Vol 92, No 9 (2018)

The heat capacity, temperatures and enthalpies of the physical transformations of a triple alternating copolymer of carbon monoxide with ethylene and butene-1 with a 46 mol % concentration of butane fragments are studied via adiabatic and differential scanning calorimetry in the region of 6−570 K. Its combustion energy in a condensed state at T = 298.15 K is measured calorimetrically. Standard thermodynamic functions of the copolymer in the region of T → 0 to 400 K and the thermodynamic characteristics of its formation at T = 298.15 K and synthesis within the range of T → 0 to 400 K are calculated. The dependences of the thermodynamic properties of the copolymer on the concentration of butane fragments in the macromolecules are obtained.

The energy of combustion of crystalline adamantanecarboxylate of tetraphenylantimony and triphenylantimony bis(1-adamantanecarboxylate) is determined at 298.15 K using a combustion calorimeter with a static bomb. The combustion enthalpies of these substances in the crystalline state at 298.15 K are calculated using the obtained experimental data. Such standard functions of formation as Δ_fH° and Δ_fG° are calculated for the studied compounds in the crystalline state at 298.15 K. The obtained thermochemical properties are analyzed, and their dependences on the molar mass of the substituent with antimony are determined.

The effect n-butylamine, tert-butylamine, piperidine, and morpholine additives have on the kinetics of complex formation between zinc acetate and hexa(m-trifluoromethylphenyl)benzoporphyrazine in benzene is studied. A possible scheme for their complexation is proposed. It is established that the rate and activation parameters of the process are affected by the proton-acceptor capacity of the base and its spatial structure.

The absorption of ozone by aspen wood with moisture contents of 45, 55, and 70% is studied. Time dependencies are obtained for the specific absorption of ozone, the degree of ozone conversion, and the content of the products of oxidation. It is shown that the resulting compounds are products of the oxidative degradation of lignin, and that the efficiency of delignification is greatest for wood with a moisture content of 55%. Water-soluble products are analyzed via HPLC, revealing the presence of oxalic, formic, and glyoxylic acids in contact solutions. Based on the dependence of the content of acids on the specific consumption of ozone, it is concluded that the acids are oxidized by ozone. The inhibiting role of the reactions between ozone and water-dissolved products of the substrate oxidation is noted.

To improve the performance of CeO₂–ZrO₂–Al₂O₃ (CZA) composite, Nd was introduced and the role of Nd was deeply investigated. The characterization results revealed that introduction of appropriate amount of Nd (4 wt %) can effectively modify the textural and structural properties of CZA, in this case, Nd selectively combines with CZ and hardly interacts with Al₂O₃, which could incorporate into the lattice of CZ to form ternary CeO₂–ZrO₂–Nd₂O₃ (CZN) solid solution, thus more lattice defects and improved oxygen mobility are obtained. However, excessive doping amount of Nd (6–8 wt %) brings about formation of Nd_0.5Ce_0.5O_1.75 and phase separation of CZ especially after thermal aging treatment. The XPS results demonstrate that the supported catalyst Pd/CZAN4 possesses higher surface Pd and Ce³⁺ concentrations compared with Pd/CZA, which consequently leads to improved reducibility and catalytic performance. Furthermore, higher thermal stability is obtained, after aging treatment, Pd/CZAN4a still exhibits enhanced reduction property along with superior three-way catalytic performance.

The effect ethonium, a dicationic surfactant, has on the physicochemical properties of a natural flavonoid, rutin, is studied spectrophotometrically in a wide range of concentrations in the region of physiological pH. It is found there are a bathochromic shift of the bands in the absorption spectra of rutin, a drop in the apparent constant of its dissociation \({\text{p}}{K}_{{{\text{a1}}}}^{{\text{a}}}\), and an increase in solubility and adsorption on the surface of nanosilica relative to aqueous solutions. The constant of bonding between rutin and ethonium is calculated.

