Synthesis and characterization of tin(IV) antimonate and study of its ion-exchange equilibria

Tin(IV) antimonate with different Sb/Sn molar ratios has been prepared. The characterization of the product materials was carried out using X-ray diffraction pattern, themal analysis and infrared spectra. The saturation capacities of sodium and cesium were found to increase with Sb/Sn molar ratios. TheK _d values on thermal treatment of tin(IV) antimonate, as a cation exchanger, have been measured for some heavy metal ions in the temperature range of 50–400 °C. The maximum adsorption of 10^–4M of the metal ions studied was obtained at 400 °C. The selectivity sequence was Eu³⁺>Co²⁺>Sr²⁺>Cs⁺ for the sample heated up to 400 °C. No adsorption was observed on the sample heated at 700 °C because of the formation of SnO₂ and Sb₆O₁₃.     

Mixed insoluble acidic salts of tetravalent metals IV. Crystalline mixed zirconium — Titanium phosphates

Mixed crystalline alpha zirconium — titanium phosphates with variable zirconium to titanium ratios have been prepared both by the well known gel reflux method and a modified HF method. Chemical analysis, X-ray, i.r. and thermal analysis were used to characterize the materials. Exchange capacities for these ion-exchangers have been evaluated by pH-titration combined with radioisotope tract technique for Na⁺, K⁺, Rb⁺ and Cs⁺.     

Evaluation of cesium sorption on natural mordenite

The kinetic and equilibrium sorption behaviors of Cs⁺ on mordenite, a zeolite which can sorb cesium well, were investigated by using the batch method. Cesium-137 and the stable CsNO₃ were used as tracer and carrier to study the influences on Cs⁺ sorption behaviors by changing Cs⁺ initial concentration, pH value, particle size of mordenite and experimental temperature. The equilibrium was reached in 3 days and the saturated amount of cesium sorbed is about 0.19 kg Cs/kg NM. The sorption data at 25°C and 90°C were fitted to Freundlich sorption model and nonlinear isotherms were found. However, linear isotherm was applicable with a Cs⁺ initial concentration less than 10^–3M. The decrease of Cs⁺ sorption at elevated temperature suggested the sorption reaction was exothermic. The use of centrifugation to separate the liquid from solid phases in traditional batch techniques was not suitable to the kinetic experiment of Cs sorbed by mordenite for lower concentrations.     

Effects of alkali-metal cations on nitrate-ion N-O bond force constants in ionic melts

Measured frequencies from pure nitrate liquids have been used to calculate the force constants for the nitrate ion and the M⁺-NO₃ ^– systems (M⁺ = Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺) by a matrix successive-approximation method based on perturbation theory in dependent coordinates. The valency force constants K_q for the N-O bonds are increased by comparison with free NO ₃ ^– . The N-O bond strengthening is not adequately explained by cation-anion interaction because there is electron-density transfer mainly by the mechanism within the NO ₃ ^– . Correction for the vibrational parameters of the interacting particles confirms the previously demonstrated acid-base mechanism for the cation-anion interaction in liquids containing nitrate.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 230–234, March–April, 1989.     

Recovery of plutonium from phosphate containing aqueous analytical waste solutions using macroporous anion exchange resin

Distribution ratios of Pu(IV) between 7.5M HNO₃+0.75M H₃PO₄+0.3M H₂SO₄ media and a macroporous anion-exchange resin Amberlyst A-26 (MP) increased from 40 to 250 when 1M aluminium nitrate was added to the aqueous medium. When 1M ferric nitrate was used in place of aluminium nitrate the distribution ratio further increased to 850. The 10% Pu(IV) breakthrough capacities with a 5 ml bed resin column, using synthetic feed solutions containing 1M aluminium nitrate, were 1.4 g l^–1, 3.2 g l^–1 at flow rates of 30 ml per hour and 10 ml per hour, respectively. The corresponding 10% Pu(IV) breakthrough capacities in the presence of 1M ferric nitrate were 8.5 g l^–1 and 12.8 g l^–1. More than 97% of plutonium could be recovered from actual analytical phosphate waste solutions.     

