Anodic dissolution of gold in alkaline
solutions containing thiourea,
thiosulfate and sulfite ions
solutions containing thiourea,
thiosulfate and sulfite ions
(1. Center for Integrated Research in Science and Engineering,
Nagoya University, Nagoya 464-8603, Japan；
2.Department of Metallurgical Science & Engineering,
Central South University, Changsha 410083, China)
Nagoya University, Nagoya 464-8603, Japan；
2.Department of Metallurgical Science & Engineering,
Central South University, Changsha 410083, China)
Abstract: 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, Na2SO3 and Na2S2O3. 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 t he alkaline solution containing these elements was also estimated by capillary electrophoresis technique.
Key words: gold selective dissolution; sulfite; alkaline thiourea solution