Anodic dissolution of gold in alkaline solutions containing thiourea, thiosulfate and sulfiteions

Gold dissolves electrochemically in alkaline solutions containing ligands to form complex ions with gold ion. Therefore, selective leaching of noble metals is expected without dissolution of base metals such as steels, aluminum alloys in scrap treatment. Gold electrodes were investigated using linear sweep voltammetry, EQCM method and potentiostatic electrolysis in alkaline solutions containing thiourea, Na 2SO 3 and Na 2S 2O 3. The solution composition, electrode potential affect gold dissolution rate and current efficiency. The gold dissolved from anode electrode forms complex ions, suspension particles as compound precipitates and deposits on cathode electrode as a metal. Anodic efficiency for gold dissolution is between 10% and 22%. This is caused by the oxidation decomposition of sulfite ions and thiourea. The stability of the alkaline solution containing these elements was also estimated by capillary electrophoresis technique.

Gold dissolves electrochemically in alkaline solutions containing ligands toform complex ions with gold ion. Therefore, selective leaching of nohle metals is expected withoutdissolution of base metals such as steels, aluminum alloys in scrap treatment. Gold electrodes wereinvestigated using linear sweep voltammetry, EQCM method and potentiostatic electrolysis in alkalinesolutions containing thiourea, Na_2SO_3 and Na_2S_2O_3. The solution composition, electrodepotential affect gold dissolution rate and current efficiency. The gold dissolved from anodeelectrode forms complex ions, suspension particles as compound precipitates and deposits on cathodeelectrode as a metal. Anodic efficiency for gold dissolution is between 10% and 22%. This is causedby the oxidation decomposition of sulfite ions and thiourea. The stability of the alkaline solutioncontaining these elements was also estimated by capillary electrophoresis technique.