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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 9    No. 1    March 1999

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DISSOLUTION THEORY OF GOLD INALKALINE THIOUREA SOLUTION(Ⅰ)①
Anodic Behavior on Gold in Alkaline Thiourea Solution Containing Na2SO3
Chai Liyuan and Masazumi Okido 

1.Department ofNonferrous Metallurgy, Central South University of Technology, Changsha 410083, P. R.China
2.Center for Integrated Research in Science and Engineering, Nagoya University, Nagoya 464, Japan

Abstract:Anodic polarization behaviors of gold and its associated elements, e.g., silver, copper, nickel and iron, in the alkaline thiourea solution with and without Na2SO3 were examined. The results showed gold is hardly dissolved in the solution with Na2SO3because of the passivation of elemental sulfur produced by irreversible decomposition of alkaline thiourea; however, the additive Na2SO3 improves the stability of thiourea in alkaline media, greatly increases anodic current of gold and accelerates the selective dissolution of gold in the alkaline thiourea solution, without changing the passivation states of the associated elements of gold. Also the factors affecting the polarization of gold anode were investigated in detail, and it was found that, the Na2SO3 obviously decreases polarization potential of gold and the apparent activation energy of gold dissolution, and the controlling step of the dissolution of gold anode in the alkaline thiourea solution is changed from the anode dissolution reaction to the solute diffusion. The mechanism for accelerated dissolution of gold in the alkaline thiourea solution with Na2SO3 was considered as electrochemical reduction and catalysis, over the Na2SO3 concentration of 0.01~0.5 mol/L, at the potential of 0.34~0.44 V.

 

Key words: alkaline thiourea sodium sulfite polarization behavior gold

ISSN 1672-7029
CN 43-1423/U

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