Cs and Sr removal from solution using potassium nickel hexacyanoferrate impregnated zeolites</p> </p>

Summary Potassium nickel hexacyanoferrate, KNiFC, was incorporated in the porous matrix of zeolites by successive impregnation with Ni(NO₃)₂ and</o:p></p> K₄Fe (CN)₆.¹ CFC and PFC exchangers were first prepared by impregnating the potassium nickel hexacyanoferrate into the clinoptilolite and the synthetic P zeolite, respectively. Ion-exchange isotherms and breakthrough curves were plotted. Results showed that the CFC sorbent is suitable for removal of Cs⁺ where PFC is more suitable for Sr²⁺. Negative effect of Na⁺ as a competing ion in these exchangers was less than in the parent zeolites. Isotherm plots fitted the Langmuir equation.</p> </p>     

Thermodynamic modeling for the removal of Cs+, Sr2+, Ca2+and Mg2+ions from aqueous waste solutions using zeolite A</p> </p>

Summary The batch removal ofCs⁺, Sr²⁺, Ca²⁺and Mg²⁺ions from aqueous solutions using synthetic zeolite A was investigated. The influence of the initial ion concentration, pH and temperature was studied. The obtained isotherm data have been correlated with Langumir, Freundlich, and Dubinin-Radushkevich(D-R) isotherm models. The effect of the temperature on the equilibrium distribution values has been utilized to evaluate the standard thermodynamic parameters such as free energy (DG), enthalpy (DH) and entropy (DS). Based on the D-R isotherm expression, the maximum ion-exchange capacity and the mean free energy of each studied ion has been determined. The selectivity sequence, deduced from the equilibrium isotherm data is: Sr²⁺>Ca²⁺>Mg²⁺>Cs⁺>Na⁺.</p> </p>     

Sorption of Co, Cs, Sr and I onto argillaceous rock as studied by radiotracers</p> </p>

Summary Sorption of⁶⁰Co,⁸⁵Sr, 137Cs and¹²⁵I have been studied on samples originated from Boda (siltstone-) claystone formation (BCF) (Hungary). The distribution of K_dvalues have been determined in static batch experiments using natural groundwater. The order of sorption of isotopes was Co>Cs>Sr>I, where iodine exhibits sorption properties in a modest extent. The sorption isotherm was determined for Cs from measurements carried out in 10^-5-10^-1M initial concentration range. The isotherm can be described with non-linear Freundlich approximation in the range of</o:p></p> 10^-7-10^-4M equilibrium concentration. At concentrations >10^-2M the isotherm achieves saturation. Hence, it is suggested that sorption of Cs on BCF is dominated by cation-exchange reactions on the illite mineral component. In the case of Co and Sr, precipitation reactions occurred during the experiments performed with carrier-containing solutions. This can be attributed to the low values of solubility product constants of SrCO₃, SrSO₄and Co(OH)₂, formed from anions present in the natural groundwater.</p> </p>     

Strontium isolation from natural samples with Sr resin and subsequent determination of 90Sr</p> </p>

The reliability of an ⁹⁰Sr determination method was tested using an Sr extraction chromatographic resin for strontium isolation. The ⁹⁰Sr-content in samples of vegetables, soil and water (obtained from Environmental Measurement Laboratory, USA) were determined and the results were controlled by classical methods and by using an anion-exchanger and an alcohol solution of nitric acid for the strontium isolation. These methods were previously tested by determining ⁹⁰Sr in IAEA 326 and 327 samples of soil. It is shown that the isolation process with Sr resin is simpler and faster than the classical and mixed solvent anion-exchange methods. The efficiency of isolation on a Sr column depends on the resin quantity and separation conditions; and is the highest with a Sr column, compared to the classical and anion-exchange methods. Experimental data and theoretical models were used to calculate the parameters that enable the estimation of optimum dimensions of the column for isolation. A simple relation is proposed for the calculation of breakthrough volume, which defines the sample and eluent volumes for an optimal strontium isolation.</p> </p>     

