Russian Journal of Physical Chemistry A

Experimental studies on the solubility, density and refractive index in the ternary system (Na₂B₄O₇ + Mg₂B₆O₁₁ + H₂O) at 308.15 K were determined with the method of isothermal dissolution equilibrium. Based on the experimental results, the phase diagram and its corresponding physicochemical properties versus composition diagram in the system were plotted. In the phase diagram of the ternary system at 308.15 K, there are one eutectic point and two crystallization regions corresponding to the large area of inderite (Mg₂B₆O₁₁ · 15H₂O) and the relative small area of borax (Na₂B₄O₇ · 10H₂O), respectively. Neither double salt nor solid solution was found in this system. The physicochemical properties (density and refractive index) of the ternary system at 308.15 K changes regularly with the increasing of sodium borate concentration. The calculated values of density and refractive index using empirical equations of the ternary system are in good agreement with the experimental values.

The solid–liquid equilibria (SLE) in the ternary nicotinic acid + ammonium sulfate + water system were experimentally studied at T = 298.15, 323.15, and 348.15 K under atmospheric pressure by an isothermal equilibrium method. Three isothermal phase diagrams of the system were established based on the measured mutual solubility data. Meanwhile, the physicochemical properties (density and conductivity) of this system were measured. The phase diagram contained three crystallization regions, two crystallization curves, and one co-saturation point at each temperature. The crystallization field of both nicotinic acid and ammonium sulfate enlarged with increase of temperature. The crystallization region of ammonium sulfate was smaller than that of nicotinic acid at each temperature.

A series of novel dendritic salicylaldimine ligands and their corresponding iron complexes have been synthesized using 1.0 generation (1.0 G) dendritic macromolecules, salicylaldehyde and FeCl₂ · 4H₂O as raw materials. The structures of the ligands and iron complexes were characterized by FT-IR, ¹H NMR, UV, ESI-MS, and elemental analysis. The dendritic salicylaldimine iron complexes presented moderate catalytic activity in ethylene oligomerization and selectivity for higher carbon number olefins products (≥C₈) when they were activated with methylaluminoxane (MAO). The catalytic activity and product selectivity were related to the co-catalyst, solvent, bridged group length and reaction parameters such as reaction temperature, Al/Fe molar ratio and ethylene pressure. The complex C3 showed the highest catalytic activity (up to 13.75 × 10⁴ g (mol Fe h)^–1) and the selectivity of higher carbon number olefins (35.31%) at the optimized conditions. Moreover, the catalytic properties of dendritic salicylaldimine iron complex C3 was better than non-dendritic iron complex.

Dimethyldichlorosilane is the most versatile of organosilicon monomers and is produced in large quantites. In this paper, MP2/6-311++G (3df, 2pd) basis set has been used to calculate the reaction mechanism of disproportionation for producing dimethyldichlorosilane by catalyst AlCl₃/(AlCl₂)\(_{Z}^{{Z + }}\)-γ-Al₂O₃ (Z = 0–2). The activation energy (Z = 0–2) of the rate-determining step of main reaction is: 73.00, 60.26, and 66.39 kJ mol^–1. By comparing the activation energy and reaction heat, it is found that the catalytic effect of AlCl₃/(AlCl₂)\(_{Z}^{{Z + }}\)-γ-Al₂O₃ (Z = 1) is the best.

Methyl Red (MR) is a synthetic mono-azo dye which is extensively used as a colorant in textile and paper printing industries. The widespread amount of MR dye in wastewater poses potential threat to ecosystem and human health. In this context, we have developed a simple and expeditious oxidative decolorization technique for the removal of MR dye by organic N-haloamines viz., chloramine-T (CAT) and bromamine-T (BAT) present in the wastewater. The reaction was focused to changes in: (i) concentration of p-toluenesulfonamide, (ii) ionic strength, (iii) dielectric permittivity, (iv) polymerization study, and (v) halide ions effects. The activation parameters were deduced. Oxidation products of MR dye were identified. The rate of oxidation of MR is about four times faster with BAT than with CAT. The chemical oxygen demand value of the dye was determined. Phytotoxicity and economic analysis were carried out for the proposed decolorization process. A plausible mechanism conforming the kinetic data, reaction stoichiometry and product analysis has been proposed. Further, the present redox system can be adopted for treating MR dye present in industrial effluents with suitable modifications to reduce the toxicity caused by MR dye in wastewater.

