This document discusses research into synthesizing lanthanide catecholate complexes and their potential use in separating lanthanide elements from used nuclear fuel via electrochemical means. Specifically, it synthesized various lanthanide catechol complexes from lanthanum to europium and characterized them using cyclic voltammetry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The results indicate binding of catechol to the lanthanide metals and differences in their electrochemical properties, demonstrating the possibility of separating lanthanides from used nuclear fuel electrochemically. This separation could reduce nuclear waste and mitigate environmental concerns with nuclear power.

1. Lanthanide Catecholate Complexes
and Their Potential Use In Nuclear Fuel Processing
Efren Gonzalez,a
Rene J. Gutierreza
, Prof. S. Chantal E. Stieberb
a
Citrus College, Glendora, CA; b
Department of Chemistry & Biochemistry, California State Polytechnic University, Pomona, CA
Currently, there is a large emphasis on alternative energy research because the negative effects of carbon-based fuels on our environment are becoming more and more apparent. Nuclear power is of particular interest as it produces significantly fewer greenhouse gases, is cost and energy efficient, and is widely researched.
However, there is currently no permanent safe storage for used nuclear fuel (UNF) and environmental concerns are high. UNF is highly radioactive as a result of intermediate fission products, such as cesium, iodine, actinides and lanthanides. Industrial scale procedures currently used to treat UNF typically only remove one or
two specific products. This work aims to replicate known syntheses of gadolinium and holmium catecholate compounds. The counterions and metals will be altered to study the effects on the electrochemical properties. Various lanthanide catechol complexes, starting with lanthanum (La) up to europium (Dy), were
synthesized and resulting products analyzed via cyclic voltammetry (CV), infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (NMR). Results indicate binding of catechol to the lanthanide metal and support differing electrochemical properties. This work demonstrates the possibility for separating
lanthanides from UNF by electrochemical means. Successful separation would reduce nuclear waste and mitigate concerns surrounding nuclear power.
Advantages of Nuclear Power
Lanthanide Processing
Catechol Ligand: 1,2-dihydroxybenzene
Lanthanide Catechol Synthesis
Infrared Spectroscopy
Characterization
Acknowledgements
• Powered by uranium-235 fission
• Low release of greenhouse gases
• Low operating cost
• Energy efficient
• Removal of fission products from used nuclear fuel (UNF)
• Safe storage of UNF
• UNF is highly radioactive, has extended high temperature
• UNF can cause severe health/environmental damages
• Limited methods to treat UNF
• Removal of one or two specific products
• Pyrometallurgy, electrometallurgy, and
hydrometallurgy
• Row 6 elements in periodic table, from La to Lu
• f-block elements
• Fission byproducts
• Quench nuclear reactions
• Difficult to remove from UNF
• +3 oxidation states
• Similar ionic radii
• successful separation of lanthanides would reduce the amount of nuclear waste
Counterions
General Synthesis
Challenges for Nuclear Power
Lanthanides
Conclusions
This work was funded through a partnership between Citrus College and Cal Poly Pomona.
Specific Aims
• Developed general bench-top synthesis for lanthanide catecholate complexes
• Demonstrates possibility for electrochemical lanthanide separation
• Future Directions:
- Expand synthesis to additional lanthanides
- Isolate and structurally characterize complexes
IR of [Dy(cat)4][PPh4]5 and Catechol
Figure 2: General composition of UNF
• Sensitive to catechol coordination
• To test for catechol coordination for a given reaction
• Test feasibility for electrochemical lanthanide separation
• Utilize redox-active ligands to tune electrochemistry
• Replicate known gadolinium catecholate synthesis.
Freeman, G. E.; Raymond, K. N. Inorg. Chem. 1985, 24, 1410.
• Inexpensive
• Commercially available
• Composed of combustible elements
• Redox-active ligand
Electrochemistry
• Does catechol coordination affect electrochemical properties?
• Tested a range of reaction conditions to determine most robust synthesis
• Initial tests conducted with Dy(NO3)3 6H2O
• A series of counterions were tested to assess effects on solubility, crystallinity and
electrochemistry.