Metals extraction from contaminated soils: Model validation and parameters estimation

In this paper a mathematical model based on the axial dispersion theory is developed to estimate copper leaching from contaminated soils in the presence of iron and calcium as competitive cation. The model considered the transport by pore diffusion-dispersion and metal complexation by ions in solution and linked solute transport of EDTA and EDTA-metal chelates to the metal solubilization process. For model validation and parameter estimation, EDTA column's extraction were performed on an artificially contaminated soil by both copper and iron: the extractions were followed by the percolation of pure water to ensure the removal of EDTA entrapped in soil. The coefficients of dispersion (αL) were calculated from the breakthrough curves of bromide ion, and the transport of EDTA and the metal- EDTA complexes was evaluated. The molar concentration profiles obtained as breakthrough curves were used to estimate the main parameters of the model. A good accordance with the experimental results was observed: the average standard deviation between predicted and experimental data was about 0.005 %. The correlation of experimental data shows that the simulated transport of metal-EDTA complexes in solution exhibited a delay effect due to the chemical adsorption of such complexes onto the soil organic matter. Copyright © 2012, AIDIC Servizi S.r.l.