Thermal detoxification and bloating of chromium(VI) with bentonite

This study stabilizes and bloats Cr(VI)-sorbed bentonite by heating at high temperature. Cr leaching decreases with increasing temperatures. Heating the sample at 1100 1C results in a non-detectable Cr concentration in the leachate, equivalent to a Cr leaching percent less than 0.001% (i.e., Cr TCLP concentration o0.018mg of Cr L 1 of leachate). Morphology observed with a scanning electron microscopy indicates the occurrence of sintering of the sample heated at 1100 1C. The heated samples also show the occurrence of a vesicant process at 1100 1C. X-ray absorption spectroscopy results indicate that heating at 500 1C for 4 h can convert approximately 87% Cr(VI) into Cr(III) that is negligibly toxic; Cr2O3 was detected to be the most abundant Cr species. After heating at higher temperatures, namely 900–1100 1C, almost all doped Cr(VI) is reduced to Cr(III) as inferred from the height of the pre-edge peak of XANES spectra and/or from XANES simulation. & 2009 Elsevier B.V. All rights reserved.