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.

Keywords:

• Continuous experiments
• Hafnium
• Solvent extraction
• Tributyl phosphate
• Zirconium
• Zirconium/Hafnium separation

Acknowledgments

The authors would like to thank FAPEMIG, CNPq, FINEP, and CAPES for financial support, and technicians from CDTN, which also contributed to the development of this work, especially Luiz C. da Silva, Marcos A. Evangelista, Liliane P. Tavares, and Ariovaldo Paganini.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by FAPEMIG, CNPq, FINEP, and CAPES.