SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS. XXXXI. ION EXCHANGE EQUILIBRIA OF ALKALI METAL IONS/HYDROGEN IONS ON TIN(IV) ANTIMONATE

Ion exchange equilibria of alkali metal ions (Li⁺, Na⁺, K⁺,, Rb⁺, and Cs⁺)H⁺, systems have been studied in MNO-j-HNOj media with ionic strength of 0.1 at 30, 45 and 60 °C on tin(IV) antimonate as a cation exchanger. The ion exchange isotherms have been measured for both forward and backward reactions by the batch technique. The isotherms showed S-shaped curves for all exchange systems studied. The selectivity coefficients (logarithmic scale) vary with the equivalent fraction X_M of alkali metal ions in the exchanger and give two linear functions of X_M with a break point (X_M= 0.14, except 0.04 for Li⁺, /H⁺) indicating two different exchanging sites. The selectivity sequence, Na⁺, ? K⁺, ? Rb⁺, ? Cs⁺, ? ? Li, holds in the range of Xu= (0 - 0.04) and the sequence, Cs < Rb ⁺, ? K ⁺, ? Na ⁺, < Li ⁺, applies when X_M is higher than 0.14.

Hypothetical thermodynamic data on “zero loading” of the ion exchange reaction was evaluated.     

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).     

Liquid Membrane Separations of Metal Cations Using Macrocyclic Carriers

Abstract

The selectivity in water and methanol solvents of macrocyclic crown ether ligands toward univalent and bivalent cations is well known. Incorporation of these ligands into chloroform liquid membranes separating water and salt solution phases results in a system showing selective cation transport. The cation transport rates of single cations across these liquid membranes have been correlated with equilibrium constant values for cation-macrocycle interaction in methanol. This correlation has been extended to binary cation mixtures of Cs⁺ with Li⁺, Na⁺, K⁺, and Rb⁺. A model for cation transport from these cation mixtures has been reduced to an equation which gives good agreement between measured and predicted transport rates across our liquid membranes.     

Extraction of Alkali Metal Cations by Lipophilic Dibenzo-14-crown-4-carboxylic Acids

Abstract

The extraction of alkali metal cations by the lipophilic crown ether, bis-t-octylbenzo-14-crown-4 (BOB14C4), three derivatives of BOB14C4 having pendant carboxylic acid sidearms, and a lipophilic carboxylic acid, 2-methyl-2-heptylnonanoic acid (HMHN) was studied by two-phase potentiometric titration and ion-chromatography. The lipophilic, ionizable crown ethers, BOB14C4-acetic acid (BOB14C4AA), BOB14C4-propanoic acid (BOB14C4PA), and BOB14C4-oxyacetic acid (BOB14C4OAA) extract cations efficiently from aqueous mixed alkali metal chloride solutions into 1-octanol by an ion-exchange mechanism in the range p[H] > 7, as does HMHN. The mode of attachment of the ionizable sidearm, via an ether linkage (BOB14C4OAA) versus a carbon linkage (BOB14C4AA and BOB14C4PA), has a significant effect on the cation selectivity and extraction efficiency of these extractants. BOB14C4 exhibits no p[H] dependent extraction behavior and has no significant effect on the extraction of alkali metal cations by HMHN in a mixture of these two compounds. Although BOB14C4AA and BOB14C4PA extract cations at lower p[H] than HMHN, all three compounds exhibit similar selectivity for Li⁺ over Na⁺, K⁺, Rb⁺ and Cs⁺. A significant reversal in selectivity is observed with BOB14C4OAA, which extracts Na⁺ and K⁺ selectively over Li⁺, Rb⁺, and Cs⁺ and at significanty lower p[H] than BOB14C4AA, BOB14C4PA, or HMHN. The unique behavior of BOB14C4OAA may be attributed to the presence of the ether linkage between the crown ether and the pendant carboxylic acid.     

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⁺.     

