Gold Electrocrystallization from a Spent Thiosulfate-Sulfite Electrolyte

Abstract

Although there are several electrolytes in the market for gold electrodeposition, a thiosulfate-sulfite mixed ligand bath has been recently developed specially for microelectronics applications. The main driver for the development of this electrolyte is long-term sustainability. At the end of a gold electrodeposition process, the spent electrolyte can contain a significant amount of gold in solution. This study has been initiated to study the feasibility of gold recovery from a used thiosulfate-sulfite electrolyte. In our work, we have used glassy carbon and graphite as electrodes. The two different forms of carbon were chosen due to the difference in their structures. It was found that at the early stages of the reduction process, the deposition of gold on glassy carbon exhibits an instantaneous nucleation. At longer times, the deposition follows the classical progressive nucleation phenomenon. Deposition of gold on graphite does not follow the classical nucleation phenomenon. Particle sizes and density can be controlled by varying the deposition potentials and time. This work is expected to elucidate information on the electrochemical behavior of a spent electrolyte at carbon electrodes, as well as studying their microstructural properties, which is likely to govern the utility of recovered gold.