Modeling of solid/liquid/gas mass transfer for environmental evaluation ofcement-based solidified waste

A physicochemical and transport model has been developed for the long term prediction of environmental leaching behavior of porous materials containin g inorganic waste solidified with hydraulic binders and placed in a reuse s cenario. The reuse scenario considered in the paper is a storage tank open to the atmosphere including material leaching with water and carbonation th rough the leachate contact with air. The model includes three levels: (i) t he physicochemical pollution source term (chemical equilibria in the pore w ater and diffusion in the porous system); (ii) chemical equilibria and mass transfer in the tank; and (iii) gas/liquid transfer of carbon dioxide. The model was, applied to the case of a material obtained through solidificati on of Air Pollution Control (APC) residues from Municipal Solid Waste Incin erator (MSWI). The simulation results are in good agreement with two scale experimental data: laboratory and field tests. Experimental data and simula tions show the main trends for release of elements contained in the materia l: (i) the release of alkaline metals and chloride is not significantly inf luenced by carbonation and (ii) the release of Ca and Pb is governed by che mical equilibria in pore water and diffusion, while their speciation in the leachate is determined by pH and the presence of carbonate ions.