NUCLEATION STUDIES OF GOLD ON CARBON ELECTRODES

Interest has grown in developing non-toxic electrolytes for goldelectrodeposition to replace the conventional cyanide-based bath for long termsustainability of gold electroplating. A solution containing thiosulphate andsulphite has been developed specially for microelectronics applications.However, at the end of the electrodeposition process, the spent electrolyte cancontain a significant amount of gold in solution. This study has been initiated toinvestigate the feasibility of gold recovery from a spent thiosulphate-sulphiteelectrolyte. We have used flat-plate glassy carbon and graphite electrodes tostudy the mechanism of nucleation and crystal growth of gold deposition fromthe spent electrolyte. It was found that at the early stages of reduction process,the deposition of gold on glassy carbon exhibits an instantaneous nucleation ofnon-overlapping particles. At longer times, the particles begin to overlap andthe deposition follows a classic progressive nucleation phenomenon. On theother hand, deposition of gold on graphite does not follow the classicalnucleation phenomena.