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Environmental Engineering Research 2006;11(1): 54-61. DOI: https://doi.org/10.4491/eer.2006.11.1.054
THE MICROSTRUCTURE OF Pb-DOPED SOLIDIFIED WASTE FORMS USING PORTLAND CEMENT AND CALCITE
Heechan Yoo1, and Dongjin Lee2
1Department of Environmental Engineering, The Catholic University of Korea, 43-1 Yeokgok-dong, Wonmi-gu, Bucheon-si, Gyeonggi-do, 420-743, South Korea
2School of Environmental Engineering, Ajou University, San 5, Wonchun-dong, Youngtong-gu, Suwon,Gyeonggi-do, 443-749, South Korea
Corresponding Author: Dongjin Lee ,Tel: +82-31 -219-2410, Fax: +82-31 -215-5145, Email: dongj7@empal.com
Received: June 7, 2005;  Accepted: February 2, 2006.
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ABSTRACT
An electron probe microanalysis (EPMA) investigation can provide quantitative and qualitative insight into the nature of the surface and bulk chemistry on solidified waste forms(SWF). The proportion of Pb in grain areas is below 0.3 wt. %, and the proportion near the border of the grain slightly increases to 0.98 u7. % but in the inter-particle areas farther from the grain, the concentration of Pb markedly increases. It is apparent that very little Pb diffuses into the tricalcium silicate(CjS) particles and most of the Pb exists as precipitates of sulfate, hydroxide, and carbonate in the cavity areas between C;S grains. Calcite additions on Pb-doped SWF are also observed to induce deeper incorporation of lead into the cement grains with EPMA line-analysis of cross-sections of cement grains. The line-analysis reveals the presence of 0.2-5 weight % Pb over 5 um from cement grain boundaries. In the inter-particle areas, the ratio of Ca, Si, Al and S to Pb is relatively similar even at some distance from the grain border and the Pb (wt. %) ratio is reasonably constant throughout the whole inter-particles area. It is apparent that the enhanced development of C-S-H on addition of calcite can increasingly absorbs lead species within the silica matrix.
Keywords: solidification | CaC03 | Lead | EPMA | Calcium-Silicate-Hydrate (C-S-H)
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