Thiosulfate leaching is a feasible alternative for cyanidation. However, thiosulfate is easily decomposed and forms the passive layer on the ore surface, thus hindering gold extraction. In this paper, by adding thiocyanate to reduce the undesirable effect, copper-ammonia-thiosulfate leaching system is utilized to extract gold from the calcine. This research investigated the factors affecting gold extraction and kinetics of the leaching system, and the potential reason and reaction mechanism of the thiocyanate for improving gold leaching efficiency were discussed and analyzed. Gold leaching percentage is increased from 62.99% to 88.45% by adding thiocyanate that is close to that of cyanidation. By using X-ray photoelectron spectroscopy, gold in the leachate may be in the form of gold(I) thiosulfate complex. The leaching mechanism and the reason for improving gold extraction by adding thiocyanate were investigated via characterization and the leaching thermodynamic analysis. The possible reason for improving gold leaching percentage lied in that the thiocyanate reduced the decomposition of thiosulfate, thus inhibiting the form of passivation layer. According to the leaching mechanism, thiocyanate is used as an additive in the copper-ammonia-thiosulfate leaching system, which is of great significance for facilitating gold recovery, lessening thiosulfate consumption, and reducing ammonia dosage.

中文翻译：

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硫氰酸盐通过抑制钝化层的形成促进硫代硫酸盐萃取金

硫代硫酸盐浸出是氰化的可行替代方案。但硫代硫酸盐易分解，在矿石表面形成钝化层，阻碍金的提取。本文通过添加硫氰酸盐来减少不良影响，采用铜氨硫代硫酸浸出系统从煅烧矿中提取金。本研究探讨了影响金提取的因素和浸出系统的动力学，并对硫氰酸盐提高金浸出效率的潜在原因和反应机理进行了讨论和分析。添加接近氰化的硫氰酸盐，金浸出率由62.99%提高到88.45%。通过使用X射线光电子能谱，浸出液中的金可能以硫代硫酸金(I)络合物的形式存在。通过表征和浸出热力学分析，研究了浸出机理以及添加硫氰酸盐提高金提取率的原因。金浸出率提高的可能原因在于硫氰酸盐减少了硫代硫酸盐的分解，从而抑制了钝化层的形成。根据浸出机理，在铜氨硫代硫酸浸出系统中使用硫氰酸盐作为添加剂，对于促进金回收、减少硫代硫酸盐消耗、减少氨用量具有重要意义。