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 Au–Ag 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 Au–Ag 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.