Physicochemical and catalytic properties of systems based on CeO<Subscript>2</Subscript>

The effect of synthesis conditions, the nature of components, and the ratio between the components on the phase composition, the texture, and the redox and catalytic properties of the Ce-Zr-O, Ce-Zr-M₁-O (M₁ = Mn, Ni, Cu, Y, La, Pr, or Nd), N/Ce-Zr-O (N = Rh, Pd, or Pt), and Pd/Ce-Zr-M₂-O/Al₂O₃ (M₂ = Mg, Ca, Sr, Ba, Y, La, Pr, Nd, or Sm) was considered. A cubic solid solution with the fluorite structure was formed on the introduction of <50 mol % zirconium into CeO₂, and the stability of this solid solution depended on preparation procedure and treatment conditions. The presence of transition or rare earth elements in certain concentrations extended the range of compositions with the retained fluorite structure. The texture of the Ce-Zr-O system mainly depended on treatment temperature. An increase in this temperature resulted in a decrease in the specific surface area of the samples. The total pore volume varied over the range of 0.2–0.3 cm³/g and depended on the Ce/Zr ratio. The presence of transition or rare earth elements either increased the specific surface area of the system or made it more stable to thermal treatment. The introduction of the isovalent cation Zr⁴⁺ into CeO₂ increased the number of lattice defects both on the surface and in the bulk to increase the mobility of oxygen and facilitate its diffusion in the Ce_{1 − x} Zr _x O₂ lattice. The catalytic properties of the Ce-Zr-M₁-O or N/Ce-Zr-M₂-O systems were due to the presence of anion vacancies and the easy transitions Ce⁴⁺ ai Ce³⁺, M₁²ⁿ⁺ ai M₁ ⁿ⁺, and N ^δ+ → N ⁰ in the case of noble metals.     

Nanostructuring in the process of the formation of mixed-anion compounds: Rare-earth borogermanates, germanophosphates, and borotungstates

Specific features of the textures (the preferred orientation of the nanometer building blocks) in the structures of mixed-anion compounds—rare-earth borogermanates, germanophosphates, and borotungstates that arise from the acid-base interaction in the Ln₂O₃-B₂O₃-GeO₂, Ln₂O₃-GeO₂-P₂O₅, and Ln₂O₃-B₂O₃-WO₃ systems (Ln = La-Gd)—have been studied. Based on characteristic texture traits, the mixed-anion compounds of early rare-earth elements can be divided into three groups: (i) Ln₂O₃: E_xO_y > 1, (ii) Ln₂O₃: E_xO_y = 1, and (iii) Ln₂O₃: E_xO_y < 1. Because of the dominant structural effect of the basic oxide Ln₂O₃ in the compounds of the first group, the structures of Nd₁₄O₈(BO₃)₆(GeO₄)₂ and Pr₁₁O₁₀(GeO₄)(PO₄)₃ are composed of infinite [LnO_n] bands and layers and discrete groups [EO_m] located in the interband and interlayer spaces. The dominant structural effect of the acid oxides [E_xO_y] in the compounds of the third group leads to the appearance of ring textures composed of [LnO_n], as well as to the appearance of chains and networks composed of [EO_m], in the structures of Ln(BGeO₅) and Ln(BO₂)(WO₄). Original Russian Text ￠ G.A. Bandurkin, N.N. Chudinova, G.V. Lysanova, K.K. Palkina, E.V. Murashcva, V.A. Krut’ko, G.M. Balagina, 2006, published in Zhurnal Neorganicheskoi Khimii, 2006, Vol. 51, No. 2, pp. 334–347.     

Lösungsmitteleinfluß auf das Redoxverhalten des Hexakismethylisonitrilmangan (I) ions

