Determination of dissolution rates of Ag contained in metallurgical2−and mining residues in the S2O3-O2-Cu2+system: Kinetic analysis

Abstract

The materials used to conduct kinetic study on the leaching of silver in the S2O32−-O2-Cu2+system were mining residues (tailings) from the Dos Carlos site in the State of Hidalgo, Mexico, which have an estimated concentration of Ag = 71 g·ton−1. The kinetic study presented in this paper assessed the effects of the following variables on Ag dissolution rate: particle diameter (d0), temperature (T), copper concentration [Cu2+], thiosulfate concentration [S2O32−], pH, [OH−], stirring rate (RPM), and partial pressure of oxygen (PO2). Temperature has a favorable effect on the leaching rate of Ag, obtaining an activation energy (Ea) = 43.5 KJ·mol−1in a range between 288 K (15°C) and 328 K (55°C), which indicates that the dissolution reaction is controlled by the chemical reaction. With a reaction order of n = 0.4, the addition of [Cu2+] had a catalytic effect on the leaching rate of silver, as opposed to not adding it. The dissolution rate is dependent on [S2O32−] in a range between 0.02 mol·L−1and 0.06 mol·L−1. Under the studied conditions, variables d0[OH−] and RPM did not have an effect on the overall rate of silver leaching.