Sequential Separation of Uranium, Hafnium and Neodymium from Natural Waters Concentrated by Iron Coprecipitation

A new ion exchange chromatography method is presented for the isolation of high field‐strength elements ( HFSE ) from freshwater and seawater samples that have undergone iron coprecipitation. Large volumes of water can be condensed through the application of iron coprecipitation, but clean separation of elements from the precipitate proves difficult. The technique described is a five‐column process designed to separate the HFSE , including rare earth elements such as neodymium and hafnium, before removing the iron and isolating uranium. Subsequent isolation of Nd and Hf was achieved using established ion exchange chromatography methods. The efficacy of our chemistry was verified by measurements of analytical reference materials – both reference solutions and seawater samples – subjected to the chemical separation methods described. Elution results indicate high yields (> 90%) determined by concentration measurements of a known reference material added to each column. Measurement results for isotopic compositions of seawater (U, Nd) and reference solutions ( NIST SRM 960, U) were identical within uncertainty to previously published values. Compositions were identical between solutions (Spex CLMS 3, Spex PLND 2) that underwent different iron coprecipitation procedures. Isotopic determinations for reference materials JN di‐1 and NIST SRM 960 measured with the mass spectrometers used in this study were in agreement with universally accepted values for these materials, and indicate high precision.