The redox behaviour of hexakismethylisonitrilmanganese(I) [MnL ₆ ⁺] has been studied in acetic acid, dichloromethane, 1,2-dichloroethane, propylenecarbonate, butyrolactone, methanol, ethanol, nitromethane, acetonitrile, N-methyl-2-pyrrolidinone, dimethylformamide, dimethyl sulfoxide and water. The reversible diffusion-controlled oxidation MnL ₆ ⁺/MnL ₆ ²⁺ could be observed in all solvents studied, on both the dropping mercury electrode and the stationary platinum electrode. Employing tetrabutylammonium perchlorate as supporting electrolyte, the oxidation MnL ₆ ²⁺/MnL ₆ ³⁺ was observable only in acetic acid, nitromethane, 1,2-dichloroethane, dichloromethane, propylenecarbonate, butyrolactone and acetonitrile. In all other solvents oxidation of the solvent preceded the oxidation MnL ₆ ²⁺/MnL ₆ ³⁺. Poorly defined polarographic waves attributable to the one electron reduction of the MnL ₆ ⁺ were observed in butyrolactone, propylenecarbonate, acetonitrile, dimethylformamide, N-methyl-2-pyrrolidinone and dimethyl sulfoxide. All potential values were recorded versus bisbiphenylchromium(I)-iodide [BBCr(I)J], the problems of measuring against external aqueous reference electrodes are discussed. The redox potential of the process MnL ₆ ⁺/MnL ₆ ²⁺ was found to be a function of the donor properties of the solvents used; the effects of outer sphere coordination on the redox behaviour of this couple are discussed. No effect of the supporting electrolytes tetrabutylammonium perchlorate, tetraethylammonium nitrate and tetraethylammonium perchlorate on the redox behaviour of MnL ₆ ⁺ was found. The UV-spectrum of MnL ₆(PF₆)₂ has been recorded.

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Mit 3 Abbildungen     

Changes in the composition of volatile monoterpenes and sesquiterpenes of Pinus armandi, P. tabulaeformis, and P. bungeana in Northwest China

The volatile mono-and sesquiterpenes obtained from the needles and resin of Pinus armandi, P. tabulaeformis, and P. bungeana growing in the Qinling, Taibai, and Huanglong Mountain forest ecosystem were analyzed by means of GC-MS. Forty-eight constituents were identified, and α-pinene, β-pinene, 1R-α-pinene, β-caryophyllene, cadindiene, α-caryophyllene, D-limonene, and 1S-β-pinene were the major components of the mono-and sesquiterpenes in the needles and resin. The components of the volatile mono-and sesquiterpenes from the needles and resin at Qinling, Taibai, and Huanglong Mountains had remarkable differences in three pine species, whereas the monopertene content such as α-pinene, β-pinene, D-limonene, and camphene were mostly changed in the growing stage. The intraspecies variation in the different ecosystems can be attributed to the species’ geography and genetic variation, and even the adaptation of the pine species to different ecological environments. Moreover, monoterpenes and sesquiterpenes can be induced by the attack of bark beetles, of which the α-pinene, β-pinene, 1R-α-pinene, 1S-α-pinene, b-myrecene, and β-caryophyllene contents had positive relations with the attacking Dendroctonus armandi and D. valens. Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 430–433, September–October, 2006.     

Effect of a metal ion on intramolecular spin exchange in spin-labeled complexes

The characteristic features of intramolecular spin exchange in 14 complexes of Ag^I, Hg^II, Ni^II, Pd^II, Pt^II, Au^III, and Pt^IV with spin-labeled ligands were studied by ESR spectroscopy. The measured values of the exchange integral ‖J‖ and the differences between the enthalpies of the efficient conformations (ΔH) were compared with the electronic polarization (refraction)R _f of the Ni^II, Pd^II, and Pt^II ions and Klopman's rigidity parameters σ_K, which characterize the total polarazibility of the ions and the degree of covalence of the bond between the metal atom and the donor atom of the ligand, respectively. Delocalization of the electron spin density and the efficiency of spin exchange are determined by the relative contributions of the s, p, and d orbitals, which produce the overlap integral of wave functions, ‖J‖, and by the geometric features of the coordination polyhedron, which affect the mutual orientation of the N−O fragments. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2005–2009, October, 1999.     

Anionic high-temperature conduction in single crystals of nonstoichiometric phases R1 ? y M y F3 ? y (R = La-Lu, M = Ca, Sr, Ba) with the tysonite (LaF3) structure

