Leaching Characteristics of Arsenic and Selenium from Coal Fly Ash: Role of Calcium
Understanding the leaching behavior of arsenic (As) and selenium (Se) in coal fly ash is important in evaluating the potential environmental impact of coal fly ash. Batch experiments were employed to systematically investigate the leaching behavior of as and Se in two major types of coal fly ashes, bituminous coal ash and sub-bituminous coal ash, and to determine the underlying processes that control as and Se leaching. The effects of pH, solid/liquid (S/L) ratio, calcium addition, and leaching time on the release of as and Se were studied. Overall, bituminous coal ash leached significantly more as and Se than sub-bituminous coal ash, and Se was more readily leachable, in both absolute concentration and relative fraction, than as for both types of fly ashes. Adsorption/desorption played a major role on as and Se leaching from bituminous coal ashes. However, calcium precipitation played the most important role in reducing as and Se leaching from sub-bituminous coal ashes in the entire experimental pH range. The leaching of as and Se from bituminous coal ashes generally increased with increases in the S/L ratio and leaching time. However, for sub-bituminous coal ashes, the leaching of as was not detected under most experimental conditions, while the leaching of Se increased with increases in the S/L ratio and leaching time. AsV and SeIV were found to be the major species in all ash leachates in this study.
T. Wang et al., "Leaching Characteristics of Arsenic and Selenium from Coal Fly Ash: Role of Calcium," Energy and Fuels, American Chemical Society (ACS), May 2009.
The definitive version is available at http://dx.doi.org/10.1021/ef900044w
Civil, Architectural and Environmental Engineering
Electric Power Research Institution
United States. Department of Transportation
Keywords and Phrases
Coal Fly Ash; Leaching Behavior; Arsenic; Selenium
Article - Journal
© 2009 American Chemical Society (ACS), All rights reserved.