Double-charged Cations Research Articles

The change of phase composition and the morphology of particles of hydrothermal titanosilicate precipitates during their aging

During the study of phase formation under conditions of hydrothermal synthesis of alkaline titanosilicate systems (NH₄)₂TiO(SO₄)₂⋅H₂O или TiOSO₄⋅H₂O-Na₂SiO₃-NaOH-H₂O it was found that the formed titanosilicate solid phases differ both in composition and structure. The process of their aging under conditions of long-term exposure without forced heating is accompanied mainly by the loss of free water without noticeable structural and morphological changes. The exposure to the temperature of 70–100°С significantly accelerates the process of solid phase transformation. In these conditions, a porous system of particles is formed, which is confirmed by an increase in their specific surface area and total pore volume, as well as by an increase in the activity of the powders to absorb single- and double-charged cations. The effectiveness of hydrochloric acid treatment of fresh and especially aged precipitates on the ordering of the structure with the formation of crystals of a clear frame shape, inherent in the minerals zorite and ivanyukite, which contributes to increasing the sorption capacity of the final product is shown. The obtained results are used to adjust the technological regulations, which are used to test the technology of titanosilicate sorbent on the pilot plant.

Study of the impurities in technical-grade 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane by gas chromatography-mass spectrometry

Polymerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane is the main method for manufacturing methylphenylsiloxane rubbers, and copolymerization of octamethylcyclotetrasiloxane and 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane is the main method for production of high- and low-molecular weight dimethylmethylphenylsiloxane rubbers. The molecular weight, viscosity, and other properties of the obtained polymers depend on the purity of cyclosiloxanes. The technology of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane production by thermocatalytic decomposition of methylphenylsiloxanes in the presence of lithium hydroxide or lithium silanolate, followed by vacuum rectification, makes it possible to obtain a product containing 1,3,5,7-tetramethyl-1,3,5,7-tetraphenylcyclotetrasiloxanes, tetraphenyldimethyldisiloxane as impurities and trace amounts of phenyl-containing siloxanes of cyclic and linear structure. The impurities of polycyclic and polyhedral structures have not been previously described. In this study, the method of gas chromatography-mass spectrometry is used to analyze compounds that can be present as impurities in technical-grade 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane. The use of the previously described regularities of the fragmentation of siloxanes of different structures made it possible to identify a number of siloxanes which are absent in the NIST 11 mass spectra library. It is shown that polycyclic and polyhedral compounds containing methylsilsesquioxane units have a short fragmentation path. They are characterized by ionization with the elimination of the methyl group and benzene in case of two phenyl groups in the molecule. The siloxane skeleton of such cations is rather stable, so they more readily lose another methyl group thus transforming into double-charged cations. The impact of electron ionization on the molecules with siloxane units containing different organic substituents at silicon leads to randomization of those substituents and rearrangement of the siloxane skeleton. Analysis of the results revealed that silanes, siloxanes of linear, cyclic, polycyclic and polyhedral structures are present in technical grade 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane.

Sodium-modified mesoporous TiO2: Sol-gel synthesis, characterization and adsorption activity toward heavy metal cations

Experimental samples of mesoporous TiO2 with protonated and sodium-modified surfaces were obtained by sol-gel method. XRD, IR, X-ray fluorescence, and energy dispersive spectroscopy were used to characterize their crystalline structure, morphology and surface functional groups. The surface area of, and pore size distribution in the obtained samples were measured by the nitrogen adsorption/desorption isotherm, and calculated using the BET and non-local DFT theories. The adsorption of the Zn(II), Sr(II) and Ba(II) cations by the protonated and sodium-modified TiO2 surfaces was studied. The dependence of adsorption of the Zn(II), Sr(II) and Ba(II) cations on agitation time, solution acidity, and equilibrium concentrations of cations was investigated in a batch mode. It was shown that the kinetic model based on the pseudo-second order equation applied to the experimental results of adsorption of heavy metal cations by both adsorbents gives the highest coefficients of linear approximation (R2 = 0,99). Two most common adsorption theories, Langmuir and Freundlich, were used to analyze equilibrium adsorption data. Nonlinear approximation shows, that the Freundlich adsorption theory provides higher R2 and lower χ2, than Langmuir adsorption theory for adsorption of heavy metal cations by sodium-modified TiO2 surface. The maximum adsorption of the Zn(II), Sr(II) and Ba(II) cations by the sodium-modified TiO2 surface exceeds that of base sorbent with protonated surface by 2,27; 2,65 and 2,64 times, respectively. Experimental maximum adsorption values of Na-TiO2 toward zinc, strontium and barium cations are 93 mg·g−1; 208,4 mg·g−1, and 274,6 mg·g−1 respectively.Higher metal cations adsorption by Na-TiO2 is due to the Na+ cations, which released, through the ion exchange process. Sodium cations cause the dissociation of water molecules and local alkalization of the aqueous medium, which leads to the reduction of double-charged zinc, strontium and barium cations to single-charged ZnOH+, SrOH+ and BaOH+ cations respectively. Sodium-modified TiO2 involves only one ≡ТіОNa adsorption center in adsorption of the MeOH+ cation, while the protonated Н-ТіО2 sorbent spends two ≡ТіОНδ+ acid centers to bind the double-charged cation.

