Abstract Jarosites are a waste product of most zinc processing plants, since these compounds are formed as a measure to eliminate iron and other impurities from zinc solutions in acidic media. However, they often occlude valuable elements, such as silver, in their structure. In the present study, an alternative is presented for the recovery of silver that is present in this type of waste. The effect of pH, temperature, oxalate concentration and solid/liquid ratio (S/L) on thiourea stability and the selective recovery of silver by acid decomposition and reductive leaching of jarosite were evaluated. The results show that increasing the temperature of the system favors the decomposition of the jarosite and the release of silver to the solution, obtaining recoveries of 86 and 100% silver at 50 and 60 °C, respectively, with 0.13 M thiourea, 0.2 M sodium oxalate, pH 2 and a S/L ratio of 50 g/L. At higher S/L ratios (500 g/L), an increase in the oxalate concentration to 1.2 M was necessary to achieve the decomposition of the jarosite, liberating both the iron and the occluded silver. Additionally, increasing the oxalate concentration is necessary to act as a complexing agent for the large amount of ferric and cupric ions released by the jarosite decomposition.

中文翻译：

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用硫脲和草酸盐从工业黄钾铁矾样品中酸分解和浸银

摘要 黄钾铁矾是大多数锌加工厂的废物，因为这些化合物的形成是为了消除酸性介质中锌溶液中的铁和其他杂质。然而，它们通常在其结构中包含有价值的元素，例如银。在本研究中，提出了回收此类废物中存在的银的替代方案。评价了 pH、温度、草酸盐浓度和固液比 (S/L) 对硫脲稳定性和通过酸分解和还原浸出黄钾铁矾选择性回收银的影响。结果表明，提高系统温度有利于黄钾铁矾的分解和银向溶液中的释放，在 50 和 60 °C 下分别获得 86% 和 100% 的银回收率，0.13 M 硫脲，0. 2 M 草酸钠，pH 2，S/L 比为 50 g/L。在更高的 S/L 比 (500 g/L) 下，需要将草酸盐浓度增加到 1.2 M，以实现黄钾铁矾的分解，释放出铁和吸留的银。此外，增加草酸盐浓度对于作为黄钾铁矾分解释放的大量铁离子和铜离子的络合剂是必要的。