Separation of hafnium and zirconium from ti- and fe-rich geological materials by extraction chromatography

This paper presents a new chemical separation method for Hf and Zr from rocks using extraction chromatographic resins prepared from inert polymeric supports and the liquid anionic exchangers tri-n-octylamine or trioctylmethylammonium chloride (Aliquat 336). The method was developed using basaltic and trachyandesitic rocks with high contents of Al, Fe, and Ti. A 100-mg rock sample was decomposed with HF-HNO(3)-HClO(4) and fumed with HClO(4). The residue of this process was dissolved in 10 M HCl and then loaded on the column (6 mm i.d. × 75 mm). The major elements (Al, Ca, Mg, Ti, etc.) were eluted with 10 mL of 10 M HCl, and then Hf, Zr, and Fe were eluted sequentially using 20 mL of 8 M HCl, 20 mL of 2 M HCl, and 5 mL of 1 M HNO(3). The removal efficiency of major elements (Al, Fe, Ca, Mg) was greater than 99% and that of Ti was greater than 95%. The recoveries of Hf and Zr were better than 90% and the Zr/Hf ratio decreased from the natural ratio of 45 in the rock sample to 0.3 in the Hf fraction. This method provides an alternative to the less straightforward procedures based on several stages of ion-exchange separation and might be used for sample preparation prior to (176)Hf/(177)Hf determinations by magnetic sector multicollection ICPMS.