Journal of Colloid and Interface Science, Jul 1, 2001
The retention properties of a synthetic carbonate fluoroapatite and a natural francolite are comp... more The retention properties of a synthetic carbonate fluoroapatite and a natural francolite are compared in the present work from an investigation of the sorption of 63 Ni at tracer scale amounts onto these solids. Two different surface complexation models were successively used to fit the experimental adsorption isotherms obtained under various experimental conditions: the nonelectrostatic model and the constant capacitance model. The results are essentially described by two main equilibria involving one proton in acidic media and three protons in basic media. The corresponding thermodynamic constants are in agreement for both models. Modeling gives also close values for both solids, despite their distinct solubility and surface acidity.
Journal of Colloid and Interface Science, May 1, 2002
As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the p... more As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the physical and surface properties of the synthetic carbonate fluoroapatite and mineral francolite retained for this work have been carefully examined. The average particle size of the powdered samples, determined by laser granulometry, is around 30 µm. Their specific surface areas, measured according to the N 2 BET method, are 8.8 ± 0.1 and 13.9 ± 0.1 m 2 • g −1 , respectively, for the synthetic and the mineral compound. The solubility of both solids has been studied under undersaturation initial conditions. The synthetic compound has a solubility product of 10 −103±2 , but the mineral francolite, which is highly substituted and poorly crystalline, is more soluble and dissolves incongruently. The amphoteric properties of the hydrous carbonate fluoroapatites surfaces have also been investigated through zeta-potential measurements and potentiometric titrations in KNO 3 medium at 25 • C. The experimental data have been interpreted using the computer program FITEQL 3.2, applying either the nonelectrostatic or the constant capacitance model. For both solids, the values of the surface acidity constants determined with the two models are very close, suggesting a weak contribution of the electrostatic interactions. Moreover, the more acidic surface of the synthetic compound compared to that of the mineral one is assigned to the differences in crystallinity and chemical composition between the two solids.
Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerr... more Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerrone, Vladimir Brandel, Nicolas Dacheux and Michel Genet Groupe de Radiochimie, Institut de Physique de Paris-Sud, 91406 Orsay, Nucleçaire, Universiteç France. ...
Two thorium phosphate compounds, Th,(P0 4) 4 and ΤΙν,ίΡΟΛΟ^Ο,), with different solubilities and s... more Two thorium phosphate compounds, Th,(P0 4) 4 and ΤΙν,ίΡΟΛΟ^Ο,), with different solubilities and structures, are compared in the present work from the point of view of their surface charge and retention capacity. The sorption of Th(IV) and Am(III) onto the phosphate powders or colloids is shown to depend essentially on the parameters characterizing the solution in contact with the solid phase: namely the pH and the nature of the electrolyte which affect the surface charge of the solid phase. Taking into account the speciation of the two actinides under consideration, two mechanisms involving one phosphate site and either one (pH < 4.7 for Th, 4 < pH < 7-8 for Am) or 3-4 exchanged protons (pH > 8 for Am, pH > 4.7 for Th) can be proposed to describe the sorption processes. However, this interpretation of the results needs to be confirmed by a better knowledge of the equilibria which involve Th and Am in the phosphate-containing solutions and also of the acid/base properties of the phosphate groups situated at the solid/solution interface.
Les apatites, en particulier les especes carbonatees (francolites), presentent, en plus d'une... more Les apatites, en particulier les especes carbonatees (francolites), presentent, en plus d'une certaine stabilite chimique et geologique, des capacites a retenir durablement de nombreux elements et sont donc susceptibles d'ameliorer les proprietes de retention des barrieres ouvragees d'un site de stockage de dechets radioactifs en formation geologique profonde. Mais il existe une grande variete de francolites, c'est pourquoi nous avons considere un materiau synthetique de formule ca 1 0(po 4) 5(co 3)(f,oh) 3 et une apatite naturelle. Dans un premier temps, nous avons etudie leur solubilite (critere important pour le choix des materiaux). Une attention particuliere a egalement ete accordee a la determination de leurs caracteristiques surfaciques et a l'etude des interactions radionucleide/solution. Des experiences de sorption ont ete realisees pour les trois radionucleides et l'influence de plusieurs parametres a ete examinee. La simulation des isothermes de so...
The program of work of the fourth phase of the OECD NEA Thermochemical Database Project (TDB-IV) ... more The program of work of the fourth phase of the OECD NEA Thermochemical Database Project (TDB-IV) contemplates a line of activity on the preparation of a state of the art report on cements. The present work aims at presenting the project, its aims and its limits.
In the framework on a study of the acido-basic and sorption properties of iron oxides, a thorough... more In the framework on a study of the acido-basic and sorption properties of iron oxides, a thorough characterization of two types of goethite powders was performed in several laboratories joined in a common project. Chemical analysis by ICPAES; high-resolution SEM, TEM, and AFM observations; XRD with line width analysis; and argon and nitrogen sorption isotherms were used for that purpose. The main crystallographic faces of goethite particles could be identified as {001}, {101}, and {121}, and their abundance correlated with the distribution of low-pressure argon adsorption local isotherms. These results will be very useful for further studies on the relationship between surface reactivity in aqueous solution and orientation of solid surfaces.
Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerr... more Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerrone, Vladimir Brandel, Nicolas Dacheux and Michel Genet Groupe de Radiochimie, Institut de Physique de Paris-Sud, 91406 Orsay, Nucleçaire, Universiteç France. ...
