A SOLUTE TRANSPORT MODEL FOR THE ACID LEACHING OF COPPER IN SOIL COLUMNS

Modeling solution mining technique has recently received much attentio n in order to estimate metal recovery rates. We studied the acid leach ing of Cu minerals found in mine tailings using a mathematical transpo rt model and lab-scale experiments on both batches and saturated soil columns. The model is a one-dimensional macroscopic solute transport m odel that considers simultaneously (i) the convection, dispersion, and consumption of H2SO4, and (ii) the convection, dispersion, solubiliza tion, and adsorption-desorption of Cu. Time-dependent batch experiment s were carried out to understand the relationship between H2SO4 consum ption and Cu extraction in tailing Cu materials under stagnant conditi ons. Additionally, miscible-displacement experiments were conducted to obtain empirical data on Cu recovery in saturated soil columns that r eceive a constant pulse of H2SO4 and were designed to check the model' s capability to simulate the transport phenomena. This was done by est imating the model parameters independently from the batch experiments. Since some findings from both experiments were consistent with each o ther, modeling assumptions, such as a second-order kinetic relationshi p for Cu dissolution (by H2SO4) and a first-order equilibrium isotherm for Cu, were appropriate in order to simulate the Cu recovery concent ration at the outlet of each column. Finally, model equations were sol ved using finite differences and analytical solutions for Cu and H2SO4 transport equations, respectively, and model parameters were estimate d using least squares techniques.