Leaching behavior of pollutants in stabilized/solidified wastes

The objective of the study is to characterize pollutant retention in wastes solidified with hydraulic binders in order to predict the long term leaching behavior. The stabilized/solidified wastes are APC MSW (air pollution control residues from municipal solid waste incineration), lead secondary smelting slag and different salts. The binders used are ordinary Portland cement (OPC 55) or blast furnace slag cement (CLK 45) and additives, such as metakaolin. Leaching tests are used in the characterization procedure. Modelling of the observed leaching behavior is conducted to improve the description of the physical and chemical phenomena involved in the release of soluble species. The main results of the study allow a distinction to be made between the species whose solubility is not sensitive to the chemical context of the porewater, and the other species, such as amphoteric metals, whose solubility is sensitive to the context (especially the pH). In the first case, a diffusion or shrinking front model is appropriate. In the second case, a coupled solubilization/diffusion model must be developed in order to describe the leaching behavior of heavy metals (lead, etc.) contained in the stabilized/solidified wastes.