Researches On Process And Mechanism Of Zr And Hf Extracion And Separation By DIBK-Cyanex923 Extraction System

As a mature and advanced clean and environmental energy,nuclear power is an important development direction for all countries in the 21st century.The physical and chemical properties of zirconium and hafnium are similar.In general,the zirconium contains 1%³%of hafnium,but different nuclear properties of zirconium and hafnium.The neutron absorption cross section of zirconium is small,and it is used as the shell material of nuclear reactor,while the neutron absorption cross section of hafnium is large,which is used as the neutron control rod of nuclear reactor,which is the core material indispensable for nuclear reactor,and requires the content of the hafnium in the atomic energy level to be less than 0.01%.Therefore,the separation of zirconium and hafnium is the key to the preparation of nuclear zirconium hafnium.However,the nuclear grade zirconium of China's nuclear power plant depends on imported from abroad,and its core separation technology is still blocked by foreign countries.Although the separation process of methyl isobutyl ketone?MIBK?has the advantage of extracting the hafnium with less hafnium content,it also has the disadvantages of high water solubility,volatile,and easy decomposition of thiocyanate to toxic substances,so it is extremely urgent to develop the green separation technology with the preferential extraction of hafnium.Using diisobutyl?DIBK?has the characteristics of the similar structure of the isobutyl ketone,to develop the synergistic extractionsystem of DIBK-Trialkyphosphine Oxide?Cyanex923?,which is a priority extraction of hafnium.We studied the process and mechanism of DIBK-Cyanex923 to extract the zirconium and the hafnium in nitric acid extraction.A single factor experiment was used to investigate the effects of water phase acidity,zirconium hafnium ion concentration,extraction agent DIBK and Cyanex923 on volume fraction,type and concentration of salting agent,extraction time and other factors on the extraction and separation of zirconium and hafnium from DIBK-Cyanex923 system.Results show that the control of water phase acidity of 2.97 mol/L,DIBK of 90%?v/v?in the extraction and 10%?v/v?Cyanex923,concentration of ammonium sulfate salting-out agent 0.8 mol/L,extraction for 10 min,the system for zirconium and hafnium extraction rate reached 15.2%and 87.1%respectively,separation factor?reached to 37.1,higher than in the United States MIBK-HSCN??=9¹0?,and it was not required to use thiocyanate,which is easy to decompose into toxic substances,and was a green preferential extraction system for the extraction of hafnium.Studies comparing different acidic media and carbonate for DIBK-Cyanex923loaded organic phase stripping performance,the results show that sulfuric acid,hydrochloric acid,nitric acid for DIBK-Cyanex923 load organic phase stripping effect is poor.The reverse stripping rate of zirconium and hafnium was less than 35%.The stripping effect of carbonate was better,and the stripping of zirconium and hafnium was61.87%and 91.67%when the concentration of potassium carbonate was 2 mol/L,phase ratio O/A=2:1.Slope method and the saturation capacity method were taken to study the Zr and Hf Extraction mechanism in DIBK-Cyanex923 system.The study of the gradient method shows that when the extraction of zirconium and hafnium is separated by DIBK alone,the compositions of extracted hafnium is Hf?NO₃?₄·DIBK,while the zirconium is basically not extracted.When Cyanex923 was used as a separate extractant,the composition of extracted specials for Zr and Hf were Zr?NO₃?₄·Cyanex923 and Hf?NO₃?₄·Cyanex923.In addition,DIBK and Cyanex923 binary hybrid system as the extractant,which has a positive synergistic effect on the extraction of zirconium and hafnium.The composition of the extracts of zirconium and hafnium is Zr?NO₃?₄·DIBK·Cyanex923 and Hf?NO₃?₄·2DIBK·Cyanex923.The results of the saturation capacity method show that molar ratio of Cyanex923 and the material extracted from the extracted zirconium and hafnium is nCyanex923:n?Zr+Hf?=1:1,which is consistent with the results obtained by the slope method.In addition,using FT-IR infrared spectroscopy methods analysis of extraction solvent and extraction ion complexing,the results show that the DIBK separately as extraction agent,appear absorption peak at 3500 cm^-1,shows that extraction compound exists in the association of water,and absorption peak C=O-in 1710 cm^-1has red shift to high wave,??=15cm^-1,show that the C=O-to participate in the coordination of zirconium and hafnium;When Cyanex923 was used as an extractant alone,the absorption peak P=O-in 1186 cm^-11 has red shift to high wave,??=164 cm^-1,indicating thatP=O-participatedinthe coordinationofzirconium hafnium.When DIBK-Cyanex923 binary mixture was used as the extractant,the absorption peak P=O-in 1294 cm^-11 has red shift to high wave,??=20 cm^-1,indicating that P=O-participated in the coordination of zirconium and hafnium.