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⁺.     

Chromium (III) removal by microporous ion exchanger Amberlite.120 (Na+): kinetic, equilibrium and thermodynamic studies

Cr (III) sorption on microporous strong cation exchanger Amberlite.120 (Na⁺) is studied as a function of time and temperature. The pH changes show the co-sorption of H⁺ ions along with the chromium. The rate constant values for Cr (III) sorption are calculated for both film and particle diffusion processes. However, the particle diffusion is found to be more dominant than the film diffusion. The temperature is found to have a positive effect on both the diffusional processes. The low values of energy of activation also confirm the diffusional nature of the process. Equilibrium data are explained with the help of Langmuir equation. Various thermodynamic parameters (??H, ??S and ??G) for Cr (III) exchange on the resin are calculated. The ??G values are found to be negative, while both the ??H and ??S values obtained are positive.     

Adsorption of Co2+ and Zn2+ on cryptomelane-type hydrous managese dioxide

Co²⁺ and Zn²⁺ ions are adsorbed on cryptomelane-type MnO₂ by exchange with surface protons and with structural ions (probably K⁺ and/or Mn²⁺) in the oxide. The latter sites are responsible for the much higher capacity to these cations, compared to Na⁺. At all pH values, two straight lines expressing the presence of mainly two groups of sites with distinctly different adsorption energies are located in the Langmuir plots for both Co²⁺ and Zn²⁺. The apparent capacities of the two groups increase with the increase of pH, indicating the involvement of protons in the adsorption process over the whole concentration range. The higher Co²⁺ capacity at relatively low pH, compared to the Zn²⁺ capacity, is probably due to a more exchange with the structural ions. Crytomelane type MnO₂ seems to be a quite heterogenous ion adsorbent whose adsorption sites could be approximated to two groups only.     

Diffusion of Cs+ and Zn2+ through Nafion-117 ion exchange membrane

This paper discusses the diffusion of Cs⁺ and Zn²⁺ ions through Nafion-117 cation exchange membrane using radiotracer technique. The validity of the Donnan's equation is checked for these ions using⁶⁵Zn and¹³⁷Cs radiotracers. The paper also discusses the diffusion of Cl^– and I^– anions studied by using³⁶Cl and¹³¹I radiotracers. The probable mechanism of diffusion of these anions in the presence of Zn²⁺ cations is suggested.     

Column chromatographic speciation of chromium for Cr(VI) and several species of Cr(III)

Summary Chromium can be present in aqueous solution as Cr(VI) or in monomeric, dimeric, trimeric and higher polymeric forms of Cr(III). Many monomeric forms of Cr(III) are possible, with the water molecules of Cr(H₂O) ₆ ³⁺ substituted by anionic or neutral species. This proliferation of Cr(III) species makes the complete speciation of chromium a continuing challenge to the analyst. A simple and effective cation exchange procedure for the separation of various of these species uses a small glass column containing 1 mL of pre-treated cation exchange resin (Na⁺ form). Stepwise elution with solutions of perchloric acid, Ca²⁺ (pH=2) and La³⁺ (pH=2) separates Cr(VI) and seven Cr(III) species from CrX₃ to tetramer. Radiometric (Cr-51), spectrophotometric and other detection methods can be employed; the use of radiochromium gives the lowest detection limit.     

基于苯并噻唑Zn2+荧光探针及其细胞造影应用

设计合成基于苯并噻唑Zn²⁺荧光增强型探针BHP,在HEPES缓冲液中测其对Zn²⁺识别性能。实验结果表明,BHP对Zn²⁺有较高的选择性,对其他金属离子如Cd²⁺,Fe²⁺,Ni²⁺,Pb²⁺,Hg²⁺,Al³⁺,Mn²⁺,Ag⁺,Cu²⁺,Co²⁺,Na⁺,K⁺,Mg²⁺和Ca²⁺无明显荧光增强响应。BHP与Zn²⁺按1：1计量比配位,在生理条件下荧光强度不受pH值影响。在HeLa细胞中对Zn²⁺的造影表明BHP可用于生物体Zn²⁺检测。     

Amorphous aluminosilicates containing trivalent chromium in a non-octahedral coordination environment

Amorphous aluminosilicates containing up to 5.8 wt.% chromium have been prepared by cation exchange on an amorphous sodium aluminosilicate using Cr(III) salts. Electronic spectroscopy has shown that the ligand arrangement around the Cr(III) sites does not correspond to the octahedral geometry. No isomorphous substitution of Al³⁺ by Cr³⁺ in the aluminosilicate occurs, and it is not possible to exchange back chromium by Na⁺ ions. The amorphous chromium-substituted aluminosilicates (abbr. ACSAS) are slightly acidic and when heated in air at 800 °C no oxidation of Cr(III) takes place. The chromium species in the ACSAS undergoes ligand replacement reactions.