The densities (ρ), speed of sound (u) values, and viscosities (η) were reported for binary mixtures of 2-chloroaniline with benzene derivatives (chlorobenzene, bromobenzene and nitrobenzene) over the entire composition range at T = 303.15–318.15 K and at atmospheric pressure 0.1 MPa. The excess properties, such as excess molar volume, excess isentropic compressibility and deviation in viscosity were calculated from experimental data. The excess properties were correlated by the Redlich–Kister equation. The partial molar volumes, partial molar isentropic compressibilities, excess partial molar volumes and excess partial molar isentropic compressibilities were calculated for all the binary systems throughout the composition range and also at infinity dilutions. The V^E results are analyzed in the light of Prigogine–Flory–Patterson theory. Analysis of each of the three contributions viz. interactional, free volume and P* effect to V^E showed that interactional and P* contributions are positive for all systems, the free volume effect is negative for all the mixtures. The variations of these parameters with composition and temperature were discussed in terms of intermolecular interactions prevailing in these mixtures.

Density and ultrasonic velocity values for solutions of pyridoxine hydrochloride in aqueous mixed solutions containing D-glucose, D-fructose, and D-lactose have been obtained for various concentrations and at temperatures 298.15–313.15 K. Volumetric and acoustic parameters such as partial molar volumes, partial molar adiabatic compressibilities, partial molar expansibilities were determined using density and ultrasonic velocity data. The analysis of the obtained data has been done by using Masson’s equation and interpretation was done in terms of solute–solute and solute–solvent interactions. The pyridoxine hydrochloride acts as a structure breaker in water as well as in binary aqueous mixed solutions of D-glucose, D‑fructose, and D-lactose.

Viscosities of solutions of manganese chloride, cobalt chloride, nickel chloride, copper chloride, cadmium chloride and magnesium chloride at different concentrations have been determined in water and in ethanol + water mixtures at 303.15 K. Effect of temperature was also studied in 5% of ethanol in water at 298–318 K. The measured viscosity data has been analyzed by using Jones–Dole equation. The obtained parameters have been interpreted in terms of ion–ion and ion–solvent interactions. Activation parameters have been determined which explain the mechanism of viscous flow. In the present study all the taken transition metal chlorides and magnesium chloride were found structure promoters in water and in water + ethanol mixtures.

The theoretical binding energies of the complexes formed by polysiloxanes with aniline and chlorophenol acetates were calculated at B3LYP/6-31G(d, p) level after the basis set superposition error (BSSE) based on B3LYP/6-31G(d) optimized geometries. The high binding energies of the complexes lead to the long experimental retention times in gas chromatography (GC). The energy gaps of the complexes are reduced owing to the formation of the hydrogen bonds. The chemical shifts of the α-C atoms connected to the amino groups in the NMR spectra of the complexes computed with B3LYP/6-31G(d) method are gradually changed downfield as the Si–O chain increases. The aromaticities of the benzene rings in the complexes are decreased due to the transfer of electron clouds from the benzene rings to the Si–O chains based on the nuclear independent chemical shifts (NICS) calculated at B3LYP/6-31G(d) level.

To assess its photocatalytic activity under visible light, Ag₃PO₄ nanopowder was prepared by precipitation of Ag₃PO₄ with Na₂HPO₄. The powder was identified by X-ray diffraction and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, thermal analysis and diffuse reflectance spectroscopy. Ag₃PO₄ grains with sizes in the range (0.8–10 µm) were obtained. The optical gap, determined from the Kubelka–Munk function, is found to be 2.49 eV and the electrical conductivity is characteristic of a classical semiconductor with activation energy of 0.18 eV. The capacitance measurement indicates n type conductivity with a valence band (2.05), deriving from Ag⁺: 5s orbital, more anodic than the level O₂/\({\text{O}}_{2}^{ \bullet }\). So, the compound was tested with success for the oxidation by \({\text{O}}_{2}^{ \bullet }\) radicals of the rhodamine B under solar light. The degradation obeys to a first order kinetic with a rate constant of 0.28 min⁻¹. Some peaks of Ag metal (~6%) appeared after the photocatalytic process and the optical gap shows red shift by 0.04 eV; such results are in contradiction with those reported by others.

