Characterizing the Metal Adsorption Capability of a Class F Coal Fly Ash


The surface physical-chemical characteristics of a class F coal fly ash were studied in an effort to establish a quantitative understanding of metal adsorption. the ash surface acidity (acid site density and acidity constant), surface electrical characteristics, and adsorption constants for selected heavy metal ions were determined using a batch titration method, an electrophoretic method, and a batch equilibrium metal adsorption method, respectively. Results showed that the fly ash has a pHzpc value of 6.2. Its surface contains three types of acid sites. the densities of these acid sites are 2.1 × 10⁻ ⁴, 1.8 × 10⁻⁵, and 5.3 × 10⁻ ⁵mol/g, with acidity constants (pKH) of 2.7, 7.8, and 11.0, respectively. Metal adsorption results indicated that, of the three types of acid sites on surface, only the acid site with 7.8 pKH is responsible for metal adsorption. the adsorption constants (log KS) of Cd(II), Cr(III), Cu(II), Ni(II), and Pb(II) are 4.8, 7.0, 6.4, 4.9, and 8.6, respectively. Adsorption results indicated that the metal adsorption is in the linear range of the Langmuir isotherm if the total metal in the system is less than 10% of the total metal binding site. Results also showed that the presence of anionic metal ions does not affect the adsorption of cationic metal ions by the fly ash.


Civil, Architectural and Environmental Engineering


Electric Power Research Institution

Keywords and Phrases

Characterizing; Class F; Coal Fly Ash; Adsorption

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Article - Journal

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© 2004 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Jan 2004