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  • Author or Editor: I. El Naggar x
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Abstract  

Tin(IV) antimonate (SnSb), cerium(IV) antimonate (CeSb), silicon(IV) antimonate(SiSb) ant titanium(IV) antimonate (TiSb) were prepared under various conditions. The ion-exchange properties and the thermal stability of these materials were examined in order to elucidate their applicability to the processing of radioactive liquid wastes. Capacity, equilibrium measurements, adsorption isotherms and the selectivity patterns for Cs+, Sr2+, Co2+ and Eu3+ ions on these sorbents at different conditions were determined. The effect of high concentrations of salts and complexing agent as interfering ions in the feed solutions on the distribution coefficient of the metals, mentioned above, was tested as a function of [HNO3]. Based on the results obtained, practical separation experiments on column were performed.

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Abstract  

Cation self-diffusion studies have been carried out by using the radiochemical technique for strontium ion in both hydrated ceria and zirconia. The particles of these exchangers are shown to behave as variable capacity ion exchangers. Self-diffusion coefficients for strontium ion were measured as a function of the variable capacity for that ion in solutions of varying acidity. The results are shown to be in qualitative agreement with the absolute rate theory. Also, it is shown that the measured self-diffusion coefficients are dependent only upon the total strontium ion capacity.

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Abstract  

This paper reports a radiochemical study of the kinetics of ion exchange of Na+ and Cs+ with H+ on hydrous titanium dioxide. The experimental conditions are set to favor the particle diffusion mechanism only, and this is confirmed by the Bt versus t plots. On the basis of these studies the various physical parameters such as the effective diffusion coefficients, activation energies and entropies of activation have been evaluated. Tentative explanations are given for these results, from which some conclusions are drawn.

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Abstract  

Doping of inorganic ion-exchange material tin silicate with zirconium ion by sol-gel technique was conducted for the production of a novel ion-exchanger. Undoped and doped tin silicate has been characterized by elemental analysis (X-ray fluorescence), Fourier transform infrared spectroscopy (FT-IR), thermal analysis and X-ray diffraction studies. The structures of two ion-exchangers were identified and the empirical formulas found as SnSi2O6·6H2O and SnZr4Si4O12·16H2O for tin silicate and zirconium doped tin silicate, respectively. The effect of zirconium ion concentration of the doped tin silicate on the crystalline size and strain of tin silicate was investigated. The probable structure of both materials was assessed by the ChemDraw Ultra program. Finally, application of these materials for the treatment of radionuclides in terms of capacity measurements was investigated.

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Abstract  

The distribution of UO 2 2+ and Th4+ in nitric acid media on crypomelane-type hydrous manganese dioxide (CRYMO) has been investigated by batch equilibrations and column break-through techniques. The parameters studied involve the media composition and concentrations of HNO3, NaNO3, UO 2 2+ and Th4+. It is found that Th4+ is more strongly adsorbed on CRYMO than UO 2 2+ with sufficient differences for chromatographic separation from each other. Uranium was quantitatively eluted from a CRYMO column with 0.1M HNO3. Th4+ has been recovered by using 1M HNO3 as eluent.

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Abstract  

Neutron irradiated 12-molybdocerate(IV) is evaluated as a column matrix for use in preparation of small chromatographic column type99mTc generators. Greater than 87% of the generated99mTc activity is immediately and reproducibly eluted with passing 10 cm3 of saline or chromated saline solutions through 3.0 g of molybdocerate column bed at flow rates of about 1.0 cm3/min. The elution performance of99mTc does not drastically change with increasing the drying temperature and/or the particles sixe of the column matrix in the range investigated. Saline eluent containing 5·10–5M CrO 4 2– increases the radiochemical purity of the eluate to >98% TcO 4 . Radionuclidic and chemical purities of the eluates satisfy the specifications for use in nuclear medicine.

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Abstract  

The preparation of insoluble 12-molybdocerate(IV) from99Mo of low specific activity, produced by thermal neutron irradiation of MoO3, is described. Samples of the material are dried at 50, 100 and 200°C and used as column matrices from which the generated99mTc activity is periodically eluted with saline solution or saline solution containing 5·10–5M K2CrO4 as an oxidant. The elution yields of99mTc are high and reproducible (95–81%) with radionuclidic purity 99.98%. Both chemical and radiochemical purity (as TcO 4 ) of the eluates decrease with increasing drying temperature of the column matrix. Using chromated saline solution as eluent improves the radiochemical purity of the99mTc eluate.

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Abstract  

Self-diffusion coefficients for chloride ion were measured as a function of chloride ion capacity in solutions of varying acdity using particles of hydrous ceric oxide heated at 50, 200 and 400°C. The measured self-diffusion coefficients are dependent only upon the total chloride ion capacity. At the same capacity, self-diffusion coefficients are almost the same for ceria particles heated at different temperatures. The trace component diffusion coefficients of chloride ion in the nitrate-form of the oxide, dried at 50°C, were also measured. Under the same conditions, the self-diffusion coefficients are somewhat higher or close to the trace component diffusion coefficient for the sample dried at 50°C.

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Abstract  

Incorporation of iron oxide into silico-antimonate of different Si/Sb molar ratios introduced a class of dual salts ion exchangers with advanced ion exchange properties. Physicochemical and equilibrium studies have been carried out to understand the ion exchange properties of these materials. Apparent investigation indicated that iron incorporation into silico-antimonate yields materials having excellent mechanical properties. On the basis of distribution studies, the materials were found to be highly selective for Sr2+ or Ce3+ depending on their Si/Sb molar ratios. Diffractogram, thermogram, IR spectra and sorption performance of crystalline FeSiSb (114) indicated that no detectable structural changes after an exposure up to 100 kGy of γ-rays. Effect of reaction temperature on the exchange process was investigated and the respective thermodynamic parameters were calculated.

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Abstract  

Cerium(IV) antimonate was prepared by dropwise addition of 0.6M antimony pentachloride and 0.6M cerium ammonium nitrate solutions by a molar ratio of Ce/Sb 0.75. Exchange isotherms for H+/Co2+, H+/Cs+, H+/Zn2+, H+/Sr2+ and H+/Eu3+ were determined at 25, 40 and 60°C. Besides, it was proved that europium is physically adsorped, while zinc, strontium, cobalt and cesium are chemically adsorbed. Moreover, the heat of adsorption of zinc, strontium, cobalt and cesium on cerium (IV) antimonate was calculated and indicated that cerium(IV) antimonate is of endothermic behavior towards these ions. Also the distribution coefficients of these ions were determined and it was found that the selectivity is in the order: Eu3+>Sr2+>Cs+>Na+.

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