Exploiting the solvation properties of ionic liquids: A novel approach for the separation of zirconium from hafnium

Hexamethylbenzene reacts differently with zirconium and hafnium tetrachloride, affording, for the former, a binuclear molecular complex Zr(η 6 -Me 6 C 6 )Cl 2 (μ-Cl) 3 ZrCl 3 and for the latter a binuclear ionic complex (Hf(η 6 -Me 6 C 6 ) Cl 3 ] + [Hf 2 Cl 9 ] - . This difference in reactivity is exploited to carry out a two-phase extraction using 1-butyl-3-methylimidazolium tetrachloroaluminate as the ionic liquid phase and a toluene/ pentane mixture as the organic phase. This technique presents the potential advantage of recovering pure zirconium chloride without the formation of highly inert oxides. GRAPHICAL ABSTRACT: Organic solvents selectively extract the zirconium complex from a mixture of neutral Zr(η 6 -Me 6 C 6) Zr(η 6 -Me 6 C 6 )Cl 2 (μ-Cl) 3 ZrCl 3 and ionic [Hf(η 6 -Me 6 C 6 ) Cl 3 ] + [Hf 2 Cl 9 ] - in ionic liquid solution.