N,N’-Dimethyl-N,N’-Dioctyl-3-Oxadiglycolamide’s On Extraction Behavior For Lanthanides(Ⅲ)

The disposal of spent fuel from the reactors of nuclear power plants and the high level liquid waste（HLLW）generated from spent fuel reprocessing is a major concern of developing safe nuclear energy.In order to improve the safety of nuclear energy,to reduce the volume of high level radioactive waste that needs to be monitored for long time in deep geological repository,and to effectively use the limited resources of fissile material,the countries of nuclear energy in the world have developed extraction processes for separating minor actinides ion and lanthanides from the high level liquid waste over the past decades.The development of new-type extractants and the design of extraction process are important.Therefore,exploring suitable extractants and extraction condition have important significance on extraction chemistry.Diamide extractants have high affinity toward actinides and lanthanides.However,the corresponding extraction chemistry and the separation behavior are not considered comprehensively.In this paper,extraction performance of Ln³⁺by extraction system using N,N’-dimethyl-N,N’-dioctyl-3-oxadiglycolamide（DMDODGA）as extract ant,with 40%1-octanol/kerosene as diluent,w as investigated in HNO₃ solution.The effect of hydrochloric acid concentration,extract ant concent ration and temperature on the extraction extraction behavior of La³⁺,Nd³⁺,Sm3⁺and Gd³⁺were investigated.The study found as below:（1）In the range of experimental nitric acid concentration,the extraction distribution ratio of La³⁺,Sm³⁺and Nd³⁺increased gradually with the increase of nitric acid concentration.When 1.5mol/L reached the inflection point,it began to decrease with the increase of nitric acid concentration.However,the extraction distribution ratio of Gd³⁺increased gradually with the increase of nitric acid concentration all the time.（2）The distribution ratio of Ln³⁺increases with the increase in the concentration of extractants under the experimental nitric acid concentration;The distribution ratio decreases with the increase in the temperature and the extraction reactions are exothermic.The equilibrium constant and thermal physical constant have been calculated.（3）The extraction mechanism was proposed via a slope approach.The extraction mechanisms are established as:for La³⁺and Sm³⁺,one lanthanide ion coordinates with three extract ant molecules,however,for Nd³⁺and Gd³⁺ion there are two extract ant molecules,in 40%1-octanol/kerosene diluent.（4）Extraction reaction of Ln³⁺is exothermic reaction.The distribution ratio decreases with the increase in the temperature and the extraction reactions are exothermic.