Reverse osmosis separations of some organic and inorganic solutes in aqueous solutions using aromatic polyamide membranes

The reverse osmosis separations of some ethers, ketones, aldehydes, monocarboxylic acids, and inorganic salts in single-solute (55–454 ppm) aqueous solution systems using aromatic polyamide membranes have been studied at 250 psig. It was found that reverse osmosis separation was essentially a function of steric parameter for ethers, and of both polar and steric parameters for ketones, aldehydes, and alcohols. Solute separations for monocarboxylic acids passed through a minimum at a pK_a value of ～4.8. The values for the free-energy parameter for Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and F^?, Cl^?, Br^?, I^?, and IO₃^? ions have been calculated for the polyamide membranes used. The above values for cations are negative and those for anions are positive, suggesting that the polyamide membrane surface behaves as if it is positively charged. Further, the data show that the polyamide membrane material is only about 40% as polar as that of the cellulose acetate membrane material studied earlier.     

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.     

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.     

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS. XLVIII. ION-EXCHANGE REACTION OF ALKALI METAL IONS/H+ ON MONOCLINIC ANTIMONIC ACID

The pH titration curves of monoclinic antimonic acid (M-SbA) showed apparently monobasic acid for the systems of alkali metal ions/H⁺. The uptake order of the metal ions were K⁺ < Rb⁺ < Cs⁺ < Na⁺ < Li⁺ throughout the pH range studied. The low uptakes of K⁺, Rb⁺, Na⁺ and Cs⁺ at high pH might be due to steric or ion sieve effects for large unhydrated cations on M-SbA. Thermodynamic data were derived for Li⁺/H⁺ exchange on M-SbA from pH titration curve.     

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS XXX III. SELECTIVITIES OF ALKALI METAL IONS ON TIN(IV) ANTIMONATE CATION-EXCHANGER PREPARED AT DIFFERENT CONDITIONS

ABSTRACT

A tin(IV) antimonate(SnSbA) cation exchanger has been synthesized under different conditions; changes in the concentration, the molar ratio of Sb/Sn in the starting solution, and hydrolysis temperature. The products obtained were characterized by powdered X-ray diffraction and thermal analysis, and infrared spectra. The pH titration curves on SnSbA showed apparently mono-basic acid, but can be expected to the presence of the number of the functional groups with overlapping different pKa values. The increased acidities were observed with increasing the molar ratio (Sb/Sn) in the exchanger. The equilibrium distribution coefficients were determined at micro-amount of alkali metal ions in the hydrochloric acid solution. The SnSbA showed an unusual selectivity for alkali metal ions compared to cation exchange resins and other inorganic ion-exchangers.

The selectivity sequence shows; Na⁺ < K⁺ < Rb⁺ < Cs⁺ < Li⁺

An extremely high selectivity of lithium ions was found on the SnSbA hydrolyzed at relatively high temperature and with high Sb/Sn molar ratio     

Counter‐ion‐specific helix formation of poly(γ‐methyl L‐glutamate) derivatives containing sulfonate group in aqueous alcohols

Charged polypeptides containing sulfonate groups were prepared by transesterification of poly(γ‐methyl L ‐glutamate) with isethionic acid. The coil–helix transition of the sulfonated polypeptides was investigated in aqueous alcohols. Marked counter‐ion specificity was observed for helix formation: Li⁺ < Na⁺ < Cs⁺ ≦ Rb⁺ ≦ K⁺; this was different to that for poly(L ‐glutamate) (PLG): Cs⁺ ? K⁺ < Li⁺ < Na⁺. Specific helix stabilization by counter‐ion mixing, which has been found for the PLG system, was not observed for the sulfonated polypeptides. The counter‐ion‐ and solvent‐specific helix formation is discussed and compared with that in PLG. © 2001 Society of Chemical Industry     

Synergistic interplay between D2EHPA and TBP towards the extraction of lithium using hollow fiber supported liquid membrane