The Ni²⁺–triglycine–L-histidine system is studied by potentiometric and calorimetric means in aqueous solutions at Т = 298.15 K (KNO₃). The formation of mixed ligand complex NiLY is registered, and standard thermodynamic characteristics (Δ_rH°, Δ_rG°, Δ_rS°) of its formation are determined. A structure of the complex is proposed.

Results from optimizing the atomic structure of anionic clusters \({\text{NbGe}}_{n}^{ - }\) (n = 8−20) are presented, along with their calculated electronic spectra. The calculations are performed within the density functional theory. The real spatial structures of the clusters are determined by comparing the calculated and known experimental data.

In present study, α-[3-(2,3-epoxy propoxy) propyl]-ω-butyl-polydimethylsiloxanes grafted gelatin (PGG) compositional gradient film was successfully fabricated by combining a solvent induced self-assembly procedure and the interaction between polymer and air/substrate induced migration. The variation of gelatin superstructures and the transformation of PGG aggregate structure with tuning volume ratio of water/ethanol studied by Atomic force microscopy (AFM), Fourier-transform infrared (FTIR) and High-resolution transmission electron microscopy (HR–TEM). At 1 : 3 vol/vol, gelatin chains self-assembled to cyclic aggregates that tended to deposit on the gelatin substrate, while PGG formed core–shell structure which should migrate to air-liquid interface driven by low free energy of PDMS chain during drying. X-ray photoelectron spectroscopy (XPS) showed that the surface of gradient film was covered with PDMS component and strong intermolecular interactions existed in between polymer and solvent molecules at 1 : 3 vol/vol. The gradients of PDMS composition along longitudinal orient in film were further confirmed by scanning electron microscopy-energy dispersive spectroscopy (SEM−EDS) with line scan. Contact angle results exhibited a successive decrease of hydrophobicity along longitudinal orient in gradient film. Dynamic mechanical analysis (DMA) results showed two tan δ and lower storage modulus in gradient than that of blank gelatin film, which led to good flexibility of gradient film.

The present investigation explores the stability of linkage isomers of cis-[Pt(PH₃)₂(NCS)₂] and [Pt(PH₃)₂(SCN)₂] by the use of MPW1PW91 quantum method. The polarity of solvent effect on dipole moment, structural parameters, and electronic properties, spectroscopic properties (IR and NMR) was studied. The selected vibrations of IR-active in different solvents were obtained and correlated with Kirkwood–Bauer–Magat equation (KBM). The d-orbitals energies of platinum were calculated by NBO analysis. It was seen good correlation were obtained between ¹⁹⁵Pt chemical shifts and the spectral parameters obtained from the energies of electronic transitions between Pt d-orbitals in the cis-[Pt(PH₃)₂(NCS)₂] complex. Also, ¹J(Pt–N) values were correlated with Pt–N distances.

The dependence of the zeta potential and hydrodynamic radii of silver sulfide nanoparticles (Ag₂S) in an aqueous colloidal solution on the concentration of stabilizer 3-mercaptopropyltrimethoxysilane (MPS) is determined. A model for the structure of a surface layer of Ag₂S nanoparticles coated with MPS is proposed that explains the observed dependence and the extrema on it. It is found that the values of the zeta potential and the hydrodynamic radii of the Ag₂S nanoparticles depend substantially on the means of creating an excess of silver ions in the solution. This dependence is explained by the dynamics of the formation of a stabilizer layer on the surface of nanoparticles.

TiO₂ nanospheres with hollow structure were obtained by a facile hydrothermal process at the temperature of 200°C. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), Raman spectrum (Raman), UV–Vis absorption spectroscopy (UV–Vis) and fluorescence spectra (FL) were used to characterize the samples, and the photocatalytic activity of the products was tested by the degradation of rhodamine B under the UV light. The formation of this hollow structure in samples prepared at 200°C can be interpreted as the preferential dissolution of the internal structure which has higher solubility. When compared with the counterparts prepared at different temperature, the hollow nanospheres showed excellent optical properties and enhanced photocatalytic acivity which can be attributed to the special hollow structure and the resulting large surface area.