Removal of strontium ions by a crosslinked copolymer containing methacrylic acid functional groups</p> </p>

Summary A tail-made polymer matrix is proposed to remove strontium ions from aqueous solutions. The removal behavior of strontium ions on a crosslinked copolymer containing methacrylic acid as functional groups was investigated as a function of sorptive concentration, time, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solution. It is found that a maximum adsorption of Sr(II) ions can be obtained on the crosslinked copolymer after 30 minutes and at pH 8. The increase of Sr(II) ion concentration in the solution resulted in an increase in the amount of Sr(II) ions adsorbed on the crosslinked copolymer containing methacrylic acid as functional groups. However, after a maximum of Sr(II) concentration in the solution, the percentage of adsorbed Sr(II) ions decreased. The adsorption data are well represented by the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The adsorption capacity of the copolymer and the free energy change were calculated by using the D-R isotherm. For the adsorption of Sr(II) ions on the crosslinked copolymer the thermodynamic parameters (DH°,DS° andDG°) were calculated.</p> </p>     

Preconcentration of 198Au in a green alga, Rhizoclonium</p> </p>

Summary The bioaccumulation of ¹⁹⁸Au radionuclide, by Rhizoclonium riparium a member of Chlorophyceae has been studied. It has been observed that accumulation of gold on Rhizoclonium is almost pH independent and slightly higher at basic pH. Accumulation of gold was studied with ¹⁹⁸Au radiotracer, 0.1, 1 and 5 ppm concentrations of gold. It has been concluded from the biochemical analysis that the gold accumulation is due to adsorption in the cellulose and not in protein, fat and carbohydrate. Accumulated gold was recovered when washed with conc. HNO₃.</p> </p>     

Removal of uranyl ions from wastewaters using cellulose and modified cellulose materials</p> </p>

Summary Three silylcellulosic derivatives with different substitution degree were examined as sorbents for uranyl ions. The adsorption rate and capacity of cellulose and modified cellulose were investigated in aqueous media, at various pH and temperature values. The polymer - metal complexes of UO₂²⁺ were characterized by infrared and electronic spectra, and thermogravimetry. The thermal behavior of cellulose (C), trimethylsilyl - cellulose (tmsc, SD= 2.85) and triphenylsilyl - cellulose (TPSC1, SD=2.89 and TPSC2, SD =2.70) and their complexes with uranyl ions in atmospheric air has been studied between room temperature and 600 °C. The Coats-Redfern method was applied to estimate the kinetic parameters. The results revealed that the complexation of C and TMSC with UO₂²⁺ increases the thermal stability.</p> </p>     

Inorganic ion-exchangers in radioactive waste management</p> </p>

Summary The uptake of indigenously synthesized amorphous stannic and zirconium phosphate was assessed for, one of the important fission fragment, cesium from aqueous solutions using a radiotracer technique. A virtual increase in sorptive concentration (from 1.0 ^. 10^-8 to 1.0 ^. 10^-2 mol ^. dm^-3) and pH (from 2.4 to 10.2) and temperature (from 303 to 333 K) enhanced the uptake of cesium on stannic phosphate. However, the extremely high degree of uptake of cesium on zirconium phosphate was almost unaffected with the dilution beyond 10^-5 mol ^. dm^-3 and pH (i.e., from 2.4 to 10.2) and temperature (from 303 to 323 K). Irreversible uptake occurring for these solids follow the Freundlich adsorption isotherm and the presence of several complexing agents viz., sulphate, phosphate, glycine and EDTA did not affect appreciably the uptake of cesium on zirconium phosphate but it did affect for stannic phosphate system. Both these solids showed good radiation stability towards a 11.1 GBq Ra-Be neutron source having neutron flux ca. 3.2 ^. 10⁶ n ^. cm^{-2 .} s^-1 and associated with a nominalg-dose of ca. 1.72 Gy/h, at least for the uptake of cesium.</p> </p>     