Extraction of lithium (Li⁺) from synthetically prepared sea bittern using di-2-ethyl hexyl phosphoric acid (D2EHPA) and tri-n-butyl phosphate (TBP) as organic extractants has been studied. The equilibrium studies conducted show synergistic effect between D2EHPA and TBP. The equilibrium constant values for Li⁺, Na⁺ and K⁺ ions were found to be 95.4 × 10^?5 m³/kmol, 4.6 × 10^?5 m³/kmol and 3.69 × 10^?5 m³/kmol, respectively. Hollow fiber supported liquid membrane (SLM) experiments with low concentrations of Li⁺, Na⁺ and K⁺ ions in feed phase showed high flux for Li⁺ ions. However, at significantly high concentrations of Na⁺ and K⁺ in the feed phase, the flux of Li⁺ ions reduced. The model predictions were found to be in good agreement with the experimental data.     

Electrochemistry-electrospray-mass spectrometry study of cesium uptake in nickel hexacyanoferrate films

The electrochemically-controlled uptake and release of Cs⁺ by nickel hexacyanoferrate thin-film electrodes that were prepared with different counter cations (Li⁺, Na⁺, K⁺, Rb⁺, or Cs⁺) were examined using a thin-layer flow cell coupled on-line with electrospray-mass spectrometry (ES-MS). A potential step technique was used to control the uptake and release of the cations by the films. Performance of the different films in terms of Cs⁺ capacity, Cs⁺ uptake selectivity versus the other alkali metal ions, film stability, and the effect of a saline matrix on Cs⁺ uptake were examined. These results show that the electrochemistry-mass spectrometry (EC-MS) combination provides rapid, Cs⁺ specific information concerning the films that is similar to or complementary to that information which might be obtained using conventional electrochemical approaches. Information that cannot be obtained electrochemically (e.g. isotopic distributions of metal ions accumulated and released) might also be gathered. Any number of electrode reactions involving ion uptake and release might be studied using this approach.     

A comparison of the electro-osmotic properties of charged polymer membranes and those predicted from binary electrolyte solution models Part I. Univalent forms of sulphonate membranes and chloride electrolyte models

By changing from the usual solvent-fixed frame of reference for flows to one based upon a fixed anion, electro-osmotic transference numbers are defined for any electrolyte, for which transport numbers are known. For sulphonate membranes, chloride electrolyte analogues were chosen. Agreement between observed transference numbers and those of the model electrolytes are shown to be excellent for both polystyrene based and perfluoro-sulphonic acid membranes.From irreversible thermodynamics it is shown that the transference number for any membrane will have a maximum value equal to the molar ratio of water to fixed charge in the membrane and independent of ionic form. The observed value is in addition, proportional to the fraction of the total water friction, which is due to water interaction with counterion. It is the latter which is estimated successfully from model electrolytes. The ionic forms used were Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and H⁺ at 25°C in membranes in which electrolyte exclusion was almost complete.     

An experimental study of electroreduction of CO2 to HCOOH on SnO2/C in presence of alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) and anions (HCO3−, Cl−, Br− and I−)

It is well-known that the electrolytes can influence the electrochemical reduction of carbon dioxide (ERCO₂) in aqueous media. In this work, we explore the effects of alkali metal cations and anions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, HCO₃⁻, Cl⁻, Br⁻, I⁻) on the current density and product selectivity for the ERCO₂ into formic acid (HCOOH) on the SnO₂/carbon paper (SnO₂/C) electrode. Results of the ERCO₂ experiments show that for the cations, the promotion effects on current density and faradaic efficiencies (FEs) are in the order of Li⁺ < Na⁺ < K⁺ < Cs⁺ < Rb⁺. For the anions, the current density values are in the order of NaHCO₃ < NaCl < NaBr < NaI and KHCO₃ < KCl ≈ KI < KBr, respectively, and that on the FEs for the formation of the HCOOH (FE_HCOOH) is HCO₃⁻ < Cl⁻ < Br⁻ < I⁻. Based on this result, the effects of alkali metal cations and anions on ERCO₂ are discussed.     

