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  • Author or Editor: B. López x
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Abstract  

Irradiation of α-Al2O3 (Corundum) was carried out in contact with acidic media and with different doses (100-to-2500 kGy) and dose-rates (0.9, 2.6 and 6.1 kGy·h−1) of γ-rays. Simultaneously parallel experiments were carried out using the same procedure, but preheated at 150°C for two days and then irradiated without acidic media. The solid thus obtained was used to determine the effect of γ-irradiation on the sorption capacities of microamounts of fission products from strongly alkaline aqueous solutions of uranium. The results revealed that the effect of γ-irradiation of α-Al2O3 and the acidic media in which it is immersed, is associated with a stable matrix resistant to significant changes in the composition of the surface layer; whilst it seems that the effect of γ-irradiation of preheated α-Al2O3, is connected with changes of surface-OH groups strongly affected by heat treatment and irradiation dose.

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Abstract  

The use of ionizing radiation to achieve some desired effect on silica gel, applicable to the adsorption of radionuclides has been investigated as a function of the dose-rate over a wide range of doses, in experiments with strongly alkaline aqueous solutions containing an excess of UO 2 2+ relative to trace concentrations of88Y,103Ru,134Cs and141Ce. The results obtained revealed that γ-irradiation of silica gel was reproduced with an uptake comparable to that measured for the unirradiated-silica gel. Radiation resistance is strongly influenced by the basic macromolecular structure, the presence of water, and the particular environmental exposure conditions.

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Abstract  

The state of trace concentrations of95Zr–95Nb and134Cs was studied at an initial pH>13 in an uranyl triperoxidate medium using the electromigration method. OH ions governing the potential are adsorbed on the colloidal Nb(V)-hydroxide which leads to an increase in its negative electric charge; while95Zr did not move during the procedure. However, the electrophoretic mobility of the134Cs could be explained in terms of their agglomerations attributed to the interaction of Cs+ ions with water molecules to give larger aggregations.

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Abstract  

A great variety in retention properties occurs as a result of different methods of preparation of the sorbents. Specific surfaces and porosities, which are mostly connected with the sorption activities, may vary widely. The activation of Al2O3, SnO2 and silica gel, to produce highly active sorbents occurs only if the oxide is contacted with acid immediately after thermal treatment. The efficiency of the separation scheme has been tested using uranium and fission products under static conditions from strongly alkaline aqueous solutions.

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Abstract  

An effective modification of the chemical processes has been obtained to dissolve uranium(IV) and extract it as uranium triperoxocomplex, which facilitates its manipulation and final conversion into uranium nitrate as a high purity concentrate.

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Abstract  

It has been established that the coexistence of chemical species structurally different from cerium, is a direct consequence of the time taken for its preparation. Its practical applications, within the scope of purifying uranium, may constitute the most important technological aspect in the process of ionic exchange, to separate141Ce from uranium.

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Abstract  

The conditions to measure the gross alpha and gross beta radioactivity in water samples from Zacatecas and Guadalupe cities in the State of Zacatecas, Mexico were established. The gross alpha and beta radioactivity of water samples were measured using a liquid scintillation detector. The results show that the gross beta radioactivity in all cases is lower than the maximum contaminant level and the gross alpha radioactivity is higher in the samples collected from Guadalupe City and in the samples collected from the Southwest of Zacatecas City.

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Abstract  

Collection of uranium by salicyliden and glutariliden chitosans /Schiff's Bases/ was investigated to obtain information on uranium recovery from ores, especially carnotites. The collection of uranium by salicyliden /SDQ/ and glutariliden /GDQ/ chitosans was very rapid during the first 20 min and was affected by the pH of the solution, contact time and temperature. Uranium collected on SDQ and GDQ was easily eluted with diluted sodium bicarbonate solution. Also uranyl and vanadyl ions were separated from each other by using these biopolymers.

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Abstract  

In the present work Lyocell fibers were subjected to graft copolymerization of poly-N-isopropylacrylamide (pNIPAAm) thermosensitive polymer. The thermal degradation and stability of lyocell/pNIPAAm copolymers gels were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). pNIPAAm/lyocell copolymers are thermally stable and more resistant to temperature than lyocell fibres. Thermal characterization was analyzed as a function of percentage by mass of the pNIPAAm grafted. It has been shown that for pNIPAAm/lyocell copolymers, degradation occurs at higher temperature when increasing the degree of grafting.

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