Due to its physical properties, metallic silver is present in numerous electronic wastes. Its recycling requires selective extraction, which involves leaching of silver as the first step. This work focusses on leaching silver with Cu(II)/NH/SO which has been widely used for gold leaching. As recently shown for the leaching of copper, using foams whose aqueous phase consists of leaching chemicals is a promising way to reduce the environmental footprint, by improving the metal oxidation caused by the fast transfer of O from bubble to bubble. In this work, metallic silver samples are dissolved by foams made of Cu(II)/NH/SO solution with bubbles composed of O-N mixtures. The main problem of the thiosulfate route is its degradation during metal oxidation hence it requires using large quantities of this reactant. The results obtained for our leaching foams show that the quantity of silver leached per quantity of thiosulfate used is about three times greater in comparison with a solution, which would bring a new approach to this problem. Moreover, we investigate the role of the bubble size and the gas composition (dioxygen partial pressure). Besides we find that the dissolved silver is inhomogeneously distributed between the foam column and the bottom solution, with an accumulation of 90 % of silver inside the foam, hence opening an interesting perspective for an easy separation of silver upon leaching. Comparing several surfactants, we show that only non-ionic surfactant polyoxyethylene oleyl ether, Brij O10, shows satisfying results, while dodecyl trimethyl ammonium chloride most likely binds with silver complexes and triggers a quick collapse of the foams.

中文翻译：

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在电子废物回收背景下使用硫代硫酸铜 (II)-氨系统进行银浸取泡沫的研究

由于其物理特性，金属银存在于许多电子废物中。它的回收需要选择性提取，第一步涉及银的浸出。这项工作的重点是用 Cu(II)/NH/SO 浸出银，该方法已广泛用于金浸出。正如最近铜浸出的研究表明，使用水相由浸出化学品组成的泡沫是减少环境足迹的一种有前途的方法，它可以改善因氧气在气泡之间快速转移而引起的金属氧化。在这项工作中，金属银样品被 Cu(II)/NH/SO 溶液制成的泡沫溶解，其中气泡由 ON 混合物组成。硫代硫酸盐路线的主要问题是其在金属氧化过程中的降解，因此需要使用大量的这种反应物。我们的浸出泡沫获得的结果表明，每单位硫代硫酸盐浸出的银量大约是溶液的三倍，这将为解决该问题带来新的方法。此外，我们研究了气泡尺寸和气体成分（分子氧分压）的作用。此外，我们发现溶解的银在泡沫柱和底部溶液之间分布不均匀，90％的银积聚在泡沫内部，因此为浸出时银的轻松分离开辟了有趣的前景。比较几种表面活性剂，我们发现只有非离子表面活性剂聚氧乙烯油基醚Brij O10表现出令人满意的结果，而十二烷基三甲基氯化铵最有可能与银络合物结合并引发泡沫的快速塌陷。