Thermal immobilization of copper contaminants in soil analogue minerals, quartz and kaolin, at low temperatures such as 300 degrees C is studied to corroborate its technical feasibility as a method for soil remediation. We use a synchrotron-based, X-ray absorption spectroscopy (XAS) technique to study the speciation of and the local structure around copper in the soil analogues that are thermally treated at 300-900 degrees C for 1 h. The toxicity characteristic leaching procedure (TCLP) method is employed to investigate the leaching behavior of copper compounds. CuO, being predominately transformed from Cu(OH)2 with a lesser amount from Cu(NO3)2 by 1-h heat application at 300-900 degrees C, is identified by the spectroscopy of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) as the key species that is leaching-resistant due to its low solubility and its chemisorption onto the soil analogue minerals. Fourier transform of EXAFS spectrum of the Cu-doped kaolin heated at 900 degrees C for 1 h indicates that the intensity of Cu-Cu peaks (2.50 and 5.48 A, both without phase shift correction) is either relatively smaller or disappearing as compared with that of kaolin samples heated at 300 and 500 degrees C. The EXAFS analysis suggests that the Cu solid phase in the 900 degrees C kaolin sample is different from the lower temperature samples, the 900 degrees C SiO2 sample, and the Cu standards. The leaching studies also support the formation of a less soluble phase in the 900 degrees C kaolin sample. An increase of heating temperature, in the range of 105-900 degrees C, reduces the Cu leaching percentage; this reduction trend is more marked for Cu-doped kaolin than for Cu-doped SiO2.

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The extent of lead dispersion can affect lead molecular environment in lead silicate. Mixtures of lead acetate and silica oxide were heated at 500 and 1100 o C for two hours. Two silica oxides (a quartz, syn and an amorphous SiO 2) of different surface areas were used in this study. The final products were investigated with X-ray absorption spectroscopy, X-ray diffraction, BET surface meter, and scanning electron microscopy. The XRD results observe the existence of PbSiO 3 , Pb(0), and PbO (litharge, syn) only in the mixture of lead acetate and quartz heated at 1100 o C, as well as SiO 2 (cristobalite, syn). The mixture of lead acetate and the amorphous SiO 2 heated at 1100 o C basically remains as amorphous although its XRD patterns do show some low-intensity peaks of SiO 2 (cristobalite, syn). Both BET and SEM results indicate that sintering occurs at 1100 o C. Results from the fitting of Fourier transformed Pb L III-edge EXAFS spectra from the heated mixtures shows that both first-shell (Pb-O) interatomic distance and coordination number depend on the type of starting materials and the thermal treatment temperature. Pb first-shell coordination number decreases with increasing temperature for both low-surface area and high-surface area mixtures. The highsurface area mixture after heating at 500 o C have greater first-shell coordination number than the corresponding lowsurface area sample. However, after thermal treatment at 1100 o C, both mixtures have similar first-shell coordination number. The interatomic distance for the first shell for all thermally treated mixtures is 2.18-2.28 Å. The high-surface area mixture treated at 1100 o C has the shortest first-shell interatomic distance (2.18 Å).