Optimum Dose Of Lime And Fly Ash For Treatment Of Hexavalent Chromium–Contaminated Soil |
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Authors: | Konstantinos Kostarelos Daniela Reale Dimitris Dermatas Ennio Rao Deok Hyun Moon |
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Affiliation: | (1) Subsurface Remediation Center, Department of Civil Engineering, Polytechnic University, Brooklyn, NY, USA;(2) W. M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ, USA |
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Abstract: | The presence of hexavalent chromium, Cr(VI), in soil is an environmental concern due to its effect on human health. The concern arises from the leaching and the seepage of Cr(VI) from soil to groundwater. In this paper, a stabilization technology to prevent this problem was simulated on an artificial soil contaminated with hexavalent chromium. The process is a physico-chemical treatment in which the toxic pollutant is physically entrapped within a solid matrix formed by the pozzolanic reactions of lime and fly ash to reduce its leachability and, therefore, its toxicity. This paper presents the optimum ratio of fly ash and lime in order to stabilize artificial soils contaminated with 0.4 wt.% of Cr (VI) in a brief term process. The degree of chromium released from the soil was evaluated using a modified Toxicity Characteristic Leaching Procedure (TCLP) by US Environmental Protection Agency (EPA). Overall, experimental results showed reduced leachability of total and hexavalent chromium from soils treated with both fly ash and quicklime, and that leachability reduction was more effective with increasing amount of fly ash and quicklime. Stabilization percentages between 97.3% and 99.7% of the initial chromium content were achieved, with Cr(VI) concentration in the TCLP leachates below the US EPA limit for chromium of 5 mg/l. Adequate treatment was obtained after 1 day of curing with just 25% fly ash and 10% quicklime. |
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Keywords: | hexavalent chromium TCLP contaminated soil groundwater pollution soil remediation stabilization fixation |
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