Incorporation and leaching of heavy metals in clay annealed with Pb, Cu and V

The leaching characteristics of annealed clay enriched with heavy metals (5 wt% PbO, CuO, V sub(2)O sub(5)) were compared with the mineral phase composition. X-ray powder diffraction analyses of the products at different annealing temperatures (up to 1,000 degree C) revealed that Pb is incorporated in a lead feldspar whereas Cu and V are mainly incorporated in the amorphous component. The phases incorporating Pb, Cu or V were investigated by thermodynamic calculations to confirm consistency to the observed solubility behaviour in pH-static experiments at pH 4, 7 and 11. Mobilization data indicate that Pb and Cu are sufficiently immobilized during annealing processes whereas the high mobility of V strongly depends on the annealing temperature.