Kinetics of gold dissolution in thiosulfate electrolytes

• Published in: Russian journal of electrochemistry Vol. 46; no. 9; pp. 987 - 992
• Main Authors: Bek, R. Yu, Shevtsova, O. N.
• Format: Journal Article
• Language: English
• Published: Dordrecht SP MAIK Nauka/Interperiodica 01.09.2010
• Subjects: Chemistry; Chemistry and Materials Science; Electrochemistry; Physical Chemistry; anodic dissolution of gold; electrochemical kinetics; thiosulfate
• ISSN: 1023-1935; 1608-3342
• DOI: 10.1134/S102319351009003X

The kinetics of gold dissolution in solutions containing Na 2 S 2 O 3 with the concentration c from 0.025 to 0.2 M and different supporting electrolytes is studied by the voltammetric method on renewable electrodes and the quartz crystal microbalance. It is shown that in the range from the steady-state potential to E = 0.3 V (from hereon, the potentials are related to the normal hydrogen electrode), the polarization curves are well approximated by straight lines in semilogarithmic coordinates. The exchange currents i 0 and the transfer coefficients α are calculated. It is shown that for c = 0.025 M, the values of i 0 and α are about 4 × 10 −6 A/cm 2 and 0.2. With the increase in the Na 2 S 2 O 3 concentration, the exchange current increases weakly and the transfer coefficient remains virtually unchanged. The reaction order of gold dissolution with respect to ligand is calculated to have the value p = = 0.25 which is independent of E . With the changeover of supporting electrolyte, the exchange current increases in the following sequence: Li + < Na + < K + , but α and p remains unchanged. Data in thiosulfate solutions is compared with analogous data obtained earlier for the gold dissolution processes in cyanide and thiocarbamide electrolytes in which complexes of the similar structure were also formed. In electrolytes under comparison, the kinetics of gold dissolution is shown to exhibit common features.