Recycling of cobalt from end-of-life lithium-ion batteries (LIBs) is gaining interest because they are increasingly used in commercial applications such as electrical vehicles. A common LIB cathode material is lithium cobalt oxide (LiCoO₂). Besides the cathode, LIBs contain other components, such as metallic aluminium and copper as current collectors, which are often separated at initial hydrometallurgical recycling stages. Leaching of cobalt from LiCoO₂ is mainly driven by reducing cobalt(III) in LiCoO₂ to cobalt(II) via adding reducing agents. In this work, a green, cheap and safe approach is proposed by using a choline chloride–citric acid deep-eutectic solvent (DES) as lixiviant. Aluminium and copper were evaluated as reducing agents for cobalt(III). After optimisation, lithium and cobalt were quantitatively leached from LiCoO₂ in the presence of aluminium and copper. Copper was the most effective reducing agent for cobalt(III), so that no additional reducing agents or a pre-separation step were required. A speciation study of the pregnant leach solution (PLS) confirmed the dominance of chloro complexes. DES leaching was compared with conventional hydrochloric acid leaching, whereby the DES avoided the formation of toxic chlorine gas. Finally, the DES PLS was used as the more polar phase in a non-aqueous solvent extraction process. This process consisted of a copper(I/II) extraction step with the extractant LIX 984, followed by selective extraction of cobalt(II) with the extractant Aliquat 336. Both metals were completely stripped from the loaded organic phases by oxalic acid. The total recovery yield of cobalt was 81%, as a 99.9% pure oxalate precipitate.

中文翻译：

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使用深共熔溶剂从锂离子电池正极材料中溶剂冶金回收钴

从报废锂离子电池（LIB）中回收钴越来越引起人们的兴趣，因为它们越来越多地用于电动汽车等商业应用中。常见的LIB阴极材料是钴酸锂（LiCoO ₂）。除阴极外，LIB还包含其他成分，例如金属铝和铜作为集电器，这些成分通常在初始湿法冶金回收阶段被分离。由LiCoO2钴的浸出₂主要通过减少钴（从动III中的LiCoO）₂至钴（II）通过添加还原剂。在这项工作中，通过使用氯化胆碱-柠檬酸深共熔溶剂（DES）作为浸滤剂，提出了一种绿色，廉价且安全的方法。铝和铜被评价为钴（III）的还原剂。优化后，在铝和铜的存在下从LiCoO ₂中定量浸出锂和钴。铜是最有效的钴还原剂（III），因此不需要其他还原剂或预分离步骤。孕妇浸出液（PLS）的形态研究证实了氯络合物的主导地位。将DES浸出与常规盐酸浸出进行了比较，从而避免了有毒氯气的形成。最后，DES PLS在非水溶剂萃取过程中用作极性更大的相。该过程包括用萃取剂LIX 984进行铜（I / II）萃取步骤，然后用萃取剂Aliquat 336选择性萃取钴（II）。草酸将两种金属从负载的有机相中完全去除。钴的总回收率为81％，为99.9％的纯草酸盐沉淀。