Conductometric Determination of the Stability Constants of the Inclusion Complexes of Alkali Cations with [22-DD] Diaza Crown Ether, [211] and [221] Cryptands in Acetonitrile

An equilibrium study concerning the association of Na⁺, K⁺, Rb⁺ and Cs⁺ with 4, 7, 13, 18-tetraoxa-1,10-diazabicyclo [8, 5, 5]-eicosane [211], 4, 7, 13, 16, 21-pentaoxa-1, 10-diazabicyclo [8, 8, 5]-tricosane [221] and 4, 13-didecyl-1, 7, 10, 16-tetraoxa-4, 13-diazacyclooctadecane [22-DD] in acetonitrile has been carried out at 25 °C by using a conductometric technique. The observed molar conductivity, Λ, of a test solution was found to decrease significantly for mole ratios less than 1:1 upon the addition of the complexing ligand. A model based on 1:1 stoichiometry has been used to analyze the conductivity data. The data have been fitted according to a non-linear least-squares analysis that provides the stability constant, K, and the molar conductivity, Λ_c, for each cation – ligand inclusion complex. The binding sequences were found to follow the order: Na⁺ > K⁺ > Rb⁺ ≫ Cs⁺ (K ≈ 0) for [211], Na⁺ > K⁺ > Rb⁺ > Cs⁺ for [221] and K⁺ > Na⁺ > Rb⁺ > Cs⁺ for [22-DD] complexes. Trends in ionic conductivities of complexed ions are also discussed.     

Preparation of hybrid ion exchanger based on acrylamide for sorption of some toxic metal ions from aqueous waste solutions

Crystalline phases of polyacrylamide titanium tungstophosphate composite material has been synthesized via sol–gel method. The properties of its were determined using different technique. The ion-exchange capacities of the hybrid material for Cs⁺, Co²⁺ and Eu³⁺ ions it was found that 6.22, 2.76 and 1.38 mequiv. g^–1 respectively. The material was found that highly selective for Eu³⁺ and the selectivity sequence for sorption of Cs⁺, Co²⁺ and Eu³⁺ ions on polyacrylamide titanium tungstophosphate was found that; Eu³⁺ > Cs⁺ > Co²⁺. Thermodynamic parameters have been calculated for the studied ions showing that the overall adsorption process is spontaneous and endothermic. The experimental isotherm data were analyzed using the Langmuir and Freundlich models.     

MnCl+ and MnSO4 association constants to 170°C

Changes in electron spin resonance (ESR) spectra of the manganese (II) ion are used to determine thermodynamic association constants for MnCl⁺ and MnSO ₄ ⁰ complexes from 25 to 170°C. The technique employed requires minimal sample handling and preparation. Pressure increase had a negligible effect on the association constants which increase from 4 m^–1 at 50°C to 200 m^–1 at 170°C for MnCl⁺ and from 200 m^–1 at 25°C to 5700 m^–1 at 170°C for MnSO ₄ ⁰ . The ratio of inner to outer sphere complexes decreases with increasing temperature to 120°C and then increases from 120 to 170°C for both chloride and sulfate complexes. Enthalpies, entropies, heat capacities, and Gibb's free energies determined for each of the reactions compare well with values determined by other methods. These results confirm the validity of the high temperature and pressure ESR approach, which can be used to study other high temperature association reactions of Mn⁺² and, by competitive effects, association reactions of metals that do not have an ESR signal.     

