Equilibrium oxygen fugacity for the synthesis of zinc ferrite solid solutions

Thermodynamic information is utilized to study the width of the zinc ferritemagnetite phase field, and to establish the oxygen fugacity in equilibrium with this solid solution. Information is provided for the specification of the phase boundaries and for the particular oxygen fugacity that corresponds to the 4/3 oxygen/ cation ratio in the strictly stoichiometric solid solution.     

Calculation of cohesive and mixing energies and equilibrium parameters of solid alkaline earth fluoride solutions

Institute of Chemistry and Chemical Metallurgical Processes, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 2, pp. 131–135, March–April, 1994.     

Enthalpies of mixing of some nitriles aqueous solutions with dodecylsurfactants micellar solutions

The enthalpies of mixing of some n-nitriles (from acetonitrile to valeronitrile) aqueous solutions with dodecyltzimethylammonium bromide, sodium dodecylsulfate and dodecyltzimethylammonium oxide micellar solutions were determined. The measurements were performed by systematically changing the surfactant concentration at a given solute concentration. The experimental enthalpies were rationalized in terms of the standard enthalpy of transfer of solute from the aqueous to the micellar phase and of the distribution constant between the two phase. Information on the effect of the nature of the surfactant on the standard thermodynamic quantities of transfer(G _t ^o , H _t ^o , TS _t ^o ) is reported. The present data are compared to those previously reported for primary alcohols and the solubilizing properties shown by the different types of micelles are discussed.     

The Cp*Si+ cation as a stoichiometric source of silicon

The Cp*Si(+) cation acts as a stoichiometric source of silicon in the reaction with the disilenide Tip(2)Si=Si(Tip)Li (Tip = 2,4,6-(i)Pr(3)C(6)H(2)) affording known neutral unsaturated silicon clusters. It thereby provides a conceptually different approach to this novel class of compounds. The proposed mechanism involves a Cp*-substituted cyclotrisilene in which Cp*(-) acts as a leaving group upon single electron reduction or in a nucleophilic substitution step.     

Assessment of a modified and optimised method for determining chemical oxygen demand of solid substrates and solutions with high suspended solid content

A modified approach to determine the chemical oxygen demand (COD) of solid substrates based on the DIN 38414-S9 standard method is proposed. The adapted procedure is assessed and compared with standard methods widely used for water and wastewater such as the American Public Health Association-American Water Works Association-Water Pollution Control Federation (APHA-AWWA-WPCF) standard methods 5220 B-open reflux (SM-OR) and 5220 D-closed reflux colorimetric (SM-CR). Solutions with high suspended concentration of solids, as well as digestates from an anaerobic reactor, were used during the comparative test. For solid substrates, the COD recovery was about 100% when the proposed method was used. For solutions with solid content higher than 20 g TS L(-1), the recovery was only completed when the proposed method was used, showing that the methods traditionally employed are not very appropriate for samples with the described characteristics. For instance, percentages of COD recovery in the ranges of 77.3-87.1% and 89.4-94.1% were achieved when the SM-OR and SM-CR methods were used, respectively.     

Electrochemistry of Na2SO4 (I) solid solutions with aliovalent cation substitution

Conductivity data of several Na₂SO₄(I) solid solutions with cation substitutions are presented. The substitution of sodium by bi- and trivalent atoms generates cation vacancy concentrations up to 30% in the structure of Na₂SO₄(I) thus creating high mobility of Na⁺. Electrochemical measurements showed that Na⁺ ion conductivity prevails and that the electronic partial conductivity is negligible. Complex impedance diagrams were used to determine the influence of the vacancy concentration on the ionic conductivity of Na₂SO₄(I) solid solutions. It was found that the conductivity is strongly correlated to the vacancy concentrations, whereas the size and the charge of the substituting ions show no effect within the accuracy of the measurements. The activation energy as function of the vacancy concentration exhibits a minimum of 0.7 eV at a vacancy concentration of 1%. The maximum of conductivity was found to be 1.5 × 10^?2 Ω^?1 cm^?1 at 500°C with 7% vacancies.     

阳离子替换磷灰石固溶体的比晶体化学

利用XTD,IR对不同阳离子替换的磷灰石(Ap)固溶体进行了比较晶体化学研究,结果表明：端元二价阳离子对Ap晶格常数(a0,c0)影响是线性的,符合Vegard规律,有较好的x-V习性,可作为阳离子半径测定的"结构尺";对于Cl-PO4体系的Ap,端元离子半径须在0.095～0.134nm之间才能形成空间群为P63/m的Ap结构;异价固溶体可以研究Ca(1)、Ca(2)位置的结晶化学差异,Ca(2)位在晶核形成期生成且决定了晶胞的框架,而Ca(1)位主要影响Co;随阳离子半径增加,[PO4]四面体的ν4,ν3,ν1红外振动峰向低频方向红移;Ap结构中发现"铅异常",形成原因是铅在Ca(2)位的较大电负性。     

Low reactivity of non-bridging oxygen defects on stoichiometric silica surfaces

Using ab initio molecular dynamics simulations we demonstrate that surfaces of stoichiometric silica exhibiting non-bridging oxygen defects can be surprisingly resistant to attack by water.     

ESR study of the interaction of oxygen and propene with solid CoO?MgO solutions under pulse conditions

An ESR study has shown that under the action of oxygen pulses, radical ions O ₂ ^– with g_I=2.0085 and g_II=2.087 are generated at room temperature on the surface of 1% CoO–MgO. Heating of the sample to 150 °C in the spectrometer results in complete disappearance of the O ₂ ^– signal from the ESR spectra. The variation of the O ₂ ^– signal intensity with time due to the interaction between propene and oxygen adsorbed on the sample surface, has been measured.