The structural difference between five sulfa drug compounds and their Ru(III) complexes with 1 : 2 molar ratio were examined using the positron annihilation Doppler broadening (PADB) spectroscopy. The PADB measurements were performed with a HPGe γ-ray spectrometer. The change of defect structure due to the Ru(III) complexation process was confirmed. The correlation between the DP line-shape parameters (S and W) and the previous reported results of the microanalytical, physicochemical, biological and positron annihilation lifetime (PAL) measurements of sulfa drug Ru(III) complexes were examined.

The invention represents a development of robust eco-friendly method use for water waste management and polluted water. The inadvertent role of peanut peels extract helps to simultaneously convert and form reduced graphene oxide gold nanocomposite (rGO@AuNCs) in single step. Fabricated nanocomposite was evaluated for its catalytic performance using reduction of 4-nitrophenol to 4-aminophenol as well as elimination of methylene blue (MB) and malachite green (MG) dyes from water. Graphene oxide (GO) and rGO@AuNCs, were synthesized using simplified approaches and preliminary characterization was done using UV–Vis spectrophotometer and Fourier transform infrared spectroscopy. Least concentration of rGO@AuNCs is required to eliminate MB and MG around 77 and 93%, respectively. Furthermore, surface morphology and elemental analysis of rGO@AuNCs confirm successful fabrication methods as well as X‑ray diffraction pattern confirms the crystalline behavior of nanocomposite. The study illustrates an environment-friendly and cost effective in situ fabrication rGO@AuNCs from industrial agro waste for an environmental remediation.

(Tm_xYb_{1 –x})₃Al₅O₁₂ (YbAG:Tm³⁺) nanoparticles (NPs) with mean diameter of 56 nm were prepared by a rapid carbonate coprecipitation method with a short calcination time of only 1 min. Our results confirmed the structure and purity of the prepared material and proved that Tm³⁺ was successfully incorporated into YbAG. The results on the upconversion luminescence show that the emission peaks were located at 486 and 684 nm, corresponding to the ¹G₄ → ³H₆ and ³F₂ → ³H₆ transitions of Tm³⁺. The transition mechanism of the blue and red emission was discussed.This rapid method could improve the production efficiency of YbAG:Tm³⁺ nanoparticles, and may have certain implications for the preparation of other upconversion nanomaterials.

Tetragonal Br-doped bismuth oxyiodide (BiOI) as visible-light-driven photocatalysts were synthesized by sonochemical method. The as-synthesized products were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM) and an X-ray photoelectron spectrometry (XPS). Among the different studied photocatalysts, 10 wt % Br-doped BiOI showed the highest activity of 98.88% in photodegradation of rhodamine B (RhB) under visible light irradiation within 180 min.

Carbon coated SnO₂ hollow nanocubes were synthesized by a facile hydrothermal route. The sample with large surface area exhibits a hollow cube particle shape with an average length of ~400–500 nm. It is found that the SnO₂@C−HNC shows a high discharge capacity of 799.1 mA h g⁻¹ with the first cycle coulombic efficiency of 53.4% at the current density of 100 mA h g^–1. At the high current density of 2 A g^–1, it can still deliver a discharge capacity of 203.1 mA h g^–1. The SnO₂@C−HNC composite exhibits a good rate capability and stable cycling performance, indicating potential available as large-scale storage device.

A novel ion-selective membrane electrochemical sensor based on Kryptofix 22 as an ionophore was constructed for determination of potassium ion in real samples. The D-optimal mixture design (D‑OMD) was used as an experimental design strategy for optimal formulation of the membrane ingredients. The fabricated electrode exhibits a Nernstian slope of 59.80 ± 0.65 mV per decade and a linear range of 1.0 × 10^–4 to 1.0 × 10^–1 mol/L with respect to potassium ion at the pH range of 3.0 to 7.0 and its detection limit was found to be 6.2 × 10^–5 mol/L. The response of the electrode is very stable and it exhibits a good reproducibility with a fast response time (~10 s). The experimental results, showed a good selectivity towards the K⁺ ion at present of interfering ions. The obtained results by using D-OMD showed a non-linear relation between the slope of the electrode and its ingredients. The proposed electrode was successfully applied for determination of potassium ion in vegetables and urine samples.

