oa South African Journal of Chemical Engineering - Solvent extraction separation of zirconium (IV) and hafnium (IV) as chloride and fluoride feedstock solutions using amine extractants
Due to lanthanide contraction zirconium (Zr(IV)) and hafnium (Hf(IV)), which have very similar chemical properties, occur together in nature. However, for the use in nuclear reactors the Zr must essentially be Hf free ((<5<50ppm). To attain this, the solvent extraction of zirconium and hafnium from fluoride and chloride solutions with tertiary (Alamine 336) and quaternary (Aliquat 336) amines in cyclohexane was investigated. Results obtained show that while, the extraction from fluoride-based compounds (K2Zr(Hf)F6) was unsuccessful for both Zr and Hf species, the extraction from the chloride- based compounds (Zr(Hf)Cl4) was possible. Both higher acid and extractant concentrations resulted in an increased extraction of both Zr and Hf. While for both Alamine 336 and Aliquat 336 the maximum extractions of Zr(IV) was achieved after 30 minutes, Aliquat 336 generally yielded higher Zr extractions, while the use of Alamine 336 mostly resulted in increased selectivities. It was subsequently shown that most of the metal species (99.8%) could be recovered from the loaded organic solution using only deionised water. Finally a numerical method was applied on this particular case study to propose a seven stage solvent extraction process for the production of nuclear grade Zr(IV).
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