Ann: Further High-Grade Niobium Results from Equador - Brazil, page-490

The beneficiation of niobium and tantalum from mica schist-associated deposits involves several key processes:

Physical separation: The ore is typically crushed and ground to liberate the niobium-tantalum minerals. Gravity separation methods like shaking tables or spiral concentrators can be used to separate the heavier niobium-tantalum minerals from lighter gangue minerals.

Magnetic separation: Since many niobium-tantalum minerals are weakly magnetic, high-intensity magnetic separators can be employed to concentrate them further.

Flotation: Froth flotation can be used to selectively separate niobium-tantalum minerals from other minerals based on surface properties. Collectors and modifiers are added to enhance the flotation of desired minerals.

Chemical processing: The concentrate may undergo acid leaching or alkali treatment to remove impurities and increase the grade of niobium and tantalum.

Smelting and refining: The final concentrate is typically processed pyrometallurgically or hydrometallurgically to produce high-purity niobium and tantalum metals or compounds.

The presence of mica in the ore can complicate beneficiation, as it may interfere with flotation and other separation processes. Careful optimization of grinding and separation techniques is often required to effectively recover niobium and tantalum from mica schist-hosted deposits.

The separation of tantalum (Ta) and niobium (Nb) from mica schist presents several challenges:

Complex mineralogy: Mica schist often contains various minerals, making it difficult to selectively extract Ta and Nb. The presence of mica itself can interfere with separation processes.

Similar chemical properties: Ta and Nb have very similar chemical properties, making their separation from each other challenging. This is evident in the continuous range of compositions found in tantalite-columbite minerals.

Low concentrations: Ta and Nb are often present in low concentrations, requiring efficient extraction methods to be economically viable.

Variable Nb/Ta ratios: The Nb/Ta ratio can vary significantly within deposits, complicating separation processes. This variability is influenced by factors such as the degree of fractionation in pegmatites.

Interfering elements: The presence of other elements like iron, manganese, and tin can complicate the separation process. For instance, the Mn/Fe ratio affects the behavior of Ta and Nb during extraction.

Fine grain size: Ta-Nb minerals in mica schist may be finely disseminated, requiring fine grinding for liberation, which can lead to losses during physical separation processes.

Environmental concerns: Some separation techniques may involve the use of hazardous chemicals, necessitating careful handling and disposal procedures.

These challenges necessitate a combination of physical, chemical, and metallurgical techniques to effectively separate Ta and Nb from mica schist-hosted deposits.