There are two major gold recovery methods: the hydrometallurgical technique, which employs cyanide solutions, and amalgamation method, which involves mercury (Hg). These methods present considerable health, safety, and environmental concerns. Past applications of alpha-cyclodextrin (α-CD) on gold scraps show that α-CD is not only inexpensive, but is also environmentally friendly. This research work used α-CD to recover gold from gold ores instead of gold scraps. The gold ore was sourced from Shanono gold deposit site Kano State, Nigeria. The gold ore was characterized by fire assay (FA) for the precious metal. The concentrate was digested with aqua regia (AR) for 24 h. Modified AR, where hydrochloric acid was replaced with hydrobromic acid, was used for the gold digestion due to the good match in molecular recognition between gold bromide ion (AuBr) − and α-CD in a second sphere coordination complex. The digestate was characterized using atomic absorption spectroscopy (AAS). Gold recovery using this technique is pH sensitive, and five pH values (2.0, 3.6, 4.0, 5.4, and 6.0) were investigated. FA analysis showed the Shanono gold ore deposit contains an average of 4.71 ppm of gold, AAS analysis showed highest gold recovery of 69% at pH 4.0, which is lower than recoveries from the metal scraps. This could be due to the presence of other gangue minerals closely associated with the ore. However, gold recovery using α-CD on Shanono gold ore has shown to have a higher yield of 69% compared to 35.5% yield obtainable by Artisan Small Scale Miners using mercury.

中文翻译：

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α-环糊精从 Shanono 金矿床中回收金

有两种主要的金回收方法：使用氰化物溶液的湿法冶金技术和涉及汞 (Hg) 的汞齐法。这些方法存在相当大的健康、安全和环境问题。α-环糊精 (α-CD) 过去在金屑上的应用表明，α-CD 不仅价格低廉，而且对环境友好。这项研究工作使用 α-CD 从金矿石中而不是金屑中回收黄金。金矿石来自尼日利亚卡诺州的 Shanono 金矿床。金矿石通过贵金属的火试金 (FA) 进行表征。浓缩物用王水 (AR) 消化 24 小时。改性 AR，其中盐酸被氢溴酸取代，由于溴化金离子 (AuBr) - 和第二个球体配位络合物中的 α-CD 之间的分子识别匹配良好，因此将其用于金消化。消化物使用原子吸收光谱 (AAS) 进行表征。使用此技术回收金对 pH 值敏感，研究了五种 pH 值（2.0、3.6、4.0、5.4 和 6.0）。FA 分析显示 Shanono 金矿床平均含有 4.71 ppm 的金，AAS 分析显示在 pH 值为 4.0 时的金回收率最高，为 69%，低于金属废料的回收率。这可能是由于存在与矿石密切相关的其他脉石矿物。然而，与 Artisan Small Scale Miners 使用汞获得的 35.5% 的产率相比，使用 α-CD 对 Shanono 金矿石的黄金回收率显示出更高的 69%。