Solidification and Immobilization of Heavy metals in Soil using with nano-metallic Ca/CaO Dispersion Mixture

¹ Department of Environmental Sciences, Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, 562 Nanatsuka-Cho, Shobara City, Hiroshima 727-0023, Japan
² Environmental Research and Management Center, Hiroshima University, 1-5-3 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8513, Japan

^a Corresponding authors. (Y. Mitoma); Tel./fax: +81 8247 41748; E-mail addresses: mitomay@pu-hiroshima.ac.jp. (T. Okuda) Tel./fax: +81 824246195; Email address: okudaenv@hiroshima-u.ac.jp.

Abstract

In the present work, the use of nano-metallic calcium (Ca) and calcium oxide (CaO) dispersion mixture for the immobilization of heavy metals (As, Cd, Cr and Pb) in soil was investigated. With simple grinding, 85-90% of heavy metals immobilization could be achieved, while it could be enhanced to 98-100% by grinding with the addition of nano-metallic Ca/CaO dispersion mixture. By SEM-EDS elemental maps as well as semi-quantitative analysis observed that the amount of As, Cd, Cr and Pb measurable on soil particle surface decreases after nano-metallic Ca/CaO treatment. The leachable heavy metals concentrations were reduced, to the concentration lower than the Japan soil elution standard regulatory threshold, i. e., < 0.01 mg/l for As, Cd and Pb and 0.05mg/l for Cr. Whereas, the effect of soil moisture and pH on heavy metals immobilization was not much influenced. The results suggest that nano-metallic Ca/CaO mixture is suitable to be used for the gentle immobilization of heavy metals contaminated soil at normal moisture conditions.