Stabilization of hazardous metals through thermal reactions with clay materials

Abstract

Thermal treatment is an effective method to remediate hazardous contaminated soil and also to convert hazardous metal wastes into ceramics useful in industry and construction, but the stabilization mechanisms have up to now not been well identified. In this study, incorporation mechanisms of nickel and copper by kaolinite and the other aluminum- or iron-rich precursors commonly found in clays were investigated under different thermal conditions. NiAl2O4, CuAl2O4, and NiFe2O4 were the product phases of a 3-h sintering process, with these quantities evaluated by the quantitative X-ray diffraction (XRD) technique. High metal transformation ratios were found, and the efficiencies were generally enhanced when the sintering temperature was increased. In prolonged leaching experiments for nickel product phases, both aluminate and ferrite spinels proved superior to nickel oxide for the immobilization of nickel.