Separation of zirconium and hafnium by extraction with 2-octanol

Abstract

Zirconium and hafnium are shown to be separable using 2-octanol (C8H18O) as an extractant. Zirconium basic carbonate was dissolved using hydrochloric acids at concentrations ranging from 5 % to 20 %. Potassium fluoride was found to be crucial to the process. Its effect was investigated in the concentration range of 1 M to 3 M. The optimum conditions obtained for extraction were 10 wt % HCl in a 1.5 M KF solution, a contact time of 15 minutes, and 100 % 2-octanol. Under these conditions, the separation factor of zirconium and hafnium is 9.2 with a maximum extraction percentage of 96.58 % of zirconium. The optimum conditions for stripping of zirconium were found to be 3 M H2SO4 as stripping agent, an A/O ratio of 1:1 and 40 minutes contact time. The McCabe-Thiele diagrams constructed from the experimental data indicate that four and five equilibrium stages are sufficient for the extraction and stripping of zirconium respectively. A recovery of 97.25 % of hafnium was obtained using a mixture of oxalic acid and nitric acid as a stripping agent. A study of chemical speciation in the two phases would be important for the improvement of the process.