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  • Author or Editor: F. Monroy-Guzman x
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Abstract  

The possible use of thiocyanate and ammonium thiocyanate-hydrofluoric acid mixtures for quantitative anion exchange separation of zirconium from hafnium and niobium from tantalum and protactinium has been investigated. Distribution coefficients of zirconium(IV), hafnium(IV), niobium(V), tantalum(V) and protactinium(V) on macroporous BIO-RAD AGMP1 resin over a wide range of SCN and SCN/HF concentrations have been determined. The simultaneous presence of these two complexing agents causes a strong decrease of the adsorption phenomena.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: J. Soriano-Rodríguez, V. Badillo-Almaraz, C. Alliot, F. Monroy-Guzmán, and P. Vitorge

Abstract  

The sorption of Pd(II) on hydroxyapatite (Ca10(PO4)6(OH)2) has been studied at 25 °C as a function of pH, in 0.01 M NaClO4, and 0.01 and 0.025 M Ca(ClO4)2 aqueous background electrolytes and Pd(II) concentration (9.3 to 47 μM), trying to minimize some types of reactions, such as solid dissolution of and metal precipitation. The radiotracer palladium, 109Pd, obtained by neutron irradiation, has been used to calculate the palladium’s distribution coefficients K d between aqueous and solid phase. A mathematical treatment of results has been made by ion-exchange theory in order to interpret palladium sorption onto treated solid. For this, we take into account the existence of active sites at the hydroxyapatite surface, and the aqueous solution chemistry of palladium as well as the effect of phosphate anions from solid dissolution. The results can be explained as evidence of sorption of the species PdOH+, and of a mixed hydroxo complex of Pd2+ like (XCaO)–PdOH+·nH2O fixed onto {≡Ca–OH} surface sites of the hydroxyapatite.

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Summary  

Ceramic samples found in San Miguel Ixtapan, Mexico State, Mexico, were analyzed by means of NAA, PIXE, SEM and XRD. Statistical treatments such as bivariate cluster and principal-components analysis were applied to the data set. The origins of these ceramic samples were classified as local, regional and foreign.

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Abstract  

Obsidian samples from San Miguel Ixtapan Mexico State, Mexico were analyzed by means of neutron activation. Statistical treatments such as bivariate, cluster and principal-components analyses were applied to the data set. Obsidians were identified as coming from three important sources: Sierra of Pachuca in the state of Hidalgo, Zinapécuaro and Zináparo-Varal in the state of Michoacán.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Monroy-Guzman, D. Trubert, L. Brillard, J. Kim, M. Hussonnois, and O. Constantinescu

Abstract  

The behaviour of the elements Zr, Hf, Nb, Ta and Pa has been investigated on macroporous anion exchange resin BIORAD AGMP 1 in HF medium (from 0.02 to 2M). All the studied elements show strong adsorption properties at low HF concentration. The adsorption was found to be highly dependent on H+ and F concentrations. The distribution of possible adsorbable complexes is discussed.

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Abstract  

Molybdate and tungstate of zirconium and titanium gels, used as matrices of 99Mo/99mTc and 188W/188Re generators, were synthesized under different conditions, in order to establish their performance and to choose the most appropriate gel to produce commercially. This type of generators demands a high content of Mo or W (>25%) in the matrices, since they use 99Mo and 188W of low specific activities. Therefore, it is of vital importance, to know the concentration of W and Mo in these gels, to determine their viability as matrices of the 99Mo/99mTc and 188W/188Re generators. There are different analytical methods to determine Mo and W, however, the presence of Zr and Ti in these gels, in many occasions, interfere in the analysis, imposing the previous separation of both metals before their determination. Therefore, the preparation time of the sample, the cost and the generation of chemical waste of these analyses are increasing. In order to eliminate these difficulties, the concentration of Mo, W and Zr of approximately 43 gels of molybdate and tungstate of zirconium and titanium, were evaluated by NAA without preparation of the samples. The results of this study reveal that the conditions of preparation of the gels influence directly their Mo and W content. In general, the titanium molybdate gels possess, on the average, a larger content of Mo (37%) than the zirconium molybdate gels (30%), while the titanium tungstenate gels contain only 8.5%.

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