This work describes the experimental determination of sucrose hydrolysis kinetics using a heterogeneous catalyst. We used
an Amberlite IR-120 strong acidic cation-exchange resin. The experiments were performed under previously determined optimal
process conditions: sucrose mass concentration, γS = 50 g L−1, catalyst mass concentration, γC = 180 g L−1, rotational frequency of the stirrer fm = 180 min−1, and temperature ϑ = 79 °C. The parameters of the supposed kinetic model were determined using experimental data. The kinetics
of sucrose hydrolysis over Amberlite IR-120 has not been reported to date. Therefore, we could not directly compare the calculated
values of kinetic parameters with those from the literature. However, the calculated values are within the range of values
determined by other types of catalysts. Furthermore, we investigated the influence of catalyst mass concentration γC on the reaction rate constant k′.
Authors:M. Shehata, B. Scholten, I. Spahn, S. Qaim, and H. Coenen
The radiochemical separation of radiogallium from radiogermanium was studied using ion-exchange chromatography (Amberlite
IR-120) and solvent extraction (Aliquat 336 in o-xylene). Both Amberlite IR-120 and Aliquat 336 in o-xylene have been used for the first time in separations involving radiogallium and radiogermanium. For tracer studies the
radionuclides 68Ge (t1/2 = 270.8 days), 69Ge (t1/2 = 39 h) and 67Ga (t1/2 = 78.3 h) were used. They were produced by the nuclear reactions natGa(p,xn)68,69Ge and natZn(p,xn)67Ga, respectively, and separated from their target materials in no-carrier-added form. Several factors affecting the separation
of radiogallium from radiogermanium were studied and for each procedure the optimum conditions were determined. The solvent
extraction using Aliquat 336 was found to be better. The separation yield of radiogallium was >95%, the time of separation
short, the contamination from radiogermanium <0.008% and the final product was obtained in 0.5 M KOH. This method was adapted
to the separation of n.c.a. 68Ga from its parent n.c.a. 68Ge. The quality of the product thus obtained is discussed.
Authors:K. Štamberg, P. Beneš, J. Mizera, D. Vopálka, and Š. Procházková
The kinetics of complexation (C) and decomplexation (D) reactions between Eu(III) and Aldrich humic acid (HA) was investigated as a function of pH (pH 4, 5, 6, 7 and 8) in the system Eu(III) - HA - Amberlite IR-120(Na) (I = 0.1). The derivation of the kinetic differential equations was based on the reactions of Eu3+ with, so called, strong (HAS) and weak (HAW) carboxylic groups of HA formulated in accordance with the new complexation model.1 The differential equations determining d[EuaHAS]/dt and d[EubHAW]/dt have the classical form applicable for reversible reactions where the forward reaction is the C-reaction and the reverse one is the D-reaction. Kinetic model used for the evaluation of experimental data includes these differential equations and the film diffusion model of sorption of Eu3+ on Amberlite IR-120(Na).
Authors:J. Plicka, J. Cabicar, A. Gosman, and K. Štamberg
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.
Authors:K. Štamberg, J. Plicka, J. Cabicar, and A. Gosman
The kinetics of Na+–UO
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
ions in the exchangers and their dependence on the content of DVB were obtained by evaluating the experimental data.
A simple and efficient method to isolate228Ra from natural thorium oxalate was developed. It consists in the coprecipitation of radium by hydrolysis of saturated solutions
of ammonium thoroxalate followed by ion-exchange chromatography on Amberlite IR-120. The final product is carrier-free and
pure enough for the preparation of thin sources for alpha and conversion electrons spectrometry. The radium coprecipitation
utilized in the first step of this method, could be used to separate thorium from most of its radioactive daughters, decreasing
the hazards of manipulation of large quantities of thorium.
Authors:K. Štamberg, J. Plicka, J. Cabicar, and A. Gosman
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.
Authors:Caroline Bosch, Pablo López-Lledó, Josep Bonjoch, Ben Bradshaw, Pieter J. Nieuwland, Daniel Blanco-Ania, and Floris P. J. T. Rutjes
An Amberlite IR 120 H-promoted one-pot Fischer indolization from a cis-decahydroquinoline using a range of phenylhydrazines led to compounds with the pyrido[2,3-a]carbazole scaffold. The process may be conducted either in batch mode or in a continuous manner in a flow reactor. The stereochemical course of the Fischer indole reaction changed in going from using free phenylhydrazine to the corresponding hydrochloride in batch conditions, whereas, with the short reaction times in continuous flow, no changes due to isomerization processes were observed.
Authors:K. Štamberg, P. Beneš, J. Mizera, J. Dolanský, D. Vopálka, and K. Chalupská
A general model, the so called Mean Molecular Weight Model (MMWM), of complexation of metal cations (Mez+) with macromolecular polyanions of humic acid (HAp-) is proposed. The model is based on the results of previous studies of the electrophoretic mobility of humate complexes and assumes that the complexation proceeds by consecutive neutralization of the dissociated carboxyl groups of the central polyanion HAp- with Mez+ cations. It reflects the macromolecular character of humic acid, applies molar concentrations of reacting components with equations for stability constants and incorporates also the mean charge of humic macromolecules. The model has been verified with experimental data obtained in the study of complexation of Eu(III) with Aldrich humic acid using ion exchange (Amberlite IR-120), over a broad range of [Eu] to [HA] ratio, at pH 4 and 7.
The determination of90Sr is extremely difficult in biological materials by chemical meth ods owing to the quantity of calcium associated. The problem
consists of the quantitative removal of calcium and of the selective extraction of90Sr using strontium carrier. It can be solved by precipitation and extraction methods, or by ion exchange chromatography. Following
our previous works, experimental evidence is presented using ion exchange technique for these purposees, where complex compounds
are used as eluents for calcium removal. For the determination of90Sr in milk and bones, calcium was removed with 1,2-diamino-cyclohexane-N,N,N′,N′-tetraacetic acid (CyDTA) eluent from Amberlite
IR-120 column. Our results show that compounds of chelatone type used as eluents with a strong acidic cation exchanger column
are the most convenient, for they prefer to compound with ligands of weaker or mean complexibility (hydrochloric acid, citric
acid and lactic acid).