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Mechanism of gold dissolving in alkaline thiourea solution

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Abstract

Reaction mechanism of gold dissolving in alkaline thiourea solution was studied by electrochemical methods, such as cyclic voltammetry, chronopotentiometry, AC impedance, linear sweep voltammetry. Apparent activation energy of anodic process of gold electrode dissolving in alkaline thiourea solution is 14.91 kJ/mol. Rate determining step is the process of gold thiourea complex diffusing away from electrode surface to solution. The results of AC impedance and chronopotentiometry indicate that thiourea adsorbs on gold electrode surface before dissolving in solution. There does not exist proceeding chemical reactions. Formamidine disulfide, the decomposed product of thiourea, does not participate the process of gold dissolution and thiourea complex. Species with electro-activity produced in the process of electrode reaction adsorbs on the electrode surface. In alkaline thiourea solution, gold dissolving mechanism undergoes the following courses: adsorption of thiourea on electrode surface; charge transfer from gold atom to thiourea molecule; Au[SC(NH2)2]ads + receiving a thiourea molecule and forming stable Au[SC(NH2)2]2 +; and then Au[SC(NH2)2]2 + diffusing away from the electrode surface to solution, the last step is the rate-determining one.

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Authors and Affiliations

  1. School of Metallurgical Science and Engineering, Central South University, Changsha, 410083, China

    Chai Li-yuang  (柴立元) & Wang Yun-yan PhD  (王云燕) (Associate professor)

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  1. Chai Li-yuang  (柴立元)
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  2. Wang Yun-yan PhD  (王云燕)
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Correspondence to Wang Yun-yan PhD  (王云燕).

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Foundation item: Project(50004009) supported by the National Natural Science Foundation of China

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Chai, Ly., Wang, Yy. Mechanism of gold dissolving in alkaline thiourea solution. J Cent. South Univ. Technol. 14, 485–489 (2007). https://doi.org/10.1007/s11771-007-0094-0

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  • DOI: https://doi.org/10.1007/s11771-007-0094-0

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