Liquid–liquid extraction of niobium and tantalum from aqueous sulphate/fluoride solutions by a tertiary amine

Niobium–tantalum ore containing euxenite, samarsakite and fergusonite was leached using sulphuric acid. Niobium and tantalum were extracted from the leach liquor with the tertiary amine, Alamine 336, using kerosene and xylene as diluents and n-decanol as a modifier. The effect of contact time, sulphate and fluoride concentrations in the aqueous phase, extractant concentration and aqueous to organic phase ratio were investigated. Both elements were extracted to different extents, with tantalum extraction slightly greater. The separation factor was greater for kerosene diluent. Selective stripping was performed using either 50 g/L potassium hydroxide or 25 g/L ammonium carbonate solutions for niobium and tantalum. Tantalum was stripped first and Ta(OH)5 was precipitated during stripping. The separation of niobium from tantalum was achieved at this point. Niobium was then precipitated by adding ammonia.