Transfer of 226Ra, 85Sr and 137Cs from milk to milk products</p> </p>

Summary Transfer of ²²⁶Ra, ⁸⁵Sr and ¹³⁷Cs from cow and sheep milk to various Syrian dairy products has been evaluated. Dairy products include Kashkivan cheese, braided cheese, Haloom cheese, Sircassian cheese, liquid cheese, native cheese, cottage, thick yogurt, butter and milk cream. The results showed that the percentage of ²²⁶Ra, ⁸⁵Sr and ¹³⁷Cs transferred from cow milk to milk cream (P_t=food processing retention factor′processing efficiency′100%) has reached 32%, 16% and 7%, respectively. Butter and liquid cheese were found to have the lowest percentage of transferred 226Ra, ⁸⁵Sr and ¹³⁷Cs. Most of the obtained P_t values of the studied radionuclides in thick yogurt were relatively low in spite of the high processing efficiencies of thick yogurt. Moreover, the transfer, P_t, of the studied radionuclides from cow milk to the prepared cheese was higher than those values determined for sheep milk. This is due to differences in chemical compositions of each type of milk. On the other hand, the treatment of Native cheese, most commonly consumed cheese in Syria, with different concentrations of NaCl solutions showed that ¹³⁷Cs was completely removed from cheese soaking in 5% NaCl solution (soaking time of 48 hours), while 40% of ²²⁶Ra and 80% of ⁸⁵Sr were also decontaminated using 0-2.5% NaCl solutions and soaking time of 48 hours. Based on the obtained results, industrialization processes of the dairy products that resulted the removal of radionuclides have been identified.</p> </p>     

Mathematical modeling of separation of microamounts of strontium from yttrium in water - HCl -nitrobenzene - 15-crown-5 - hydrogen a dicarbollylcobaltate extraction system</p> </p>

Summary A rapid separation of microamounts of Sr²⁺ from Y³⁺ using HCl, 15-crown-5 (15C5) and hydrogen dicarbollylcobaltate (H⁺B^-) in the two-phase water - nitrobenzene extraction system was developed. The reached separation factor a(Sr/Y) was approximately 10. ^5.4</p> __</p>     

A new Na+ and K+ carrier from chemically modified monensin studied in human erythrocytes by 23Na nuclear magnetic resonance,K+ atomic absorption and H+ potentiometry

The transporting ability of a new monensin derivative 26-(1,2-diphenyl-1-ethoxy) monensin, highly active against Gram-positive bacteria, was explored with the human erythrocyte model using three technical approaches: ²³Na nuclear magnetic resonance (internal Na⁺), K⁺ atomic absorption (external K⁺) and H⁺ potentiometry (external H⁺) and compared with monensin 1 and 26-(4-chlorophenylurethane) monensin 3 of known transport selectivities for sodium and potassium respectively. Compound 2 proved to be a good carrier for both Na⁺ and K⁺ under our experimental conditions, thus constituting a new type of monensin derivative. The introduction of Li⁺, Rb⁺ or Cs⁺ in the external buffer as a replacement for Na⁺ led us to propose the transport sequence K⁺, Na⁺ ⪢ Rb⁺ > Li⁺ > Cs⁺ for 2.     

Sorption and desorption of UO2 2+, Th4+ and Ru3+ on the synthetic analogue of muscovite</p> </p>

Summary Sorption and desorption of UO₂²⁺, Th⁴⁺ and Ru³⁺ on the synthetic analogue of the mica mineral muscovite has been studied by a batch technique. The synthesized gel was characterized by XRD, EDXRFS, FTIR, TGA and SEM and was found to have a composition K_1.4Al_4.2(Si₆Al₂O₂₀)(OH)₄ ^. 2H₂O. Different parameters like acid concentration, contact time, amount of gel, composition of gel: OPC admixture, effect of temperature, desorption of metal ions from loaded muscovite and effect on crystal morphology due to loading of metal ions were studied. The results has been expressed in terms of distribution coefficient (K_d).</p> </p>     

