Uptake of cesium and strontium cations by potassium-depleted phlogopite

Phlogopite mica was equilibrated with 1.0 N sodium chloride (NaCl)–0.2 N sodium tetraphenylborate (NaTPB)–0.01 M disodium ethylenediaminetetraacetic acid (EDTA) solution at room temperature resulting in an almost complete removal (92%) of the mica's interlayer K. X-ray powder diffraction analysis provides additional evidence that hydrated Na⁺ ions had almost completely replaced the interlayer K⁺. Following equilibration, the c-axis spacing of the mica increased from 10.0 Å to approximately 12.2 Å. Cesium and Sr ion exchange isotherms indicate that K-depleted phlogopite is highly selective for both elements, the Cs⁺ exchange capacity is 1.26 meq/g or 65% of the theoretical cation exchange capacity and the Sr²⁺ exchange capacity is 1.94 meq/g or 100% of the theoretical exchange capacity of the mica. Kielland plots indicated that the mica was selective for Cs⁺ when the equivalent exchange capacity of Cs⁺ in the exchanger phase (X¯_Cs) was < 0.66 and selective for Sr²⁺ when X¯_Sr < 0.41. At equivalent fractions greater than these levels, layer collapse and/or steric effects limit the diffusion of these ions into the interlayers of the mica. Analysis of the Cs⁺ equilibrated mica utilizing XRD indicated that a collapse of the c-axis spacing had occurred. Based on the high selectivity of < 45-μm K-depleted phlogopite for Sr²⁺ and Cs⁺, this material may prove useful as an inorganic ion exchanger for these radioactive isotopes.     

Rapid Separation of Tl+ and Pb2+ from Various Binary Cation Mixtures Using Dicyclohexano-18-crown-6 Incorporated into Emulsion Membranes

Abstract

Relative transport rates of metal cation nitrates (Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Tl⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Pb²⁺) in a water-toluene-water emulsion membrane system were measured. The toluene component contained the surfactant Span 80 and the crown ether dicyclohexano-18-crown-6. The aqueous receiving phase contained Li₄P2O₇. When each metal cation was individually present in the aqueous source phase, metal extraction was complete within 10 min with the order of extraction being Tl⁺ > Cs⁺ > Ag⁺ > Rb⁺ > K⁺ ≥m Na⁺ and Pb⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ for uni-and bivalent cations, respectively. Significant extraction was found for all cations except Na⁺, K⁺, and Ba²⁺. Some metal ions were concentrated nearly 10-fold in a 10-min period. Relative transport rates were determined when binary cation mixtures of either Tl⁺ or Pb²⁺ were present at equal concentrations with each of the remaining metal ions in the source phase. Tl⁺, when present with either Na⁺, Cs⁺, or Rb⁺, was selectively extracted from the source phase. Complete and nearly exclusive extraction of Pb²⁺ was observed in the presence of all cations including Tl⁺. The enrichment ratios of Pb²⁺ in the binary mixtures were approximately 10 while those of the second cation were less than 0.5 except for Sr²⁺ which was 0.86. Corresponding separation factors for Pb²⁺ ranged from 1000 to > 6000.     

THERMODYNAMICS OF ALKALI AND ALKALINE EARTH METAL ION - EXCHANGE ON CERIUM(IV) HYDROGEN PHOSPHATE

ABSTRACT

Thermodynamics of alkali and alkaline earth metal ions/hydrogen ions exchange on a fibrous cerium(IV) hydrogen phosphate have been investigated. Selectivities for alkali and alkaline earth metal ions increase in the order; Na⁺<<K⁺<Rb⁺<Cs⁺ and Mg²⁺<Ca²⁺<Sr²⁺<Ba²⁺, respectively. The enthalpy changes for alkali metal and Ba2+ ions/H⁺ exchange are negative, those for the other alkaline earth metal ions/H⁺ exchange are positive, indicating that the enthalpy changes for monovalent ions are more favorable than those for divalent ions. In comparison with ions of the same valency, the enthalpy change decreases with the atomic number of the metal ion corresponding to a decrease in the entropy change of dehydration in response to enthalpy-entropy compensation.     