A structural study of saturated aqueous solutions of some alkali halides by X-ray diffraction

The structure of nearly saturated or supersaturated aqueous solutions of NaCI [6.18 mol (kg H₂O)^–1], KCI [4.56 mol (kg H₂O)^–1], KF [16.15 mol (kg H₂O)^–1] and CsF [31.96 mol (kg H₂O)^–1] has been investigated by means of solution X-ray diffraction at 25°C. In the NaCI and KCI solutions about 30% and 60%, respectively, of the ions form ion pairs and the Na⁺–Cl^– and K⁺–Cl^– distances have been determined to be 282 and 315 pm, respectively. The average hydration numbers of Na⁺ and Cl^– ions are 4.6 and 5.3, respectively, in the NaCI solution and those of K⁺ and Cl^– ions in the KCI solution are both 5.8. In the KF solution, clusters containing some cations and anions, besides 1:1 (K⁺–F^–) ion pairs, are formed. The K⁺–F^– interatomic distance has been determined to be 269 pm, and nonbonding K⁺...K⁺ and F^–...F^– distances in the clusters are 388 and 432 pm, respectively, and the average coordination numbers n _KF , n _KK and n _FF have been estimated to be 2.3, 1.9, and 1.6, respectively. In the highly supersaturated CsF solution an appreciable amount of clusters containing several caesium and fluoride ions are formed. The Cs⁺–F^– distance in the cluster has been determined to be 312 pm, while the nonbonding Cs⁺...Cs⁺ and F^–...F^– distances are estimated to be 442 and 548 pm, respectively, the distances being about and times the Cs⁺–F^– distance, respectively. The coordination numbers n _CsF , n _CsCs , and n _FF in the first coordination sphere of each ion are 3.3, 2.3 and 5.3, respectively, and the result shows the formation of clusters of higher order than 1:1 and 2:2 ion pairs. These ion pairs and clusters may be regarded as embryos for the formation of nuclei of crystals and the results obtained in the present diffraction study support observations for the nucleation of the alkali halide crystals studied by molecular dynamics simulations previously examined.     

ESR investigation on the phase transitions of DPPC vesicles in presence of high concentrations of Li+, Na+, K+ and Cs+

The partition of the spin label TEMPO in the hydrophobic region of di-palmitoyl-phosphatidylcholine unilamellar vesicles has been used to investigate the influence of high concentration (up 3M) of Li⁺, Na⁺, K⁺, and Cs⁺ on the phase transitions at 20–60°C. All of the above salts increase the permeation of TEMPO. The efficiency of monovalent cations in inducing the partition of the spin label in the hydrophobic environment of the bilayer increases in the order: Cs⁺+++. The disappearing of the pretransition and the downward shift of the main phase transition temperature from 37°C to 33.5°C is related to the increased permeation of TEMPO into the bilayer. The presence of salts in the bulk solution disturbs the hydration of the zwitterionic polar head of the DPPC molecules and changes the electrical interaction between the polar groups of the bilayer. This reduces the packing density of the lipid molecules and promotes the permeation of TEMPO.     

Heat capacities of concentrated multicomponent aqueous electrolyte solutions at various temperatures

The specific heat capacities of the aqueous multicomponent system NaCl +KCl+MgCl₂+CaCl₂ with ionic strength between 8.3 and 9.6 (resembling Dead Sea waters) were measured between 15°C and 45°C. The obtained data were fitted to an empirical equation as a function of concentration and temperature. The thermodynamic functions of the studied multicomponent system were found to be strongly influenced by changes in MgCl₂ concentrations. The application of Young's rule to such concentrated systems was checked at 25°C. The calculated (by Young's rule) specific heat capacitiesC _p and apparent molar heat capacities C_p, of these multicomponent electrolyte solutions were in reasonable agreement with the measured values (–0.008 J-g^–1-K^–1 and –2.6 J-mol^–1-K^–1, respectively).     

Distribution studies of metal ions on arsenophosphates of Sn(IV) and Cr(III) and on amine Sn(II) hexacyanoferrates (II) using radio tracers: Separation of Sr2+−Cs+, Hg2+−Ag+ and Hg2+−Zn2+

Summary Distribution studies of some metal ions have been made on Sn(IV) and Cr(III) arsenophosphates and on some samples of Sn(II) amine hexacyanoferrates(II), using radiotracers. The K_d values of Cs⁺ and Rb⁺ have been followed at varying HNO₃ concentrations also. As a result 3 useful binary separations have been achieved on Sn(IV) and Cr(III) arsenophosphates, such as Sr²⁺–Cs⁺, Hg²⁺–Ag⁺ and Hg²⁺–Zn²⁺.     

