How does liquid-liquid solvent extraction separate niobium from tantalum?

In the context of niobium processing, the separation of niobium from tantalum is achieved through a liquid-liquid solvent extraction process following the decomposition of the ore or ferroalloy in hydrofluoric acid.1

The process functions as follows:

• Preparation: The tantalum-niobium material is dissolved into a slightly acidic aqueous feed solution.1
• Extraction: An organic solvent, typically methyl isobutyl ketone, is mixed into the aqueous solution.1
• Separation: Due to the chemical properties of the metals in this environment, the tantalum is extracted as a fluoride into the organic solution, while the niobium remains in the aqueous residue, known as the raffinate.1

Once separated, the niobium can be recovered from the aqueous phase by precipitation with ammonium hydroxide, followed by further processing to produce niobium pentoxide. This method is essential because the two elements are chemically very similar, making their individual identification and separation historically difficult.123