The separation of Pa from carnotite from Sierra Goméz Chihuahua, México, has been studied, using233Pa as tracer. Protactinium lost during the separation and the efficiency of the method was determined through measurements of the radioactivity of233Pa.
In this paper the cation exchange capacities (CEC) of zeolites A, X,Y, ZSM-5 and erionite were determined and the results obtained were comparedwith the retention of cadmium by zeolites A (determined in this work), X,Y and erionite as well as with the retention of cobalt by zeolites A, X, Y,ZSM-5 and erionite reported elsewhere.
A solvent extraction technique to separate different chemical species of thorium is presented. The products formed by the chemical effects of the /n,/ reaction on the Th/acac/4 were separated by this method and the retention value was measured.
Complex formation of humic acids (HA)n with La3+ and Eu3+ was studied. Commercial (HA)n was purified and characterized. The stability constants were determined at several pH values and 0.2 M NaClO4 ionic strength by the Shubert’s method of radiochemical ionic exchange. The slopes of the lines
was determined as well for higher values of the j parameter and these values were: 12.2 ± 0.1 (j = 2, pH 7.7 ± 0.2), 15.6 ± 0.2
(j = 3, pH 4.9 ± 0.4) and 16.05 ± 0.07 (j = 3, pH 5.9 ± 0.1), for lanthanum and 13.18 ± 0.03 (j = 2, pH 5.9 ± 0.1) for europium.
A discussion is presented about the complex formation regarding pH and [(HA)n].
The sorption behaviour of cobalt and cadmium by Mexican erionite was studied at different pH values and the ion exchange isothems were determined. Sorption experiments were performed with cobalt and cadmium solutions. The cobalt, cadmium and sodium content in the aluminosilicate samples were determined by neutron activation analysis. It was found that the sorption for cadmium was higher than for cobalt, however, the selectivity for both cations was low in this zeolite.
Many factors affect the ion exchange process in zeolites. In this work the influence of different anions such as acetate,
chloride and nitrate on the ion exchange of cobalt in zeolite ZSM-5 is discussed. After the ion exchange in the presence of
those anions no change was found in the zeolite structure, by X ray diffraction and IR spectroscopy. The retention of cobalt
by zeolite ZSM-5 at low concentrations (from 0.001 to 0.3N) was higher when the exchange was done with cobalt nitrate and
chloride. This behavior was different in the case of 1N cobalt salts, since the highest sorption uptake was found when working
with cobalt acetate and its sorption was directly proportional to its concentration.
The sorption of cobalt from aqueous solutions was studied for two Mexican clinoptilolite rich tuffs zeolitic rocks and kaolinite
clay. The effects of pH and contact time on the sorption were examined. Cobalt was determined by neutron activation analysis
of the exchanged aluminosilicates. The sorption of cobalt by the aluminosilicates was similar in the pH range from 4 to 7.
Kinetic studies showed a rapid sorption in the first 5 hours and equilibrium in about 24 hours. Sorption kinetics was best
described by the second-order Ritchie modified model. The experimental results obtained at different concentrations and room
temperature for both zeolites were fitted to Freundlich, Langmuir and Freundlich-Langmuir isotherms. The sorption pattern
was found to follow the Freundlich model.
Authors:M. Olguín, I. García-Sosa, and M. Solache-Ríos
The apparent diffusion coefficient of Sr2+ in natural Mexican erionite from Sonora at different pH and concentrations were determined. Neutron activation was applied to measure the sorption of strontium. The apparent diffusion coefficient values showed that the mobility of Sr2+ through the cavities of the erionite depended on the concentration of strontium and the pH of the solution. As a consequence the sorption of this ion by the erionite was affected by these parameters and the maximum sorption of Sr2+ was at pH higher than 3 and 0.0094 mol·l–1 strontium nitrate solution.
Authors:A. López-Bautista, M. Olguín, and M. Solache-Ríos
Organic waste solutions containing tritium present two problems: the high toxicity of the solvents and the radioactivity of
tritium. In this paper the sorption behavior of the radioactivity of tritium from aqueous and organic waste solutions, containing
tritium labeled compounds, was studied in Sephadex, mineral coal and alumina. It was found that the tritium retention depends
on the composition of the waste solutions. Mineral coal was the best of the three materials studied to retain the organic
compounds labeled with this radionuclide.
Authors:I. García-Sosa, M. Solache-Ríos, and D. Hernández-Zarate
The sorption behavior of cobalt by zeolite ZSM-5 was studied. Parameters such as temperature, hydration of the zeolite (before the sorption), as well as the presence and absence of ethylenediamine during the ion exchange at room temperature and 80 °C were considered. The highest retention of cobalt was found when the sorption experiments were done at 80 °C in the presence of ethylenediamine.