APPLICATION OF LIQUID-LIQUID EXTRACTION FOR THE SEPARATION OF ZIRCONIUM FROM HAFNIUM

The use of liquid-liquid extraction for the separatJ?n of zirconium from hafnium was demonstrated. Hafnium spectrographically free of zirconium was prepared in quantity on a continuous basis. High purity fractions of zirconium were also prepared. Many single and multistage extractions employing immiscible organic solvents were carried out on aqueous solutions of the compounds to be separated. Analyses of the equilibrium phases allowed calculation of individual distribution coefficients and their separation factors. Single stage extractions were employed to obtain data from which the operation conditions for the multistage countercurrent extractions were estimated. A mixture composed of about 97 per cent hafnium and about three per cent zirconium as oxychlorides was dissolved in nitric acid. Extractions of this aqueous solution showed that zirconium was preferentially extracted by tributyl phosphate. The presence of nitric acid increased mass transfers to the organic phase but decreased the hafniumZirconium separation factors. A pilot plant continuous operation employing a 17 stage countercurrent extractor yielded 90 per cent of the hafnium spectrographically free of zirconium. * This report is based on a Ph.D. thesis by Raymond A. Foos submitted June~ · 1954 to Iowa State College, Ames, Iowa. This work was done under contract with the Atomic Energy Commission.