EMK-Messungen in binären unsymmetrischen Salzschmelzen aus Strontiumchlorid und Alkalimetallchloriden

The EMF of cells with transference of the type Cl₂, C/MeCl ? SrCl₂? MeCl(x)/C, Cl₂ is measured in the molten mixtures SrCl₂? MeCl (Me ? Li, Na, K, Rb, Cs). From the EMF-values and values of aktivities from another independent methods the transference numbers of the cations Sr²⁺ and Me⁺ relative to the chloride ion in the molten mixtures SrCl₂? LiCl, SrCl₂? NaCl and SrCl₂? KCl are calculated. The values of aktivities for the systems SrCl₂? LiCl and SrCl₂? NaCl are calculated from cryoscopic analysis of the eutectic phase diagrams.     

Removal of Some Radionuclides Using Stannic Silicovanadate as Inorganic Ion Exchanger

Adsorption of cesium (Cs⁺), strontium (Sr²⁺), and europium (Eu³⁺) onto stannic silico vanadate as ion exchange material, and the effects of experimental conditions on adsorption were considered. The material were characterized by X-ray diffractometer system (XRD), scanning electron microscopy (SEM), X-ray fluorescence spectrometry (XRF), infrared (IR), and thermal analysis (TGA and DTA). The selectivity coefficients for different cations determined by mixed solution method were found to be less than unity. The thermodynamic parameters such as ΔG*, ΔS*, and ΔH* have also been calculated for the adsorption of Cs⁺, Sr²⁺, and Eu³⁺ onto stanic silicovanadate, showing that the overall adsorption process is spontaneous and endothermic.     

Experimental and Modeling Study of Ion Exchange Between Aqueous Solutions and the Zeolite Mineral Clinoptilolite

Ion-exchange experiments were conducted at 25°C between the zeolite mineral clinoptilolite and aqueous solutions of Na⁺/Sr²⁺ (0.005, 0.05, and 0.5 N), K⁺/Sr²⁺ (0.05N), and K⁺/Ca²⁺ (0.05 N). The isotherm data were used to derive equilibrium constants and Gibbs energies for the ion-exchange reactions and Margules parameters for the zeolite solid solution. The Margules model, in combination with the Pitzer equations for activity coefficients of aqueous ions, was used to predict isotherms for ion exchange involving clinoptilolite and aqueous solutions of Na⁺/Sr²⁺, K⁺/Sr²⁺, and K⁺/Ca²⁺ over wide ranges of solution composition and concentration. The ion-exchange isotherms are strongly dependent on the total solution concentration. For Na⁺/Sr²⁺ ion exchange, isotherm values at 0.005 and 0.5 N predicted using thermodynamic parameters derived from the 0.05 N data showed excellent agreement with measured values. The model was also applied to calculations of aqueous composition based on the chemistry of coexisting zeolite phases. The results show that the aqueous composition can be predicted well from the composition of the zeolite, at least for systems that involved binary (two-cation) exchange. Because the thermodynamic model can be easily extended to ternary and more complicated mixtures, it may be useful for modeling ion-exchange equilibria in multicomponent systems.     

Cation exchange, interlayer spacing, and thermal analysis of Na/Ca-montmorillonite modified with alkaline and alkaline earth metal ions

Na-montmorillonites were exchanged with Li⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺, while Ca-montmorillonites were treated with alkaline and alkaline earth ions except for Ra²⁺ and Ca²⁺. Montmorillonites with interlayer cations Li⁺ or Na⁺ have remarkable swelling capacity and keep excellent stability. It is shown that metal ions represent different exchange ability as follows: Cs⁺?>?Rb⁺?>?K⁺?>?Na⁺?>?Li⁺ and Ba²⁺?>?Sr²⁺?>?Ca²⁺?>?Mg²⁺. The cation exchange capacity with single ion exchange capacity illustrates that Mg²⁺ and Ca²⁺ do not only take part in cation exchange but also produce physical adsorption on the montmorillonite. Although interlayer spacing d ₀₀₁ depends on both radius and hydration radius of interlayer cations, the latter one plays a decisive role in changing d ₀₀₁ value. Three stages of temperature intervals of dehydration are observed from the TG/DSC curves: the release of surface water adsorbed (36?C84?°C), the dehydration of interlayer water and the chemical-adsorption water (47?C189?°C) and dehydration of bound water of interlayer metal cation (108?C268?°C). Data show that the quantity and hydration energy of ions adsorbed on montmorillonite influence the water content in montmorillonite. Mg²⁺-modified Na-montmorillonite which absorbs the most quantity of ions with the highest hydration energy has the maximum water content up to 8.84%.     

