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  • Author or Editor: J. Lesný x
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Abstract  

Ion exchange isotherms have been measured and plotted for the uptake of cesium, barium, cobalt, zinc, silver and amonium onto clinoptilolite- and mordenite-rich tuffs of Slovakian origin selectively for both the natural and near homoionic Na form as well, using the radioanalytical determination. The higher quality clinoptilolite-rich tuff has been proven to be effective for a potential radionucleides removal in native form according to the following selectivity sequence: Ag+,Ba2,Cs+>NH4 +>Co2+, while parent tuff in Na exchanged variety exhibited a little different sequence according to: Ag+ > NH4 + > Ba2+ > Cs+. The raw and Na exchanged mordenite-rich tuffs proved subsequently more or less similar selectivity : Ag+ > Zn2+ > Cs+, Ba2+ > Co2+ and Ag+ > Zn2+.

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Abstract  

The paper presents a fundamental study of adsorption equilibria for aqueous solutions of iron(III) chloride with natural and Na+-converted indigeneous and Chinese clinoptilolites. Adsorption isotherms for systems studied at ambient as well as elevated temperatures were measured. In order to evaluate the process enthalpy a plot of logK versus 1/T was drawn.

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Abstract  

The possibility to use the monoionic Ag+-form (eventually Hg+- and Hg2+- forms) of clinoptilolite of domestic origin for radioactive iodide elimination from waters has been studied. The capacity of the monoforms of clinoptilolite towards iodide exceeds many times that of the capacity of clinoptilolite in natural form. Due to the low solubility product of AgI, Hg2I2 and HgI2 iodides generate precipitates on the zeolite surface. Rtg analyses of the silver form of clinoptilolite after sorption of iodide demonstrate the formation of new crystals on the zeolite surface. The influence of interfering anions on the adsorption capacity of silver clinoptilolite towards iodide was investigated, too. Kinetic curves of iodide desorption from the surface of silver and mercury clinoptilolite were compared. Simultaneously, adsorption isotherms for the systems aqueous iodide solution/Ag, Hg-clinoptilolite were determined.

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Abstract  

The subject of this paper was to study Co2+-ion removal from aqueous solutions by means of natural mordenite and clinoptilolite. The mentioned zeolites were of Slovak origin (SFR). The static and dynamic equilibrium adsorption of Co2+-ions by zeolites, the influence of pH, quality and quantity of interfering ions on adsorbate/adsorbent system were investigated. The influence of flow rate, activation and initial concentration on the shape of the breakthrough curve was examined in dynamic regime. Mathematical expression was found for the breakthrough curve description.

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Abstract  

The aim of this study was to evaluate the quantitative and qualitative influence of some ions (ammonium, cesium, barium) on the adsorption capabilities of natural and chemically modified clinoptilolite towards Cs and Ba ions. Na–Cs–Ba — ternary ion-exchange isotherms at 23 °C were measured and plotted in a triangular diagram. Using statistical methods, linearized forms of isotherms (Freundlich, Langmuir, BET) for the systems studied are given.

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Abstract  

Uptake of iodide radionuclide from model solutions has been tested by means of three various deposit clinoptilolites (of Niný Hrabovec — Slovakia, Mád — Hungary and Wyoming —USA). The samples were chemically modified into more or less Ag-forms and the tests on adsorption were performed using columns packed with grain-sized zeolites. Breakthrough properties of iodide in dependence of competive chloride and phosphate ions were examined, respectively. Mathematical expressions of the adsorption profiles of iodide in Ag-columns as well as some Shilov constants of dynamic experiments were estimated. The highest capacity data to iodide were exhibited by the Ag-modified Slovakian clinoptilolite (102.7 mg/g) and the lowest one by the Hungarian sample (71.6 mg/g).

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Abstract  

The theoretical errors of VCV, CVV variants and its subvariants are outlined and compared to previous study of other variants. Simple complex forming separation reaction is used and optimal conditions for the analysis are discussed.

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Abstract  

Theoretical errors of the VVV variant and its subvariants are outlined and confronted with the earlier study of other variants. Simple complex forming separation reaction is assumed. Optimal conditions of the analysis are discussed.

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Abstract  

Cyclic 3, 5-adenosine monophosphate labeled with a radioactive isotope was determined in the 0.05–4.1 pmol.ml–1 concentration range.

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Abstract  

Trace amounts of thyroxine in model samples (160.0 ng.ml–1 and 20.0 ng.ml–1), and thyroxine and 3,5,3-triiodothyronine in blood plasma were determined by sub- superequivalence isotope dilution analysis and radio-immunoassay technique. Hormones were labelled by125I. The separation of antibody-bound hormone from free hormone was performed by ultracentrifugation. The results show higher accuracy of the sub- super-equivalence isotope dilution method over that of radioimunoassay.

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