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Amorphe Alumosilicate mit dreiwertigem chrom in nicht-oktaedrischer Koordinationsumgebung

Zusammenfassung Bis zu 5,8 Gew.% Chrom enthaltende amorphe Alumosilicate wurden durch Kationenaustausch am amorphen Natriumalumosilicat unter Anwendung von Cr(III)-Salzen hergestellt. Elektronenspektroskopische Untersuchungen zeigten, daß die Ligandanordnung um die Cr(III)-Lagen nicht der oktaedrischen Geometrie entspricht. Im Alumosilicat erfolgt keine isomorphe Substitution von Al³⁺ durch Cr³⁺ und es ist nicht möglich, Chrom durch Na⁺ zurückzuersetzen. Die amorphen durch Chrom ersetzten Alumosilicate (abgekürzt ACSAS) sind schwach sauer und wenn sie in der Luft auf 800 °C aufgeheizt werden, erfolgt keine Oxydation von Cr(III). Das in den ACSAS vorliegende Chrom unterliegt Ligandaustauschreaktionen.

     

Thermodynamic characteristics of ion-exchange sorption of Co2+ cations on Na-vermiculite

The exchange of Na⁺ ions of vermiculite for Co²⁺ cations is measured by sorption-analytical and microcalorimetric methods. The previously revealed growth of the equilibrium constant with a rise in the degree of filling θ of vermiculite exchange sites with Co²⁺ cations is confirmed. This result is explained by the segregation of Co²⁺ and Na⁺ cations being exchanged in separate interlayer regions of vermiculite. The negative heats of exchange of Na⁺ cations for Co²⁺ cations are associated with the energy consumption for the rearrangement of the segregated interlayer regions in vermiculite. The positive entropy changes resulting from the exchange indicate the formation of a more disordered Co-Na-layered “cake” in comparison with the initial Na-form vermiculite. A decrease in the integral molal free-energy change ΔG _m of the mixed form of the mineral is determined by the entropy factor. It is shown that, as θ increases, the ΔG _m(θ) dependence passes from a positive to a negative range of values. This pattern of the curve may be interpreted as a gradual phase transition from the Na-form to the mixed Co-Na-segregated form. The first derivatives of the enthalpy and entropy changes with respect to the degree of filling θ exhibit distinct maxima at θ ～ 0.20 as a result of the transition from the ideal mixing of Co²⁺ and Na⁺ cations being exchanged to their segregation.     

STRUCTURAL FEATURE AND EXCHANGE KINETICS OF CARBOXYLATED POLYPROPYLENE ION EXCHANGE RESIN

The present article deals with the exchange process of bivalent metal ions, such as Zn~(2+), Cd~(2+) and Hg~(2+), etc., taken up by non-crosslinked earboxylated polypropylene (CPP) resin. The control factor of the exchange rate deduced from the kinetic data is governed basically by the chemical reaction rather than the mass transfer effect particle diffusion and/or liquid film diffusion. In solution, all the graft chains in the outer shell of a CPP resin could form a "quasi-macromolecular solution" domain. This opinion further demonstrates the structural pattern of CPP resin proposed in earlier paper.     

Separation of radionuclides by isotopic exchange using metal chelates and fixed metal sulphide precipitates

The possibilities of radioanalytical separation by isotopic exchange with metal chelate complexes and metal sulphide precipitates fixed in paper have been examined on the model system²⁰³Hg²⁺+⁵⁸Co²⁺+⁶⁵Zn²⁺+²⁴Na⁺.     

Electrochemical properties of a network polymer based on tetra(sulfonatophenyl)-meta-cyclophanoctol

Conductivity of the network polymer based on tetra(sulfonatophenyl)-meta-cyclophanoctol in the H⁺, Na⁺, Cu²⁺, Zn²⁺, and Ni²⁺ forms is studied, and the self-diffusion coefficients and activation energies of diffusion of the metal cations in the polymer phase are estimated.     

Dynamic capacity and mass transfer for removal of Na+ by a composite hydrated antimony pentoxide-organic ion exchanger

The removal of Na⁺ by a composite hydrated antimony pentoxide-sulfonated phenol-formaldehyde ion exchanger (C-HAP) from 4M HCl was studied using the breakthrough technique. The dynamic removal capacity for Na⁺ from 4M HCl is 12.3 mg Na⁺/g and 9.87 mg Na⁺/g at 0.2 ml/min and 0.8 ml/min, respectively. Height equivalent to a theoretical plate varies almost linearly with flow rate indicating particle diffusion control.     

