Design of an Extractive Distillation Column for the Environmentally Benign Separation of Zirconium and Hafnium Tetrachloride for Nuclear Power Reactor Applications (original) (raw)
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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 m...
Arab Journal of Nuclear Sciences and Applications, 2020
Green liquid emulsion membrane (LEM) was developed for separation of zirconium and hafnium from nitric acid medium. The membrane is based on the use of CYANEX-272 diluted with corn oil (green diluent) as a carrier, span 80 as a surfactant and citric acid as a stripping agent. The factors affecting the stability of the LEM were investigated under chosen conditions. The parameters affecting the permeation of Zr and Hf from nitrate medium were also studied. The metal ion content in the inner phase obtained by demulsifying the loaded CC-LEM using the freeze-thaw method is 22.8 g/l Zr and 2.05 mg/l Hf i.e. the contamination of the recovered Zr is 89.91 mg Hf/ kg Zr which is below the limit for the use of zirconium in nuclear applications.
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The extraction of zirconium and hafnium from aqueous HCl solutions by means of Aliquat 336 in organic diluents was systematically studied. The following three aspects were discussed: the extraction dependence on HCl, the Aliquat 336 concentrations, and the nature of diluents. Both of the metals were stripped with deionized water and the influence of phase ratio on the efficiency of the stripping has been investigated. The stoichiometry of the extracted Zr and Hf species from single metal ion were studied and a possible extraction mechanism for the Zr-Hf mixture is discussed in the light of the results obtained.