A Review on the Separation of Niobium and Tantalum by Solvent Extraction

ABSTRACT

Niobium and tantalum are found together in natural minerals. Leaching with concentrated acid solution or alkaline roasting followed by water/dilute acid leaching results in a solution containing these two metals. In this work, we reviewed the extraction and separation of Nb(V) and Ta(V) from leach liquors in the absence and presence of hydrofluoric acid by acidic, neutral extractants and amines. Several solvent extraction systems were compared in the light of the requirement of hazardous chemicals, extraction/separation efficiency, and stability/solubility of extractants. Since the cationic species of Nb(V) and Ta(V) are unstable in the aqueous solution, the application of acidic extractants for extraction and separation of these metals is limited. Amines can extract Nb(V) as well as Ta(V) irrespective of the presence of fluoride ion but the separation of these metals from the loaded amines should be carried out in stripping process, resulting in process complexity. Another disadvantage encountered for amine is related to high viscosity in extraction process. Neutral extractants are considered as promising extractants which are effective to separate Ta(V) and Nb(V) from either non-fluoride or to moderate fluoride ion concentration in terms of extraction, separation and stripping efficiency. Compared to the traditional methyl iso-butyl ketone (MIBK) based system, methyl isoamyl ketone (MIAK) is found to be a promising extractant to separate Nb(V) and Ta(V).

초록

니오비움과 탄탈륨은 광석에 같이 존재한다. 진한 무기산 또는 알칼리로 배소한 다음 물이나 묽은 산으로 침출하면 두 금속이 용해된 용액을 얻을 수 있다. 본 논문에서는 침출액에서 불산 존재 여부에 따라 산성, 중성 및 염기성 추출제로 니오비움(IV)과 탄탈륨(IV)의 추출분리에 대해 조사하였다. 유독 화학물질의 필요, 추출 및 분리 효율, 추출제의 안정성과 용해도의 측면에서 여러 용매추출계를 비교하였다. 수용액에서 니오비움(4)과 탄탈륨(4) 양이온 화학종은 불안정하므로 산성 추출제로 두 금속을 분리하는 것은 제한적이다. 염기성 추출제는 불소이온의 존재 여부와 관계없이 두 금속을 잘 추출하여 탈거로 두 금속을 분리해야 하므로 공정이 복잡하다. 또한 염기성 추출제의 단점은 높은 점성도이다. 불소이온이 전혀 없거나 적당한 농도가 함유된 침출용액의 경우에는 중성추출제가 두 금속의 분리추출 및 탈거측면에서 더욱 효과적이다. 전통적인 MIBK 추출계에 비해 MIAK 가 두 금속의 분리에 더 유망하다.

KEYWORDS:

• Leaching
• niobium
• tantalum
• separation
• solvent extraction

주제어:

• 침출
• 니오비움
• 탄탈륨
• 분리
• 용매추출

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Additional information

Funding

This work was supported by the National Research Foundation of Korea [grant number 2018R1D1A1B07044951].