The continuous miniaturization of modern green and advanced technologies is increasing the demand of rare earth elements (REEs). Consequently, REEs are listed as the critical metals concerning their crucial role for a clean environment. However, their resources are limited which in turn disrupt their supply chain. To tackle the supply issue and to meet future demand, there is need to exploit recycling schemes for the recovery REEs from secondary resources. This review describes comprehensively various processes developed for the separation of REEs and transition metals from secondary resources. It focuses on the hydrometallurgical route, especially solvent extraction employed to separate REEs and transition metals from potential wastes originated from different industries. The use of different commercial extractants for the recycling purposes and mechanisms involved in the extraction has been discussed in detail.

现代绿色技术和先进技术的不断小型化正在增加对稀土元素（REE）的需求。因此，稀土元素因其对清洁环境的关键作用而被列为关键金属。但是，他们的资源有限，这反过来又扰乱了他们的供应链。为了解决供应问题并满足未来需求，需要利用回收计划从二次资源中回收稀土元素。这篇综述全面描述了为从二次资源中分离稀土元素和过渡金属而开发的各种工艺。它着重于湿法冶金路线，尤其是用于从不同行业产生的潜在废物中分离出REE和过渡金属的溶剂萃取。