Speciation of copper in the incineration fly ash of a municipal solid waste

Abstract

The speciation of copper and zinc in the incineration fly ash of a municipal solid waste in Taiwan was investigated in the present work. By the least-squares fitted X-ray absorption near edge structural (XANES) spectroscopy, we found that CuCO 3, Cu(OH) 2, and CuO (fractions of 0.09, 0.39 and 0.51, respectively) were the main copper species in the fly ash. Quantitative analysis of the extended X-ray absorption fine structural (EXAFS) spectra indicated that the bond distance of CuO in the fly ash was 1.96 Å with a coordination number (CN) of 3.9 in the first shell of copper. In the second shell, the bond distance and CN of Cu(O)Cu were 2.91 Å and 2.7, respectively. In addition, speciation of Zn was also examined in the same X-ray absorption energy (8780–9970 eV). The bond distance of ZnO and ZnOZn were 1.97 and 2.94 Å, respectively. However, the ZnOCu structure was not found because of the physically unreasonable σ 2 (Debye–Waller factor) values in the EXAFS data fitting process.