Global kinetics of thermal immobilization of lead‐doped alumina

Abstract

Lead‐doped alumina powders were thermally stabilized in the fixed‐bed mode of an electrically heated, laboratory‐scale fluidized‐bed incinerator in the 200–900 °C range for various treatment duration. The Pb contents in the doped alumina were 5000 and 10000 ppm.

To examine the effectiveness of Pb immobilization with thermal treatment, the toxicity characteristics leaching procedure (TCLP) was carried out for the Pb/alumina mixtures prior to and after the thermal treatments. Higher treatment temperature and longer treatment duration favored Pb immobilization. The results from a global kinetics model indicated that the reaction mechanisms in the lower‐ and higher‐temperature regions were different from each other. The thermal treatments of the 10000‐ppm mixture gave a lower activation energy (5.07 kcal/mole K) than that of the 5000‐ppm mixture (8.2–9.4 kcal/mole K); this might be explained by the difference of type of Sorption sites on the same ALO, surface, and/or by the slower diffusion process during the thermal treatment of the 10000‐ppm mixture in 60 minutes or less.

Key words:

• thermal immobilization
• Pb‐contained waste
• Pb‐contaminated soil