The Research Of Complexation Chemistry For Ln（Ⅲ） With TBP, H₂O In Ionic Liquids

Ionic liquids(ILs) are anticipated as diluents to repalce flammable, volatile organic solvents in spent nuclear fuel reprocessing, such as kerosene and dodecanoic. Because of their fascinsting properties such as high thermal and chemical stability, negligible vapor pressure and successful in the extraction of metal ions. The complexation chemistry between metal ions and the TBP has achieved deep and extensive research, but which is carried out in two phase systems and has done a little research in homogeneous phase. Even though a few researches study the complexation reactions of lanthanides(Ⅲ)/nitrate in ionic liquids. They don’t study the Ln(Ⅲ)/nitrate complexation reactions in ionic liquids with different water content.This work studys the complexation chemistry behavior of the Ln(Ⅲ)/TBP(Ln=Nd,Eu) in water-saturated and different water content’s 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide(C4mim NTf2) by using spectrophotometric titrations. And focus on how different water content in C4 mim NTf2 influence on the complexation reactions of Ln(Ⅲ)/TBP. It is anticipated that this study will help in development of more effective strategies to design aqueous separation processes using ILs as solvent. The conclusions of this work are as follows:(1) The stability constants(lgβ) of Nd(Ⅲ)/TBP in the water-saturated C4 mim NTf2 at 10℃, 25℃, 40℃, 55℃ and 70℃are calculated to be 0.68±0.03, 0.77±0.02, 0.89±0.03, 0.97±0.03, 1.04±0.03; ΔH is 11.52 k J/mol. Researches show that in the case of the Nd(Ⅲ) / TBP, the limiting complex in water-saturated C4 mim NTf2 is found to be the Nd(TBP) 3-.The complexation ability strengthened along with the temperature rised. We also have the titration spectra, molar absorption spectra and species distribution curve.(2)The stability constants(lgβ) of Eu(Ⅲ)/TBP in the water-saturated C4 mim NTf2 at 25℃are calculated to be be 0.78±0.06,the value is very close Nd(Ⅲ)/TBP.(3) The luminescence lifetime of Eu(Ⅲ)/TBP in water-saturated C4 mim NTf2 increases from 0.102 ms to 0.168 ms. The exponential decay function shows the number of water molecules in the primary complexation sphere of Eu(Ⅲ) is calculated from nine to five, that is one TBP can replace four water molecules, the result is impossible, because of this formula is suitable for aqueous solution,which may not apply to ionic liquid systems, so the result remains to be further researched.(4) Researches show that in water-saturated C4 mim NTf2, at 25℃, when CH2O: CNd(Ⅲ)=40, the limiting complex of Nd(Ⅲ)/TBP is found to be Nd(TBP) 3-. The stability constants(lgβ) are calculated to be 0.77±0.02. when CH2O:CNd(Ⅲ)=10, the stability constants(lgβ) are calculated to be 2.62±0.09, 5.37±0.12, 7.65±0.21, 9.52±0.24. The complexation ability strengthened along with the temperature rised. With water content decreasing, the stability constants and complexation number of Nd(Ⅲ) /TBP is increased.