Extraction of alkaline-earth elements from nitric acid with a solution of HDBP zirconium salt

Extraction of alkaline-earth metals with acidic zirconium salt of dibutyl hydrogen phosphate (HDBP AZS) increases in the order Ba < Sr < Ca. Magnesium is extracted substantially better than Ba, but by an order of magnitude worse than Ca. The maximal recovery of Sr is observed at Zr: HDBP ratio of 1: 9, similarly to extraction of TPE and REE. The recovery of Sr is possible from weakly acidic solutions (<0.5 M HNO₃); as the acidity increases, the Sr distribution coefficient decreases in proportion to [H⁺]^?3. The presence of TBP in the extractant slightly decreases the Sr extraction but simultaneously increases the extractant capacity. The latter effect is substantially less pronounced than for TPE and REE. In the experiment with model solutions on a bench of centrifugal extractors, the Sr decontamination factor from REE and TPE as high as 50–100 was attained.