Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

A spectrophotometric study of the impact of pH and metal-to-ligand ratio on the speciation of the Pu(vi)-oxalate system

Journal Article · · Physical Chemistry Chemical Physics. PCCP
DOI:https://doi.org/10.1039/d3cp04010k· OSTI ID:2281495
The oxalate ligand is prevalent throughout the nuclear fuel cycle. While the Pu(III)- and Pu(IV)-oxalate systems are well studied due to their use in plutonium metal and PuO2 production, the effect of oxalate on Pu(VI) remains understudied. Absorption spectroscopy was employed to probe the solution behavior of the Pu(VI)-oxalate system as a function of pH (1, 3, 7) and metal-to-ligand ratio (M/L; 10 : 1–1 : 10). Peak changes in the UV-vis-NIR spectra were associated with the formation of multiple Pu(VI)-oxalate species with increasing oxalate concentration. Some insight into identification of species present in solution was gained from the limited Pu(VI)-oxalate literature and comparisons with the assumed isostructural U(VI)-oxalate system. A peak in the UV-vis-NIR spectrum at 839 nm, which corresponds to the formation of a 1 : 1 PuO2(C2O4)(aq) complex, was observed and used to determine the formation constant (log β° = 4.64 ± 0.06). A higher coordinated Pu(VI)-oxalate peak at 846 nm was tentatively assigned as the 1 : 2 complex PuO2(C2O4)22₋ and a preliminary formation constant was determined (log β° = 9.30 ± 0.08). In conclusion, the predominance of both complexes was shown in speciation diagrams calculated from the formation constants, illustrating the importance of considering the Pu(VI)-oxalate system in the nuclear fuel cycle.
Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
89233218CNA000001; SC0018231
OSTI ID:
2281495
Alternate ID(s):
OSTI ID: 2222826
Report Number(s):
LA-UR--24-20293
Journal Information:
Physical Chemistry Chemical Physics. PCCP, Journal Name: Physical Chemistry Chemical Physics. PCCP Journal Issue: 48 Vol. 25; ISSN 1463-9076
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English

References (36)

On the Hydrolysis of the Dioxouranium(VI) Ion in Oxalate Solutions journal May 2005
Hydrolysis of Plutonium(VI) at Variable Temperatures (283-343 K) journal August 2011
Thermodynamic and Structural Trends in Hexavalent Actinyl Cations: Complexation of Dipicolinic Acid with NpO 2 2+ and PuO 2 2+ in Comparison with UO 2 2+ journal October 2013
Quantitative Microstructural Characterization of Plutonium Oxalate Auto‐Degradation and Evidence for PuO 2 Nanocrystal Formation journal July 2021
The Photochemical Behavior of the Uranyl Ion (UO$\rm{{_{2}^{2+}}}$): a Dimer Perspective and Outlook journal November 2009
The thermal decomposition of hydrated plutonium(IV) oxalates journal January 1964
X-ray powder crystallographic data on plutonium and other oxalates—I journal January 1965
X-ray powder crystallographic data on plutonium and other oxalates—II journal January 1965
EPR and ENDOR studies of self(α)-irradiation effects in Pu(VI) oxalate: evidence for participation of 5f electrons of 239Pu in chemical bonding with CO2− journal December 2000
Spectroscopic investigation of the formation of PuO2Cl+ and PuO2Cl2 in NaCl solutions and application for natural brine solutions journal October 1999
Spectrophotometric study of uranyl–oxalate complexation in solution journal June 2002
Actinide oxalates, solid state structures and applications journal May 2014
Solubility of plutonium(VI) carbonate in saline solutions journal June 2007
Reaction mechanisms of the thermal conversion of Pu(IV) oxalate into plutonium oxide journal October 2007
A review of plutonium oxalate decomposition reactions and effects of decomposition temperature on the surface area of the plutonium dioxide product journal October 2015
Raman and infrared spectra of plutonium (IV) oxalate and its thermal degradation products journal April 2022
Reactivity of nitrate and organic acids at the concrete–bitumen interface of a nuclear waste repository cell journal March 2014
Dioxouranium(VI)–carboxylate complexesA calorimetric and potentiometric investigation of interaction with oxalate at infinite dilution and in NaCl aqueous solution at I=1.0molL−1 and T=25°C journal February 2007
Pu(VI) Hydrolysis:  Further Evidence for a Dimeric Plutonyl Hydroxide and Contrasts with U(VI) Chemistry journal February 2006
Crystal Growth and First Crystallographic Characterization of Mixed Uranium(IV)–Plutonium(III) Oxalates journal April 2013
Multiscale structural characterizations of mixed U( iv )–An( iii ) oxalates (An( iii ) = Pu or Am) combining XAS and XRD measurements journal January 2016
Raman spectral titration method: an informative technique for studying the complexation of uranyl with uranyl( vi )–DPA/oxalate systems as examples journal January 2017
Visible-NIR absorption spectroscopy study of the formation of ternary plutonyl(vi) carbonate complexes journal January 2020
Ligand rigidity and electronic effect on the complexation of hexavalent plutonyl with three dicarboxylic acids: a combined spectrophotometric and computational study journal January 2020
Dioxouranium(VI) oxalate complexes † journal January 2000
Thermodynamics of the complexation of uranium(vi) with oxalate in aqueous solution at 10–70 °C journal January 2009
Synthesis and study of Np(V) sesquioxalates journal April 2007
Electronic absorption spectra of crystalline Pu(V) compounds journal December 2007
Actinide oxalate complexes formation as a function of temperature by capillary electrophoresis coupled with inductively coupled plasma mass spectrometry journal January 2015
Initial Hydrolysis of Plutonium(VI) journal March 1993
Spectroscopic Study of the Hydrolysis of PuO2+2 in Aqueous Solution journal January 1995
Reduction of Np(VI) and Pu(VI) by Organic Chelating Agents journal January 1998
Thermodynamic study on the U(VI) complexation with dicarboxylates by calorimetry journal November 2008
Effect of reduction on the stability of Pu(VI) hydrolysis species journal November 2010
Literature Review for Oxalate Oxidation Processes and Plutonium Oxalate Solubility report February 2012
Precipitation Of Plutonium(IV) Oxalate report March 1954

Similar Records

Absorption spectra and speciation of plutonium(VI) with phosphate
Technical Report · Wed Jan 31 23:00:00 EST 1996 · OSTI ID:188547

Spectroscopic investigation of the formation of PuO{sub 2}Cl{sup +} and PuO{sub 2}Cl{sub 2} in NaCl solutions and application for natural brine solutions
Journal Article · Fri Oct 01 00:00:00 EDT 1999 · Geochimica et Cosmochimica Acta · OSTI ID:20003988