Effect of Electrolyte Temperature upon Passivity of Copper Anodes

The known effect of increasing electrolyte temperature in preventing anode passivation in copper refining was extensively reviewed.It has been found that a layer of anode slimes formed at a higher electrolyte temperature tends to become more porous with the simultaneous decrease in slime fall. While this increased permeability allows the diffusing ability of Cu2 ions away from the surface of a corroding anode to increase, a gravitational flow of the electrolyte also becomes more pronounced within the slime layer. That is, a more concentrated copper electrolyte at the anode surface streams downwards through the micro pores and cracks, and this type of mass transport removes excessive Cu2+ ions far more efficiently.A thorough investigation of electrolyte properties such as diffusion coefficient of Cu2+ ions, viscosity, solubility of copper sulfate and vapor pressure etc. measured using copper electrolyte of a nominal composition over the temperature range 45-65°C, proves the fact that the gravitational flow is a predominant factor contributing to the decreased tendency to passivate at a higher temperature.That anode passivation occurs more readily at a lower level of anode height is also explainable by this claim.