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Cement stabilization of heavy-metal-containing wastes

By
C. Annette Johnson
C. Annette Johnson
Swiss Federal Institute of Environmental Science and Technology (EAWAG), Dübendorf, Switzerland johnson@eawag.ch
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Published:
January 01, 2004

Abstract

Cement has found wide usage in the stabilization of heavy-metal-containing wastes as cement minerals can substantially reduce heavy metal solubility as a result of precipitation, adsorption to the surfaces and incorporation. The solubility of some heavy metal cations is limited by the precipitation of hydroxides, while that of some oxyanions is limited by the formation of Ca salts. Only ions that are sufficiently soluble in basic media will be incorporated in or sorbed to hydrated cement minerals to a significant degree. Heavy metal cations may sorb quite strongly to calcium silicate hydrate (C-S-H). The cations diffuse into the C-S-H particles where they are probably sorbed to the silicate chains. Pure phases of oxyanion-substituted ettringite (3CaO·Al2O3·3(CaSO4)·32H2O, an AFt phase) and monosulphate (3CaO·Al2O3·CaSO4·12H2O, an AFm phase) phases and solid solutions with forumla and OH have been synthesized. Some thermodynamic data are available for the pure phases. For most elements an approximate range of solubility has recently become known. However, it is not possible to predict solubility from the available data.

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Geological Society, London, Special Publications

Energy, Waste and the Environment: a Geochemical Perspective

R. Gieré
R. Gieré
Universität Freiburg, Germany
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P. Stille
P. Stille
ULP-École et Observatoire des Sciences de la Terre-CNRS, Strasbourg, France
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Geological Society of London
Volume
236
ISBN electronic:
9781862394841
Publication date:
January 01, 2004

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