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- Author or Editor: J. Cabicar x
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Abstract
The kinetic and solvent isotope effects during the maleic acid heterogeneous catalytic hydrogenation and deuteration in the light and heavy water have been studied. Also the effect of the γ and neutron irradiation on the Ni−ZnO catalysts (with various ratios of components) on the reaction kinetics and mechanism has been measured, as well as the effect of pH on the adsorption behaviour of maleic acid and the temperature depencence of the reaction rate. Existence of different adsorption centers for hydrogen and maleic acid could be deduced from these experiments. A reaction mechanism based on the two-dimensional diffusion of components in the surface is proposed.
Study of kinetics, equilibrium and isotope exchange in ion exchange systems. II
Kinetics of isotope exchange in238U(VI)-233U(VI)-strongly acidic cation exchanger systems
Abstract
The kinetics of isotope exchange in the238U(VI)-233U(VI)-strongly acidic cation exchanger Ostion KS system was studied in the temperature range 275–307K and for total uranium concentration 2.94·10−4–1.75·10−2 mol·l−1 in UO2(NO3)2 solution. The experimental results were evaluated by means of the “two-film mass-transfer model” and by the use of Fick's diffusion equations which have been proved more suitable for the system studied than McKay's equation. The influence of the temperature was evaluated using the Arrhenius equation. The diffusion character of the process follows also from the value of the activation energy (15.12 kJ·mol−1). In comparison with the UO 2 2+ ↔H+ ion exchange6 the isotope exchange studied is faster and less dependent on temperature (the activation energy is substantially lower).
Study of kinetics, equilibrium and isotope exchange in ion exchange systems
IV. Gel kinetics of ion exchange in Na+−Mg2+-strongly acidic cation exchanger system
Abstract
The kinetics of ion exchange in the Na+–Mg2+-strongly acidic cation exchanger system in a batch stirred reactor has been studied. The samples of exchangers OSTION KS (containing DVB in range of 1.5–12%) and AMBERLITE IR 120 for experimental work were used; the concentration of the aqueous nitrate solution was always 0.2M. The Nernst-Planck equation for description of diffusion of ions in a particle was used. The values of diffusion coefficients of magnesium ions in the exchangers and their dependence on the content of DVB were obtained by evaluating the experimental data and using the self-diffusion coefficients of sodium.
Kinetics, equilibrium and isotope exchange in ion exchange systems
III. Gel kinetics of isotope exchange in23Na-22Na-strongly acidic cation exchanger system
Abstract
The kinetics of isotope exchange in the23Na-22Na-strongly acidic cation exchanger system was studied in a batch stirred reactor. Samples of exchangers OSTION KS (containing DVB in range of 1.5–12%) and AMBERLITE IR 120 were used for experimental work. In all cases the concentration of the aqueous solution was 0.2M NaNO3. Fick's equation was used for description of diffusion of ions in the particle. By evaluating the experimental data values were obtained for the self-diffusion coefficients of sodium ions in the exchangers and their dependences on the content of DVB and on the concentration of functional groups in the resin particle.
Study of kinetics, equilibrium and isotope exchange in ion exchange systems
V. Gel kinetics of Na+−UO 2 2+ and Mg2+−UO 2 2+ ion exchange on strongly acidic cation exchangers
Abstract
The kinetics of Na+–UO 2 2+ and Mg2+–UO 2 2+ ion exchange on strongly acidic cation exchangers in a batch stirred reactor has been studied. The exchangers Ostion KS (containing DVB in the range of 1.5–12%) and Amberlite IR 120 for experimental work were used; the concentration of the aqueous nitrate solution was always 0.2 mol·l–1. The Nernst-Planck equation was applied for description of ion diffusion in the particle. The diffusion coefficients of UO 2 2+ ions in the exchangers and their dependence on the content of DVB were obtained by evaluating the experimental data.
Study of kinetics, equilibrium and isotope exchange in ion exchange systems
VI. The kinetic model of ion exchange sorption in ternary systems
Abstract
The description of kinetics of ion exchange in ternary system was based upon three Nernst-Planck equations, each of them describing the particle diffusion flux of a given counterion as an independent process. For experimental verification, the strongly acidic cation exchanger OSTION KS 08 the shallow-bed technique, and 0.2 mol·dm–3 aqueous nitrate solutions were chosen. The kinetics of ion exchange in the system of cations Na+–Mg2+–UO 2 2+ was studied. The values of diffusion coefficients obtained by evaluating of kinetics of isotope exchange and binary ion exchange were used for calculation. The comparison of calculated exchange rate curves with the experimental ones was made. It was found that the exchanging counterions were affected by each other.
Study of kinetics, equilibrium and isotope exchange in ion exchanger systems
I. Kinetics of sorption in the U(VI)—Strongly acidic cation exchanger systems
Abstract
The kinetics of sorption of uranium(VI) from aqueous uranyl nitrate solutions on strongly acidic cation exchanger Ostion KS was studied. The influences of the concentration of UO2(NO3)2 in the range 10−3–10−1M and of the temperature (275 K–313 K) were examined. The results were evaluated by means of “two-film mass-transfer model” modified for systems with non-linear equilibrium isotherms. It has been found that the applicability of the kinetic model used depends significantly on the solution cencentration. The effects of temperature was evaluated by the Arrhenius equation. The activation energy amounts to 23.36 kJ/mol, which corresponds to the assumption on the diffusion character of the ion exchange process.
