Clay Formation and Metal Fixation during Weathering of Coal Fly Ash

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• 作者：Chris Zevenbergen ; John P. Bradley ; L. Piet van Reeuwijk ; A. K. Shyam ; Ole Hjelmar ; and Rob N. J. Comans
• 刊名：Environmental Science & Technology
• 出版年：1999
• 出版时间：October 1, 1999
• 年：1999
• 卷：33
• 期：19
• 页码：3405 - 3409
• 全文大小：103K
• 年卷期：v.33,no.19(October 1, 1999)
• ISSN：1520-5851

文摘

The enormous and worldwide production of coal fly ashcannot be durably isolated from the weathering cycle, andthe weathering characteristics of fly ash must be knownto understand the long-term environmental impact. We studiedthe weathering of two coal fly ashes and comparedthem with published data from weathered volcanic ash,it's closest natural analogue. Both types of ash containabundant aluminosilicate glass, which alters to noncrystallineclay. However, this study reveals that the kinetics ofcoal fly ash weathering are more rapid than those of volcanicash because the higher pH of fresh coal fly ash promotesrapid dissolution of the glass. After about 10 years ofweathering, the noncrystalline clay content of coal fly ashis higher than that of 250-year-old volcanic ash. Theobserved rapid clay formation together with heavy metalfixation imply that the long-term environmental impact ofcoal fly ash disposal may be less severe and the benefitsmore pronounced than predicted from previous studieson unweathered ash. Our findings suggest that isolating coalfly ash from the weathering cycle may be counterproductivebecause, in the long-term under conditions of freedrainage, fly ash is converted into fertile soil capable ofsupporting agriculture.