DETERMINATION OF METAL BEHAVIOR DURING THE INCINERATION OF A CONTAMINATED MONTMORILLONITE CLAY

The goal of this study was to develop an understanding of metals behav ior during thermal treatment. Clay samples, contaminated with metals t o obtain a surrogate waste, were analyzed prior-to and following therm al treatment using nitric acid and/or hydrogen fluoride digestion, fol lowed-by inductively coupled plasma emission spectrophotometry analysi s. Techniques were used to examine particle surface and metal distribu tion within cross sections. Lead, cadmium, and chromium results are di scussed. With hydrogen fluoride-digested samples, the results indicate d that vaporization increased slightly with increasing temperature for cadmium and lead. Chromium did not show increased vaporization. At hi gher temperatures, the nitric acid digestions did not completely remov e the metals. Scanning electron microscope pictures showed that, at hi gher temperatures, the particle structure became compact and glassy; t he electron microprobe results indicated that lead and cadmium were lo cated in regions with high silicon, suggesting reactions with the sili con. Chromium distribution remained uniform, suggesting that chromium was immobilized due to structural changes not reactions.