The structural features and a series of properties of (x = 0-0.3) aluminates have been studied. The limits of stability of the cubic perovskite structure under the isomorphic substitution La3+ -> Ca2+ have been determined by X-ray diffraction analysis. The dependence of the state of oxygen on the surface of the obtained samples on their composition has been studied by X-ray photoelectron spectroscopy (XPS). Based on a comparison of the XPS data with the catalytic properties of samples in the oxidation of C1-C3 alkanes, it was concluded that point defects (oxygen radical ions O- and surface OH- groups) are involved in the activation of reactant molecules, hydrocarbons and oxygen.
The effect of modification of SBA-15 with Mg2+, Ca2+, and Zn2+ ions on the sorption of quercetin under static and dynamic conditions is considered. An IR spectroscopy study confirmed that the ordered structure is preserved as a result of modification of the SBA-15 analog by impregnation and revealed a change in hydration of silicas modified with metal ions. This study reports on the feasibility of employing Me2+-SBA-15 for the solid-phase extraction of flavonoids. The sorption properties of Me2+-SBA-15 sorbents were studied by the breakthrough curve method. During the sorption of quercetin under dynamic conditions for the modified samples, the significant increase in the capacity of silicas is accompanied by an increase in the efficiency of the chromatographic system. In view of the specific changes in the sorption properties, the ordered analogs of SBA-15 modified with calcium, magnesium, and zinc ions can be used at the sample preparation stage for the extraction, purification, and concentration of flavonoids for their subsequent spectrophotometric or chromatographic determination. The nanostructured silicas can also be used in biomedical applications involving the sorption of hydrophobic quercetin by nanostructured solid-phase supports.
The known correlation dependencies B0 = B0(β), B0 = B0(ω), and B0 = B0(β, ω) relating the critical amplitude of the liquid-gas coexistence curve B0 with the critical index β of the saturation line and with the acentric factor ω are analyzed. Based on the dependence B0 = B0(β, ω), it is shown that correlations for B0 that depend only on one individual parameter of the substance ω do not allow taking into account the behavioral features of B0 for substances such as, for example, water and heptane. Therefore, to more fully take into account the behavioral features of the coexistence curve in an asymptotic neighborhood of the critical point, the correlation dependence B0 = B0(β, ω, Zc) = C0 + C1ω + C2Zc + C3β, where Zc is the critical compressibility factor and C0, C1, C2, and C3 are the constant coefficients, is proposed. In the proposed correlation dependence, β, ω, and Zc are the independent variables. The correlation B0 = B0(β, ω, Zc) is tested in the ranges of 3.0 ≤ β ≤ 3.85 and –0.398 ≤ ω ≤ 3.65 of the data on the critical amplitude B0 of 25 substances (89 points (B0, β)). The proposed correlation B0 = B0(β, ω, Zc) describes the experimental data with a maximum deviation of up to 6
The adsorption of the anthraquinone dye Acid Blue 80 on bentonite modified with aluminum and iron oxides has been studied. It was found that clay modification leads to an increase in the specific surface area and sorption capacity. The effect of physicochemical parameters on adsorption has been investigated. It was determined that the adsorption capacity increases with an increase in the pH of the medium from 3.5 to 4.1 and decreases with a further increase to pH 10. It was also found that adsorption decreases with increasing sorbent loading and increases with increasing initial dye concentration. At an initial concentration of 210 mg/L, the adsorption is 40 mg/g. The equilibrium isotherm of the dye adsorption is analyzed using the Langmuir, Freundlich, and Temkin models. According to the values of the correlation coefficients, the experimental isotherm best correspond to the Freundlich model describing polymolecular adsorption on an inhomogeneous surface. The kinetics of the dye adsorption satisfies the pseudo-first order kinetic model. The results showed that the modified bentonite is a highly effective sorbent of the Acid Blue 80 and has prospects for use as a sorbent for removing anthraquinone dyes from wastewater.
The electrical conductivity of 1-alkylpyridinium ionic liquids with the bromotrichloroferrate anion in acetone in the temperature range of 298–318 K has been studied. According to the obtained conductometric data, the ion association constants (Ka), the limiting molar electrical conductivities (λ0), and the Gibbs energy of association ( Δ G_a^0 ) in solutions were calculated for the studied compounds by the Lee–Wheaton method. The values of enthalpy ( Δ H_a^0 ) and entropy ( Δ S_a^0 ) of association are obtained from the temperature dependence of the equivalent electrical conductivity (EC). The Walden–Pisarzhevsky product was calculated for all the studied compounds. The activation energies (Eκ) of the specific electrical conductivity are calculated. Conclusions are drawn regarding the influence of the structure of 1-alkylpyridinium bromotrichloroferrates on the thermodynamic parameters of association and the activation energy of electrical conductivity in acetone solutions.
