Abstract Glycine has recently gained plenty of attention in gold processing as an alternative lixiviant to cyanide due to its non-toxicity, efficiency in metal dissolution as well as selectivity for valuable metals. This paper presents an investigation on the combination of agitated reactor leaching and recovery of gold from mildly refractory ore in cyanide-free alkaline glycine media. Optimal leaching parameters for gold extraction were evaluated using response surface methodology. The investigated parameter range was 0.5–2 M for glycine concentration, pH of 10–12 and temperatures of 23–60 °C, with constant leaching time (24 h) and solid/liquid ratio (100 g/L). Based on the experimental series, a mathematical tool was built to predict gold extraction. It was found that, in the investigated parameter range, glycine concentration did not have a statistically significant effect on gold dissolution. Conversely, both temperature and pH had a substantial role in leaching kinetics. The statistical model suggested that the optimal conditions for gold dissolution were 1.25 M of glycine, pH = 12, and T = 60 °C, corresponding to a predicted 87% gold extraction. The experimental verification showed good reliability of the model with 90% extraction of gold achieved under the predicted optimum conditions. The addition of 15 g/L of activated carbon to the pregnant leach solution (PLS) could provide 100% recovery of gold from solution onto activated carbon, i.e. holistic recovery of 90%. Presence of carbon in leach (CIL) resulted in slightly lower (95%) gold uptake from solution and significantly decreased the holistic gold recovery down to 77%. Additionally, the applicability of direct electrochemical carbon-free recovery method, namely electrodeposition–redox replacement (EDRR), was investigated. In the synthetic solution, a gold recovery as high as 88% was achieved (1247 cycles). However, in the real PLS, only 35% of gold was recovered, which is attributed to different speciation of metals and presence of the other dissolved elements.

中文翻译：

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在无氰甘氨酸介质中从矿石中浸出和回收金

摘要 最近，甘氨酸作为氰化物的替代浸出剂在金加工中受到广泛关注，因为它具有无毒、金属溶解效率以及对有价值金属的选择性。本文研究了在无氰碱性甘氨酸介质中搅拌反应器浸出和从温和难熔矿石中回收金的组合。使用响应面方法评估金提取的最佳浸出参数。研究的参数范围是甘氨酸浓度为 0.5-2 M，pH 值为 10-12，温度为 23-60 °C，具有恒定的浸出时间（24 小时）和固液比（100 克/升）。基于实验系列，建立了一个数学工具来预测黄金提取。发现，在研究的参数范围内，甘氨酸浓度对金溶解没有统计学上的显着影响。相反，温度和 pH 值对浸出动力学都有重要作用。统计模型表明，金溶解的最佳条件是 1.25 M 甘氨酸、pH = 12 和 T = 60 °C，对应于预测的 87% 金提取率。实验验证表明该模型具有良好的可靠性，在预测的最佳条件下实现了 90% 的金提取。将 15 g/L 的活性炭添加到富集浸出溶液 (PLS) 中可以提供 100% 的金从溶液到活性炭的回收率，即 90% 的整体回收率。浸出 (CIL) 中碳的存在导致溶液中的金吸收率略低 (95%)，并将整体金回收率显着降低至 77%。此外，研究了直接电化学无碳回收方法，即电沉积-氧化还原置换（EDRR）的适用性。在合成溶液中，金回收率高达 88%（1247 个循环）。然而，在实际的 PLS 中，只有 35% 的金被回收，这归因于金属的不同形态和其他溶解元素的存在。