EXAFS and XANES Studies of Copper in a Solidified Fly Ash

• Published in: Environmental science & technology Vol. 35; no. 12; pp. 2532 - 2535
• Main Authors: Hsiao, M. C, Wang, H. Paul, Yang, Y. W
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.06.2001
• Subjects: Air Pollutants - analysis; Applied sciences; Contamination; Copper; Copper - analysis; Copper - chemistry; Environmental Monitoring - methods; Exact sciences and technology; Hazardous materials; Hydroxylation; Incineration; Other industrial wastes. Sewage sludge; Pollution; Refuse Disposal; Spectrometry, X-Ray Emission; Spectroscopy, Fourier Transform Infrared; Waste disposal; Wastes; XANES spectrometry; Waste treatment; Crystal chemistry; Portland cement; EXAFS spectrometry; Heavy metal; Solidification; Fly ash; Industrial waste; Solid waste; Lixiviation; Coordinence; Copper; Speciation
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es001374v

Speciation of copper in the fly ash solidification process has been studied by X-ray based spectroscopies in the present work. Fourier transformed EXAFS (extended X-ray absorption fine structural) spectra of the solidified fly ashes showed that the bond distance of Cu−O (first shell) was 1.96 Å with a coordination number (CN) of about 3.0. However, in the second shell of copper atoms, the bond distance of Cu−(O)−Cu was decreased by 0.12−0.22 Å during solidification, which might cause the stabilization of the CuO species in the solidified fly ash matrix. By the least-squares fits of the XANES (X-ray absorption near edge structural) spectra, fractions of the main copper species in the solidified fly ashes such as CuCl2 (0.08−0.11), Cu2O (0.07−0.09), Cu(OH)2 (0.31−0.33), and CuO (0.49−0.52) were observed. Combined EXAFS and XANES observations suggested that chemical reactions such as hydroxylation of CuCl2 and oxidation of Cu2O and/or metallic Cu might involve in the solidification process, which also led to a significant reduction of the leachability of copper from the solidified fly ashes.