The document summarizes research on synthesizing and testing new bidentate ligands for extracting f-block elements from nuclear waste. Various ligands were synthesized by modifying the electron donating atoms on an existing ligand class. Extraction efficiency testing was done by liquid-liquid extraction and UV-Vis spectroscopy. Preliminary results show the new selenium-containing ligand extracts uranium, thorium, and lanthanum more efficiently than the original ligand or ligands modified with sulfur. Future work will further evaluate extraction properties and compile data on all metals.

1. The Change in Extraction Efficiency of f-block elements with the Variation
of Electron Donor Atoms in Bidentate Ligands
Jeremy Cunningham, Brian Rawls, Paul T. Morse and Shannon M. Biros*
Grand Valley State University, Department of Chemistry, Allendale, MI 49401
Figure 1: Tributyl Phosphate structure, used in PUREX, and General
CMPO structure, used in TRUEX.
Synthesis of the cis-dppE Class Ligands
Table 2: All gathered extraction efficiency data to date. Ongoing
research will generate more inter-ligand comparative data.
Figure 6: Arsenazo III-Metal Complex
Future Plans:
Our lab’s future work lies in compiling data for extraction efficiencies of
all heavy metals with all of our current ligands. Further attempts at X-
ray crystallography structures are ongoing. We strive to determine the
impacts of atomic radius, f-orbital shape, type of chelating group,
distance between chelating groups, and other factors on complex
properties and extraction efficiencies.
Figure 8: Shown above are two proposed future ligands for analysis.
On the left is a proposed linear metal polymer in which the bridge
between the β-phosphoryl groups is undetermined. The structure on
the right shows a benzene ring replacing the bridge carbons, which
may prove able to donate electron density to the complex.
Figure 2: Bidentate Phosphoryl Ligands synthesized for initial study.
Structure Characterization:
Attempts at growing cis-dppE crystals in various solvent systems have
allowed for the determination of exact spacial orientation and physical
structure of the cis-dppE-metal complexes by way of X-Ray crystallography.
Figure 3: Synthesis of cis-dppESe.
Acknowledgements:
As part of the Grand Valley State University Chemistry Research Program, we would like to thank all of the staff of the GVSU
Chemistry Department, especially Professor Jim Krikke and Professor Randy Winchester, along with our student research partners,
Ben Nicholson, Brian Rawls, and Jeremy Cunningham. Additionally, we would like to thank Professor Eric Werner (University of
Tampa), Dr. Richard Staples (Michigan State Univeristy), and Dr. Tom Guarr (Michigan State University Bioeconomy Institute).
We also thank the GVSU chemistry department, GVSU NSF ADVANCE, GVSU OURS, the Weldon Fund, NSF-REU, and the
IUCr crystallographic travel fund from Crystallographic Resources, Inc. for providing financial support. Finally, we would like to
thank the kittens for their emotional support.
References:
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Ongoing Work:
Extraction efficiency studies are currently being preformed on the ligands
using liquid-liquid extraction and UV-Vis spectroscopy. The ligand, in an organic
solvent, and aqueous metal solution are mixed and allowed to equilibrate.
Extraction efficiency is measured by mixing the remaining aqueous metal
solution with the optically active compound, Arsenazo III. By measuring the
absorption of the solution at 655 nm (Ln) or 665 nm (An) before and after
extraction, a percent extraction efficiency is recorded.
Abstract:
Experts predict that the maximum possible oil production will occur in the next 5-
25 years1 using current methods and, consequently, the need for alternative sources
of energy is growing. For most of Europe, nuclear power is the dominant source of
electricity, whereas the United States gets 83% of its energy by way of fossil fuels
while only 8% comes from nuclear power2. In addition to wind and solar, nuclear
energy is an attractive alternative, with the ability to generate significant amounts
of energy with low atmospheric emissions. However, critical issues surrounding
the use of nuclear power include: Long-term nuclear waste storage and waste
remediation. Due to environmental and economic concerns, a recent resurgence in
the chemistry of actinides has been inspired to develop new separation
technologies.
Background:
Figure 4: Crystal structure obtained from cis-
dppESe. One Selenium atom (shown in yellow)
is projecting out of the plane while the other Se
is directed into the plane. The sp3 hybridized
phosphorus has a tetrahedral geometry.
Figure 5: Crystal structure obtained from
cis-dppEO-thorium complex. Two cis-dppEO
ligands surround the Th4+ center. The alkene
segment of the third cis-dppEO has been
converted to an epoxide. This is likely (a) an
impurity from the ligand preparation, or (b) a
reaction between the ligand and the Th(IV)
center, as it has been shown that Th(IV) can
catalyze conversion of alkenes to epoxides.
Two nitrate groups reliably participate in the
primary coordination sphere while two other
nitrate groups exist in a disordered state in the
secondary coordination sphere (not shown).
The goal of nuclear waste remediation is to reuse the products
produced from the nuclear fission process. Much of the waste generated is
composed of unspent, energy-rich, fissile elements called high level waste
(HLW) that can be reused for fission reactions in next generation fission
reactor. The remediation of HLW has been achieve through the PUREX
(Plutonium-URanium EXtraction) process which utilizes an organic ligand
called tri-butyl phosphate.
While the PUREX, and similar processes, present major advances in
the overall reduction of HLW generated, there are still products generated
from fission called intermediate level waste (ILW) and low level waste
(LLW). The goal of nuclear waste remediation is to eliminate all levels of
waste generated, making nuclear energy an attractive, zero carbon, energy
source.
The goal of the Biros research group at GVSU is to analyze a class of
organic molecules known to have high binding affinity toward the specific
metals in intermediate and low level waste. The molecules under
observation are derivatives of a class of compounds used in the TRUEX
(TRans Uranium EXtraction) process. These remediation compounds are
called CMPO (carbamoylmethylphosphine oxide) ligands, and are known to
have a high degree of binding affinity toward a range of metal cations. The
Biros lab is observing how the variation of the election donating atoms on
the ligand effects the extraction efficiency of f-block metals.
Starting Material Reactant Reaction
Conditions
Product
Cis-dppE H2O2 THF
Reflux, 4hrs
Cis-dppEO
Cis-dppE S8 THF
25°C
3 Hours
Cis-dppES
Cis-dppE 2 Se Toluene
25°C
4 Hours
Cis-dppESe
+ 2 Se(s)
Element
Metal Extraction
Percentage for
cdppeO
Metal Extraction
Percentage for
cdppeS
Metal Extraction
Percentage for
cdppeSe
Uranium
UO2(NO3)2
91% 92% 99%
Thorium
Th(NO3)4
83% 97%
Ytterbium
Yb(NO3)3
10% 13%
Dysprosium
Dy(NO3)3
10% 5.0%
Europium
Eu(NO3)3
21% 5.9%
Lanthanum
La(NO3)3
9.5% 18% 7%