THERMODYNAMICS OF ALKALI AND ALKALINE EARTH METAL ION-EXCHANGE ON ZIRCONIUM SULPHOPHOSPHONATES

The thermodynamics of alkali and alkaline earth metal ion exchange on a layered zirconium sulphophosphonate having the general composition Zr(O₃PC₆H₄SO₃H) _×(HPO₄) _2?× yH₂O have been investigated. Enthalpy and entropy changes accompanying the M²⁺ - H⁺ exchange (M = Na⁺, Cs⁺, Mg²⁺ and Ba²⁺)were determined by the temperature variation method. For the monovalent ions, Na⁺ and Cs⁺, the enthalpy terms favor exchange whereas the entropy terms are unfavorable. In contrast, for the divalent ions, Mg²⁺ and Ba²⁺, the exchange is due to highly favorable entropy terms.     

Rapid and phase pure synthesis of microporous copper silicate (CuSH–1Na) with 12-ring channel system

Phase pure sample of the microporous copper silicate CuSH–1Na has been obtained by simplified hydrothermal method without using additives (H₂O₂ and Na₂HPO₄). Ion exchange of Na⁺ by Cs⁺, Ca²⁺ and Sr²⁺ ions showed that the structure can suffer partial replacement of the charge compensating cations. Ion exchange with Cs⁺ resulted in distinct dehydration while the ion exchange with Sr²⁺ increased the total amount of water. Water content in the Ca-exchanged sample is comparable to the as-synthesized sodium phase. Raman spectroscopy revealed that the divalent cations as Ca²⁺ and Sr²⁺ induce stronger local structural deformations than the monovalent Cs⁺. These structural changes have been also followed by the refined lattice distortions. Magnetic analyses showed that CuSH–1Na presents a very weak ferromagnetic interaction along the Cu²⁺ chains with a nearly vanishing Curie–Weiss temperature. This magnetic coupling is associated with super-super-exchange interactions through Cu–Na–O–Na–Cu paths. Antiferromagnetic coupling, attributed to inter-chains super-super-exchange interactions, competes with the ferromagnetic one and prevails at the lowest temperature.     

LITHIUM-ION SIEVE PROPERTY OF λ;-TYPE MANGANESE OXIDE

The adsorptive properties of A-Mn0₂for mono and divalent metal ions were investigated by pH titration and by measurements of the distribution coefficients(Kd's) of the metal ions. The pH titration curve showed an apparently monobasic acid type for a H⁺-Li⁺exchange. Those for H⁺-K⁺and H⁺-Cs⁺exchanges were nearly the same as that for blank titration. The lithium ion uptake increased with increasing solution pH and reached 5 meq/g at pH 11. X-ray diffraction analyses showed that the adsorption of lithium ions caused an increase in the lattice constant of a cubic unit cell. The potassium and cesium ion uptakes were nearly zero over a pH range between 4 and 11. A-Mn0₂showed a remarkably high Kd value for lithium ions, compared to a cation exchange resin. The selectivity sequences were Na⁺< K⁺< Rb⁺< Cs⁺<< Li⁺for alkali metal ions, Mg²⁺< Ca²⁺< Sr²⁺< Ba²⁺for alkaline earth metal ions, and Ni²⁺< Zn²⁺< Co²⁺< Cu²⁺for transition metal ions.     

Non-stationary radiotracer method for diffusion coefficients of Cs+, Ba2+, Eu3+ tracers in Nafion-117 membrane

The ion-exchange kinetics of A^z+_sol ? Na⁺_mem (A^z+ = Cs⁺/Ba²⁺/Eu³⁺) in Nafion-117 have been measured using non-stationary radiotracer technique for trace concentrations of A^z+ ions in external solution. A method based on non-steady state Nernst–Planck approach has been developed and used to fit the experimental ion-exchange profiles to obtain the diffusion coefficients (DCs) of these ions. The DCs, thus obtained, have been found to be appreciably lower than the literature-reported self-diffusion coefficients, indicating slower rate of ion-exchange. The results show that membrane DCs of these ions are modified by bulk electrolyte solution.     

Adsorption Kinetics and Equilibria of Strontium onto Kaolinite

Adsorption of Sr²⁺ onto kaolinite has been studied by means of a radiotracer technique using the ⁹⁰Sr isotope. Bangham’s and McKay models have been applied to kinetic results in Sr²⁺ concentrations between trace ?0.1 mol.L^?1. The magnitudes of film and intra-particle diffusion coefficients are 10?10 and 10?14 m²·s^?1, respectively. Concentration dependence of diffusion coefficients indicated that Sr²⁺ ions are adsorbed on two different adsorption sites by an exothermic and spontaneous process. The Freundlich isotherm parameters and exchange equilibrium constants derived from selectivity coefficients indicate that Sr adsorption are depressed by competing cations in the order of Na⁺< Mg²⁺< Al³⁺.     

