The determination of leachability of radioisotopes of cesium and cobalt from preloaded zeolites in distilled water, base solution and acid solution has been studied. For the experiment, we used natural and chemically treated zeolites. The zeolites before leaching were calcined at different temperatures.
A composite scintillation detector consisting of two scintillators with different scintillation decay times, exhibiting a very low sensitivity to isotropic -radiation is presented in the paper. Detection characteristics of several such detectors have been experimentally verified and the rules for their design are given.
The sorption ability of clinoptilolite treated by NaOH solution has been studied. The distribution coefficients of137Cs and60Co were studied by the radiochemical method. The variation of distribution coefficients with pH was studied. Also the influence of competitive ions on distribution coefficients were investigated. The total cation exchange capacity and XRD analysis were also measured.
The Fe(III) uptake from aqueous solutions by natural and chemically modified zeolites was investigated using a gradual radioexchange
method and AAS technique. The leachability of Fe(III) from loaded zeolites was studied too. The Fe-uptake reached the value
of 60 mg·g−1 for the zeolite chemically treated with 6 mol·l−1 solution of NaOH and it is more than twelve times higher than that of the raw zeolite. The leachability of the loaded zeolite
samples in water and alkaline solution was up 5%. The leachability of the same zeolites in acid solution depended on the concentration
of modifying solution. The leachability at pH=2.6 in the range 2–20% at pH=1.9 was many times higher. The results of the radioexchange
and AAS methods were compared.
The influence of some cations on the exchange ability of chemically treated clinoptilolites has been studied. The natural clinoptilolites were treated by NaOH, NH4OH, NaCl and KCl. The modified clinoptilolites surface characteristics and ion exchange ability were studied as well.
Clinoptilolites were treated by NaOH, NH4NO3, NaNO3, KNO3 and HCl solutions. The sorption ability has been measured by a radiochemical technique. The sorption coefficients were calculated for Co and Cs.
The ion-exchange ability of NaOH-treated clinoptilolites with regard to Cs+ and Co2+ have been studied by a radiochemical method, enabling to calculate the sorption coefficient. The surface characteristics, total cation exchange capacity and X-ray structural analysis were measured as well. The measurements were done on Slovak clinoptilolite. Comment are made on a possible explanation of increasing sorption coefficient.
Natural and chemically modified zeolites from the Slovak Republic and Ukraine have been investigated as the adsorbents for the uptake of Cr(III). Model water solution of low radioactivity was used. The adsorption and desorption kinetics of chromium were established with the gradual radioexchange technique (tracer 51Cr) and flame AAS. The effect of the factors studied are examined and explained. The sorption coefficient , distribution coefficient KD, sorption capacity , sorption rate S, and leachability of Cr were calculated in neutral, alkaline and acidic aqueous solutions. The sorption capacity of the modified zeolites was found to be greater by a factor of 2 to 16 than that of the unmodified ones depending on the modifying solution applied. The leachability of chromium from loaded zeolites into the neutral solution was negligible. The leachability into alkaline and acidic solutions increased over 40%.
The uptake of plutonium from model solution of boric acid labelled with239Pu by natural sorbents was studied. The range of pH of solution was from 5.1 to 8. For the uptake of Pu were used different
natural and chemically modified natural sorbents of different mineralogical composition and from different deposits. The distribution
coefficients for plutonium uptake were calculated and the best conditions for uptake were evaluated.
Authors:M. Földesová, P. Lukáč, P. Dillinger, V. Balek, and S. Svetík
Zeolites chemically modified with 1, 4 or 6 M aqueous solutions of NaOH were studied by DTA, TG and ETA (emanation thermal analysis) in the temperature range 201–200°C. The structural changes in the modified zeolites at room temperature and in the modified zeolites annealed at 1000°C were studied by XRD analysis. Thermal analysis demonstrated dehydration, dehydroxylation, structural changes and a glass transition. A gradual loss in crystallinity of the chemically modified zeolites was also observed. XRD analysis revealed structural changes caused by chemical treatment and also by annealing.