Series of ion conducting system (KI)_4 – x‒(CuI)_x‒PbI₂, x = 0.0‒0.4, have been prepared by solid state reaction method and studied by powder X-ray diffraction, DTA techniques and conductivity measurements. Room temperature XRD reveals the presence of the orthorhombic KPbI₃ as the major component in the sample. The X-ray diffraction analysis also confirms the presence of both KI and CuPbI₃ in the samples. DTA of x = 0.0 composition shows an endothermic peak at 349°C attributed to the melting of the compound. AC impedance spectroscopy revealed that the contribution of grain is strong over the grain boundary. The addition of CuI content results in the increase of electrical conductivity of the samples. The maximum ionic conductivity σ = 6.33 × 10^–1 S cm^–1 was shown by x = 0.3 composition at 633 K with lowest activation energy of ~0.11eV in the temperature range of 298‒633 K.

Non-ionic surfactant block copolymer of polypropylene glycol flanked by two blocks of polyethylene glycol known as pluronic. Pluronic F127 or poloxamer 407 is used to improve the solubility and enhance the bioavilability of many drugs. The interactions of pluronic F127 was studied in Rhodamine B dye and effects of inorganic cations through fluorescence data were observed. Fluorescence quenching were studied by series cations of salts viz CdSO₄, MnSO₄, ZnSO₄, FeSO₄, CuSO₄ in the above system. Cu²⁺ was found to be extremely efficient quencher, Cd²⁺ and Fe²⁺ were moderate quenchers. Apart from fluorescence, lifetime, DLS, and SEM were used as characterization for the above study.

Reactive Blue 255 (RB 255) is a textile dye with global usage and is found in the wastewater of textile industries in large quantities. In the present study, silver-doped TiO₂ (Ag/TiO₂) nanoparticles with various Ag doping (wt %) were prepared by a combination of sol-gel and ultrasonication techniques. Ag/TiO₂ nanoparticles were characterized by EDXA, SEM, TEM, and XRD methods. Based on the Taguchi method, photocatalytic degradation of RB 255 azo dye was investigated with Ag/TiO₂ nanoparticles under visible light irradiation. By using this method, operation factors such as Ag doping (wt %), pH, catalyst load, and RB 255 concentration were optimized successfully. The results showed that pH, when compared to the other factors, plays an important role in the photocatalytic degradation of RB 255 azo dye. The isotherm study shows that Weber–Van Vliet and Fritz–Schlunder (IV) models are the best descriptors of equilibrium behavior. The experimental kinetic study results may be well described by a pseudo first-order model.

Ternary nano-composites of polypyrrole/iron oxide/fly ash cenosphere (PPY/Fe₃O₄/FAC) were synthesized and used as magnetic photocatalyst. The synergistic effect of FAC, a buoyant carrier and polypyrrole, a conducting polymer enhanced the photocatalytic activity. Different composites were synthesized by varying the concentration of Fe₃O₄ and FAC to evaluate its effect on the photocatalytic properties of composites. The presence of Fe in Fe²⁺ and Fe³⁺ oxidation states at binding energies of 709.3 and 711.4 eV respectively was depicted by XPS curve. PPY/Fe₃O₄/FAC (1 : 3) composite showed the highest photocatalytic activity with rate constant (k) 0.0058 min^–1. The removal efficiency of BPA was found to be around 75% and ~62% total organic content (TOC) was eliminated at optimized conditions from the solution. Transmission electron microscopy (TEM) showed the cluster morphology of the PPY/Fe₃O₄/FAC nano-composites with ~6–10 nm size of Fe₃O₄. X-ray diffraction studies elucidated the characteristic peaks of both PPY and Fe₃O₄ at 2θ ~ 20°–30°, and 26.04°, respectively in the composites which also confirmed the interaction of PPY with Fe₃O₄.

The effect of dissolved sodium acetate (5 and 10%), potassium acetate (5 and 10%) and zinc acetate (5 and 10%) on the endothermic enthalpy of mixing in the binary system methanol–carbon tetrachloride has been investigated at 303.15 K in a displacement calorimeter with vapor space. Experimental values were fitted into a Redlich–Kister equation. Experimental values and predicted values were plotted against mole fraction of methanol and deviations were reported. The data obtained may be of interest to specialists in the field of thermodynamic of solutions.