Syntheses and the crystal chemistry of the perfluoridotitanate(IV) compounds templated with ethylenediamine and melamine

Chemical reactions between ethane-1,2-diamine [C2H4(NH2)2; ethylenediamine, abbr. en] and 1,3,5-triazine-2,4,6-triamine [C3H6N6; melamine, abbr. mel], with titanium tetrafluoride (TiF4) were carried out in liquid anhydrous hydrogen fluoride (aHF). The latter acted in a dual role: as a reagent and as a solvent. The n(en): n(TiF4) = 2:1, 1:1, 1:3, 1:4, and n(mel): n(TiF4) = 2:1, 1:1, 1:2, 1:3, 1:4 M ratios were studied. Crystallizations of the products from the saturated HF solutions yielded single crystals of [enH2]F2·2HF, previously known [enH2][TiF6] and three new perfluoridotitanate(IV) salts, i.e., [enH2][TiF6]·HF, [enH2]0.5[TiF5] and [melH2][TiF6]·HF. Their crystal structures were determined including the crystal structure of the low-temperature modification of [enH2][TiF6]. The [enH2]0.5[TiF5] phase represents the first example of a structurally characterized perfluoridotitanate(IV) compound with a double charged cation, where instead of the usual octahedral [TiF6]2− monomer, another kind of anion is present, i.e., polymeric chain-like ([TiF5]−)∞ anion. The reactions in en/TiF4/HF and mel/TiF4/aHF systems are not selective enough to enable syntheses of individual [enH2]2+ and [melH2]2+ perfluoridotitanates(IV) in large quantities.

Mono- and Binuclear Chloride and Bromide Complexes of Bi(III) with Double-Charged Cations Based on Pyridine: Syntheses and Crystal Structures

The reactions of solutions obtained by the reactions of Bi2O3 with 2 M HCl and HBr with the salts containing bis(pyridyl)alkane cations afford mono- and binuclear halide complexes (Py-(CH2)3-Py)3[Bi2Br9]2 (I), (H3O)(Py-(CH2)4-Py)[BiCl6] ⋅ 3H2O (II), and (H2Bpp)2[Bi2Br10] ⋅ 2H2O (Bpp is 1,3-bis(4-pyridyl)propane) (III). The structures of the synthesized compounds are determined by X-ray diffraction analysis (СIF files CCDC no. 1583338–1583340, respectively).

Evaporation Study of an Ionic Liquid with a Double-Charged Cation

The evaporation of a dicationic ionic liquid, 1,3-bis(3-methylimidazolium-1-yl)propane bis(trifluoromethanesulfonyl)amide ([C3(MIm)22+][Tf2N-]2), was studied by Knudsen effusion mass spectrometry. Its evaporation is accompanied by a partial thermal decomposition producing monocationic ionic liquids, 1,3-dimethylimidazolium and 1-(2-propenyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)amides, as volatile products. This decomposition does not affect the vaporization characteristics of [C3(MIm)22+][Tf2N-]2, which were established to be as follows. The vaporization enthalpy (550 K) is equal to (155.5 ± 3.2) kJ·mol-1; the saturated vapor pressure is described by the equation ln( p/Pa) = -(18699 ± 381)/( T/K) + (30.21 ± 0.82) in the range of 508-583 K. 1,3-Bis(3-methylimidazolium-1-yl)propane bis(trifluoromethanesulfonyl)amide is the first dicationic ionic liquid, the vaporization characteristics of which were determined with an acceptable accuracy.

