상온제련을 위한 네오디뮴의 비수계 전해 기초연구
A Basic Study on Non-aqueous Electrolysis of Neodymium for Room-temperature Metallurgy
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본 연구에서는 네오디뮴의 상온제련의 가능성을 알아보기 위하여 비수계 전해액에서 네오디뮴의 전기화학적 레독스 거동을 조사하였다. 비수계 전해질로는 이온성액체인 [C 4 mim]PF 6 , [C 4 mim]Cl, [P 66614 ]PF 6 와 함께 네오디뮴 염에 대한 용해도가 높은 에탄올과전기화학적 안정성이 높은 탄산염계 유기용액을 기반으로 한 혼합전해질을 대상으로 하였다. 다른 전해액에 비하여 ethylene carbonate (EC)/di-ethylene carbonate (DEC)의 경우가 네오디뮴의 전기화학적 레독스 특성이 우수한 것으로 판단되었으며, 물성향상을 위하여에탄올을 첨가하는 실험을 수행하였다. 순수한 1 : 1 EC/DEC와 에탄올의 혼합 비율, 그리고 NdCl 3 의 농도에 따른 이온전도도를 측정한 결과, 에탄올 함량 50 vol%, NdCl 3 농도 0.5 M에서 전해질 특성이 가장 우수한 것으로 판단된다. 순환전위법과 선형전위법을이용해.3.8 V (vs. Pt-QRE)에서 네오디뮴의 환원반응으로 추정되는 전류피크가 관찰된다. 상온에서.6 V (vs. Pt-QRE)에서 18시간 동안 정전압법으로 전해한 결과, 금속 네오디뮴이 전착되었음을 확인하였다.
Abstract
In this study, the electrochemical redox behavior of neodymium in non-aqueous electrolytes was investigated to confirm the possibility of neodymium metallurgy at room temperature. The non-aqueous electrolytes include ionic liquids such as [C 4 mim]PF 6 , [C 4 mim]Cl, and [P 66614 ]PF 6 , ethanol which are highly soluble in neodymium salts, and mixed electrolytes based on carbonate with highly electrochemical stability. The electrochemical redox properties of neodymium were better than those of other electrolytes in the case of the mixed electrolyte based on ethylene carbonate (EC)/di-ethylene carbonate (DEC). Ethanol was added to improve the physical properties of the mixed electrolyte. Thorough the analysis about ionic conductivity of EC/ DEC ratio, ethanol content and NdCl 3 concentration, the best electrolyte composition was 50 vol% content of ethanol and 0.5 M of NdCl 3 . Using cyclic voltametry and linear sweep voltametry, a current peak estimated at .3.8 V (vs. Pt-QRE) was observed as a limiting current of neodymium reduction. Potentiostatic electrolysis for 18 hours at room temperature at .6 V (vs. Pt-QRE) confirmed that metallic neodymium was electrodeposited.
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