Modelling of silver anode dissolution and the effect of gold as impurity under simulated industrial silver electrorefining conditions

As Au content causes passivation during silver electrorefining process, a kinetic study and modelling of AuAg alloy in synthetic silver electrolyte is presented. In this research, the possibility to process high gold Doré efficiently through the simple adjustment of electrolyte conditions and the pr...

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Bibliographic Details
Published in:	Hydrometallurgy Vol. 189; p. 105105
Main Authors:	Aji, Arif T., Halli, Petteri, Guimont, Amaury, Wilson, Benjamin P., Aromaa, Jari, Lundström, Mari
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 01-11-2019 Elsevier
Subjects:	Au – Ag alloy Condensed Matter Cyclic polarization Kinetic modelling Materials Science Passivation Physics Silver electrorefining Silver electrorefining Au – Ag alloy Cyclic polarization Kinetic modelling Passivation
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Summary:	As Au content causes passivation during silver electrorefining process, a kinetic study and modelling of AuAg alloy in synthetic silver electrolyte is presented. In this research, the possibility to process high gold Doré efficiently through the simple adjustment of electrolyte conditions and the process current density is demonstrated. Measurements of binary AuAg alloys in a synthetic silver electrolyte with silver concentration ([Ag+]) of 40, 70 and 100 g/dm3 were conducted at temperatures between 25 and 45 °C. Results show that efficient processing of Doré with a higher gold content up to 20% can be achieved in a low [Ag+] (40 g/dm3) electrolyte with a current density (j) of 180–300 A/m2. For an intermediate electrolyte with [Ag+] of 70 g/dm3, for Au limit of 13–14%, the current density can be increased to j of 500–600 A/m2, for a Au content of 13–14%. Finally, using high concentration electrolyte of [Ag+] = 100 g/dm3, a high current density ˃1000 A/m2 can only be efficiently applied when Au content is limited to 6–8%. Based on empirical kinetic modelling, this study shows an effective approach on the processing Doré with wide range of Au content. [Display omitted] •Gold in silver anode cause anode passivation in silver electrorefining.•Processing anode with up to 20% Au is efficient for low j ˂ 200 A/m2.•Lower [Ag+] electrolyte (40 g/dm3) is efficient for process at low j ˂ 200 A/m2.•For efficient high j operation (˃1000 A/m2), wt%Au is required to be below 8%.•Electrolyte with [Ag+] of 100 g/dm3 is required for high j of ˃1000 A/m2.
ISSN:	0304-386X 1879-1158
DOI:	10.1016/j.hydromet.2019.105105