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, 1% CoO–MgO - O ₂ ^– g_I=2.0085 g_II=2.087. 150 °C - O ₂ ^– . O ₂ ^– .

     

Impact of cation concentrations on fouling in membrane bioreactors

In this study, the interaction of calcium, magnesium, and sodium as well as impact of monovalent to divalent (M/D) cation ratio and magnesium to calcium (Mg/Ca) ratio in the feed wastewater on membrane fouling in submerged membrane bioreactor (MBR) was investigated. The protein and carbohydrate content of soluble microbial products (SMP) and extracellular polymeric substances (EPS) as well as their relative hydrophobicities was examined. The mixed liquor and its components (soluble and suspended solids) were analyzed for their filtration resistance, as reflected by the modified fouling index (MFI). Based on the findings of this study, the optimum conditions with respect to fouling rate were calcium and sodium concentrations of 36 and 140 mg/L, respectively, M/D of 1:1 and Mg/Ca of 5:1, with all parameters on an equivalent basis. High sodium concentration at high M/D ratio was found to decrease the floc size and increase the fouling rate. At the low M/D ratio of 1:1, introduction of magnesium was beneficial in reducing the fouling rate by increasing the EPS concentration and floc size and decreasing the SMP concentration and relative hydrophobicity in the supernatant. The fouling rate was found to be statistically correlated with the concentrations of Ca, Mg, and Na, with both Ca and Na adversely impacting fouling and Mg alleviating fouling propensity.     

Potassium-cationic conductivity in the mixed ferrite-aluminate solid electrolytes with five-charged cation additives

New potassium-conducting solid electrolytes in the mixed ferrite-aluminate K_1.80(Fe_{1 ? x} Al _x )_1.90V_0.10O₄ and K_1.85(Fe_{1 ? x} Al _x )_1.925P_0.075O₄ are synthesized and studied. In the first system, the conductivity only slightly depends on the composition; therefore, the composition of solid electrolyte can be optimized with respect to the conductivity-stability characteristics. In the second system, extremes and considerable negative deviations from the additivity are observed in the conductivity isotherms. Possible reasons for this phenomenon are discussed.     

Biomass torrefaction under different oxygen concentrations and its effect on the composition of the solid by-product

Torrefaction is a thermal treatment used to improve the properties of biomass in relation to thermo-chemical processing techniques for energy generation. It is a thermo-chemical treatment method primarily characterized by an operating temperature within the 200–300 °C range. It is carried out under conditions of atmospheric pressure and in the presence of a minimum amount of oxygen in order to avoid spontaneous combustion. The aim of this study was to evaluate the combined effect of the temperature (240 and 280 °C) and oxygen concentration (2, 6, 10 and 21%) on the physical and chemical properties of large particles of Eucalyptus grandis. A statistical analysis was carried out. The different oxygen concentrations did not significantly affect the composition of the solid by-product for low temperatures. At 280 °C, the high oxygen concentration affected some of the properties studied.     

Fluorescence spectrum of the benzene radical cation in solid argon

Argon/benzene samples were condensed at 12 K with continuous argon resonance radiation. Laser excitation at 421 nm produced a weak emission with structure at 19770, 19140 and 18290 cm^?1, assigned to the ²A_2u → ²E_1g emission of C₆H₆⁺. Observation of 630 and 1480 cm^?1 intervals for the vibrations v₁₈ (e_2g) and v₆ (e_2g), respectively, supports this assignment.     

Solubility of oxygen in glucose solutions

A knowledge of the solubility of oxygen in glucose-containing solutions is essential for the determination of the kinetics of the glucose oxidase-catalysed glucose oxidation. The enzyme glucose oxidase was used in a new glucose sensor. Combination of data for the dynamic viscosity and density from the literature and data from measurements with a rotating disc electrode (RDE) for hydrogen peroxide and hydroquinone showed that the factor ηD (η = dynamic viscosity; D = diffusion coefficient) remains constant in solutions with a glucose concentration ranging from 0 to 1 M. Assuming that this is also valid for oxygen, the diffusion coefficient of oxygen in glucose solutions was calculated and the solubility of oxygen was determined with RDE measurements. At both 25 and 37°C the relationship between the solubility of oxygen and the glucose concentration is a second-degree polynomial.     

Heterogeneous reactions of singlet molecular oxygen with solid polymers

The effect of gas-phase singlet molecular oxygen (¹ΔO₂) upon several solid polymers was investigated by using electron paramagnetic resonance, infrared spectroscopy, and chemical detection techniques. The study was performed by use of ¹ΔO₂ produced by microwave discharge. The application of this method to polymer studies was closely examined. The saturated-chain polymers polystyrene, polyurethane, and polyethylene were found to be inert within the experimental conditions to reaction with ¹ΔO₂, while the unsaturated polymers cis-polybutadiene, trans-polybutadiene, and trans-polyisoprene were found to react quite readily in an apparently surface or near-surface limited reaction to produce hydroperoxide and/or peroxide groups. The introduction by homogeneous mixing of some known metal-chelate ¹ΔO₂ quenchers into the polymer trans-polyisoprene appeared to significantly decrease the rate of oxidation observed.     

Ordering of nonstoichiometric solid solutions

Summary Experimental confirmation of the results of the present work is provided by the existence of the ordered phases Fe₇Al [23], Cu₅Pd₃ [24], Pt₇Cu [25] (see Fig. 1.2). The unit cells of Fe₇Al and Cu₅Pd₃ are not given in [23, 24], but in our view they can be deseribed by Figs. 1.4 and 3.3 respectively.Civil Engineering Institute, Tomsk. Translated from Zhurnal Strukturnci Khimii, Vol. 18, No. 1, pp. 80–88, Junuary–February, 1977.