The separation of zirconium and hafnium from (NH4)3Zr(Hf)F7 using amine-based extractants

Abstract

The suitability of the amine-based extractants Alamine 336, Aliquat 336 and Uniquat 2280 (10 wt%) for the selective extraction of zirconium (Zr) and hafnium (Hf) from a (NH4)3Zr(Hf)F7 solution was investigated. The extractant-containing organic phase consisted of cyclohexane and 5 v/v% 1-octanol as phase modifier. The (NH4)3Zr(Hf)F7 was dissolved in either hydrochloride acid or sulphuric acid (0.01-8.0 mol/dm3). The following variables were investigated: (i) the type and concentration of the acid, (ii) the equilibrium time, (iii) the organic/aqueous phase ratio and (iv) the extractant to metal ratio. Subsequently, using the optimized extraction conditions, the stripping of extracted metals from the organic phase was investigated using sodium chloride and sulphuric acid. The metal content in the aqueous phase was determined using ICP-OES before and after extractions. When using sulphuric acid solutions, extractions of >80% were reached both for Zr and Hf. In all cases equilibrium was achieved in less than 25 minutes of contact between the organic and the aqueous phase. Stripping of metals was achieved with >40% separation and 50% extraction using a sodium chloride (0.7 mol/dm3) stripping solution