Electrophysical properties of single crystals of nonstoichiometric phases R_{1 − y} M _y F_{3 − y} , where R = La-Lu, M = Ca, Sr, or Ba, with the tysonite (LaF₃) structure, which are present in a metastable state after being grown and cooled, are measured in the temperature interval extending from 300 to 1073 K. It is discovered that, during a sufficiently long high-temperature investigation, solid solutions R_{1 − y} Ca _y F_{3 − y} , where R = Tb, Dy, or Ho, undergo irreversible variations in the phase composition in the temperature region 723 to 823 K. This level of temperatures, which correspond to partial decomposition of phases R_{1 − y} Ca _y F_{3 − y} with the rare-earth elements of the end of the period, lies above the temperatures to which the fluoride solid electrolytes are usually heated when used in solid-state electrochemical devices. The temperature and concentration dependences of the phases’ electroconduction are explained in the framework of the vacancy mechanism of anionic transport. Original Russian Text ? N.I. Sorokin, B.P. Sobolev, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 4, pp. 420–431. The paper is dedicated to the memory of Prof. M.W. Breiter, formerly of the Vienna Technical University, Austria.     

非晶态镍硼酸盐结构的EXAFS研究

由摩尔比分别为1:2和1:8的NiCl₂·6H₂O和Na₂B₄O₇·10H₂O作为反应物, 合成两种非晶态镍硼酸盐, 同时通过水热法合成β-Ni(OH)₂. 化学分析和热重-微商热重法(TG-DTG)分析结果确定两种非晶态镍硼酸盐的分子组成分别为NiO·0.8B₂O₃·4.5H₂O和NiO·B₂O₃·3H₂O. 激光拉曼(Raman)实验结果表明镍硼酸盐样品中主要存在的硼氧阴离子为B₃O₃(OH)₅^2-和B₂O(OH)₆^2-. 同步辐射扩展X射线吸收精细结构(EXAFS)方法对样品进行结构解析, 通过数据拟合给出样品中Ni 原子周围近邻配位原子种类、配位数以及原子间距离. 用不同晶体结构作为标准对两种非晶态镍硼酸盐进行拟合的结果表明, 样品中Ni 原子周围局域结构与Ni₃B₂O₆晶体(ICSD No.31387)中的吻合较好. Ni 原子周围配位原子为O、B和Ni, 对于NiO·0.8B₂O₃·4.5H₂O, 配位数分别为5.7、3.8和3.8, 配位距离分别为0.208、0.263 和0.311 nm; 对于NiO·B₂O₃·3H₂O, 配位数分别为6.0、4.0 和4.0, 配位距离分别为0.207、0.262和0.310 nm.     

Studies with inorganic precipitate membranes. III. Consideration of energetics of electrolyte permeation through membranes

The permeability of various electrolytes through parchment-supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium has been measured at 10, 15, 20, 25, and 30°C. The order of permeability at a given temperature was Cl^- > NO₃^- > CNS^- > CH₃COO^- > SO₄^2- for both monovalent and divalent cations. For any given anion, the cations followed the sequence NH₄⁺ > Li⁺ > Ba²⁺ > Ca²⁺ > Mg²⁺ > Al³⁺. This sequence has been correlated with the size of the hydrated ion. Further, the data have been considered from the standpoint of the theory of rate processes and the values for the entropy of activation (ΔS′) have been derived assuming an equilibrium distance of 3 Å in the membrane. The values of ΔS′ were all negative and decreased with increasing valence of the ions. This was interpreted to mean electrolyte permeation with partial immobilization in the membrane.     

A pilot study for the production of a certified reference material for trace elements in honey

In the context of the general mandate of the European Union Community Reference Laboratory (CRL) for residues in living animals and their products established at the Istituto Superiore di Sanità, a pilot study was undertaken to assess the possibility of producing a new certified reference material (CRM) for trace elements in a matrix of honey. The elements considered were As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sn, V and Zn. Their determination was performed by inductively coupled plasma (ICP)-based techniques. Data obtained with different ICP techniques were generally in good agreement. In light of these results, the next step was the effective production of a candidate CRM in a honey matrix. In the preliminary phase, two different types of honey, i.e., Eucalyptus (solid and sticky) and Robinia (viscous and sticky), were pretreated at the Institute for Reference Materials and Measurements, Joint Research Centre, European Commission (EC-JRC-IRMM) in order to produce the materials candidate for the certification process. Approximately 600 ampoules were thus produced for the Robinia honey and 450 ampoules for the Eucalyptus honey, each ampoule containing 5 g of an aqueous solution of honey (with 20% and 30% high purity water, respectively) and sealed under inert gas (Ar). A ring test to determine the levels of the chemical elements and a long-term study to evaluate the stability of the samples is in progress. Tentative figures for the analytes of interest are (in ng g⁻¹): Robinia, As, 1.28±0.09; Cd, 0.59±0.08; Cr, 2.36±0.21; Cu, 57.6±3.2; Fe, 209±9; Mn, 90.8±3; Ni, 18.1±0.6; Pb, 23±1.5; Sn, 8.10±0.35; V, 1.19±0.37; and Zn, 178±4; Eucalyptus, As, 3.18±0.21; Cd, 0.70±0.08; Cr, 2.73±0.22; Cu, 141±6; Fe, 926±16; Mn, 1905±81; Ni, 7.77±0.4; Pb, 138±4; Sn, 7.97±0.16; V, 3.47±0.15; and Zn, 405±9.     

