Heterogeneous Reduction of PuO2 with Fe(II): Importance of the Fe(III) Reaction Product

Journal Article · Sun May 01 04:00:00 EDT 2011 · Environmental Science & Technology, 45(9):3952-3958

DOI:https://doi.org/10.1021/es104212g· OSTI ID:1015893

Felmy, Andrew R; Moore, Dean A; Rosso, Kevin M; Qafoku, Odeta; Rai, Dhanpat; Buck, Edgar C; Ilton, Eugene S

Abstract Heterogeneous reduction of actinides in higher and more soluble oxidation states to lower more insoluble oxidation states by reductants such as Fe(II) has been the subject of intensive study for more than two decades. However, Fe(II)-induced reduction of sparingly soluble Pu(IV) to the more soluble lower oxidation state Pu(III) has been much less studied even though such reactions can potentially increase the mobility of Pu in the subsurface. Thermodynamic calculations are presented that show how differences in the free energy of various possible solid-phase Fe(III) reaction products can greatly influence aqueous Pu(III) concentrations resulting from reduction of PuO2(am) by Fe(II). We present the first experimental evidence that reduction of PuO2(am) to Pu(III) by Fe(II) was enhanced when the Fe(III) mineral goethite was spiked into the reaction. The effect of goethite on reduction of Pu(IV) was demonstrated by measuring the time-dependence of total aqueous Pu concentration, its oxidation state, and system pe/pH. We also re-evaluated established protocols for determining Pu(III) [(Pu(III) + Pu(IV)) - Pu(IV)] by using thenoyltrifluoroacetone (TTA) in toluene extractions; the study showed that it is important to eliminate dissolved oxygen from the TTA solutions for accurate determinations. More broadly, this study highlights the importance of the Fe(III) reaction product in actinide reduction rate and extent by Fe(II).

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1015893
• Report Number(s): PNNL-SA-76908; 34494; KP1702030
• Journal Information: Environmental Science & Technology, 45(9):3952-3958, Journal Name: Environmental Science & Technology, 45(9):3952-3958 Journal Issue: 9 Vol. 45; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACTINIDES
DISSOLVED GASES
Environmental Molecular Sciences Laboratory
FREE ENERGY
GOETHITE
OXYGEN
THERMODYNAMICS
TIME DEPENDENCE
TOLUENE
TTA
VALENCE