Abstract
There is considerable interest in extraction of rare earth elements from NdFeB magnets to enable recycling of these elements. In practical extraction methods using wet processes, the acid waste solution discharge is a problem that must be resolved to reduce the environmental impact of the process. Here, we present an encouraging demonstration of rare earth element extraction from a NdFeB magnet using a closed-loop hydrochloric acid (HCl)-based process. The extraction method is based on corrosion of the magnet in a pretreatment stage and a subsequent ionic liquid technique for Fe extraction from the HCl solution. The rare earth elements are then precipitated using oxalic acid. Triple extraction has been conducted and the recovery ratio of the rare earth elements from the solution is approximately 50% for each extraction process, as compared to almost 100% recovery when using a one-shot extraction process without the ionic liquid but with sufficient oxalic acid. Despite its reduced extraction efficiency, the proposed method with its small number of procedures at almost room temperature is still highly advantageous in terms of both cost and environmental friendliness. This study represents an initial step towards realization of a closed-loop acid process for recycling of rare earth elements.
Highlights
Roasting of the NdFeB magnet[7,8,9] as a pretreatment process improves the selectivity between the rare earth elements and Fe, but the rare earth element recovery ratio is usually rather low because of acid leaching at room temperature
We demonstrate that reuse of the hydrochloric acid (HCl) solution in a near-room temperature process is feasible when using our method
60% of the Fe ions are contained in the insoluble material that is obtained after acid leaching
Summary
Roasting of the NdFeB magnet[7,8,9] as a pretreatment process improves the selectivity between the rare earth elements and Fe, but the rare earth element recovery ratio is usually rather low because of acid leaching ( with HCl) at room temperature. The waste acid’s recyclability is critically dependent on efficient extraction of the constituent elements of the magnet from the used acid. ® If Cyphos IL101 works well when used in our method, we may demonstrate a closed-loop acid process that operates near room temperature, which would be highly advantageous. After separation of the rare earth ions through an oxalic acid precipitation process, the HCl solution can be reused for a subsequent extraction. We demonstrate that reuse of the HCl solution in a near-room temperature process is feasible when using our method
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