Lanthanide Ternary Complexes Relevant to the Nuclear Fuel Cycle

50 Pages·2012·1.15 MB·English

by  Georgina Roughley

Lanthanide Ternary Complexes Relevant to
the Nuclear Fuel Cycle

A Dissertation submitted to The University of Manchester for the degree of Master of
Science by Research in the Faculty of Engineering and Physical Sciences

2012

Georgina Roughley

School of Chemistry

  1
Contents

List of Figures 4
List of Tables 5
List of Equations 6
Abstract 7
Declaration 8
Copyright Statement 9
Acknowledgements 10
List of Abbreviations 11

Chapter 1: Introduction
1.1 The Nuclear Fuel Cycle 12
1.2 The TALSPEAK Process 15
1.3 The f – elements 18
1.4 The Lanthanides 19
1.4.1 Lanthanide Hydrolysis 20
1.4.2 Lanthanide Carbonate Complexes 20
1.4.3 Lanthanum 21
1.4.4 Europium 21
1.4.5 Lutetium 22
1.5 EDTA 23
1.6 Potentiometry 25
1.7 Speciation Diagrams 26
1.8 Ultraviolet-Visible Spectroscopy 27
1.9 Aims 29

Chapter 2: Experimental
2.1 Potentiometric Titration Solution Preparation 30
2.1.1 Lanthanide(III) Nitrate Solutions 30
2.1.2 Ligand Solutions 30
2.1.3 Lanthanide(III) : EDTA Binary Complex Solutions 31
2.1.4 Lanthanide(III) : EDTA : Na CO Ternary Complex Solutions 31
2 3
2.1.5 Carbonate free NaOH 31

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2.2 Instrumentation 32
2.2.1 Potentiometry 32
2.2.2 UV-Vis Spectroscopy 32

Chapter 3: Results/Discussion 33
3.1 Binary Complexes 34
3.1.1 La(III) : EDTA (1:1) 35
3.1.2 Eu(III) : EDTA (1:1) 36
3.1.2 Lu(III) : EDTA (1:1) 37
3.2 Ternary Complexes 38
3.2.1 La(III) : EDTA : Carbonate (1:1:1) 39
3.2.2 Eu(III) : EDTA : Carbonate (1:1:1) 40
3.2.3 Lu(III) : EDTA : Carbonate (1:1:1) 41
3.3 UV-Vis Spectroscopy Titrations for Eu:EDTA:Carbonate (1:1:1) 42
3.4 Potentiometric Results Summary 44

Chapter 4: Conclusion 45

Chapter 5: Future work 46

Chapter 6: References 47

Word Count: 8,450

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List of Figures

Figure 1: Representation of the nuclear fuel cycle.1
Figure 2: Diagrammatic representation of the dry method of conversion for
yellowcake to uranium hexafluoride.
Figure 3: Diethylenetriaminepentaacetate (DTPA5-).
Figure 4: A basic diagrammatical representation of the TALSPEAK process.
Figure 5: A basic diagrammatical representation of the reverse TALSPEAK process.
Figure 6: Diagrammatic representations of f orbitals.16
Figure 7: Ethylenediaminetetraacetate (EDTA4-)
Figure 8: Metrohm751 GPD Titrino apparatus.28
Figure 9: Example of a speciation model from Hyperquad.
Figure 10: To show transitions between two energy levels.
Figure 11: Speciation diagram of the deprotonation of EDTA complexes.
Figure 12: Potentiometric titration of La3+ /EDTA complexation at 25 oC. I = 0.1 M
NaNO . V0 = 10 mL. C = C = 10 mM. Titrant = 0.1 M NaOH.
3 La EDTA
Figure 13: Potentiometric titration of Eu3+ /EDTA complexation at 25 oC. I = 0.1 M
NaNO . V0 = 10 mL. C = C = 10 mM. Titrant = 0.1 M NaOH.
3 La EDTA
Figure 14: Potentiometric titration of Lu3+/EDTA complexation at 25 oC. I = 0.1 M
NaNO . V0 = 10 mL. C = C = 10 mM. Titrant = 0.1 M NaOH.
3 La EDTA
Figure 15: Speciation diagram for carbonate.
Figure 16: Potentiometric titration of La3+/EDTA/Carbonate complexation at 25 oC. I
= 0.1 M NaNO . V0 = 10 mL. C = C = C = 10 mM. Titrant = 0.1 M
3 La EDTA carbonate
NaOH.

