Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9632615 | Hydrometallurgy | 2005 | 8 Pages |
Abstract
The recycling of silver from metallic scraps can be performed through O3 leaching at an ambient temperature and low (â¼0.1 M) H2SO4 concentration. The main by-product is O2, which can be recycled to the O3 generation or used as leaching agent in a pretreatment step. The stoichiometry and the effects of the stirring speed, ozone and acid concentration and temperature on the leaching of silver were investigated. Silver dissolved as Ag2+(aq) in the range 10â3-1 M H2SO4, but for pH â¥4, insoluble Ag2O2 was the main reaction product. Kinetics appeared to be controlled by mass transfer of O3(aq) to the solid-liquid interface, showing first order dependency with respect to [O3]aq and PO3. Specific rates were only slightly dependent on the temperature in the interval 10-50 °C, but decreased at 60 °C due to the fall in O3 solubility. The mass transfer coefficients showed an average activation energy of 17 kJ/mol. No significant effect of [H2SO4] on mass transfer coefficients was observed for 10â2-1 M. Leaching rate gradually diminished for pH >2, as a consequence of the influence of the [H+] in the transport control.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
J. Viñals, E. Juan, A. Roca, M. Cruells, J. Casado,