POTENTIAL APPLICATION OF ETTRINGITE GENERATING SYSTEMS FOR HAZARDOUS-WASTE STABILIZATION

The potential of ettringite generating systems in hazardous waste stab ilization processes is studied by means of a mixture of anhydrous calc ium sulphoaluminate and anhydrite doped with the nitrates of the six h eavy metals Cu, Cr, Cd, Pb, Zn and Fe. The study has been carried out by means of differential thermal and X-ray diffraction analyses, infra -red spectroscopy, scanning electron microscopy coupled with an energy dispersion system and three different leaching tests. The presence of the metals has only a small negative effect on the hydration kinetics . The hydrated samples retain their structural integrity when submitte d to the dynamic leaching test in water and pH 4 HNO3 solution, while they are disintegrated when the leachant is a pH 4.74 acetate buffer. The sulphoaluminate phases can partially accommodate any metal in the crystal lattice, thus giving rise to chemical entrapment.