Microwave assisted versus convention Cu2+ exchange in mordenite

Sodium mordenite was Cu2+-exchanged by conventional methods at ambient temperature (accepted as 20 °C) and with microwave radiation at 100 ± 1 °C. To increase the copper content, we repeat the exchange procedure several times. Both the degree of Cu2+ exchange and the environment of the Cu2+ ions depend on the method of exchange. Neither conventional, nor microwave methods do not destruct the topology of mordenite framework. XRD pattern of the mordenite persists, but slight elastic deformation and some dealumination of the surface layer occurs. For all the studied samples, all the copper ions are in Cu2+ state, neither Cu1+ nor Cu0 were detected. All the copper ions play the role of charge-balancing counter-cations. Their placement into the interior of zeolite causes the channel contraction due to electrostatic interactions of double charged cations with [AlO4]δ– units. The increase of copper content is accompanied by increasing of number of water molecules per unit cell. In fully hydrated samples the copper cations are effectively separated from the zeolite framework and are fully surrounded by a water ligand shell.

Removal of radionuclides, macrocomponent metal ions, and organic compounds from solutions by nanofiltration

Removal of Mg2+, Сa2+, Cu2+, Ni2+, Zn2+, Fe3+, and Pr3+ ions, tracer amounts of 137Cs, 85Sr, and 60Co radionuclides, and oxalate and ethylenediaminetetraacetate ions from solutions using a polymeric nanofiltration (NF) membrane produced by RM Nanotekh (Russia) was studied. The selectivity (S) of the NF membrane to multicharged metal cations is considerably higher than to single-charged cations. The NF membrane exhibits the highest selectivity (S = 94–97%) to triple-charged Fe3+ and Pr3+ ions and double-charged Cu2+ ions. The selectivity to double-charged Mg2+ and Zn2+ ions is somewhat lower (90–94% on the average). Among doublecharged cations, the NF membrane exhibits the lowest selectivity (80–88%) to Ni2+ and Cа2+ ions. The NF membrane shows high performance in retention of tracer amounts of Sr (S = 95%) and Co (S > 99%) radionuclides, and also of oxalate (S = 94.5%) and ethylenediaminetetraacetate (S = 97.5%) ions. Examples of using the nanofiltration method for removing 60Co from a model solution simulating NPP bottom residue and for removing transition metal impurities from a LiCl solution are presented.

Adequacy of the new formulation of the Periodic Law when fundamental variations occur in blocks and periods

In the Periodic Tables the transition from atoms to double-charged cations is accompanied by alterations in the composition of s and p blocks and reciprocal location of blocks, as well as by changes in the composition and length of periods. We have previously described the relationship between the atom properties and the total number of differentiating electrons. This paper demonstrates that, despite the above transition-related alterations, this relationship is also valid for the description of the properties of double-charged cations. This can be exemplified by the dependence of the ionization energy on the total number of p electrons in p block, d electrons in d block, and f electrons in f block. Furthermore, a single periodic equation is sufficient for the description of properties of all of double-charged cations from each block.

Removal of charged micropollutants from water by ion-exchange polymers – Effects of competing electrolytes

A wide variety of environmental compounds of concern, e.g. pharmaceuticals or illicit drugs, are acids or bases that may predominantly be present as charged species in drinking water sources. These charged micropollutants may prove difficult to remove by currently used water treatment steps (e.g. UV/H2O2, activated carbon (AC) or membranes). We studied the sorption affinity of some ionic organic compounds to both AC and different charged polymeric materials. Ion-exchange polymers may be effective as additional extraction phases in water treatment, because sorption of all charged compounds to oppositely charged polymers was stronger than to AC, especially for the double-charged cation metformin. Tested below 1% of the polymer ion-exchange capacity, the sorption affinity of charged micropollutants is nonlinear and depends on the composition of the aqueous medium. Whereas oppositely charged electrolytes do not impact sorption of organic ions, equally charged electrolytes do influence sorption indicating ion-exchange (IE) to be the main sorption mechanism. For the tested polymers, a tenfold increased salt concentration lowered the IE-sorption affinity by a factor two. Different electrolytes affect IE with organic ions in a similar way as inorganic ions on IE-resins, and no clear differences in this trend were observed between the sulphonated and the carboxylated cation-exchanger. Sorption of organic cations is five fold less in Ca2+ solutions compared to similar concentrations of Na+, while that of anionic compounds is three fold weaker in SO42- solutions compared to equal concentrations of Cl−.

Formation of Ionic Pairs between Single-Charged Anions and Double-Charged Cations with Separated Charge

The stability constants and extinction coefficients of ethyl viologen–iodide ionic pairs were calculated using the modified Kosover equation, and the effective cation charge was found by an analysis of the crystal structure of ethyl viologen diiodide.