Diffusion of Sr, Cs, Co and I in argillaceous rock as studied by radiotracers</p> </p>

Summary Diffusions of⁸⁵Sr,¹³⁷Cs,⁶⁰Co and¹²⁵I radionuclides have been studied in borecore samples from Boda siltstone/claystone formation (BCF) under ambient and in situ conditions. In-diffusion (⁸⁵Sr,¹³⁷Cs,⁶⁰Co and¹²⁵I) and through-diffusion measurements (¹²⁵I) were performed at ambient conditions, and for iodine, in-diffusion measurements were also carried out at in situ conditions (100 bar, 50 °C). In the case of cationic species carrier-containing solutions were also applied.⁶⁰Co was detected only in the first slice of borecore at each sample, while¹³⁷Cs was detected also in the first-, second- and third slices according to the concentration-increase of inactive carrier. Among the investigated cations,⁸⁵Sr exhibited the fastest diffusion rate with 2.7-6.0 ^. 10^-12m²/s apparent diffusivity values. In the course of in-diffusion measurements 4.7 ^. 10^-11 m ² /s, during through-diffusion investigations 1.4-1.6 ^. 10^-12m²/s and at in situ conditions 5.0-8.0 ^. 10^-12 m²/s apparent diffusivities were obtained for¹²⁵I.Modest sorption of¹²⁵I can also be deduced from the results.</p> </p>     

Cation-exchange separation of uranium from thorium in nitric acid medium</p> </p>

Summary Sorption behavior of Th and U on cation-exchange resins was investigated from nitric acid medium by both batch and column methods. The cation-exchange studies involved the sorption of UO₂²⁺ and Th⁴⁺ and their cationic complexes onto Dowex 50Wx8 and Dowex 50Wx4 resins (50-100 mesh). The batch data yielded a separation factor (K_d,Th/K_d,U) value of >100 for the cation-exchanger, Dowex 50Wx4 at 1-2M HNO₃. Separation of uranium from thorium was also carried out by column method in nitric acid medium using cation-exchangers, Dowex 50Wx4 as well as Dowex 50Wx8. While uranium elution was possible at 1M HNO₃, Th could be eluted only at higher concentration of nitric acid (>6M). The stripped solution emanating from a mixer settler employing di-2-ethyl hexyl isobutyramide as extractant and feed solution similar to THOREX process comprising 350 mg/l U and 380 mg/l Th in 0.75M HNO₃ was loaded on the column and the decontamination factor value for U in the product was >1000.</p> </p>     

Factors affecting the sorption of Eu(III) on modified silica gel</p> </p>

Summary 8-Hydroxyquinoline in benzene, xylene, chloroform and toluene diluents was used to modify silica gel as a solid phase extractant (SPE) for the sorption of Eu(III) in batch extraction techniques. Influences of solid/liquid ratio, pH, metal ion concentration, particle size and temperature were studied. The optimum initial pH is 4.2, while the maximum sorption capacities for the prepared impregnated resins in benzene, xylene, chloroform and toluene diluents are 18.52, 14.98, 14.79 and 5.94 mg ^. g^-1, respectively. The sorption process is found to be affected by both metal ion concentration and particle size of the impregnated resin. Thermodynamic parameters for the sorption of Eu(III) were determined and the reaction is found to be exothermic and spontaneous with enthalpy-14.23 and-23.71 kJ ^. mol^-1 for benzene and xylene as diluents. Release of the element from the loaded solid particles into 0.01M HNO₃ is@85% and@53% from 8-HQ/benzene/silica gel and 8-HQ/xylene/silica gel.</p> </p>     

Diffusion mobility of alkali metals in perfluorinated sulfocationic and carboxylic membranes as probed by <Superscript>1</Superscript>H, <Superscript>7</Superscript>Li, <Superscript>23</Superscript>Na,and <Superscript>133</Superscript>Cs NMR spectroscopy

Water self-diffusion and ion mobilities in various ionic forms (H⁺, Li⁺, Na⁺, Rb⁺, Cs⁺, and Ba²⁺) of perfluorinated sulfocationic membranes MF-4SK were studied by NMR and impedance spectroscopy. When degrees of hydration are low, the self-diffusion coefficients of water and ionic conductivities are considerably affected by the water content of the membrane. The self-diffusion coefficients decrease in the order H⁺ > Ba²⁺ > Cs⁺ > Rb⁺ > Na⁺ > Li⁺, whereas the ion mobility decreases in the order H⁺ > Li⁺ > Na⁺ > Cs⁺ > Ba²⁺.     

