Influence of additives on electrodissolution of Au in a thiosulfate Electrolyte

与使用氰化物浸出黄金有关的环境问题促使人们作出相当大的努力，开发更环保的技术。其中，硫代硫酸盐似乎是氰化反应最有希望的替代品。然而，在从硫代硫酸盐电解液中浸金时，金的钝化显著减缓了这一反应。已观察到某些有机添加剂，如硫脲、硫代乙酰胺和磺胺，显著改善了金在硫代硫酸盐溶液中的溶解。人们对硫代硫酸盐溶液中金的钝化性质和有机添加剂对金浸出的影响知之甚少。这项建议中描述的研究目的是利用原位红外反射吸收光谱(IRRAS)、表面增强拉曼光谱和表面成像技术(如原子力显微镜和扫描隧道显微镜)来确定钝化层的性质和有机添加剂的作用。具体地说，我们将确定吸附在金电极表面的物种的性质，并将确定这些物种的表面浓度作为电极电位和电解液组成的函数。我们将确定Au+与有机添加剂(配体)之间的络合物是否在电极表面形成。我们将提供有关吸附的添加剂的取向的信息。我们将测定添加剂对金的溶解速度的影响以及金溶解反应的机理。该项目提供的信息将被Barricks Gold Corporation用于开发从矿石中浸金的新技术。

The environmental concerns related to the use of cyanide in the leaching of gold have stimulated considerable efforts to develop more environmentally friendly technologies. Of these thiosulfate appears to be the most promising alternative to cyanidation. However, passivation of gold during leaching from the thiosulfate electrolyte slows down this reaction significantly. It has been observed that certain organic additives such as thiourea, thioacetamide and sulphanilamide significantly improve the dissolution of gold in thiosulfate solutions. The nature of the passivation of gold and the effect of organic additives on leaching of gold in thiosulfate solutions are poorly understood. The objective of research described in this proposal is to employ in situ infrared reflection absorption spectroscopy (IRRAS), surface enhanced Raman spectroscopy and surface imaging techniques such as atomic force microscopy and scanning tunneling microscopy to determine the nature of the passive layer and the role of the organic additives. Specifically we will identify the nature of species adsorbed at a gold electrode surface and will determine surface concentrations of these species as a function of the electrode potential and electrolyte composition. We will determine if a complex between Au+ and the organic additive (ligand) is formed at the electrode surface. We will provide information concerning orientation of the adsorbed additive. We will determine the effect of the additive on the rate of gold dissolution and the mechanism of the gold-dissolution reaction. The information provided by this project will be used by Barricks Gold Corporation for the development of new technologies of gold leaching from ores.