Liquid-liquid separation of zirconium and hafnium from nitric liquor in order to obtain nuclear zirconium oxide using TBP as extractant

Abstract

A specific process to obtain nuclear grade zirconium oxide from a nitric acid liquor is described in this work. The liquor was obtained after alkali fusion and water leaching of a zircon concentrate. The production of nuclear zirconium oxide is possible when tributyl phosphate (TBP) is used as extractant with a high acidity nitric liquor. This study comprises steps: (i) batch experiments in order to select the best conditions for the process and (ii) continuous experiments carried out in counter current mixer-settler circuits. The batch experiments indicated that an increase in nitrate concentration did not correspond to a rise in the separation factor among Zr and Hf. Acidity has a significant influence on the Zr/Hf separation. For the organic phase containing 2.5 mol L-1 of TBP and an aqueous/organic ratio of the 1/1, 94% of the Zr was extracted and a separation factor of the 13.8 was obtained in one contact of the aqueous and organic phase. In the optimized continuous circuit, a product containing 99% of Zr and 0.03% of Hf (200 mg kg(-1)), which meets the nuclear zirconium specifications, was obtained.