Synthesis of a highly selective bis-rhodamine chemosensor for naked-eye detection of Cu ions and its application in bio-imaging

A bis-rhodamine based fluorescent chemosensor for naked-eye detection of Cu²⁺ with enhanced sensitivity as compared to mono-rhodamine derivative has been synthesized, and its selectivity for Cu²⁺ in the presence of other competitive metal ions (Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺), and application in bio-imaging are demonstrated.     

Synthesis of a highly selective bis-rhodamine chemosensor for naked-eye detection of Cu2+ ions and its application in bio-imaging

A bis-rhodamine based fluorescent chemosensor for naked-eye detection of Cu²⁺ with enhanced sensitivity as compared to mono-rhodamine derivative has been synthesized, and its selectivity for Cu²⁺ in the presence of other competitive metal ions (Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺), and application in bio-imaging are demonstrated.     

Transport Studies of Monovalent Ions through Nafion-117 Ion Exchange Membrane in Presence of Polyacrylate

The results of equilibrium distribution and transport kinetics of monovalent (Li⁺, Na⁺, and Cs⁺) ions through Nafion-117 ion exchange membrane in presence of polyacrylate anion have been presented. For Na⁺-Li⁺ system, equilibrium distributions in the presence and absence of polyacrylate have been found to be the same indicating that the Donnan membrane equilibrium is not affected by the presence of polyacrylate. For the Na⁺-Cs⁺ system, a favored transport of Cs⁺ ion to the polyacrylate compartment has been observed, indicating the binding of Cs⁺ ion with polyacrylate is stronger than other monovalent ions. This is due to the lower hydration radius of Cs⁺ ions. The deviation from Donnan membrane equilibrium condition has been used to obtain information about the fraction of counter-ions bound to the polyacrylate. The transport profile in the presence of polyacrylate has also been calculated based on the modified Nernst Planck (NP) approach, taking into account the fraction of counter-ions bound to the polyacrylate ion. The Donnan relation has been used to obtain the concentration of ions at the solution/membrane interface. The self-diffusion coefficients of ions and membrane ion exchange capacity have been given as input parameters in the calculations. The calculated time profile has been found to agree well with the experimental time profile.     

Effect of particle size on cesium exchange kinetics by K-depleted phlogopite

Cation exchange mechanism and rate of Cs⁺ exchange were investigated in < 2 μm and 20–2 μm particle size fractions of K-depleted phlogopite (Na-phlogopite). The K-depleted phlogopite was prepared from a natural phlogopite by a potassium removal method using sodium tetraphenylborate (NaTPB) at room temperature. X-ray diffraction (XRD) patterns revealed that interlayer K⁺ ions were completely replaced with sodium ions after the potassium removal treatment. Ion exchange isotherms and kinetics were determined for Na⁺ → Cs⁺ exchange with two particle size fractions. The isotherms indicated that both particle size fractions showed high selectivity for Cs⁺. Based on the isotherm tests, ΔG^o values of < 2 μm and 20–2 μm particle fractions were − 6.83 kJ/mol and − 7.08 kJ/mol, respectively. Kinetics of Cs exchange revealed that the 20–2 μm particle size fraction of the K-depleted phlogopite took up more Cs⁺ ions than the < 2 μm particle size fraction. Various kinetic models were applied to describe Na⁺ → Cs⁺ exchange process. Elovich model described the kinetic data of the < 2 μm particle size fraction well, while the modified first-order model or parabolic diffusion model described the data of the 20–2 μm particle size fraction well.     

ION EXCHANGE PROPERTIES OF THE SODIUM PHLOGOPITE AND BIOTITE

ABSTRACT

The ion exchange behavior of three sodium micas (phlogopite, Ward's Sci.; phlogopite, Suzorite Inc., biotite, Ward's Sci.) towards Li⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺. Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺ Hg²⁺, Co²⁺, Cu²⁺ Cd²⁺ and Zn²⁺ ions has been studied. The ion exchange isotherms of alkali, alkaline earth and some other divalent cations were determined and concentration equilibrium constants as a function of metal loading and temperature were analyzed. Sodium micas exhibit high affinity for heavy alkali metals with the selectivity order Rb⁺ > Cs⁺ > K⁺. By studying the cesium uptake in the presence of NaNO₃, CaCl₂, NaOH, NaOH+KOH, HNO₃ electrolytes (in the range of 0.01–6 M) it was found that sodium micas could remove cesium efficiently in neutral and alkaline media, which make them promising for certain types of nuclear waste treatment.     