Experimental evaluation of single ion activities

When an ion-exchange membrane separates two electrolyte solutions having two different co-ions and a common counterion a bi-ionic potential (bi-co-ionic potential) appears across the membrane. If the membrane is ideally permselective for counterions and the activities of counterions on both sides of the membrane are equal to each other, the membrane potential Δψ becomes zero. We selected KCl as a reference electrolyte because of a symmetrical electrolyte in aqueous solutions. Then, the mean activity of ions in KCl may be assumed to be equal to each single ion activity at low molalities. Single ion activity in a test electrolyte containing K⁺ ion or Cl⁻ ion was estimated from the molality of KCl at Δψ=0 by interpolating bi-co-ionic potential to zero for KCl/membrane/LiCl, NaCl, C₆H₅COOK, or p-CH₂CHC₆H₄SO₃K systems. The values of single ion activity coefficients estimated in this work were fairly different not only from the mean activity coefficients of ions but also from the single ion activity coefficients estimated by Debye–Hückel formula.     

The association of hexacyanoferrate(II) ions and group IIA cations

A thermodynamic study has been made of the equilibrium $$M^{2 + } {\text{ + }}Fe(CN)_6^{4 - } {\text{ }} \rightleftharpoons {\text{ }}MFe(CN)_6^{2 - } $$ in dilute aqueous solution by a potentiometric method using a divalent-cation electrode where, M²⁺ is a group IIA cation. Ion pairing was found to be quite extensive: Thus, at 25°C, the association constants extrapolated to zero ionic strength were 5840, 4730, 4560, and 6080M ^?1 for M²⁺=Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺, respectively. In each case, ion pairing is slightly endothermic, the corresponding ΔH ^o values being 18.0, 13.0, 7.8, and 17.5 kJ-mole^?1. However, the values of ΔS ^o are larger and positive, thus favoring ion pairing: the values are 133, 115, 96, and 131 J^o-K^?1-mole^?1 for the same series of cations. There was also some indication of a small amount of ion triplet formation, M₂Fe(CN)₆. Comparisons were made with the predictions of the Fuoss theory, and these support the view that the bonding in the ion is largely electrostatic and not covalent.     

Thermodynamics of the formation of Sm3+-ethylenediamine-N,N′-disuccinic acid complexes in aqueous solutions at 298.15 K

The thermodynamic parameters of the formation of the complexes of ethylenediamine-N,N′-disuccinic acid (H₄Y) with Sm³⁺ ion are determined by means of calorimetry and measuring pH at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 (KNO₃). The values of logK, Δ _r G, Δ _r H, and Δ _r S are calculated for the formation of SmY^? and SmHY complexes at fixed and zero values of ionic strength. The resulting values are interpreted.     