Solitonic waves in polyene dications and principles of charge carrier localization in π-conjugated organic materials

The quantum-chemical investigations by ab initio method (restricted Hartree–Fock/6-31G**) have been performed for a series of unsubstituted, monosubstituted, and disubstituted neutral polyenes and their double charged cations. The waves of charge alternation (characterized by the difference in the electron densities at the nearest carbon atoms or Δq function) and bond length alternation (characterized by the lengths difference of the nearest carbon–carbon bonds or Δl function) are reported. Comparisons are made with the corresponding monocationic polymethine molecules. We found that ionization by two electrons results in formation of two solitonic waves of charge alternation, rather than superposition of two overlapping solitonic waves into one. These waves behave similar to two independent elastic particles, which do not penetrate into each other despite the special confinement by the length of chromophore π-system. In monosubstituted polyene dication, Δq and Δl functions contain two waves each; however, only one wave is mobile and sensitive to a change of the chemical nature of the terminal group, whereas the second wave remains practically unchanged. The introduction of one oxymethyl or phenyl terminal groups leads to a relatively small shift of the mobile wave from the center to a direction of the terminal group. The effect of the amino or tropilium terminal groups is much more pronounced and leads to a shift of the mobile wave to the end of the molecule. In disubstituted polyene dication, both solitonic waves become mobile and shift symmetrically to both ends. The general principles of the charge localization described in this study may be used in molecular design and fine-tuning of the charge transport properties in plastic photovoltaics and other organic semiconducting materials. © 2012 Wiley Periodicals, Inc.

Anodic synthesis of Np(VII) compounds from acetate solutions

A procedure was suggested for the synthesis of Np(VII) compounds by electrochemical oxidation in acetate solutions. The conditions for preparing compounds of type MNpO4·nH2O, where M is a single-charged cation of alkali metals, ammonium, silver, guanidinium, or tetraalkylammonium, and of Np(VII) compounds with double-charged cations of alkaline-earth metals, Cu, Cd, and Zn were studied in detail. The compounds were characterized by chemical analysis and by IR and electronic spectroscopy.

Substituted Phosphonium and Double Charged Cation Based Electrolytes for Nonaqueous Supercapacitors

not Available.

Computational Exploration of Mobile Ion Distributions around RNA Duplex

Atomically detailed distributions of ions around an A-form RNA are computed. Different mixtures of monovalent and divalent ions are considered explicitly. Studies of tightly bound and of diffusive (but bound) ions around 25 base pairs RNA are conducted in explicit solvent. Replica exchange simulations provide detailed equilibrium distributions with moderate computing resources (20 ns of simulation using 64 replicas). The simulations show distinct behavior of single and double charged cations. Binding of Mg(2+) ion includes tight binding to specific sites while Na(+) binds only diffusively. The tight binding of Mg(2+) is with a solvation shell while Na(+) can bind directly to RNA. Negative mobile ions can be found near the RNA but must be assisted by proximate and mobile cations. At distances larger than 16 A from the RNA center, a model of RNA as charged rod in a continuum of ionic solution provides quantitative description of the ion density (the same as in atomically detailed simulation). At shorter distances, the structure of RNA (and ions) has a significant impact on the pair correlation functions. Predicted binding sites of Mg(2+) at the RNA surface are in accord with structures from crystallography. Electric field relaxation is investigated. The relaxation due to solution rearrangements is completed in tens of picoseconds, while the contribution of RNA tumbling continues to a few nanoseconds.

A theoretical study of the neutral and the double-charged cation of cyclo[8]pyrrole and its interaction with inorganic anions

Abstract A theoretical study of the complexation of cyclo[8]pyrrole dication, 2, and the corresponding system in neutral form, 3, with six anionic molecules has been carried out up to the B3LYP/6–311++G(2d,2p) computational level. The effect of the water solvation has been taken into account by means of the PCM method. The gas phase results correspond to the very large interaction energies expected for the interaction of molecules of opposite charge. In all the complexes, the analysis of the electron density by means of the Atoms In Molecules (AIM) methodology shows the presence of eight intermolecular interactions between the individual molecules. The results, using the water solvent model, indicate that the 2:SO42− complex is more stable than the 2:NO3−, in agreement with experimental results.