Kinetics of Exchange of Cs+, Co2+ and Sr2+ on Synthetic Hydrous Titanium Oxides

Abstract

In the present work, a study of the kinetics of adsorption of Cs⁺, Co²⁺, and Sr²⁺ on four hydrous titanium oxides, prepared in different media, and designated as Ti‐I, Ti‐II, Ti‐III, and Ti‐IV, was carried out. In the aqueous medium, the internal diffusion coefficients, D_i for Cs⁺ were found to be equal to 3.7×10^?9, 3.7×10^?9, 2.3×10^?9, and 1.5?10^?9 cm²/s, in Ti‐I, Ti‐II, Ti‐III, and Ti‐IV, respectively. For Co²⁺ and Sr²⁺, these values are equal to 0.96×10^?9 and 0.64×10^?9 cm²/s, respectively for Ti‐IV. In Ti‐IV, D_i for all ions generally increases on adding methanol or propanol. This is probably due to greater dehydration, leading to faster ion diffusion, and, hence, to a decrease of ion mobility due to stronger interaction with the surface. In all media in Ti‐IV, the order: D_i(Cs⁺)>D_i(Co²⁺)≥D_i(Sr²⁺) was found which is due to a stronger interaction of the bivalent ions with the exchange sites.     

STUDIES OF THE HYDROUS NIOBIUM(V) OXIDE ION EXCHANGER. VII.RATE OF THE ISOTOPIC EXCHANGE OF CESIUM IONS BETWEEN THE EXCHANGER IN THE Cs+ FORM AND AQUEOUS SOLUTION

ABSTRACT

The isotopic exchange rate of Cs⁺ between hydrous niobium(V) oxide in the Cs⁺ form and aqueous solutions was determined radiochemically. The rate was controlled by the diffusion of Cs⁺ in the exchanger particle at varying pH. The diffusion coefficients at 10°C increased with pH up to pH7; from 3.0x10^?11 m²s^?1 at pH6 to 4.0×10^?11 m²s^?1 at pH7, and became constant above pH8 (5.0x10^?11 m²s^?1). While the diffusion coefficients of Na⁺ monotonously decrease with increasing pH; from 7.9×l0^?11 m²s^?1 at pH6.5 to 2.8×l0^?11 m²s^?1 at pHll. The difference in the dependence of diffusion coefficients on pH between Cs⁺ and Na⁺ was interpreted in terms of strength of interaction between counterions and ion-exchange sites since hydrous niobium(V) oxide has selectivity higher for Cs⁺ than for Na⁺.     

Synthesis and properties of a cellulose exchanger with the crown ether diaminodibenzo-17-crown-5 as anchor group

A new cellulose exchanger was synthesized from “o-aminophenolcellulose” by diazotation and coupling with diaminodibenzo-17-crown-5. The distribution coefficients for Ca²⁺, Sr²⁺, Ba²⁺, Na⁺ and K⁺ were determined in water/methanol mixtures as a function of the water content. Separation of Ca²⁺, Na⁺ and K⁺ and fractionation of the calcium isotopes ⁴⁸Ca and ⁴⁰Ca were investigated. The enrichment factor ε = 4.9 · 10^?3 for ⁴⁸Ca²⁺ is appreciably higher than that found for cation exchange resins with ? SO₃H groups, but lower than that reported for certain cryptands.     

Modification and magnetization of MOF (HKUST-1) for the removal of Sr2+ from aqueous solutions. Equilibrium,kinetic and thermodynamic modeling studies

