Kinetics of oxido-reduction reactions of Np in nitric solutions. Oxidation of Np(IV) into Np(V), oxidation of Np(V) into Np(VI) by nitric acid catalyzed by nitrous acid
Creators
Description
In nitric solutions, only the reaction kinetics of Np(IV), (V) and (VI) are slow enough to be measurable. The kinetics of the reactions: Np4++1/2NO3-+3/2H2O→NpO2++1/2HNO2+5/2H+ (I) and NpO2++1/2NO3-+3/2H+→NpO22++1/2HNO2+1/2H2O (II) are investigated. The reaction I is experimentally studied by absorption spectrophotometry. Three reaction kinetics laws are observed in 1M nitric solutions for an initial concentration in Np(IV) of about 10-2. The oxidation mechanism of Np(IV) is compared with that of the similar reactions of U(IV) and Pu(IV). The importance of catalysis phenomena of metallic ions (in particular iron) are observed in the oxidation reactions of tetravalent uranides. The reaction II is experimentally studied by solvent extraction of Np(VI) produced and absorption spectrophotometry. It is shown that the reaction kinetics law depends on the value of the HNO2/Np(V) ratio. The reaction of Np(V) takes place by the action of the intermediary protonated state NpO2H2+ with N2O4. The results are compared with those of the similar reactions of U and Pu
Abstract (French)
En milieu nitrique seuls Np(IV), (V) et (VI) ont des reactions suffisamment lentes pour etre mesurables. On a etudie la cinetique des reactions: Np4++1/2NO3-+3/2H2O→NpO2++1/2HNO2+5/2H+ (I) et NpO2++1/2NO3-+3/2H+→NpO22++1/2HNO2+1/2H2O (II). L'etude experimentale de la reaction est faite par spectrophotometrie d'absorption. En milieu nitrique 1M et pour une concentration initiale de Np(IV) voisine de 10-2, trois lois de vitesses sont observees. On a compare le mecanisme de l'oxydation de Np(IV) avec ceux des reactions analogues de U(IV) et Pu(IV). On montre aussi l'importance des phenomenes de catalyse par les ions metalliques, comme ceux du fer, dans les reactions d'oxydation des uranides tetravalents. L'etude experimentale de la reaction II est faite par l'extraction par solvant de Np(VI) produit par la reaction et spectrophotometrie d'absorption. On montre que la loi de vitesse de la reaction II depend de la valeur du rapport HNO2/Np(V). On montre que Np(V) reagit sous une forme protonee NpO2H2+ avec N2O4. On compare ces resultats avec ceux des reactions similaires deFiles
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Additional details
Additional titles
- Original title (French)
- Cinetiques des reactions d'oxydo-reduction du neptunium en solution nitrique. Oxydation du neptunium (IV) en neptunium (V), oxydation du neptunium (V) and neptunium (VI) par l'acide nitrique, catalysee par l'acide nitreux
Publishing Information
- Imprint Pagination
- 204 p.
- Report number
- FRNC-TH--701
- University
- Paris-6 Univ
- Degree
- PhD
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 9404277
- Subject category
- S38: RADIATION CHEMISTRY, RADIOCHEMISTRY AND NUCLEAR CHEMISTRY;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- CATALYSIS; CATIONS; CHEMICAL REACTION KINETICS; NEPTUNIUM COMPOUNDS; NITRIC ACID; NITROUS ACID; OXIDATION; REDUCTION
- Descriptors DEC
- ACTINIDE COMPOUNDS; CHARGED PARTICLES; CHEMICAL REACTIONS; HYDROGEN COMPOUNDS; INORGANIC ACIDS; IONS; KINETICS; NITROGEN COMPOUNDS; OXYGEN COMPOUNDS; REACTION KINETICS; TRANSURANIUM COMPOUNDS