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Title: Leaching behavior of lime-fly ash mixtures

Abstract

As part of a larger investigation that included numerical and field-based components, the use of lime to reduce the leachability of a coal combustion fly ash was evaluated in the laboratory. The focus of this paper is on the experimental assessment of lime-fly ash leachability through sequential leach (SL), freeze-thaw (FT), and wet-dry (WD) leaching as well as multileachant sequential extraction (SE) tests. The results suggest that lime addition reduces the leachability for Cd, Se, and to some extent As. They also suggest that Cr is rendered more leachable with increasing lime content, for the conditions and low levels tested. It appears that there is a threshold lime content ({gt} 1.0%) that must be exceeded prior to reducing the leachability of As and Se. In particular, this threshold likely corresponds to the level at which appreciable cementitious reactions have developed. For example, in the case of As after the first cycle of leaching, the concentration was below the reporting limit (10 {mu} g/L) for 0% lime. However, at 0.5% lime amendment, the leached concentration increased to nearly 50 {mu} g/L. Subsequent lime additions reduced this concentration. No such threshold was observed for Cd leachability as was expected as a directmore » consequence of hydroxide precipitation, which is well established under the measured pH conditions. As such, Cd mobility is insensitive to the extent to which cementitious reactions are initiated. Overall, the results suggest that while lime stabilization may be effective for reducing leachability, sufficient amounts must be added; otherwise, the leachability of some constituents can actually be exacerbated.« less

Authors:
;  [1]
  1. University of North Carolina, Charlotte, NC (United States). Dept. of Civil Engineering
Publication Date:
OSTI Identifier:
20712183
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Engineering Science; Journal Volume: 23; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; FLY ASH; CALCIUM HYDROXIDES; LEACHING; INHIBITION; TRACE AMOUNTS; ELEMENTS; CADMIUM; SELENIUM; CHROMIUM; CONCENTRATION RATIO

Citation Formats

Daniels, J.L., and Das, G.P. Leaching behavior of lime-fly ash mixtures. United States: N. p., 2006. Web. doi:10.1089/ees.2006.23.42.
Daniels, J.L., & Das, G.P. Leaching behavior of lime-fly ash mixtures. United States. doi:10.1089/ees.2006.23.42.
Daniels, J.L., and Das, G.P. Sun . "Leaching behavior of lime-fly ash mixtures". United States. doi:10.1089/ees.2006.23.42.
@article{osti_20712183,
title = {Leaching behavior of lime-fly ash mixtures},
author = {Daniels, J.L. and Das, G.P.},
abstractNote = {As part of a larger investigation that included numerical and field-based components, the use of lime to reduce the leachability of a coal combustion fly ash was evaluated in the laboratory. The focus of this paper is on the experimental assessment of lime-fly ash leachability through sequential leach (SL), freeze-thaw (FT), and wet-dry (WD) leaching as well as multileachant sequential extraction (SE) tests. The results suggest that lime addition reduces the leachability for Cd, Se, and to some extent As. They also suggest that Cr is rendered more leachable with increasing lime content, for the conditions and low levels tested. It appears that there is a threshold lime content ({gt} 1.0%) that must be exceeded prior to reducing the leachability of As and Se. In particular, this threshold likely corresponds to the level at which appreciable cementitious reactions have developed. For example, in the case of As after the first cycle of leaching, the concentration was below the reporting limit (10 {mu} g/L) for 0% lime. However, at 0.5% lime amendment, the leached concentration increased to nearly 50 {mu} g/L. Subsequent lime additions reduced this concentration. No such threshold was observed for Cd leachability as was expected as a direct consequence of hydroxide precipitation, which is well established under the measured pH conditions. As such, Cd mobility is insensitive to the extent to which cementitious reactions are initiated. Overall, the results suggest that while lime stabilization may be effective for reducing leachability, sufficient amounts must be added; otherwise, the leachability of some constituents can actually be exacerbated.},
doi = {10.1089/ees.2006.23.42},
journal = {Environmental Engineering Science},
number = 1,
volume = 23,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}