HEAVY METAL (Cu, Pb, AND Zn) REMOVAL FROM PIEDMONT SOILS
E.N. Njikam, M.R. Reddy and W.A.R.N. Fernando
Department of Natural Resources and Environmental Design, North Carolina A &T State University, Greensboro, NC 27411
Abstract: The contamination of soils with heavy metals remains a serious problem across the globe and the clean up of these soils remains a difficult task. One possible technique is ex-situ washing of the contaminated soils with chelants. The strong transition metal chelant [S,S] stereoisomer of ethylene dissucinic acid ([S,S]-EDDS) which is biodegradable, and a modified cyclodextrin Carboxymethyl-ß-cyclodextrin (CMCD), were investigated for their applicability for the washing of heavy metals from contaminated soils. An Enon sandy loam soil (fine, mixed, thermic Aquic, Hapludults) from the North Carolina Piedmont region was loaded with 1mM of Cu, Pb, and Zn. Batch experiments were conducted to determine the extraction efficiency of S,S-EDDS and CMCD. All washings were carried out at pH 7. Data showed that [S,S]-EDDS removed 69%, 65% and 54% of Cu, Pb, and Zn, respectively whereas CMCD removed 2.6%, 1.7% and 8.5% of Cu, Pb, and Zn, respectively. Overall, the extraction efficiency of [S,S]-EDDS was significantly (p=0.05) higher than that of CMCD. This difference can be attributed to the complexation strengths of these extractants with the heavy metals. The removal of Cu, and Zn, by [S,S]-EDDS was significantly different (p=0.05). Heavy metal removal was also found to be independent of the extractant concentration. The results of this study provide an insight into the remediation of heavy metal contaminated soils using these biodegradable and cost-effective chelants.
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