An IR and Raman study of trigonal triple molybdates M 5 I M 0.5 II Hf1.5(MoO4)6 (MI = K, Tl; MII = Ca, Sr, Ba, Pb)

The vibration spectra of triple molybdates M 5 I M 0.5 II Hf1.5(MoO4)6 (MI = K, Tl; MII = Ca, Sr, Ba, Pb) were examined. The internal vibration frequencies of molybdate groups were assigned. The double-charged cations affect the symmetric stretching (v1), bending, and translation vibration frequencies in the Raman spectra. In the IR spectra, the triply degenerate stretching vibration of the MoO4 group (∼890–720 cm−1) is split, and the splitting increases with an increase in the radius of the double-charged cation.

Analysis of electrochemical impedance of polypyrrole|sulfate and polypyrrole|perchlorate films

PPy|SO 4 and PPy|ClO 4 films have been synthesized and investigated in K 2SO 4, ZnSO 4 and NaClO 4 aqueous solutions by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and electron probe microanalysis (EPMA) methods. On the basis of obtained data and calculated impedance parameters as the potential functions, the role of different processes (diffusion of ions, double-layer charging, adsorption and charge transfer) in oxidized, partially reduced and reduced PPy films is estimated. The lowest pseudocapacitance values (from n × 10 −6 to n × 10 −4 μF cm −2 for 1 μm film), independent of solution concentration, were established for PPy|SO 4 in ZnSO 4. This phenomenon is related with strongly aggravated film reduction process in the solution of double-charged cations. In the case of PPy|ClO 4 in NaClO 4 and PPy|SO 4 in K 2SO 4,where the mono-charged cations participate in redox process, the capacitance values are in the range from: n × 10 −3 to n × 10 −2 μF cm −2 and even somewhat higher for PPy|ClO 4 system at oxidized state. The calculated effective diffusion coefficients of ions D remain inside the range from n × 10 −12 to n × 10 −14 cm 2 s −1 for PPy|SO 4 in 0.1 M K 2SO 4 and PPy|ClO 4 in 0.1 M NaClO 4 aqueous solution. In the case of PPy|SO 4 film in ZnSO 4 solution the D values are essentially lower.

Molecular-dynamics simulations of alkaline-earth metal cations in water by atom-bond electronegativity equalization method fused into molecular mechanics

Intermolecular potential for alkaline-earth metal (Be(2+), Mg(2+), and Ca(2+)) cations in water has been derived using the atom-bond electronegativity equalization method fused into molecular mechanics (ABEEM/MM), and it is consistent with what was previously applied to the hydration study of the monovalent cations. Parameters for the effective interaction between a cation and a water molecule were determined, reproducing the ab initio results. The static, dynamic, and thermodynamic properties of Be(2+)(aq), Mg(2+)(aq), and Ca(2+)(aq) were studied using these potential parameters. Be(2+) requires a more complicated form of the potential function than Mg(2+) and Ca(2+) in order to obtain better fits. Strong influences of the twofold charged cations on the structures of the hydration shells and some other properties of aqueous ionic solutions are discussed and compared with the results of a previous study of monovalent cations in water. At the same time, comparative study of the hydration properties of each cation is also discussed. This work demonstrates that ABEEM/MM provides a useful tool in the exploration of the hydration of double-charged cations in water.

Behavior of Trace Amounts of Cd and Zn in Sorption and Coprecipitation in Tetrahydrofuran Solutions

Sorption of trace amounts of 109Cd and 65Zn on zeolites NaX and NaA in the presence of divalent lanthanides Ln2+ (Ln = Tm, Dy, Nd) from tetrahydrofuran (THF) solutions is studied. In contrast to 137Cs+ and similar to 85Sr2+, trace amounts of 109Cd and 65Zn are not practically sorbed on zeolites (about 99% of these radionuclides remains in the solution). The distribution coefficients Kd of 109Cd and 65Zn are ∼0.3 and ∼0.4 ml g−1, respectively. In THF solutions, Tm2+ is oxidized to Tm3+, and TmI3 ⋅ 3THF is precipitated. Study of cocrystallization of trace amounts of 109Cd and 65Zn and also of 85Sr with this precipitate from THF solutions containing Tm2+ revealed that, in contrast to 85Sr2+, 109Cd and 65Zn traces cocrystallize with the solid solvate phase. The cocrystallization coefficients D of 109Cd and 65Zn increase with increasing Tm3+/Tm2+ ratio in the solution. The mechanism suggested is that, in the presence of Tm2+, 109Cd2+ and 65Zn2+ are reduced to single-charged cations M+, which then rapidly react with the double-charged cations M2+ with the formation of dimers M 2 3+ (M = Cd, Zn).