Synthesis and sorption properties of new synthesized rare-earth-doped sodium titanate

A series of rare-earth-doped sodium titanates with the chemical formula R _x H _y Na_{4 − (x+y)}TiO₄·nH₂O (where R = Ce³⁺, Nd³⁺ and Sm³⁺) were grown employing solid-state fusion reaction technique. The physico-chemical investigations indicated that the new materials were self engineered into large particles enough to be used in sorption process and having crystalline structures containing localized Na⁺ ions. Equilibrium studies revealed that an enhancement in sorption efficiency of sodium titanate after rare-earth doping. The neodymium-rich sodium titanate exhibited a better exchange affinity for Cs⁺ compared to the other studied series. Data on the kinetics of cesium exchange fit well to pseudo-second order and intra-particle diffusion models. In a separate experiment, it was reported that the R-HNaTi series showed responsible sorption affinity toward Ce, Nd and Sm ions in their solution mixture with insignificant selectivity trend which reflects the high stability of titanate matrices.     

Study of transport processes in plants by radioabsorption and microradiographic methods

The passive transport processes in plants of²²Na⁺,¹³⁷Cs⁺,⁴⁵Ca²⁺,⁶⁵Zn²⁺,⁵⁹Fe³⁺ and³²PO ₄ ³⁻ ions and the plant-protecting agent “Saphidon (¹⁴C)” were studied by a radioabsorption method. The parameters of the passive transport processes of²¹²Pb²⁺, borate and tetraborate ions in plants were measured by quantitative microradiographic methods, using photoemulsion and solid state nuclear track detectors. Ion diffusion concentration profiles within the plants were determined at various diffusion times and temperatures. The equation of linear diffusion combined with convection was used to determine the diffusion coefficients characteristic of the transport processes.     

Separation of rare earth and transplutonium elements by displacement chromatography on KU-2 cation exchange resin in the Cu2+ form under ionizing radiation

Changes in chromatographic parameters (pH, REE concentration, eluent concentration, separation coefficients) under irradiation using the KU-2 cation exchange resin in the Cu²⁺ form are studied experimentally and theoretically depending on the absorbed dose and respective destruction of the eluent. It is found that the use of the cation exchange resin in the Cu²⁺ form in the field of ionizing radiation leads to a more effective separation of REEs than in the case of using the Zn²⁺ and H⁺ forms of cation exchange resin.     

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).     

Kinetics of liquid-solid ion-exchange reactions of transition metal ions in tin(IV) phosphate

A simple approach to liquid-solid ion exchange kinetics of Cu²⁺, Zn²⁺, Cd²⁺, Co²⁺ ions in tin(IV) phosphate under different conditions of temperature, exchange ion concentration, and the particle size of the exchanger has been reported. The kinetics were controlled by particle diffusion and the $\text{t}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ law operated to about 65–75% of exchange. The diffusion coefficients and activation energies were calculated. The activation energies of Cu²⁺ and Co²⁺ ions were found to be low when compared with Zn²⁺ and Cd²⁺ ions due to Jahn-Teller distortion.     

Na+/K+-ATPase: Activity and inhibition

The aim of the study was to give an overview of the mechanism of inhibition of Na⁺/K⁺-ATPase activity induced by some specific and non specific inhibitors. For this purpose, the effects of some ouabain like compounds (digoxin, gitoxin), noble metals complexes ([PtCl₂DMSO₂], [AuCl₄]⁻, [PdCl₄]²⁻, [PdCl(dien)]⁺, [PdCl(Me₄dien)]⁺), transition metal ions (Cu²⁺, Zn²⁺, Fe²⁺, Co²⁺), and heavy metal ions (Hg²⁺, Pb²⁺, Cd²⁺) on the activity of Na⁺/K⁺-ATPase from rat synaptic plasma membranes (SPM), porcine cerebral cortex and human erythrocytes were discussed. The article is published in the original.     

Studies on ion exchange equilibria and kinetics: V. UO 2 2+ −Na+−H+ ternary cation exchange kinetics

The kinetics of particle-diffusion controlled ion exchange in the ternary system of cations UO ₂ ²⁺ –Na⁺–H⁺–001×7 strong acidic resin has been studied. In the [R–H⁺]/(Na⁺+UO ₂ ²⁺ ) system, the change of the amount of Na⁺ in the resin phase with time showed a high peak. In the [R–Na⁺]/(H⁺+UO ₂ ²⁺ ) system, the change of the amount of H⁺ in the resin phase with time also showed a high peak. In the [R₂–UO ₂ ²⁺ ]/(H⁺+Na⁺) system, the change of amount of H⁺ in the resin phase with time showed merely a small peak. This kinetic character of the ternary ion exchange system in the finite solution volume has been analyzed according to the Nerst-Planck equation, and on the whole, the trend of the experimental results is consistent with the resulting numerical solution of the set of Nerst-Planck equations.