| Zirconium and hafnium are important strategic resources, importantmaterial to build nuclear reactors. They are not only similar in outerelectronic structure, but also quite alike in their atomic radius, ionic radiusand characteristic for the reason of lanthanide contraction effect. In nature,zirconium and hafnium is often symbiotic, almost all of the zirconiumcontains1%～3%hafnium. Zirconium and hafnium are quite different innuclear properties, zirconium has a low thermal neutron absorption area(0.18±0.02b), and the zirconium alloy cladding material is effective toprevent nuclear radiation and nuclear leak. On the contrary, hafnium has ahigh thermal neutron absorption area (150b), can effectively absorb thermalneutrons of thermonuclear reactions to control the speed of the nuclearreaction. Therefore, Hafnium content should below0.01%while useatomic-scale zirconium to build nuclear reactors. Therefore, effectiveseparation of hafnium from zirconium is particularly important.More than2/3of the zirconium sponge is produced by the method ofextraction separation of zirconium and hafnium by methylisobutylketone-thiocyanate (MIBK-HSCN) system. In the system, the water phaseof extractant (MIBK) solubility is high and loss easily, the flash point is lowand volatile, also there is some toxicity. Considering that the two methylisobutyl ketone (DIBK) not only has similar structure and extraction abilitylike the MIBK, but also has advantages of lower aqueous solubility, higherflash point and lower toxicity. So our researchers proposed a newtechnology of the two methyl isobutyl ketone-tributyl phosphate(DIBK-TBP) synergistic extraction system for zirconium and hafniumseparation in order to reduce solvent loss and improve the operatingenvironment. Preliminary research has only been done on the extractionmechanism and thermodynamics of using DIBK-TBP system extraction zirconium and hafnium. It’s necessary to study the dynamics to understandthe dynamic control type and the apparent activation energy of this verysystem, so it will show a complete theoretical guiding significance inindustrial applications.Inductively coupled plasma atomic emission spectrometry (ICP-AES)or inductively coupled plasma mass spectrometry (ICP-MS) is usually usedto measure the content of hafnium and zirconium, but these tests costs a lotand equipment requirements are high. In order to overcome theseshortcomings and to improve actionable of the ordinary laboratorydetermination of zirconium and hafnium content actionable, the method ofMIBK-HSCN system extraction separation zirconium and hafnium thendeterminate by arsenazo III spectrophotometric, was innovatively used. Theoptimum coloration conditions of arsenazo III method was investigated, theresults showed that the best volume of0.1%(wt) arsenazo Ⅲ chromogenicagent is4.0mL, the best volume of5%urea protective agent is4.0mL, andwhen the coloration environment is in8.0mol/L nitric acid solutions, themeasured total amount of raw material zirconium and hafnium is98.81%,zirconium and hafnium component was97.34%and1.867%respectively.The verified total amount is98.103%measured by xylenol orangespectrophotometric. Zirconium and hafnium component in raw material isrespectively96.923%and1.863%, which verified by two steps such asfollow, zirconium and hafnium extraction separation by TBP-HNO3-HClsystem, and then determinate with arsenazo III method. To verified themethod of MIBK-HSCN system extraction separation of zirconium andhafnium, internal standard method was used, by which certain volumes ofstandard hafnium solution was added in the raw material solution, extractionseparation and then determination in the same way, the results showed thatthe error between hafnium content added value with the theoretical is-0.472%～3.414%, and zirconium content basic unchanged. Constant interface pools was used for examine the stirring speed andinterfacial area influence on the initial extraction rate of DIBK-TBPsynergistic extraction system extraction zirconium and hafnium. Combinedwith the characteristics of the constant interface pools and organic solventextraction of metal, these facts are revealed, that in DIBK-TBP system, theextraction reaction is first order kinetic reaction, hafnium extraction processis mixed control type, however, zirconium extraction is phase reactioncontrol type.The temperature influence on the initial extraction rate of DIBK-TBPsystem was also studied. Combined with the differential coefficient and theArrhenius formula, zirconium and hafnium apparent activation energies ofthe extraction process were calculated, the results are-16.024kJ/mol and-43.106kJ/mol respectively. |
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