Artificial K+ Channels Formed by Pillararene‐Cyclodextrin Hybrid Molecules: Tuning Cation Selectivity and Generating Membrane Potential

A class of artificial K⁺ channels formed by pillararene‐cyclodextrin hybrid molecules have been designed and synthesized. These channels efficiently inserted into lipid bilayers and displayed high selectivity for K⁺ over Na⁺ in fluorescence and electrophysiological experiments. The cation transport selectivity of the artificial channels is tunable by varying the length of the linkers between pillararene and cyclodexrin. The shortest channel showed specific transmembrane transport preference for K⁺ over all alkali metal ions (selective sequence: K⁺ > Cs⁺ > Rb⁺ > Na⁺ > Li⁺), and is rarely observed for artificial K⁺ channels. The high selectivity of this artificial channel for K⁺ over Na⁺ ensures specific transmembrane translocation of K⁺, and generated stable membrane potential across lipid bilayers.     

Alkalikationen-Spezifität und Träger-Eigenschaften der Antibiotica Nigericin und Monensin

It is shown by means of IR. spectroscopic methods that nigericin and monensin have a cyclic conformation similar to that of their silver salts. Complex formation constants with sodium and potassium ions follow the selectivity order determined by EMF. measurements on liquid membranes: nigericin: K⁺ > Rb⁺ > Na⁺ > Cs⁺ > Li⁺; monensin: Na⁺ > K⁺ > Li⁺ > Rb⁺ > Cs⁺. Transport experiments show that nigericin and monensin facilitate the diffusion of potassiumions across model membranes, although in electrolytic transport experiments the permeability is not affected.     

Preparation of a K+‐imprinted polymer for the selective recognition of K+ in food samples

An analytical method is reported for the preparation of K⁺‐imprinted nanoparticles using cryptand 222 as the complexing agent, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the crosslinker and 2,2′‐azobisisobutyronitrile as the radical initiator. The prepared particles have a diameter of 200–250 nm. The maximum adsorption capacity of potassium ion‐imprinted polymer particles was 120 μmol/g. The optimum pH for quantitative extraction was 9.0. The nature of the eluent, eluent concentration, adsorption and desorption times, weight of the polymer material, aqueous phase, and desorption volumes were also studied. The relative selectivity coefficients of K⁺/Li⁺, K⁺/Na⁺, K⁺/Rb⁺ and K⁺/Cs⁺ were 48.10, 4.80, 29.70, and 43.4, respectively. The relative standard deviation and limit of detection of the method were obtained 1.61% and 4.62 ng/L, respectively. Finally, the method was applied for the determination of potassium ions from different samples using flame photometry.     

Synthesis and adsorption investigations of zeolites MCM-22 and MCM-49 modified by alkali metal cations

Ion exchange was made on MCM-22 and MCM-49 zeolites with different Si/Al molar ratios, with Li⁺, Na⁺, K⁺, and Cs⁺ ions and the study of the influence of alkali metal cations on CO₂ adsorption properties was performed. The degree of ion-exchange decreased for larger cations (Cs⁺) apparently due to steric hindrances. The exchange with different cations led to a decrease in the surface area and the micropore volume. Our study shows that the adsorption capacity of the tested zeolites depends significantly on the nature and the concentration of the charge-compensating cations. The highest CO₂ adsorption capacity was obtained on the MWW zeolites with the lowest Si/Al molar ratio and the Li⁺ or K⁺ cations.