Journal of Colloid and Interface Science, Jul 1, 2001
The retention properties of a synthetic carbonate fluoroapatite and a natural francolite are comp... more The retention properties of a synthetic carbonate fluoroapatite and a natural francolite are compared in the present work from an investigation of the sorption of 63 Ni at tracer scale amounts onto these solids. Two different surface complexation models were successively used to fit the experimental adsorption isotherms obtained under various experimental conditions: the nonelectrostatic model and the constant capacitance model. The results are essentially described by two main equilibria involving one proton in acidic media and three protons in basic media. The corresponding thermodynamic constants are in agreement for both models. Modeling gives also close values for both solids, despite their distinct solubility and surface acidity.
Journal of Colloid and Interface Science, May 1, 2002
As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the p... more As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the physical and surface properties of the synthetic carbonate fluoroapatite and mineral francolite retained for this work have been carefully examined. The average particle size of the powdered samples, determined by laser granulometry, is around 30 µm. Their specific surface areas, measured according to the N 2 BET method, are 8.8 ± 0.1 and 13.9 ± 0.1 m 2 • g −1 , respectively, for the synthetic and the mineral compound. The solubility of both solids has been studied under undersaturation initial conditions. The synthetic compound has a solubility product of 10 −103±2 , but the mineral francolite, which is highly substituted and poorly crystalline, is more soluble and dissolves incongruently. The amphoteric properties of the hydrous carbonate fluoroapatites surfaces have also been investigated through zeta-potential measurements and potentiometric titrations in KNO 3 medium at 25 • C. The experimental data have been interpreted using the computer program FITEQL 3.2, applying either the nonelectrostatic or the constant capacitance model. For both solids, the values of the surface acidity constants determined with the two models are very close, suggesting a weak contribution of the electrostatic interactions. Moreover, the more acidic surface of the synthetic compound compared to that of the mineral one is assigned to the differences in crystallinity and chemical composition between the two solids.
Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerr... more Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerrone, Vladimir Brandel, Nicolas Dacheux and Michel Genet Groupe de Radiochimie, Institut de Physique de Paris-Sud, 91406 Orsay, Nucleçaire, Universiteç France. ...
Two thorium phosphate compounds, Th,(P0 4) 4 and ΤΙν,ίΡΟΛΟ^Ο,), with different solubilities and s... more Two thorium phosphate compounds, Th,(P0 4) 4 and ΤΙν,ίΡΟΛΟ^Ο,), with different solubilities and structures, are compared in the present work from the point of view of their surface charge and retention capacity. The sorption of Th(IV) and Am(III) onto the phosphate powders or colloids is shown to depend essentially on the parameters characterizing the solution in contact with the solid phase: namely the pH and the nature of the electrolyte which affect the surface charge of the solid phase. Taking into account the speciation of the two actinides under consideration, two mechanisms involving one phosphate site and either one (pH < 4.7 for Th, 4 < pH < 7-8 for Am) or 3-4 exchanged protons (pH > 8 for Am, pH > 4.7 for Th) can be proposed to describe the sorption processes. However, this interpretation of the results needs to be confirmed by a better knowledge of the equilibria which involve Th and Am in the phosphate-containing solutions and also of the acid/base properties of the phosphate groups situated at the solid/solution interface.
Les apatites, en particulier les especes carbonatees (francolites), presentent, en plus d'une... more Les apatites, en particulier les especes carbonatees (francolites), presentent, en plus d'une certaine stabilite chimique et geologique, des capacites a retenir durablement de nombreux elements et sont donc susceptibles d'ameliorer les proprietes de retention des barrieres ouvragees d'un site de stockage de dechets radioactifs en formation geologique profonde. Mais il existe une grande variete de francolites, c'est pourquoi nous avons considere un materiau synthetique de formule ca 1 0(po 4) 5(co 3)(f,oh) 3 et une apatite naturelle. Dans un premier temps, nous avons etudie leur solubilite (critere important pour le choix des materiaux). Une attention particuliere a egalement ete accordee a la determination de leurs caracteristiques surfaciques et a l'etude des interactions radionucleide/solution. Des experiences de sorption ont ete realisees pour les trois radionucleides et l'influence de plusieurs parametres a ete examinee. La simulation des isothermes de so...
The program of work of the fourth phase of the OECD NEA Thermochemical Database Project (TDB-IV) ... more The program of work of the fourth phase of the OECD NEA Thermochemical Database Project (TDB-IV) contemplates a line of activity on the preparation of a state of the art report on cements. The present work aims at presenting the project, its aims and its limits.
In the framework on a study of the acido-basic and sorption properties of iron oxides, a thorough... more In the framework on a study of the acido-basic and sorption properties of iron oxides, a thorough characterization of two types of goethite powders was performed in several laboratories joined in a common project. Chemical analysis by ICPAES; high-resolution SEM, TEM, and AFM observations; XRD with line width analysis; and argon and nitrogen sorption isotherms were used for that purpose. The main crystallographic faces of goethite particles could be identified as {001}, {101}, and {121}, and their abundance correlated with the distribution of low-pressure argon adsorption local isotherms. These results will be very useful for further studies on the relationship between surface reactivity in aqueous solution and orientation of solid surfaces.
Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerr... more Page 1. Solubility of thorium phosphate-diphosphate§ Blandine Fourest,* Geçrard Lagarde, JanePerrone, Vladimir Brandel, Nicolas Dacheux and Michel Genet Groupe de Radiochimie, Institut de Physique de Paris-Sud, 91406 Orsay, Nucleçaire, Universiteç France. ...
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