Binuclear Pd(II) complexes with chiral ethylenediaminodioxime (H2L) and bis-α-thiooxime (H2L1), the derivative of monoterpenoid(+)-3-carene. Crystal structures of [Pd2(H2L)Cl4] and [Pd2(H2L1)Cl4] · 3CDCl3

Diamagnetic Pd(II) complexes with the chiral ethylenediaminodioxime (H 2 L) and bis-α-thiooxime (H₂L¹), the derivatives of monoterpenoid (+)-3-carene, of the composition Pd₂(H₂L)Cl₄(I), Pd₂(H₂L¹)Cl₄ (II), and the solvate Pd₂(H₂L¹)Cl₄·3DCl₃ (III) were synthesized. The crystal structures of complex I and solvate III were determined from X-ray diffraction data. The structures consist of acentric binuclear molecules with the coordination cores PdN₂Cl₂ (in I) and PdNSCl₂ (in III) in the form of the distorted squares. In complex I, each Pd atom coordinates two N atoms of the tetradentate bridge-cyclic ligand H₂L and two Cl atoms; in compound III, one N and one S atom of the tetradentate bridge-cyclic ligand H₂L¹, and 2 Cl atoms. The CDCl₃ molecules in compound III lie in the cavities formed by the molecules of complex II. In both structures, the PdCl₂ fragments are in the trans-positions. The ¹H NMR spectra indicate that the structures of complexes I, II in solutions are similar to the structures of compounds I, III in the solid state. Original Russian Text ? T.E. Kokina, L.I. Myachina, L.A. Glinskaya, A.V. Tkachev, R.F. Klevtsova, L.A. Sheludyakova, S.N. Bizyaev, A.M. Agafontsev, N.B. Gorshkov, S.V. Larionov, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 2, pp. 120–132.     

Quantum Chemical Calculation of Conformations and Rotation Barriers of Functional Groups in Arylsulfonyl Halides

The semiempirical PM3 method is used to calculate the potential functions of internal rotation of the functional groups –SO₂Cl, –NO₂, –CH₃, –OCH₃, and –NH₂ of benzenesulfonyl halide molecules (PhSO₂Hal, Hal = F, Cl, Br, I) and twelve substituted derivatives of benzenesulfonyl chloride. Molecular conformations have been determined and internal rotation barriers of the functional groups have been calculated. For meta- and para-substituted benzenesulfonyl chlorides, the projection of the S–Hal bond is perpendicular to the plane of the benzene ring. The rotation barriers of the –SO₂Hal group of benzenesulfonyl halides increase in the series Hal = F, Cl, Br, I. The rotation barriers of the –SO₂Cl group of benzenesulfonyl chloride with meta- and para-substituents slightly increase with the electron-donor properties of the substituent. The rotation barriers of the functional groups of ortho-substituted benzenesulfonyl chlorides are 3 or 4 times as high as those of the meta- and para-isomers. For para-substituted benzenesulfonyl chlorides, the rotation barriers of the functional groups increase in the order –CH₃, –NO₂, –SO₂Cl, –OCH₃, –NH₂.     

