Effect of Temperature on Gold Dissolution in Acidic Media

Temperature has a tremendous effect on the rate and amount of gold dissolution. In potentiodynamic experiments the total amount of dissolved gold increases by a factor of 4.5 when the temperature is increased from 25 to 75°C. Moreover, the previously reported correlation between the onset of oxide formation and the commencement of the dissolution process is found to be correct for all studied temperatures. Negative shift in the advent of oxidation is accompanied by a similar shift in the dissolution onset potential. Similarly, the dissolution rate rises significantly with temperature during potentiostatic and galvanostatic polarization steps. A correlation between the temperature-dependent oxygen evolution reaction (OER) and gold dissolution is found. Arrhenius plots for the OER and gold dissolution are used to obtain information on the apparent activation energy E A for both processes. It is found that for OER and Au dissolution E A = 57 kJ mol −1 . The later finding suggests that there is a common intermediate for both reactions, the formation of which constitutes the rate-determining step.