The Influence of Anions on the Distribution Coefficients of Hard Acid-Metals for Anion-exchange Resin in HF–H3BO3 Media

Abstract

Abstract The distribution coefficients, Kd, of eighteen hard acid-metal ions for a strongly basic anion-exchange resin were determined in HF–H3BO3 media in the presence of Cl− or NO3−, SO42−, and ClO4−, and the relation between the adsorbabilities of the coexisting anions and the Kd values of the metal ions was discussed. The fluoride-ion concentration is quite low in HF–H3BO3 media because of the complex formation of the fluoride ion with boric acid, and most of the hard acid-metal ions have lower Kd values in HF–H3BO3 media than those in a hydrofluoric acid solution. By varying the kinds of coexisting anions and their concentrations in HF–H3BO3 media containing less than 0.02 M(1M=1 mol dm−3) of fluoroborate ions, the Kd values of metal ions can be controlled to allow the anion-exchange separations. As fluoroborate ions, e.g., BF4− or BF3OH−, are strongly adsorbed on the resin, metal ions which are strongly held on the resin can be eluted by media including fluoroborate ions in higher concentrations. By using HF–H3BO3 media and selecting the coexisting anions, an effective mutual separation of titanium–zirconium, titanium–uranium, tin–niobium, and molybdenum–tungsten can be attined.