L?sungsmitteleinflu? auf das Redoxverhalten des Hexakismethylisonitrilmangan (I) ions

The redox behaviour of hexakismethylisonitrilmanganese(I) [MnL ₆ ⁺] has been studied in acetic acid, dichloromethane, 1,2-dichloroethane, propylenecarbonate, butyrolactone, methanol, ethanol, nitromethane, acetonitrile, N-methyl-2-pyrrolidinone, dimethylformamide, dimethyl sulfoxide and water. The reversible diffusion-controlled oxidation MnL ₆ ⁺/MnL ₆ ²⁺ could be observed in all solvents studied, on both the dropping mercury electrode and the stationary platinum electrode. Employing tetrabutylammonium perchlorate as supporting electrolyte, the oxidation MnL ₆ ²⁺/MnL ₆ ³⁺ was observable only in acetic acid, nitromethane, 1,2-dichloroethane, dichloromethane, propylenecarbonate, butyrolactone and acetonitrile. In all other solvents oxidation of the solvent preceded the oxidation MnL ₆ ²⁺/MnL ₆ ³⁺. Poorly defined polarographic waves attributable to the one electron reduction of the MnL ₆ ⁺ were observed in butyrolactone, propylenecarbonate, acetonitrile, dimethylformamide, N-methyl-2-pyrrolidinone and dimethyl sulfoxide. All potential values were recorded versus bisbiphenylchromium(I)-iodide [BBCr(I)J], the problems of measuring against external aqueous reference electrodes are discussed. The redox potential of the process MnL ₆ ⁺/MnL ₆ ²⁺ was found to be a function of the donor properties of the solvents used; the effects of outer sphere coordination on the redox behaviour of this couple are discussed. No effect of the supporting electrolytes tetrabutylammonium perchlorate, tetraethylammonium nitrate and tetraethylammonium perchlorate on the redox behaviour of MnL ₆ ⁺ was found. The UV-spectrum of MnL ₆(PF₆)₂ has been recorded.     

Solubility of HFCs in lower alcohols

This work is inserted in a research program that consists mainly in the experimental and theoretical study of the effect of association between solute and solvent molecules in the solubility of gases in liquids.The solubilities of hydrofluorocarbons, HFCs, (CH₃F, CH₂F₂, CHF₃) in lower alcohols (methanol, ethanol, 1-propanol, 1-butanol) have been determined in the temperature range [284, 313] K, at atmospheric pressure. An automated apparatus based on Ben-Naim-Baer and Tominaga et al. designs was used, which provides an accuracy of 0.6%. A precision of the same order of magnitude was achieved.To represent the temperature dependence of the mole fraction solubilities, the equation R ln x₂ = A + B/T + C ln T was used. From this equation, the experimental Gibbs energies, enthalpies and entropies of solution at 298 K and 1 atm partial pressure of the gas, were calculated.A semiempirical correlation has been developed between the solubilities of HFCs in alcohols at 298 K and the Gutmann acceptor number of solvents, AN, and reduced dipole moment of the gases, μ*.     

Radical addition reactions: factors determining the transition-state geometry

Interatomic distances in the reaction centers of the addition reactions of (i) H^· to the C=C, C=O, N≡C, and C≡C bonds, (ii) ^·CH₃ radical to the C=C, C=O, and C≡C bonds, and (iii) alkyl, aminyl, and alkoxyl radicals to olefin C=C bonds were determined using a new semiempirical method for calculating transition-state geometries of radical reactions. For all reactions of the type X^· + Y=Z → X— Y—Z^· the r ^# _X...Y distance in the transition state is a linear function of the enthalpy of reaction. Parameters of this dependence were determined for seventeen classes of radical addition reactions. The bond elongation, Δr ^# _X...Y, in the transition state decreases as the triplet repulsion, electronegativity difference between the atoms X and Y in the reaction center, and the force constant of the attacked multiple bond increase. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 894–902, April, 2005.     

Improvement of HS-SPME for analysis of volatile organic compounds (VOC) in water samples by simultaneous direct fiber cooling and freezing of analyte solution

