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Environmental Engineering Research 2004;9(2): 66-74. DOI: https://doi.org/10.4491/eer.2004.9.2.066
LEACHABILITY OF Pb-DOPED SOLIDIFIED WASTE FORMS USING PORTLAND CEMENT AND CALCITE : II. INVESTIGATION OF SEM/EDS
Dong Jin Lee
School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia
Corresponding Author: Dong Jin Lee ,Tel: +61-2-9385-5562, Fax: +61-2-9385-6139, Email: dongj7@empal.com
Received: November 6, 2003;  Accepted: April 2, 2004.
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ABSTRACT
This study was examined to assess leachability of Pb of solidified waste forms (SWF), which are prepared from lead nitrate, in conjunction with Portland cement and calcite. The effect of calcite in the solidification/stabilization of lead was particularly assessed. Compressive strength and leach were basically examined to investigate effects of lead and calcite on SWFs. SEM (scanning electron microscopy) was used for identifying mineral transformations and microstructure changes of the SWF during leaching processes. It was found that lead contaminated materials (KP5, KP10 and KP20) were highly leached. SEM showed that rapid release of lead at the attack of acid is mainly related to larger pores and their openness in cavities. The leached SWFs showed flaky substances of "honey-comb" microstrucre after initially leached. The flask substances were then disappeared after the fifth leach. It is noted, however that the SWFs containing calcite before leaching showed dense microstructure with portlandite appearing as "needle-shaped" silicate crystals. The surface of SWFs was initially covered with the "jungle-shaped" silicate crystals, and in the fifth leaching it was then covered with the thick "lumpy-shaped" crystals. These results as above confirm the slow diffusion of lead in the presence of calcite.
Keywords: Solidification/stabilization (S/S) | Calcite | Lead | SEM | Leachability
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