Solar thermal vitrification of mining contaminated soils

Vitrification of hazardous mine wastes and mine tailings from old mercury and Ag–Pb mines in SE Spain, was studied using solar technology. Six samples were treated in a solar furnace, reaching temperatures of 1050 to 1350 °C. DRX and SEM-EDS microanalysis of the thermally treated samples showed the presence of a dominant vitreous phase with blebs resulting from gas escape, with metals (especially Zn, Cu, Ni) in solid solution. EDX analysis of samples showed the presence of Fe, Ti as well as Si, Al, Ca and Mg, which may be associated to neoformed silicates and/or to glassy phases. leachability of the thermally treated samples demonstrates the immobilization of Fe, Mn, Ni, Cu and Zn in the samples treated at the highest temperatures (1350 °C), whereas Mn, Ni, Cu and Zn were mobilized in samples treated at lower temperatures (1050 °C). Therefore, temperature is the key factor in the immobilization of heavy metals in soil samples when using a solar heating source, showing a low metal-mobility of the samples treated at elevated temperatures.