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Solubility of tetravalent actinides in alkaline CaCl2 solutions and formation of Ca4[An(OH)8]4+ complexes: A study of Np(IV) and Pu(IV) under reducing conditions and the systematic trend in the An(IV) series
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D. Fellhauer
Published/Copyright:
November 23, 2010
Abstract
The solubility of Np(IV) and Pu(IV) hydrous oxides was studied at 22±2 °C under reducing conditions in alkaline CaCl2 solutions. Redox conditions were adjusted either with 2 mM Na2S2O4 or additions of iron powder. In 2.0 and 4.5 M CaCl2 and pHc=11–12, the neptunium and plutonium concentrations increase with a slope of +4 (log[An] vs. pHc) as expected for the formation of the complex Ca4[An(OH)8]4+ recently identified for Th(IV). At CaCl2 concentrations ≤1.0 M this effect is negligible for both Np(IV) and Pu(IV). The conditional equilibrium constants log*Ks,(4,1,8) for the reaction
An(OH)4(am) + 4 H2O + 4 Ca2+ ⇔ Ca4[An(OH)8]4+ + 4 H+
are evaluated with the SIT and Pitzer model using the parameters derived from analogous data for Th(IV) in 0.5–4.5 M CaCl2. The log*K°s,(4,1,8) values and the complex formation constants logβ°(4,1,8) follow systematic trends in the series Th(IV), Np(IV) and Pu(IV) which allows the estimation of the corresponding data for U(IV).
Published Online: 2010-11-23
Published in Print: 2010-11
© by Oldenbourg Wissenschaftsverlag, Karlsruhe, Germany
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Articles in the same Issue
- Preface
- Solubility of tetravalent actinides in alkaline CaCl2 solutions and formation of Ca4[An(OH)8]4+ complexes: A study of Np(IV) and Pu(IV) under reducing conditions and the systematic trend in the An(IV) series
- Solubility of triuranyl diphosphate tetrahydrate (TDT) and Na autunite at 23 and 50 °C
- Effect of reduction on the stability of Pu(VI) hydrolysis species
- Retention and redox behaviour of uranium(VI) by siderite (FeCO3)
- Neptunium(V) complexation by natural pyoverdins and related model compounds
- Complexation of Nd(III) with tetraborate ion and its effect on actinide(III) solubility in WIPP brine
- Complexation of Tc(IV) with acetate at varying ionic strengths
- Uranyl photochemistry: decarboxylation of gluconic acid
- Influence of Boom Clay organic matter on the adsorption of Eu3+ by illite – geochemical modelling using the component additivity approach
- The role of green rust in the migration of radionuclides: An overview of processes that can control mobility of radioactive elements in the environment using as examples Np, Se and Cr
- A comparative batch sorption and time-resolved laser fluorescence spectroscopy study on the sorption of Eu(III) and Cm(III) on synthetic and natural kaolinite
- U(VI) sorption on granite: prediction and experiments
- Quantum chemical study of inner-sphere complexes of trivalent lanthanide and actinide ions on the corundum (0001) surface
- Quantum chemical modeling of uranyl adsorption on mineral surfaces
- Interaction of PuO2 thin films with water
- Molecular interactions of plutonium(VI) with synthetic manganese-substituted goethite
- Chlorine speciation in nuclear graphite: consequences on temperature release and on leaching
- Chemical status of U(VI) in cemented waste forms under saline conditions
- Influence of iron redox transformations on plutonium sorption to sediments
- Modelling of a large-scale in-situ migration experiment with 14C-labelled natural organic matter in Boom Clay
- Sorption and diffusion of Eu in sedimentary rock in the presence of humic substance
- Diffusion and sorption of neptunium(V) in compacted montmorillonite: effects of carbonate and salinity
- Uranium(VI) diffusion in low-permeability subsurface materials
- Distribution of Cs and Am in the solution-bentonite colloids-granite ternary system: effect of addition order and sorption reversibility
- Mechanisms of plutonium sorption to mineral oxide surfaces: new insights with implications for colloid-enhanced migration
- Understanding uranium behaviour at the Askola uranium mineralization
Articles in the same Issue
- Preface
- Solubility of tetravalent actinides in alkaline CaCl2 solutions and formation of Ca4[An(OH)8]4+ complexes: A study of Np(IV) and Pu(IV) under reducing conditions and the systematic trend in the An(IV) series
- Solubility of triuranyl diphosphate tetrahydrate (TDT) and Na autunite at 23 and 50 °C
- Effect of reduction on the stability of Pu(VI) hydrolysis species
- Retention and redox behaviour of uranium(VI) by siderite (FeCO3)
- Neptunium(V) complexation by natural pyoverdins and related model compounds
- Complexation of Nd(III) with tetraborate ion and its effect on actinide(III) solubility in WIPP brine
- Complexation of Tc(IV) with acetate at varying ionic strengths
- Uranyl photochemistry: decarboxylation of gluconic acid
- Influence of Boom Clay organic matter on the adsorption of Eu3+ by illite – geochemical modelling using the component additivity approach
- The role of green rust in the migration of radionuclides: An overview of processes that can control mobility of radioactive elements in the environment using as examples Np, Se and Cr
- A comparative batch sorption and time-resolved laser fluorescence spectroscopy study on the sorption of Eu(III) and Cm(III) on synthetic and natural kaolinite
- U(VI) sorption on granite: prediction and experiments
- Quantum chemical study of inner-sphere complexes of trivalent lanthanide and actinide ions on the corundum (0001) surface
- Quantum chemical modeling of uranyl adsorption on mineral surfaces
- Interaction of PuO2 thin films with water
- Molecular interactions of plutonium(VI) with synthetic manganese-substituted goethite
- Chlorine speciation in nuclear graphite: consequences on temperature release and on leaching
- Chemical status of U(VI) in cemented waste forms under saline conditions
- Influence of iron redox transformations on plutonium sorption to sediments
- Modelling of a large-scale in-situ migration experiment with 14C-labelled natural organic matter in Boom Clay
- Sorption and diffusion of Eu in sedimentary rock in the presence of humic substance
- Diffusion and sorption of neptunium(V) in compacted montmorillonite: effects of carbonate and salinity
- Uranium(VI) diffusion in low-permeability subsurface materials
- Distribution of Cs and Am in the solution-bentonite colloids-granite ternary system: effect of addition order and sorption reversibility
- Mechanisms of plutonium sorption to mineral oxide surfaces: new insights with implications for colloid-enhanced migration
- Understanding uranium behaviour at the Askola uranium mineralization
