Gold Dissolution in Acidic Thiourea and Thiocyanate Solutions
Gold dissolution in acidic solutions containing thiourea (Tu) and thiocyanate was studied using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and surface enhanced Raman spectroscopy (SERS). A synergistic response found in that mixed ligand system promoted a higher dissolution rate than either lixiviant alone. The passivation of gold occurs in a Tu only solution, but when thiocyanate is mixed with Tu, passivation is significantly alleviated. The dissolution rate of gold in the mixed lixiviant system increases with increasing Tu and thiocyanate concentration. Results from LSV and EIS indicate that gold dissolution is controlled by a combination of charge transfer and diffusion in the mixed lixiviant system. The optimum concentration for Tu and thiocyanate is about 5 mM and 0.05 M, respectively for the rate of gold dissolution. SERS results suggest a possible formation of a mixed ligand complex involving the interaction of Au(Tu)2+ and SCN−. Further study is necessary to identify the mixed ligand complex.
X. Yang et al., "Gold Dissolution in Acidic Thiourea and Thiocyanate Solutions," Electrochimica Acta, Elsevier, Apr 2010.
The definitive version is available at http://dx.doi.org/10.1016/j.electacta.2010.01.105
Materials Science and Engineering
Keywords and Phrases
Gold Dissolution; Thiourea; Thiocyanate; Synergistic Response; Impedance
Article - Journal
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