Thermodynamic Properties of NaCl Solutions at Subzero Temperatures

Heat capacities at infinite dilution of NaCl (aq) for the temperature range 0 to –25°C and apparent molar volumes at infinite dilution for 0 to –15°C have been estimated from a synthesis of experimental data collected at subzero temperatures. The parameters of the Helgeson–Kirkham–Flowers (HKF) equation for Na⁺ (aq) have been obtained, from which the Gibbs energies of Na⁺ and Cl^– have been calculated. The estimated values of Pitzer-equation parameters for thermal and activity-coefficient properties have been adjusted for subzero temperatures. The experimental phase diagram for the NaCl–H₂O system could be reproduced with these data, demonstrating the low-temperature applicability of the HKF model to extrapolate thermodynamic properties of aqueous-solution species at infinite dilution.     

Free energies of transfer of alkali metal halides in isodielectric acetonitrile and ethylene glycol mixtures at 25°C

Standard free energies of transfer (G _t ^o ) of alkali metal chlorides MCl (M=Li, Na, K, Rb, Cs) and of potassium bromide and iodide from ethylene glycol to its isodielectric mixtures containing 20, 40, and 60 wt. % acetonitrile have been determined from emf measurements at 25°C. The standard potentials of the M/M⁺, the Ag–AgBr, and the Ag–AgI electrodes have been calculated using auxiliary emf measurements. All electrolytes were found to be increasingly destabilized in mixed solvents of increasing acetonitrile content; the relative order of cation destabilization is Li⁺>Na⁺>K⁺>Rb⁺>Cs⁺ and that of anion destabilization is Cl^–>Br^–>I^–, both following (a) the order of increasing softness of ions and increasing interaction with the soft base, acetonitrile,and (b) the order of decreasing hydrogen-bonding propensity of ions and decreasing interactions with the hard base, ethylene glycol.     

Composite Zn(II) Ferrocyanide/Polyethylenimine Cryogels for Point-of-Use Selective Removal of Cs-137 Radionuclides

The feasibility of several approaches to the fabrication of monolith composite cryogels containing transition-metal ferrocyanides for Cs⁺ ion uptake has been evaluated. Although in the series of investigated metal ion precursors (Cu(II), Zn(II), Ni(II), and Co(II)), in situ formation of the sorption active phase in polyethyleneimine (PEI) cryogel was feasible only in the case of Zn(II) ferrocyanide, this approach has shown significant advantages over the immobilization of ex situ synthesized ferrocyanide nanoparticles. Nanoparticles of the mixed ferrocyanide Zn_1.85K_0.33[Fe(CN)₆] formed in situ had an average size of 516 ± 146 nm and were homogeneously distributed in the monolith located at the polymer surface rather than embedded in the matrix. The Young modulus of the PEI cryogel increased after modification from 25 to 57 kPa, but composites maintained high permeability to the flow. Sorption of Cs⁺ ions has been investigated at superficial velocity up to 8 m/h. Steep breakthrough profiles and uptake efficiency of >99.5% until breakthrough point confirmed that a supermacroporous structure of the monolith composite assured good mass transfer, so that intraparticle diffusion was not the limiting stage of sorption kinetics. Application of the rate-constant distribution model (RCD model) to analyze the breakthrough curves of Cs⁺ sorption allowed the identification of two types of sorption sites with a difference in sorption rate constants of ~1 log unit. Most likely, sorption on “fast” sorption sites was governed by ion exchange between Cs⁺ ions in solution and K⁺ ions in the ferrocyanide lattice. Cs-137 radionuclide removal was investigated using the monolith composite columns of various geometries at superficial velocity up to the 6.6 m/h; specific gamma activity was reduced from 265 kBq/L to the background level, showing high potential of these materials for POU application.     

