Sorption of Cs<Superscript>+</Superscript> and Sr<Superscript>2+</Superscript> by ion exchanger based on titanium phosphate

Sorption capacity of a composite ion exchanger based on titanium phosphate for Cs⁺ and Sr²⁺ cations was studied. The effect of pH and concentration of salts and, in particular, sodium chloride in solution on the sorption efficiency and distribution coefficient was analyzed. The diffusion coefficients were calculated for the Cs⁺ and Sr²⁺ cations and the time of half-exchange of the Na⁺ cation for the Cs⁺ and Sr²⁺ cations was found.     

Kinetic aspects of the ion-exchange reactions of Cs<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, Sr<Superscript>2+</Superscript>and Eu<Superscript>2+</Superscript> ions on the H<Superscript>+</Superscript> form of chromium hexacyanoferrate(II)

Summary This paper reports the radiochemical study of the ion-exchange of Cs⁺, Na⁺, Sr²⁺ and Eu³⁺ ions with H⁺ by chromium hexacyanoferrate(II) which was prepared in a granular form using a gel method. The slow steps which determine the rate of exchange of these ions are directly proportional to the particle diameter and this is confirmed from the linearity test of Bt vs. t plots at different particle diameters. Boyed’s equation and Reichenberg’s tables were used for evaluating all the kinetic parameters. The results reveal that the effective particle radii are unchanged for both chromium hexacyanoferrate(II) dried at 60 and 120 °C. The obtained data were analyzed using McKay plots and Arrhenius equation and the kinetic and thermodynamic parameters, e.g., effective diffusion coefficient, activation energies and entropies of activation have been evaluated. The mobility of these ions inside the particles of chromium hexacyanoferrate(II) decrease in the order of Eu³⁺>Sr²⁺>Na⁺⊃Cs⁺.     

Removal of <Superscript>60</Superscript>Co<Superscript>2+</Superscript> and <Superscript>137</Superscript>Cs<Superscript>+</Superscript> ions from low radioactive solutions using <Emphasis Type="Italic">Azolla caroliniana</Emphasis> willd. water fern

This study concerns the removal of the ¹³⁷Cs⁺ and ⁶⁰Co²⁺ β+γ-radioactive ions in Azolla caroliniana Willd. water fern. The living fern and two different types of biosorbent prepared from Azolla caroliniana were tested to remove the above-mentioned radioactive ions from dilute solutions, in the absence and in the presence of the ionic competition. Effective ¹³⁷Cs⁺ and ⁶⁰Co²⁺ ions removal from low radioactive wastewaters was demonstrated. The time dependent K _d (t) values were calculated from the absorption data. These results indicate that removal process achieved equilibrium in about 120 min and that it involves two steps: rapid and slow absorption; the active process (metabolic bioaccumulation on the living fern) was responsible for above one half of the total removal process. A thin layer radiochromatography study leads to the conclusion that the biochemical components in which ¹³⁷Cs⁺ and ⁶⁰Co²⁺ place themselves are of a polysaccharide and lipoid fractions.     

Batch and continuous fixed-bed column adsorption of Cs+ and Sr2+ onto montmorillonite–iron oxide composite: Comparative and competitive study

A montmorillonite–iron oxide composite (MIOC) was prepared to assess its effectiveness in the removal of Cs⁺ and Sr²⁺ from aqueous solution. A comparative and competitive adsorption study was conducted in single and binary systems. Used materials have been characterized by X-ray diffraction (XRD) and Infrared spectroscopy. Adsorption of Cs⁺ and Sr²⁺ as a function of contact time and pH was investigated, adsorption data of single metal solutions were well fitted to the Freundlich–Langmuir isotherm models. Equilibrium isotherms for the binary removal of Cs⁺ and Sr²⁺ by MIOC have been analyzed by using non modified and extended Langmuir models with a satisfactory R ² values. Neutral solution pH was found to be favorable for both single and binary systems. The adsorption model analysis revealed that MIOC was more selective for Sr than Cs. The maximum adsorption capacities for individual Cs⁺ and Sr²⁺ solutions were 52.6 and 55.5 mg g^?1, respectively. While the maximum uptakes in the binary system were 41.6 and 47.6 mg g^?1 for Cs⁺ and Sr²⁺, respectively. Column adsorption experiments were carried out at room temperature under the effect of various operating parameters such as bed depth, initial cation concentration and flow rate, Breakthrough curves were well fitted to the Thomas model. Desorption experiments were also conducted to assess the possibility for the reuse of adsorbent and the recovery of cations.     

