Determination of dissolution rates of Ag contained in metallurgical2−and mining residues in the S2O3-O2-Cu2%2bsystem: Kinetic analysis

The materials used to conduct kinetic study on the leaching of silver in the S2O3 2−-O2-Cu2%2bsystem 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%2b], thiosulfate concentration [S2O3 2−], 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%2b] had a catalytic effect on the leaching rate of silver, as opposed to not adding it. The dissolution rate is dependent on [S2O3 2−] 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. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

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