The sensitivity and precision of headspace solid-phase micro extraction (HS-SPME) at an analyte solution temperature (T _as) of +35 °C and a fiber temperature (T _fiber) of +5 °C were compared with those for HS-SPME at T _as and T _fiber of −20 °C for analysis of the volatile organic compounds benzene, 1,1,1-trichloroethane, trichloroethylene, toluene, o-xylene, ethylbenzene, m/p-xylene, and tetrachloroethylene in water samples. The effect of simultaneous fiber cooling and analyte solution freezing during extraction was studied. The compounds are of different hydrophobicity, with octanol/water partition coefficients (Kow) ranging from 126 and 2511. During a first set of experiments the polydimethylsiloxane (PDMS) SPME fiber was cooled to +5 °C with simultaneous heating of the aqueous analyte solution to +35 °C. During a second set of experiments, both SPME fiber holder and samples were placed in a deep freezer maintained at −20 °C for a total extraction time of 30 min. After approximately 2 min the analyte solution in the vial began to freeze from the side inwards and from the bottom upwards. After approximately 30 min the solution was completely frozen. Analysis of VOC was performed by coupling HS-SPME to gas chromatography-mass spectrometry (GC-MS). In general, i.e. except for tetrachloroethylene, the sensitivity of HS-SPME increased with increasing compound hydrophobicity at both analyte solution and fiber temperatures. At T _as of +35 °C and T _fiber of +5 °C detection limits of HS-SPME were 0.5 μg L⁻¹ for benzene, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene, 0.125 μg L⁻¹ for toluene, and 0.025 μg L⁻¹ for ethylbenzene, m/p-xylene, and o-xylene. In the experiments with T _as and T _fiber of −20 °C, detection limits were reduced for compounds of low hydrophobicity (Kow<501), for example benzene, toluene, 1,1,1-trichloroethane, and trichloroethylene. In the concentration range 0.5–62.5 μg L⁻¹, the sensitivity of HS-SPME was enhanced by a factor of approximately two for all compounds by performing the extraction at −20 °C. A possible explanation is that freezing of the water sample results in higher concentration of the target compounds in the residual liquid phase and gas phase (freezing-out), combined with enhanced adsorption of the compounds by the cooled fiber. The precision of HS-SPME, expressed as the relative standard deviation and the linearity of the regression lines, is increased for more hydrophobic compounds (Kow>501) by simultaneous direct fiber cooling and freezing of analyte solution. Background contamination during analysis is reduced significantly by avoiding the use of organic solvents.     

Substituent effects on the redox potentials of dihydroxybenzenes: theoretical and experimental study

The redox reactions of p-hydroquinone and pyrocatechol undergo a two-proton-two-electron process in aqueous solution. We calculated their redox potentials at the B3LYP/6-311+G(d,p) level, and verified the values by employing cyclic voltammetry experiments. Then we selected seven substituent groups (–F, –Cl, –OH, –COOH, –CN, –NH₂, and –NO₂ groups) to systematically investigate the substituent effect, including the sort, position, and number of the substituent, on the redox potentials of p-hydroquinone and pyrocatechol. The calculated results show that –NH₂ and –OH groups can decrease the redox potentials, while –F, –Cl, –COOH, –CN, and –NO₂ groups increase the potential values of p-hydroquinone and pyrocatechol. The calculations can accurately predict the substituent effects on the redox potentials of pyrocatechol and p-hydroquinone. We would expect that the accurate calculation results for the model systems could be applied in the prediction of electrode potentials of other molecules.     

Surface and internal modification of composite ion exchange membranes for removal of molybdate,phosphate, and nitrate from polluted groundwater

Al₂O₃/chitosan-multiwall carbon nanotubes (MWCNTs) were created to increase the exchange capacity of polyvinylidene fluoride (PVDF) ion-exchange membranes. The composite membranes were made by mixing Al₂O₃ nanoparticles into the PVDF cast solution, then applying a thin coating of chitosan functionalized carbon nano tubes (Cs-MWCNTs) to the PVDF membrane surface. The structure and characteristics of the hybrid membranes were described using XRD, SEM, IR, and TG-DTA. The Al₂O₃-PVDF/Cs-MWCNTs membrane beat the other Al₂O₃-PVDF/Cs, Al₂O₃-PVDF, and PVDF membranes in terms of molybdate, phosphate, and nitrate adsorption. The removal efficiency, pH solution, adsorption capacity, and desorption process of molybdate, phosphate, and nitrate anions by Al₂O₃-PVDF and PVDF membranes were investigated. The removal effectiveness of molybdate, phosphate, and nitrate, according to the testing findings, was 94.3, 65.6, and 85.78 %, respectively. The adsorption of MoO₄^2?, PO₄^3?, and NO₃^? increased as the pH increased initially until the best adsorption was achieved, and then decreased significantly as the pH increased further. The total adsorption capabilities of MoO₄^2?, PO₄^3?, and NO₃^?for the Al₂O₃-PVDF/Cs-MWCNTs membrane were 65.50, 61.22, and 59.77 mg/g, respectively. Using regeneration and reuse experiments for the simultaneous adsorption of molybdate, phosphate, and nitrate during three consecutive cycles, the adsorption/desorption of Al₂O₃-PVDF/Cs-MWCNTs was assessed. Al₂O₃-PVDF/Cs-MWCNTs offer a lot of promise when it comes to eliminating MoO₄^2?, PO₄^3?, and NO₃^?from actual wastewater samples.     