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>     

Structures of the nearest surroundings of the K<Superscript>+</Superscript>, Rb<Superscript>+</Superscript>, and Cs<Superscript>+</Superscript> ions in aqueous solutions of their salts

Published data on structural characteristics of hydration of K⁺, Rb⁺, and Cs⁺ ions in aqueous solutions of their salts under standard conditions, including authors’ X-ray diffraction data, are summarized and correlated. The structural parameters of the nearest surrounding of the K⁺, Rb⁺, and Cs⁺ ions, such as the coordination numbers, interparticle distances, and types of ionic association, are discussed. It is noted that, because of weak tendency of these cations to hydration, the parameters of their coordination spheres strongly depend on the concentration and chemical nature of counterions.     

Facile one-pot synthesis of nano-zinc hydroxide by electro-dissolution of zinc as a sacrificial anode and the application for adsorption of Th<Superscript>4+</Superscript>, U<Superscript>4+</Superscript>, and Ce<Superscript>4+</Superscript> from aqueous solution

Facilely synthesized zinc hydroxide nanoparticles by electro-dissolution of zinc sacrificial anodes were investigated for the adsorption of thorium (Th⁴⁺), uranium (U⁴⁺) and cerium (Ce⁴⁺) from aqueous solution. Various operating parameters such as effect of pH, current density, temperature, electrode configuration, and electrode spacing on the adsorption efficiency of Th⁴⁺, U⁴⁺ and Ce⁴⁺ were studied. The results showed that the maximum removal efficiency was achieved for Th⁴⁺, U⁴⁺ and Ce⁴⁺ with zinc as anode and stainless steel as cathode at a current density of 0.2 A/dm² and pH of 7.0. First- and second-order rate equations were applied to study the adsorption kinetics. The adsorption process follows second order kinetics model with good correlation. The Langmuir, Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The experimental adsorption data were fitted to the Langmuir adsorption model. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°), and entropy changes (ΔS°) for the adsorption of Th⁴⁺, U⁴⁺ and Ce⁴⁺ were computed to predict the nature of adsorption process. Temperature studies showed that the adsorption was endothermic and spontaneous in nature.     

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⁺.     

Affinity and removal of radionuclides mixture from low-level liquid waste by synthetic ferrierites

The affinity and removal efficiency of ¹³⁷Cs⁺, ¹³³Ba²⁺, ⁸⁵Sr²⁺ and ²⁴¹Am³⁺ mixture from aqueous solutions using two synthetic ferrierites HSZ 700KOA and 700KOD commercially used as a catalyst in oil industry were investigated. The uptake of metal ions as a function of different parameters has been studied using batch equilibrium technique. Kinetic curves showed that the equilibrium was mostly reached within 45 min for Cs⁺ and Ba²⁺ and revealed to be longer for Sr²⁺ and Am³⁺. Using Freundlich and Langmuir adsorption isotherms, the results showed that the affinity and adsorption capacity of 700KOA and 700KOD follow the order: Cs⁺ > Ba²⁺ > Sr²⁺ > Am³⁺ with higher values for first material. Both adsorbents exhibited significant high capacity for Cs⁺ relative to other cations giving q _max 1.97 and 1.78 mmol g⁻¹ for 700KOA and 700KOD, respectively. All metals uptake found to be concentration dependant and independent of the pH over 2 to 10 range except Am³⁺; this reveals that the adsorption mechanism is controlled mainly by pure ion exchange reaction for Cs⁺, Ba²⁺, Sr²⁺ and by surface complexation mechanism for Am³⁺. These simple nontoxic materials are recommended to be used for radioactive waste treatment especially fission product ¹³⁷Cs and activation product ¹³³Ba.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Cation binding by 2<Superscript>1</Superscript>,3<Superscript>1</Superscript>-diphenyl-l <Superscript>2</Superscript>,4<Superscript>2</Superscript>-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2 (2,3),3(3,2)-diindolizinacyclopentadecaphane and its acyclic analog

The binding of cations Li⁺, Na⁺, K⁺, Cs⁺, Ag⁺, Zn²⁺, Ni²⁺, Co²⁺, NH₄ ⁺ (group I), H⁺, Mg²⁺, Al³⁺, Ga³⁺ (group II), and Ca²⁺, Pb²⁺ (group III) by 2¹,3¹-diphenyl-l ²,4²-dioxo- 7,10,13-trioxa-l,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane (1), which contains two indolizine and two quinoxaline fragments and 3,6,9-trioxaundecanes spacer, and by its acyclic analog (2) was studied using cyclic voltammetry in MeCN/0.1 M Bu₄NBF₄. It was concluded that the ions of group I are not bound by these compounds, the ions of group II exhibit the reversible redox-switched binding by the carbamoyl groups of the quinoxaline fragments, whereas the ions of group III are bound not only by the initial compounds and radical cations 1 and 2, but also by dication 1. This binding of the Ca²⁺ and Pb²⁺ ions stabilizes dication 1.     

