aging appeared to have no significant impact on cadmium elution behavior for either solution. In a majority of cases, the measured enhanced-removal factors for the contaminant elution curves were similar to the values expected based on complexation/solubilization theory.