In this research, metal-organic framework MOF(HKUST-1) was synthesized, magnetized and modified by hexacyanoferrate in order to prepare an efficient adsorbent for the removal of Sr²⁺ from aqueous solutions. The synthesized adsorbent was characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, thermal methods (TG-DTG[Themogravimetry- Derivative Theromogravimetry]), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) surface area and scanning electron microscopy (SEM). The non-magnetized (MOF/KNiFC[potassium nickel hexacyanoferrate]) and magnetized (MOF/Fe₃O₄/KNiFC) adsorbents were then employed for the removal of Sr²⁺ from aqueous solutions. The adsorption capacity of 110 and 90 mg.g^?1 was obtained, respectively, for MOF/KNiFC and MOF/Fe₃O₄/KNiFC. The adsorption process was kinetically fast and the equilibration was established within 45 min. The magnetic capability of the adsorbent examined by the vibrating sample magnetometer (VSM) technique indicated that the used adsorbent was capable of separating from the solution by applying an external magnetic field. The adsorbent showed good selectivity toward Sr²⁺ in the presence of Cs⁺, Na⁺, Mg²⁺, Ca²⁺ and Ba²⁺. The regenerated adsorbent retained more than 90% of its initial capacity. Different isotherm models including Langmuir, Freundlich, Tempkin, Sips and Redlich–Peterson were employed to examine the applicability of the isotherms to the experimental data. It was concluded that the data was best fitted to the Langmuir isotherm model. The thermodynamic parameters showed that the process was endothermic.     

Ion exchange characteristics of ceric tungstate: Kinetics of exchange

The kinetics of exchange of Cs⁺, Ag⁺, Zn²⁺ and Sc³⁺ on ceric tungstate were studied under particle diffusion control conditions at different temperatures. At the studied temperatures, the mobility of the monovalent ions in the prepared exchanger is higher than that of the multivalent ones, presumably due to weaker electrostatic interaction with the exchange sites. The activation energy data point to a substantial or complete dehydration of the ions diffusing in the narrow pores of the exchanger. The highest activation energy is displayed by Cs⁺ having the largest crystallographic radius.     

Ion-Exchange Properties of lon-Sieve-Type Manganese Oxides Prepared by Using Different Kinds of Introducing Ions

Abstract

Three ion-sieve-type manganese oxides, HMnO(Li), HMnO(Na), and HMnO(K), were prepared by acid treatments of Li⁺-, Na⁺-, and K⁺-introduced manganese oxides, respectively. Three oxides were obtained from γ-MnO² and the corresponding alkali metal hydroxides by heating at 600°C. The ion-exchange properties of the adsorbents were investigated by pH titration, K_d measurements, and the adsorption of metal ions from seawater. The selectivity sequences of alkali metal ions were Na⁺ < Cs⁺ < Rb⁺ < K⁺ < Li⁺ for HMnO(Li) and Li⁺ Na⁺ < Cs⁺ < K⁺ < Rb⁺ for HMnO(Na) and HMnO(K). The high selectivity of Li⁺ on HMnO(Li) can be ascribed to an ion-sieve effect of spinel-type manganese oxide which was produced from LiMn₂O₄ Since HMnO(Na) and HMnO(K) had [2 × 2] tunnels of edge-shared [MnO₆] octahedra, the high selectivities of K⁺ and Rb⁺ on these samples were used to explain that the sizes of the [2 × 2] tunnels were suitable for filling ions of about 1.4 Å in radius in a stable configuration. The order of metal-ion uptake from seawater was Sr²⁺ < K⁺ < Mg²⁺ < Ca²⁺ < Na⁺ < Li⁺ for HMnO(Li), Li⁺ < Sr²⁺ < Mg²⁺ < Ca²⁺ < Na⁺ < K⁺ for HMnO(Na), and Li⁺ < Sr²⁺ < Ca²⁺ < Mg²⁺ < K⁺ < Na⁺ for HMnO(K).     

Adsorption behavior of cesium and strontium onto chitosan impregnated with ionic liquid

We briefly studied the adsorption behavior of chitosan impregnated with an ionic liquid (1-ethyl-3-methyl imidazolium chloride) in solutions with Cs⁺ and Sr²⁺ ions. The impregnation of chitosan was realized by ultrasonication method. The impregnated chitosan was analyzed by FTIR, SEM, and EDX in order to show that the chitosan was impregnated with the studied IL. The adsorptive properties of ionic liquid-impregnated chitosan for the removal of Cs⁺ and Sr²⁺ ions from aqueous solutions were studied in a batch adsorption system. The adsorption kinetic was found to follow a pseudo-second-order kinetic model. The experimental data showed good fit to the Langmuir isotherm. The adsorption properties of the chitosan impregnated with the studied ionic liquid were determined in binary, tertiary, and quaternary systems. The adsorption capacity of the IL impregnated chitosan is not significant influenced in the binary systems. The adsorption capacity of the IL impregnated chitosan decreases with the increase of the number of the cation present in solutions. It was observed that the studied adsorbent has a higher affinity for Cs⁺ ions than for Sr²⁺ ions.