Sorption of Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> by Natural Biomaterial: Duck Feather

Feather fibers were modified by treatment with 5% tannic acid (TA) solution. Kinetics of the modification was investigated as a function of the reaction time. The maximum loading of TA on feather reached 8.3% after being treated by TA for 9 h. The adsorption of metal cations (Cu²⁺, Zn²⁺) by unmodified and TA-modified feather fibers was investigated as a function of fiber weight gain, temperature, and pH of the metal solution. The adsorption was enhanced at alkaline pH and ambient temperature and increased with the weight gain of TA. The maximum uptake of metal cations (Cu²⁺, 0.77 mmol/g; Zn²⁺, 0.95 mmol/g) was obtained by TA-modified feather at weight gain: 8.3%, pH 11, while at the acidic pH, the adsorption of metal cations by either unmodified or TA-modified feather was negligible. The influence of anions on the adsorption of metal cations was also studied. The uptake of Cu²⁺ from chloride was higher and faster than that from nitrate. Desorption of the metals was performed at acidic pH 2.5 for 48 h. The feather–TA–metal complexes exhibited higher stability for metal cations than the feather–metal complexes. All these experiments reveal that TA-modified feather fibers have good adsorption to metal cations and can be used as metal adsorbent in wastewater treatment.     

Ultrasensitive Detection of Cu<Superscript>2+</Superscript> Using a Microcantilever Sensor Modified with L-Cysteine Self-Assembled Monolayer

A microcantilever was modified with a self-assembled monolayer (SAM) of L-cysteine for the sensitively and selectively response to Cu(II) ions in aqueous solution. The microcantilever undergoes bending due to sorption of Cu(II) ions. The interaction of Cu(II) ions with the L-cysteine on the cantilever is diffusion controlled and does not follow a simple Langmuir adsorption model. A concentration of 10^?10 M Cu(II) was detected in a fluid cell using this technology. Other cations, such as Ni²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Ca²⁺, K⁺, and Na⁺, did not respond with a significant deflection, indicating that this L-cysteine-modified cantilever responded selectively and sensitively to Cu(II).     

Synthetic calcium aluminosilicates and their sorption properties with respect to Sr<Superscript>2+</Superscript> ions

Sorption characteristics of synthetic calcium aluminosilicates (CAS) obtained in the multicomponent CaCl₂–AlCl₃–KOH–SiO₂–H₂O system are presented. The isotherms of Sr²⁺ sorption on CAS from aqueous solutions containing no additional salts were measured for Sr²⁺ concentration from 0.5 to 11.1 mmol/L and solid to liquid phase ratio S: L = 1: 100. The maximum sorption capacity of synthetic CAS was determined, the phase distribution constants of Sr²⁺ ions at different S: L ratios were found. The recoveries of Sr²⁺ ions from solutions containing 0.01 mol/L Ca(NO₃)₂ and from a solution simulating water of the Mayak plant sewage pond No. 11 were determined.     

In situ synthesis of MnO<Subscript>2</Subscript>-loaded biocomposite based on microcrystalline cellulose for Pb<Superscript>2+</Superscript> removal from wastewater

We fabricated a new MnO₂-loaded biocomposite based on microcrystalline cellulose (MCC–MnO₂) by an in situ synthesis method and investigated its adsorption behavior and mechanism for Pb²⁺ removal from aqueous medium. As-prepared MCC–MnO₂ was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses. The effects of pH value, initial Pb²⁺ concentration, contact time, and solution temperature on the uptake of Pb²⁺ onto MCC–MnO₂ were investigated using a batch system. Adsorption equilibrium could be achieved in 3 h for various studied initial concentrations, and a pseudo-second-order model could fit the adsorption behavior well. The equilibrium data could be well described by the Langmuir isotherm model, and the maximum monolayer adsorption capacity of MCC–MnO₂ (with 7.98% MnO₂ loading) for Pb²⁺ was estimated to be 247.5 mg/g at 313 K. Thermodynamic studies indicated a spontaneous and endothermic adsorption process. X-ray photoelectron spectroscopy (XPS) was used to analyze the adsorption mechanism, revealing that the chemical speciation of Pb²⁺ on MCC–MnO₂ was similar to the compound PbO. Moreover, no variations in the valence of Mn were observed after adsorbing Pb²⁺. The regeneration study showed that the adsorption capacity retained about 89.6% of its initial value at the fifth sequential regeneration cycle, indicating that this material is an efficient and renewable hybrid adsorbent for Pb²⁺ removal.     

A new ecomaterial zirconyl molybdopyrophosphate for the removal of 137Cs and 90Sr from HLLW

A new ecomaterial, zirconyl molybdopyrophosphate (ZMPP), was prepared by a coprecipitation method. The removal of Cs⁺ and Sr²⁺ ions from simulated strong acid HLLW using the ion exchange process on ZMPP had been investigated. It showed that there are more than 90% Cs⁺ and Sr²⁺ removed from the simulated HLLW on ZMPP despite the presence of other metal ions, such as Na⁺, Al³⁺, Fe³⁺, etc. in excess. Then ZMPP may likely be a selective ion exchanger for the removal of ¹³⁷Cs and ⁹⁰Sr directly from strong acid HLLW.     