Biosorption of strontium from aqueous solutions onto spent coffee grounds

A set of experiments was carried out to evaluate the strontium uptake potential of spent coffee grounds (SCG) by batch tests in aqueous medium. Adsorption of Sr²⁺ as a function of contact time and adsorbent dose, pH, particles size, agitation speed, temperature and co-ions presence was investigated. Obtained results revealed that the maximum adsorption took place at pH range of 5–8 and temperature values between 283 and 333 K. Particles size effect was not very significant and agitation speed influenced on the equilibrium time. Competitive adsorption experiments allowed us to classify the negative effect on the Sr²⁺ uptake according to this order Al³⁺ ? Co²⁺ > Mg²⁺ > Ca²⁺ ? Na⁺ > K⁺ > Cs⁺. Kinetic study indicated that the Sr²⁺ uptake was fast and it was well fitted by the pseudo second order reaction model. Adsorption isotherm was well interpreted by Langmuir model. The maximum adsorption capacity was found to be 69.01 mg g^?1 at pH 7, 293 K, particles sizes = 200–400 μm and agitation speed 250 rpm. The thermodynamic study revealed that the process was spontaneous (ΔG ⁰ < 0), exothermic (ΔH ⁰ < 0) with a raised affinity for Sr²⁺ (ΔG ⁰ < 0, ΔS ⁰ > 0) and occurred by physical adsorption (E _a = 8.37 kJ mol^?1). FTIR analysis showed carboxylic acid and amino group presence on SCG surface playing a vital role in Sr²⁺ biosorption.     

Comparative study of the gas-phase bond strengths of CO2 and N2O with the halide ions

Thermodynamic data, ΔH _{n-1, n} ^o and ΔS _{n-1, n} ^o, for clustering reactions of halide ions X^?(X = F, Cl, Br, and I) with N₂Owere measured with a pulsed electron beam high-pressure mass spectrometer. In contrast to the fact that CO₂ forms a covalent bond with the fluoride ion to yield the fluoroformate ion, FCO₂ ^?, the interaction between F^? and N₂O is mainly electrostatic. It was found that the cluster ions F^? (N₂O)_n complete the first shell at n = 6, thus forming an octahedral structure. The difference between F—CO₂ ^? and F^? ... N₂O is discussed in terms of Coulombic, exchange, and charge-transfer interactions. The X^? (N₂O)₂ clusters (X = Cl, Br and I) are found to be of C_2h symmetry, while F^? (N₂O)₂ is of a twisted form and is slightly asymmetric due to a slight participation of covalency (charge transfer) in the core ion F^? ... N₂O.     

Preparation of PFSA/PSf hollow fiber composite membranes with recovered PFSA for the pervaporation separation of EtOH/H2O

Perfluorosulfonic acid/Polysulfone(PFSA/PSf) hollow fiber composite membranes have been prepared by dip-coating method using PSf ultrafiltration (UF) membrane as substrate with recovered PFSA. The composite membranes were applied to the pervaporation separation of 95% ethanol (EtOH)/H₂O mixture. SEM images show that the thickness of the PFSA skin layer of the composite membranes is about 2 μm, much thinner than those of other PFSA composite membranes revealed in the literatures. Effects of annealing temperature, coating solution concentration and counter-ions of PFSA on the pervaporation performances of the composite membranes were investigated. The total flux decreases and separation factor increases with the increase of annealing temperature. The highest permeation flux of 3230 g m^?2 h^?1 and a separation factor of 5.4 is obtained for the composite membrane annealed at 80°C. The lowest permeation flux of 396 g m^?2 h^?1 and a separation factor of 27.7 is obtained for the composite membrane annealed at 160°C. The permeation performances of the PFSA/PSf composite membrane are evidently influenced by the counter-ions of PFSA. The flux sequence of the PFSA/PSf composite membranes with different counter-ions is H⁺>Li⁺>Ca²⁺>Mg²⁺>Na⁺>K⁺>Ba²⁺>Fe³⁺>Al³⁺, and the separation factor sequence is H⁺<Li⁺<Al³⁺<Na⁺<Mg²⁺<Ca²⁺<K⁺<Ba²⁺<Fe³⁺. The apparent activation energy ΔE _app values of the composite membranes with different counter-ions were calculated by Arrhenius law. The sequence of ΔE _app values for the membranes with monovalent counter-ions is Li⁺>Na⁺>K⁺. There are very little variations of ΔE _app values between the composite membranes with three divalent counter-ions (Mg²⁺, Ca²⁺ and Ba²⁺), and the ΔE _app values of the composite membranes with two trivalent counter-ions (Fe³⁺ and Al³⁺) are relatively high.     