Migration of radiocesium in a zeolite-solution system

Some properties of natural zeolite from Zaloka gorica, Slovenia, Yugoslavia were investigated to establish its applicability in solidification and for storage purposes of radioactive waste. It was found that this material is a rather good sorber for cesium, with a capacity of about 0.6 meq g^–1. The migration rate of Cs⁺ in a system ion exchanger-aqueous solution was investigated and correlated with the sorption behaviour of cesium in a system. The leaching rate of cesium from concrete containing zeolite was measured.     

Partial molal volumes of ions in organic solvents from ultrasonic vibration potential and density measurements. III. Dimethylsulfoxide

The partial molal volumes of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Cl^–, Br^–, I^–, and NO ₃ ^- in DMSO at 25°C have been determined from ultrasonic vibration potential data and density data for solutions of uni-univalent electrolytes. Hepler's semiemprirical equation has been used to split ionic partial molal volumes into geometric and electrostrictive contributions. The results obtained in this work confirm the conclusion of our previous studies, namely, that the contribution of electrostriction is essentially determined by the properties of that layer of atoms, 0.3 to 0.4 nm thick, in contact with the ion and by the degree of steric hindrance of the poles of the dipole of the solvent molecule. On the other hand, the geometric contribution depends on the size of the solvent molecule and also on the arrangement of the solvent molecules about the ions. It is shown that the geometric contribution to the partial molal volume of ions is largely increased when ions cannot come close enough to the poles of the solvent-molecule dipole, owing to steric hindrance.     

Adsorption of cesium from spent nuclear fuel basin water

Summary Batch equilibrium and kinetic measurements were performed for Cs⁺ exchange in silicotitanate zeolite (Ionsiv^® TIE-96) at 30 and 60 °C. The Langmuir isotherm equation provided a good fit of the equilibrium data. The heats of exchange reaction between Cs⁺ in the aqueous solution and Na⁺ in the zeolite structure were derived from the equilibrium data. The results indicate that the exchange mechanism is different from that of physical adsorption on heterogeneous materials. The apparent diffusion coefficients and activation energy were derived from the kinetic data and the values obtained for inter-diffusion of Cs⁺ and Na⁺ cations in the zeolite structure were 1.33 ^. 10^-12 and 1.04 ^. 10^-12 cm^{2 .} s^-1 at 30 and 60 °C, respectively. The activation energy for Cs⁺ was 1.7 kcal/mol, suggesting that the Cs⁺ cation can access easily all the sites in the zeolite framework. Thus, the exchange of Cs⁺ with Na⁺ in the zeolite was not hindered by ion-sieve effects.     

Influence of alkali metal and ammonium cations on the structure of iron(II) and cobalt(III) hexacyanide complexes encapsulated in faujasite

Changing the cation composition (Na⁺ to K⁺, NH₄ ⁺ Cs⁺) of faujasite with hexacyanoferrate(II) encapsulated in the large pores causes distortion of the octahedral symmetry of the complex.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 5, pp. 293–297, September–October, 1994.     

Potassium and cesium thiocyanate complexes with diphenyloxa-21-crown-7: Synthesis and vibration spectra. Selective properties of dipnehyloxa-21-crown-7

Novel K and Cs complexes with diphenyloxa-21-crown-7 (2,3,5,6-dibenzo-1,4,7,10,13,16,19-heptaoxacyclo-heneicosadiene-2,5; DPO21C7) are synthesized and isolated in a solid state, and their IR spectra (4000–400 cm^–1) are studied. Only four ether O atoms of crown ether are involved in coordination. Conformation of a macrocycle in the complexes depends on the cation size. The potentiometric selectivity of diphenyloxa-21-crown-7 toward Cs⁺ ions was found to be the greatest.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 163–167.Original Russian Text Copyright © 2005 by Ivanova, Dorokhov, Pyatova, Galkina, Yakshin, Tsivadze.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.