Hydration of the H<Superscript>+</Superscript>, Li<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, and Cs<Superscript>+</Superscript> ions in MF-4SK perfluorinated sulfonic acid cation-exchange membranes modified with inorganic dopants

The hydration, state, and mobility of protons and Li⁺, Na⁺, and Cs⁺ ions in MF-4SK perfluorinated sulfonic acid cation-exchange membranes doped with silicon dioxide and phosphotungstic acid have been investigated by NMR and impedance spectroscopy. The dopants increase the moisture content of the membrane and change the system of pores and channels in which ion transport takes place. At low humidities, the dopant particles are involved in ion transport. The greatest effect is observed for the membranes doped with both SiO₂ and phosphotungstic acid. The water molecules sorbed by dopant particles as a material participate in the hydration of alkali metal cations in the membrane.     

Effect of the Support on the Nature of Metal-Promoter Interactions in Ru-Cs<Superscript>+</Superscript>/MgO and Ru-Cs<Superscript>+</Superscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for Ammonia Synthesis

The Ru-Cs⁺/MgO and Ru-Cs⁺/γ-Al₂O₃ catalysts, which were prepared by an impregnation method using RuOHCl₃ and Cs₂CO₃ as precursor compounds and reduced with H₂ at 450°C, are characterized by X-ray diffraction, high-resolution transmission electron microscopy (with X-ray microanalysis), and X-ray photoelectron spectroscopy (XPS). The Cs⁺/MgO(Al₂O₃) systems, Ru-Cs⁺ black, and model systems prepared by cesium sputtering onto polycrystalline ruthenium foil are studied as reference samples. It is found that, in the Ru-Cs⁺/MgO sample, cesium is present as a Cs_{2 + x}O cesium suboxide, which weakly interacts with the support, localized on the surface of Ru particles or near them. In the case of Ru-Cs⁺/γ-Al₂O₃, cesium occurs as a species that is tightly bound to the support; this is likely surface cesium aluminate, which prevents promoter migration to Ru particles. The Ru-Cs⁺/MgO sample exhibits a considerable shift of the Ru3d line in the XPS spectra toward lower binding energies, as compared to the bulk metal. It is hypothesized that this shift is due to a decrease in the electron work function from the surface of ruthenium because of the polarizing effect of Cs⁺ ions in contact with Ru particles. Based on the experimental results, the great difference between the catalytic activities of the Ru-Cs⁺/MgO and Ru-Cs⁺/γ-Al₂O₃ systems in ammonia synthesis at 250–400°C and atmospheric pressure is explained.     

A new chelating resin containing 2-aminothiophenol: Synthesis characterization and determination of mercury in waste water using <Superscript>203</Superscript>Hg radiotracer

A new stable chelating resin was synthesized by incorporating 2-aminothiophenol into Merrifield polymer through C-N covalent bond and characterized by elemental analysis, IR and thermal study. The sorption capacity of the newly formed resin for Hg²⁺ as a function of pH has been studied using ²⁰³Hg radioisotope. The resin exhibits no affinity to alkali or alkaline earth metal ions and common anions. The separation of mercury(II) in presence of different alkali and alkaline earth metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), common anions (ClO₄ ⁻, SO₄ ²⁻) and other diverse ions (Ag⁺, Cu²⁺, Pb²⁺, Fe³⁺, Ni²⁺ and Zn²⁺) has been checked. In column operation it has been observed that Hg²⁺ content of the waste water can be removed at usual pH of natural water. Mercury was determined by isotope dilution method and the concentration of Hg²⁺ in the waste water spiked with ²⁰³Hg was found to be 0.05 to 0.09 μg/ml.     

Time-dependent inhibition of Na<Superscript>+</Superscript>/K<Superscript>+</Superscript>-ATPase induced by single and simultaneous exposure to lead and cadmium

Time-dependent interactions of Na⁺/K⁺-ATPase, isolated from rat brain synaptic plasma membranes (SPMs), with Cd²⁺ and Pb²⁺ ions in a single exposure and in a mixture were investigated in vitro. The interference of the enzyme with these metal ions was studied as a function of different protein concentrations and exposure time. The aim of the work was to investigate the possibility of selective recognition of Cd²⁺ and Pb²⁺ ions in a mixture, on the basis of the different rates of their protein-ligand interactions. Decreasing protein concentration increased the sensitivity of Na⁺/K⁺-ATPase toward both metals. The selectivity in protein-ligand interactions was obtained by variation of preincubation time (incubation before starting the enzymatic reaction). The text was submitted by the authors in English.