| Abstract
| - The objectives of this research were to understand theeffect of aging time on chloropyromorphite stabilityby dissolution, to examine physical and chemical alterationsof the pyromorphite samples, and to model the kineticdata collected from the dissolution experiments. The resultsof this investigation indicate that chloropyromorphiteformation is kinetically rapid and that its dissolution inacid is thermodynamically stable, ideal conditions for Pbimmobilization that has emerged as a potential remediationstrategy. In terms of aging prior to dissolution, X-rayabsorption fine structure (XAFS) and X-ray diffraction (XRD)spectroscopies were unable to distinguish fundamentaldifferences in progressively aged samples; however, high-resolution thermogravimetric analysis (HRTGA) diddemonstrate that the thermostability of the chloropyromorphitematerial increased with increasing residence time. Thestirred-flow and batch dissolution studies suggest that theaging process ceased within 24 h and that the dissolutionrate of the 1-day aged sample was not significantly differentthan the 1-year aged specimen. The amount of Pbreleased peaked at 21% (1-h sample, stirred-flow, pH 2.0)and was as low as 0.17% (1-year sample, batch method,pH 6.0). Postdissolution analyses of chloropyromorphite withXAFS, XRD, and HRTGA revealed no detectable chemicalalterations of the pyromorphite samples signifying only releaseof dissolved Pb to solution and no formation of secondaryproducts during dissolution.
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