Ion-exchange separation and spectrophotometric determination of zirconium, thorium and uranium in silicate rocks with arsenazo III

Abstract

A combined chromatographic-spectrophotometric method has been developed for the simultaneous determination of thorium, zirconium and uranium in silicate rocks. After sample decomposition with a mixture of perchloric and hydrofluoric acids, the three metals are precipitated with iron(III) and aluminum hydroxides, and adsorbed by anion-exchange on a Dowex l-column from dilute sulfuric acid containing hydrogen peroxide. The adsorbed thorium, zirconium and uranium are separated by elution with acid ammonium sulfate solution, hydrochloric acid and perchloric acid, respectively. The sorption from sulfate media and subsequent elution provide selective separation of thorium, zirconium and uranium, allowing their direct spectrophotometric determination with arsenazo III. Results on the determination of thorium, zirconium and uranium in standard rocks of the U.S. and Japan Geological Survey are quoted. © 1974.