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.     

Preparation of unsaturated polyester–styrene beads using gamma irradiation and chemical polymerization routes for use in the recovery of some alkali metal ions

Suspension polymerization of unsaturated polyester–styrene was carried out in different media using different routes of polymerization. The effects of matrix type and concentration hold up, viscosity, irradiation dose, and the agitation speed on the resultant polymer characteristics were examined. The formed beads were physically identified using scanning electron microscopy, hardness, and particle size analysis techniques. They were smooth having typical spherical surfaces; the beads diameters were in the range of about 5–200 μm. The size of the resin beads was found to decrease with increase in the concentration and viscosity of the dispersant and impeller speed. The resultant beads were applied in the recovery of Li⁺, Na⁺, K⁺, and Cs⁺ ions from acidic media. The distribution coefficients of the alkali metal ions were calculated; the order of selectivity was Li⁺ > Na⁺ > K⁺ > Cs⁺ in case of the chemically processed resin beads, while the selectivity lies in the order of Li⁺ < Na⁺ < K⁺ < Cs⁺ in case irradiation processed ones. Finally, the economics of production of the unsaturated polyester–styrene resins using different methodologies was studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1149–1160, 2007     

Extraction of Alkali Metal Tetraphenylborates by Polyurethane Foam

Abstract

The extraction of alkali metal tetraphenylborates by polyurethane foam was investigated. The extractability sequences are K⁺ ≈ Rb⁺ > Cs⁺ and K⁺ ≈ Rb⁺ ≈ Cs⁺ for polyether and polyester foams, respectively. The high extraction of K⁺ by polyether foam can be explained by the cation chelation mechanism.     

CO<Subscript>2</Subscript> retention ability on alkali cation exchanged titanium silicate,ETS-10

ETS-10 was ion exchanged by various alkali cations (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) and the BET surface area and pore volume was exactly consistent with cationic size; that is, in the order of Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺. It was observed that a single point adsorption capacity was inversely proportional to cationic size. The largest CO₂ capacity was observed for Li⁺-ETS-10 and it is attributed to greater cation–quadrupole interactions with CO₂ than larger cation. The results also suggests that as the CO₂ loading is increased, the accessibility of adsorbing CO₂ to framework basic O⁻ sites should have become difficult with the increase in cationic size due to the blocking effect by extra-framework CO₂-M⁺. The slight decrease in the slope of adsorption capacity with temperature, especially beyond 373 K for Li⁺-ETS-10 and K⁺-ETS-10 suggests that the adsorption of CO₂ on small alkali cation exchanged-ETS-10 at high temperature is somewhat associated with basic oxygen anion sites in framework due to the existence of large pore. The CO₂-TPD results show that the amount of desorbed CO₂ at higher temperature was proportionally increased due to the increased basicity of oxygen anions in framework. It also shows that the desorption temperature associated with alkali cations in extra-framework (corresponding to low temperature desorption peak) has been lowered with the increase in cationic size, indicating weak cation–quadrupole interactions with CO₂ for larger cations.     

Diffusion and Selective Transport of Alkali Cations on Cation-Exchange Membrane

Abstract

The diffusion coefficients and selective transport for alkali metal cations through a charged polysulfonated ICE-450 ion-exchange membrane were measured as a function of pH at 25°C. The permeability and diffusion coefficients were found to increase in the sequence Cs⁺ ≥ K⁺ > Na⁺ > Li⁺. The relationship between the permeability and the diffusion coefficients, and the hydrated radii of cations in the membrane were shown. This sequence was also explained by considering the hydration of ions in the membrane. The selectivity transport of K—Na and K—Li binary systems at various pH gradients through the membrane were also investigated under various conditions. In the selective transport of metal ions, the selectivity depended on both the hydrated ionic size and the interaction between the fixed groups in the membrane and the metal ions.