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Abstract  

Natural bentonite clay was treated in order to remove impurities to increase the cation exchange capacity of the montmorillonite and to obtain a more effective radioactive cesium sorption. It was found that the treatment of the clay determines the amount of sorbed cesium. On the other hand it was shown that montmorillonites may retain cesium through several mechanisms which provide strongly retained cations occupying cationic sites into the clay structure or sorbed cesium which may be lost by purification treatments.

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Abstract  

The potential uses of zeolites in the treatment of radioactive wastes may be conditioned to the physico-chemical properties of these materials. This work compares the Co sorption behavior of zeolite 4A and radiation treated zeolite 4A. Sorption experiments were performed with solutions containing labeled cobalt. No radiation effect (100 Mrad) in the zeolite structure or in the Co sorption behavior was found.

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Abstract  

Radioactive elements may be retained by clays. The ability of natural Mexican clays to retain radioactive Co from aqueous solutions, is discussed. Experiments were performed with solutions containing labeled cobalt. The effect of contact time on Co2+ retention was studied. It was found that the Co2+ uptake value in dehydrated montmorillonites is between 0.30 and 0.70 meq g–1 of clay. A sorption sequence was obtained for the various clays. The samples were characterized, before and after cobalt exchange, by X-ray diffraction.

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Abstract  

The sorption of radioactive iodide anion from aqueous solutions on hydrotalcite in the nitrate form has been investigated as a function of the Al/(Mg+Al) ratio. It was found that I can replace only a small fraction of the nitrates in hydrotalcites and that I sorption depends highly on Al/(Mg+Al) ratio.131I was sorbed by anion exchange in the interlayer of hydrotalcite with an Al/(Mg+Al) ratio of 0.20 and, for higher ratios,131I sorption increased more than 3 times. Hydrotalcites in the nitrate form were prepared using microwave irradiation in the hydrotreatment step. The radionuclide content was determined by Γ-spectrometry. Solids were characterized by BET, X-ray diffraction and atomic absorption analyses.

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Abstract  

The ability of synthetic and natural Mexican zeolites and clays to remove radioactive Co from aqueous solutions is discussed. In the various samples, crystallinity was determined by X-ray diffraction. The amount of radionuclide sorbed by the aluminosilicates was determined by -spectrometry.

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Abstract  

The ability of some antural Mexican clays to sorb radioactive Co from aqueous solution and then desorb it has been measured. The clay cations seem to be exchanged with cations present in the solution. It was observed that the amount of sorbed Co2+ depends nearly linearly on the Na++K+ content in the montmorillonites. It was found that the crystallinity was not altered after Co2+ sorption. Crystallinity of clays, before and after cobalt exchange, was determined by X-ray diffraction.

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Abstract  

Several attempts have been made to synthesize mixed-valence compound of antimony at low temperature in view of studying the isotopic exchange in solids. The experimental procedure for the synthesis, at 263 K of Cs4(SbIIICl6)(SbVCl6) has been established. This compound seems very promising for isotopic exchange studies in the solid state.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Olguin, J. Duque, R. Pomés, M. Villafuerte-Castrejón, L. Sansores, P. Bosch, and S. Bulbulian

Abstract  

The present study discusses the incorporation of uranyl ion into Y-zeolite framework. The UO 2 2+ sorption was measured by neutron activation analyses. The Y-zeolite framework distorts in response to the cations present in the structure. Hence, depending on the amount and the location of the exchanged cations, the features of the X-ray diffraction pattern may vary. From the Rietveld analysis of these patterns, the positions occupied by the UO 2 2+ cations in the zeolite network were determined.

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Abstract  

A Mexican montmorillonite clay was intercalated on the one hand with aluminium or zirconium polyhydroxications, and on the other with two organic compounds. Radioactive cobalt was used to study the Co2+ sorption curves in the original and pillared clays. It was found that pillaring in general does not favour the diffusion of cobalt between the layers specially the organic pillared clays. In equilibrium, the cobalt retention reached the highest level, around 0.7 meq/g in the Zr pillared clay.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Olguin, M. Solache-Rios, D. Acosta, P. Bosch, and S. Bulbulian

Abstract  

The capacity of bentonite and purified bentonite to remove UO 2 2+ ions from aqueous solutions has been investigated. The UO 2 2+ uptake in these clays was determined for 0.2 and 0.002M uranyl nitrate solutions. It was found that under these conditions (0.2M) the maximum UO 2 2+ uptake was 1.010±0.070 meq UO 2 2+ /g of bentonite and 0.787±0.020 meq UO 2 2+ /g of purified bentonite. In purified bentonite UO 2 2+ sorption is irreversible up to 50 hours as no desorption was observed. Such is not the case in the natural bentonite. X-ray diffraction, thermal analyses, and transmission electron microscopy were used to characterize the solids. The uranium content was determined by neutron activation analysis.

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