Determination of Dissolution Rates of Ag Contained in Metallurgical and Mining Residues in the S 2 O 3 2? -O 2 -Cu 2+ System: Kinetic Analysis

摘要

The materials used to conduct kinetic study on the leaching of silver in the S 2 O 3 2? -O 2 -Cu 2+ 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 (d 0 ), temperature (T), copper concentration [Cu 2+ ], thiosulfate concentration [S 2 O 3 2? ], pH, [OH ? ], stirring rate (RPM), and partial pressure of oxygen (PO 2 ). Temperature has a favorable effect on the leaching rate of Ag, obtaining an activation energy (Ea) = 43.5 kJ?mol ?1 in 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 [Cu 2+ ] had a catalytic effect on the leaching rate of silver, as opposed to not adding it. The dissolution rate is dependent on [S 2 O 3 2? ] in a range between 0.02 mol·L ?1 and 0.06 mol·L ?1 . Under the studied conditions, variables d 0 , [OH ? ] and RPM did not have an effect on the overall rate of silver leaching.