Raman spectra and structural features of ClOF2 + cation in a solution of anhydrous HF

The Raman spectra of ClOF₂ ⁺ cation in solutions of anhydrous HF were studied. In the ClOF₂ ⁺HF₂ ⁻ and ClOF₂ ⁺BF₄ ⁻−HF systems, this cation exists as a pyramidal structure (C _s symmetry), while in the ClOF₂ ⁺AuF₆ ⁻−HF system, it exists as a planar structure (C _2v symmetry). Based on nonempirical calculations by the Hartree-Fock-Roothaan method, an explanation for the dependence of the structure of the ClOF₂ ⁺ cation on the nature of the anion was proposed. For the Cl−O bond vibrations, the correlation functions of vibrational and rotational relaxations were calculated, and the characteristic times of these processes were determined. The main contribution to the formation of the band contours corresponding to the above-mentioned modes is made by the vibrational dephasing. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 432–437, March, 1998.     

A proton NMR study on aggregation of cationic surfactants in water: effects of the structure of the headgroup

 ¹H NMR chemical shifts of solutions of the following cationic surfactants in D₂O were determined as a function of their concentrations: cetyltrimethylammonium chloride, CTACl, a 1 : 1 molar mixture of CTACl and toluene, cetylpyridinium chloride, CPyCl, cetyldimethylphenylam-monium chloride, CDPhACl, cetyldimethylbenzylammonium chloride, CDBzACl, cetyldimethyl-2-phenylethylammonium chloride, CDPhEtACl, and cetyldimethyl-3-phenylpropylammonium chloride, CDPhPrACl. Plots of observed chemical shifts versus [surfactant] are sigmoidal, and were fitted to a model based on the mass-action law. Satisfactory fitting was obtained for the discrete protons of all surfactants. From these fits, we calculated the equilibrium constant for micelle formation, K, the critical micelle concentration, CMC and the chemical shifts of the monomer, δ_mon and the micelle δ_mic. ¹H NMR-based CMC values are in excellent agreement with those which we determined by surface tension measurements of surfactant solutions in H₂O, allowing for the difference in structure between D₂O and H₂O. Values of K increase as a function of increasing the size of the hydrophilic group, but the free energy of transfer per CH₂ group of the phenylalkyl moiety from bulk water to the micellar interface is approximately constant, 1.9±0.1 kJ mol^-1. Values of (δ_mic–δ_mon) for the surfactant groups at the interface, e.g., CH₃–(CH₂)₁₅–N+(CH₃)₂ and within the micellar core, e.g., CH₃–(CH₂)₁₅–N⁺ were used to probe the (average) conformation of the phenyl group in the interfacial region. The picture that emerges is that the aromatic ring is perpendicular to the interface in CDPhACl and is more or less parallel to it in CDBzACl, CDPhEtACl, and CDPhPrACl. Received: 23 February 1996 Accepted: 29 August 1996     

Oxygen nonstoichiometry and the thermodynamic and structural properties of double perovskites PrBaCo2 ? xCuxO5 + δ

The special features of the structure, electrophysical properties, and oxygen nonstoichiometry of new double perovskites PrBaCo_{2 − x} Cu _x O_{5 + δ} were studied. Within the homogeneity region with respect to copper 0 < x ≤ 1, solid solution samples had an orthorhombic structure (space group Pmmm) with the parameters a _p × 2a _p × 2a _p , where a _p ≈ 3.8 ?. The oxygen nonstoichiometry of PrBaCo_{2 − x} Cu _x O_{5 + δ} changes as the copper content increases approximately as δ ≈ 0.85 − x/2. The content of oxygen was measured by coulometric titration over wide temperature and oxygen pressure ranges. The partial thermodynamic functions of labile oxygen were calculated and the limits of the thermodynamic stability of the solid solution were established. Original Russian Text ? A.Yu. Suntsov, I.A. Leonidov, A.A. Markov, M.V. Patrakeev, Ya.N. Blinovskov, V.L. Kozhevnikov, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 954–960.