Characterization of the nitrate complexes of Pu(IV) using absorption spectroscopy, {sup 15}N NMR, and EXAFS

Conference · Wed Dec 01 04:00:00 EST 1993

OSTI ID:10107616

Veirs, D K; Smith, C A; Zwick, B D; Marsh, S F; Conradson, S D

Nitrate complexes of Pu(IV) are studied in solutions containing nitrate up to 13 molar (M). Three major nitrato complexes are observed and identified using absorption spectroscopy, {sup 15}N nuclear magnetic resonance (NMR), and extended x-ray absorption fine structure (EXAFS) as Pu(NO{sub 3}){sub 2}{sup 2+}, Pu(NO{sub 3}){sub 4}, and Pu(NO{sub 3}){sub 6}{sup 2{minus}}. The possibility that Pu(NO{sub 3}){sub 1}{sup 3+}, Pu(NO{sub 3}){sub 3}{sup 1+} and Pu(NO{sub 3}){sub 5}{sup 1{minus}} are major species in solution is not consistent with these results and an upper limit of 0.10 can be set on the fraction for each of these three nitrate complexes in nitrate containing solutions. Fraction of the three major species in nitric acid over the 1--13 M range were calculated from absorption spectra data. The fraction of Pu(NO{sub 3}){sub 6}{sup 2{minus}} as a function of nitric acid concentration is in good agreement with the literature, whereas the fraction of Pu(NO{sub 3}){sub 2}{sup 2+} and Pu(NO{sub 3}){sub 4} species differ from previous studies. We have modeled the chemical equilibria up to moderate ionic strength ( < 6 molal) using the specific ion interaction theory (SM. Comparison of our experimental observations to literature stability constants that assume the presence of mononitrate species is poor. Stability constant at zero ionic strength for the dinitrato complex is determined to be log({beta}{sub 2}{sup 0})=3.77 {plus_minus} 0.14 (2{sigma}).

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 10107616
• Report Number(s): LA-UR--93-3281; CONF-930905--21; ON: DE94003980
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400702
NITRIC ACID
PLUTONIUM COMPLEXES
PLUTONIUM NITRATES
PROPERTIES OF RADIOACTIVE MATERIALS
SOLUTIONS
STABILITY