Abstract

DE BEER, L.; VAN DER WESTHUIZEN, D.J.  and  KRIEG, H.M.. Solvent extraction and separation of hafnium from zirconium using Ionquest 801. J. S. Afr. Inst. Min. Metall. [online]. 2016, vol.116, n.1, pp.93-99. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2016/v116n1a14.

The solvent extraction (SX) characteristics of Ionquest 801 were investigated to determine if the selective extraction of hafnium (Hf) over zirconium (Zr) is possible. Firstly, Ionquest 801 was screened for its suitability as a function of acid concentration. The solvent consisted of 5wt % extractant, corresponding to a extractant to metal ratio (E:M_Zr) of 14:1, in cyclohexane with 5% v/v 1-octanol added as modifier. Aqueous solutions of ZrCl₄ with 3 wt% HfCl₄ were prepared by dissolution of the salts in HNO₃ to obtain 1.0 g/l Zr(Hf)Cl₄(aq) feed solutions (aged 24 hours). Subsequently, the extractant concentration was varied at optimal acid molarities. The most favourable extraction percentages were attained at 0.7 M HNO₃ and an E:M_Zr ratio of 5:1. Artifices in the form of aqueous additives were used to maximize the Hf selectivity at these optimal conditions. These included the addition of 1.5 M NaCl, NaNO₃, Na₂SO₄, and NaClO₄.H₂O, as well as tartaric, oxalic, mandelic, and citric acid with and without the addition of 6 wt% hydrogen peroxide (H₂O₂). Exploratory studies on the influence and usability of the most promising factors such as [SO^-₄²], [H₂O₂], and combinations thereof in a SX system were undertaken.

Keywords : solvent extraction; Ionquest 801; PC88A; organophosphorus; hafnium; zirconium.

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