공융용매를 활용한 폐 NdFeB자석으로부터 희토류 침출 거동
Leaching Behavior of Rare Earth Elements from Waste NdFeB Magnets Utilizing Deep Eutectic Solvents
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폐 NdFeB 자석으로부터 공융용매를 활용한 희토류 침출 거동 연구를 수행하였다. 8개의 공융용매를 제조하여 Nd2O3, Fe, Fe2O3 등 Nd, Fe 화합물에 대한 기초 침출 거동 실험을 우선 수행하였다. Nd2O3에 대한 침출 결과 GUC-LAC, ChCl-LAC, EG-MA 등 3가지 공융용매를 침출제로 사용 시64-100%의 Nd 침출율을 획득하였다. 해당 3개의 용매를 사용하여 Fe, Fe2O3에 대한 침출을 수행한결과, Fe는 모든 용매에서 94% 이상의 높은 침출율을 나타낸 반면, Fe2O3는 용매에 상관없이 침출율이 7% 이하로 낮게 나타났다. 기초 연구 결과를 토대로 NdFeB 자석에 대해 산화배소 유무에 따른 침출 실험을 수행한 결과 산화배소 후 NdFeO3 복합 산화물 형성으로 인해 Nd, Fe의 침출율이 각각 27%, 4.7%로 전처리하지 않은 자석의 침출에 비해 현저히 낮은 수준을 나타내었다. 따라서NdFeB 자석에서 Nd를 선택적으로 회수하기 위해서는 적절한 전처리 방법의 적용을 통해 Nd2O3 및 Fe2O3와 같이 각 산화물로의 상분리가 우선 진행되어야 함을 확인하였다.
Abstract
The leaching behavior of a rare earth element, neodymium, from waste NdFeB magnets using deep eutectic solvents (DESs) was investigated. Eight different DESs were prepared for leaching tests. The basic tests were conducted on Nd and Fe compounds, Nd2O3, Fe, and Fe2O3. Using GUC-LAC, ChCl-LAC, and EG-MA, Nd2O3 was leached by 64–100%. With the three DESs, Fe exhibited a leaching efficiency of over 94% in all DESs, while that of Fe2O3 remained low at <7%. Based on the results, leaching tests were conducted on NdFeB magnets with and without oxidative roasting. The leaching efficiencies of Nd and Fe significantly decreased after the roasting, at 27% and 4.7%, respectively. This was attributed to the formation of NdFeO3 during the roasting. Therefore, to selectively recover Nd from NdFeB magnets, the application of the appropriate pre-treatment method is necessary, prioritizing the separation of individual oxides to Nd2O3 and Fe2O3.
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