Thermodynamics of ion exchange in a sulfonated polymer based on <Emphasis Type="Italic">cis</Emphasis>-tetraphenylmetacyclophanoctol

The thermodynamic characteristics of proton exchange in SO₃H groups of a sulfonated network polymer based on cis-tetraphenylmetacyclophanoctol for Na⁺, Cu²⁺ cations from aqueous solutions were considered for the first time. Microcalorimetric measurements of the heat effects of N^a+-H⁺ and Cu²⁺-H⁺ exchanges were performed, equilibrium compositions of polymer and solution were determined. The changes of Gibbs energy, enthalpy and entropy of ion exchange were calculated.     

Kinetics and mechanism of some fast anation reactions of a series of substituted dien complexes of palladium(II). Temperature and pressure dependencies in weakly acidic aqueous solution1

Anation reactions of the type [Pd(L)(H₂O)]²⁺ + X^? »[Pd(L)X]⁺ + H₂O with L = 1, 4, 7-Et₃dien, 1, 1, 7, 7-Me₄dien and 1, 1, 4, 7, 7-Me₅dien and X^? = Cl^?, Br^?, I^? and N₃? have been studied kinetically as a function of [X?], temperature and pressure (up to 1 kbar). Second-order anation rate constants decrease with an increase in the size of L, and are accompanied by an increase in ΔH≠. For a given L the sequence Cl^? < Br^? < I^? < N₃^? holds, and the values of ΔS≠ and ΔV≠ are consistent with an associative mechanism. The results are discussed with reference to similar anation reactions previously investigated.     

Oxoacidity reactions in molten LiCl+KCl eutectic (at 470°C): Potentiometric study of the equilibria of exchange of O2− between Al(III) systems and carbonate and water systems

The reactions between aluminium chloride and oxide anion were studied in molten LiCl+KCl eutectic at 470°C. For that purpose, a pO^2? indicator electrode made with a membrane in yttria-stabilized zirconia has been used and tested by means of a carbonate ion whose dissociation constant, 10^?2.15 atm, was determined. Then, the electrode has allowed us to obtain the formation constant of AlO⁺ (solvated by Cl^?) and the solubility product of Al₂O₃ (S): 10^10.7 and 10^?27.4, respectively (molality scale). The equilibrium constant of the following system: 2HCl (g)+O^2? agH₂O (g)+2Cl^? has also been determined: 10^?9.93 atm mol kg^?1. The conditional solubility of alumina in LiCl+KCl melt is discussed.     

Zur Abtrennung des Spaltstrontiums aus Kernbrennstoffen an Ammoniummolybdatophosphat

The separation of fission strontium from solutions of prolonged cooled nuclear fuel has been performed using ammoniummolybdatophosphate (AMP) columns. The sorption mechanism of bivalent ions on AMP has been investigated by column and batch experiments. A pure ion exchange of Sr²⁺ for two H⁺ or NH ₄ ⁺ ions has been established. Conditions for the sorption and elution of fission strontium and other fission products on AMP columns are described.     

聚二烯丙基二甲基氯化铵在质子交换膜表面静电自组装过程的热力学研究

本文通过热化学方法设计了PDDA滴定质子交换膜,并研究了高分子的静电自组装过程。通过非线性拟合数据分析,求出了自组装过程的焓变（ ）和结合常数（K）。根据该反应过程中的热力学参数,可知自组装过程是“焓驱动”反应。热量的放出代表着能量的降低,有利于反应的发生;而自由度的减小不利于反应的发生。对于每个离子键的形成,单分子DDA的焓变超过了PDDA,这是因为小分子能够更加自由地结合到膜上,而高分子PDDA有一定的位阻效应。     

Synthesis and Photocatalytic Activity of Poly(triazine imide)