Figure 17: Potentiometric titration of Eu3+/EDTA/Carbonate complexation at 25 oC.
I = 0.1 M NaNO . V0 = 10 mL. C = C = C = 10 mM. Titrant = 0.1 M
3 La EDTA carbonate
NaOH.

Figure 18: Potentiometric titration of Lu3+/EDTA/Carbonate complexation at 25 oC. I
= 0.1 M NaNO . V0 = 10 mL. C = C = C = 10 mM. Titrant = 0.1 M
3 La EDTA carbonate
NaOH.

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List of Tables

Table 1: Ionic radii for Ln3+ ions.4
Table 2: Hydrolysis constants for selected lanthanides.18
Table 3: Stability constants of Ln3+ complexation with carbonate; I = 0.7 M
NaClO .18
4
Table 4: Stability constants for the deprotonation of Na EDTAH in solution.18
2 2
Table 5: Stability constants for lanthanides La3+, Eu3+ and Lu3+ ions with EDTA4-
ligand.18
Table 6: Table to show the concentrations and volumes used for each titration.
Table 7: Stability constants of La(III) complexation with EDTA and hydroxide; I =
0.1 M NaNO .
3
Table 8: Stability constants of Eu(III) complexation with EDTA and hydroxide; I =
0.1 M NaNO .
3
Table 9: Stability constants of Lu(III) complexation with EDTA and hydroxide; I =
0.1 M NaNO .
3
Table 10: Stability constants of La(III) complexation with EDTA and carbonate; I =
0.1 M NaNO .

3
Table 11: Stability constants of Eu(III) complexation with EDTA and carbonate; I =
0.1 M NaNO .
3
Table 12: Stability constants of Lu(III) complexation with EDTA and carbonate; I =
0.1 M NaNO .
3
Table 13: Summary of Log K values found when conducting potentiometry
experiments

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List of Equations

Equation 1: Equation to calculate the distribution factors of solutes
Equation 2: Equation to calculate separation factors
Equation 3: The parameter pH is related the concentration of protons
Equation 4: The Beer- Lambert law.32

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Abstract

This project has been focused on modelling actinide behaviour using lanthanide
analogues. Ternary complexes of Lanthanides-EDTA-Carbonate have been studied
with techniques such as potentiometry and ultraviolet-visible absorption spectroscopy.
It was found that ternary complexes of Ln-EDTA-Carbonate and Ln-EDTA-OH do
exist for La, Eu and Lu. Log K values were calculated from potentiometry titrations
which involve the formation of these ternary species. For lanthanum, the log K values
for the complexes [La(EDTA)]-, [La(EDTA)(OH)]2- and [La(EDTA)(CO )]3- were
3
14.20, -9.22 and 4.70, respectively. For europium, the log K for the complexes
[Eu(EDTA)]-, [Eu(EDTA)(OH)]2- and [Eu(EDTA)(CO )]3- were 13.77, -10.35 and
3
4.55, respectively. For lutetium, the results for the complexes [Lu(EDTA)]-,
[Lu(EDTA)(OH)]2-, [Lu(EDTA)(OH) ]2- and [Lu(EDTA)(CO )]3- were 17.38, -12.40,
2 3
-22.97 and 3.30, respectively.
The results are useful for helping to understanding solution chemistry of lanthanides
with EDTA in aqueous environments, which is applicable to actinide-lanthanide
separations and actinide/lanthanide behaviour in storage pond conditions within the
area of nuclear waste management.

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Declaration

No portion of this work has been submitted in support of an application for another
degree or qualification of this or any other university or other institute of learning.

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Copyright Statement

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dissertation) owns any copyright in it (the “Copyright”) and she has given The
University of Manchester the right to use such copyright for any administrative,
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Further information on the conditions under which disclosure, publication and
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and/or Reproductions described in it may take place is available from the Head of
School of Chemistry.

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Acknowledgements

I would like to thank my supervisor Dr. Clint Sharrad for all his brilliant guidance and
help!
Lucy Jones, Dan Whittaker, Nick Bryan and the rest of The University of Manchester
Radiochemistry Department for all their help and support throughout my masters.
And a massive, huge, gigantic thank you to Tamara Griffiths for being amazingly
patient, supporting and for just generally everything she has done over this past year.

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