Environmental and technological effectiveness of a process for the stabilization of a galvanic sludge.

A binding matrix containing calcium silicate beta-2CaO.SiO(2) and sulphoaluminate 4CaO.3Al(2)O(3).SO(3), and CaSO(4) that gives calcium silicate and trisulphoaluminate hydrates upon hydration has been used for the stabilization of a solid waste from a galvanic treatment process. The waste is to be disposed of in a hazardous wastes landfill to prevent the risk of cadmium, chromium and nickel release. Anhydrous calcium silicate and sulphoaluminate of the binder have been synthesized using a mixture containing powdered tuff in addition to bauxite and calcium carbonate and sulphate. Powdered tuff is quarry dust and is, as such, a true residue. Experiments have been carried out with mixtures containing up to 60% waste and have been addressed towards the environmental and technological assessment of the effectiveness of the stabilization process. Specifically, the study has been carried out taking into account requirements from three different points of view, that is the influence of the waste on the hydration process and on the technological properties of the stabilized products, the leaching behavior under some selected conditions and the effect of the leaching medium on the binding matrix in the stabilized system.