Poly(triazine imide) was synthesized with incorporation of Li⁺ and Cl^? ions (PTI/Li⁺Cl^?) to form a carbon nitride derivative. The synthesis of this material by the temperature‐induced condensation of dicyandiamide was examined both in a eutectic mixture of LiCl–KCl and without KCl. On the basis of X‐ray diffraction measurements of the synthesized materials, we suggest that a stoichiometric amount of LiCl is necessary to obtain the PTI/Li⁺Cl^? phase without requiring the presence of KCl at 873 K. PTI/Li⁺Cl^? with modification by either Pt or CoO_x as cocatalyst photocatalytically produced H₂ or O₂, respectively, from water. The production of H₂ or O₂ from water indicates that the valence and conduction bands of PTI/Li⁺Cl^? were properly located to achieve overall water splitting. The treatment of PTI/Li⁺Cl^? with [Pt(NH₃)₄]²⁺ cations enabled the deposition of Pt through ion exchange, demonstrating photocatalytic activity for H₂ evolution, while treatment with [PtCl₆]^2? anions resulted in no Pt deposition. This was most likely because of the preferential exchange between Li⁺ ions and [Pt(NH₃)₄]²⁺ cations.     

Study of the thermal decomposition of cellulose-hyphan and its complexes with some transition and indium metal ions

The studied complexes formed by the chelating ion exchanger were characterized by reflectance and infrared spectrometry. The thermal degradation of pure cellulose-hyphan (CH) and its complexes with Hg²⁺, In³⁺, Cr³⁺, Mo⁴⁺ and Mn²⁺ under an atmosphere of air has been studied using thermal gravimetry (TG) and differential thermal analysis (DTG). The results showed that four different stages are accompanying the decomposition of (CH) and its complexes with the studied metals. These stages were found to be affected by the presence of the investigated metal ions. On the bases of the applicability of a non-isothermal kinetic equation it was found to be a first-order reaction with the rate of degradation,k, ranging from 8.3·10^?5 to 6.2·10^?3 for (CH) and from 1.7·10^?5 to 6.6·10^?3 s^?1 for its complexes. The activation energy,E _a, the entropy change, ΔS°, the enthalpy change, ΔH° and Gibbs free energy, ΔG° are calculated by applying the rate theory of the first-order reaction. The effect of the different central metal ions on the calculated thermodynamic parameters is discussed.     

Thermodynamic studies of hydrogen iodide in dioxane-water mixtures from electromotive force measurements

The standard potentials of the silver-silver iodide electrode were measured in 10,20,30 and 40% (w/w) dioxane-water mixtures at 15,25,35 and 45°C. These values have been used to determine the thermodynamic quantities ΔG_t°, ΔS_t°, ΔH_t° for the transfer of H⁺I^? from water to various dioxane-water mixtures. The ionic ΔG_t° values for H⁺, Cl^?, Br^? and I^? are determined using Feakins method. The chemical and electrical contributions of ΔG_t° are also calculated using the method proposed by Roy and co-workers. The significance of these thermodynamic functions is discussed in relation to the acid—base character of the solvents.     

Optical detection of SrCl2 precipitates in KCl

In order to study the nature of Sr²⁺ precipitates, formed in strontium doped potassium clhoride, doubly doped crystals of KCl:Sr²⁺(Pb²⁺) were grown. Annealing of samples at 250°C produces an absorption (emission) band at 249 nm (290 nm) which is due to Pb²⁺ ions incorporated in SrCl₂ precipitated particles. These particles remain stable up to 350°C.On the other hand, it has been found that the 249 nm band (A band) is a temperature dependent doublet due to a dynamical Jahn-Teller effect.     

Enthalpies of formation of solid cobalt-tellurium alloys

The enthalpies of formation of solid Co?Te alloys were determined at room temperature with an isoperibol solution calorimeter of the submarine type. Co?Te alloys and mechanical mixtures of the pure components were dissolved in separate experiments in a saturated hydrochloric acid (8.000n)—bromine mixture and the enthalpies of formation obtained by difference. For the NiAs-type β-phase ΔH _f ^o(N_Te)=(4.079–15.017N _Te) kcal·g-atom^?1 and for the marcasitetype γ-phase ΔH _f ^o(N _Te)=(3.787–14.400N _Te) kcal·g-atom^?1. Combining these results with data from the literature integral thermodynamic properties of solid Co—Te alloys were calculated at room temperature and at 600°C.