The batch sorption kinetics described by a nonlinear equation with a variable equilibrium parameter for the interface was considered. It was shown that a difference equation of this type can be reduced, with a certain approximation, to the pseudo first- and pseudo second-order kinetic equations with constant parameters that are convenient for processing the experimental data. The errors of this approximation are smaller than the characteristic experimental errors in constructing the kinetic curves. For the linear sorption isotherm and Langmuir isotherm, the sorption kinetics can be approximated by the pseudo first-order equation. In addition, for the Langmuir isotherm and BET isotherm of polymolecular sorption, the kinetics can be described by the sum of the pseudo first- and pseudo second-order equations, or only by the pseudo second-order equation. For all these cases, it was shown how the parameters of kinetic equations are related with the equilibrium characteristics of sorbents. Our analysis shows that the possibility of describing the experimental data obtained in batch kinetic experiments using pseudo first- or pseudo second-order models is related to the possibility of mathematical approximations and transformations and cannot be used to characterize the kinetic mechanisms.

A comparative study of the sorption properties of lignocellulosic plant materials (aspen and pine wood and wheat straw) is performed using the cationic dye methylene blue (MB). Experimental data on the adsorption of MB from water solutions are described by the Langmuir model. It is established that the isotherms of MB adsorption on softwood and hardwood samples are almost the same and the maximum sorption capacity is 26.4 ± 0.7 mg/g. The amount of MB adsorbed by wheat samples at the same equilibrium concentrations is greater and reaches a maximum of ~46 mg/g. The estimated specific surface area accessible to dye molecules is 52 m²/g for the wood and 91 m²/g for the straw. It is shown that the ozonation of aspen wood reduces the affinity of the adsorbent surface toward MB but has no effect on its adsorption capacity.

The use of the developed composite sorbent based on the plant wastes (sunflower seed husks) and montmorillonite clay was shown to be highly effective for water purification from iron ions and potentially pathogenic microorganisms. It was shown experimentally that the developed composite sorbent at concentrations of up to 50 mg/L is capable of purifying water from iron ions under static and dynamic conditions. When a suspension of Escherichia coli was filtered at a rate of 10 mL/min, 1 g of the composite sorbent adsorbed 556 million E. coli colony-forming units (CFUs), showing that the sorbent is 1.7 times more effective than the complex sorbent of the replaceable Barrier-4 filter cartridge.

The kinetic patterns of oxidative processes involving highly reactive oxygen-containing radicals generated in situ in the aqueous medium affected by acoustic cavitation of the megahertz range (1.7 MHz) and UV radiation (254 nm) are established using 4-chlorophenol as an example. The results indicate the substantial activation of 4-chlorophenol oxidation processes upon both UV irradiation and the combined influence of high-frequency ultrasound of the megahertz range and UV irradiation in the Fenton-like iron-persulfate system Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\). Full conversion of 4-chlorophenol in the hybrid oxidative system US/UV/Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\) is attained after 60 min of treatment, while the mineralization of the organic substance after 180 min of treatment is 83.2%. The activation of a coupled radical-chain mechanism in the oxidative systems US/UV/Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\) and UV/Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\) is confirmed by high values of the synergic indices in both cases for the conversion of 4-chlorophenol (φ₁ > 1) and the mineralization of dissolved organic matter (φ₂ ≫ 1). The considered sono- and/or photoinduced oxidative systems can be arranged in the following order according to the effectiveness of the oxidative degradation of 4-chlorophenol US/UV/Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\) > UV/Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\) ≫ US/Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\) > Fe²⁺/\({{{\text{S}}}_{{\text{2}}}}{\text{O}}_{8}^{{2 - }}\) > US/UV.

Mn₂O₃ microsheets were successfully synthesized via a facile electrospinning method followed by post-calcination process. MnO particles, Mn₃N₂/MnO/C composite particles and Mn₃N₂/C rods were respectively obtained via reduction and nitridation of the prepared Mn₂O₃ microsheets in NH₃ atmosphere at 500, 950, and 1000°C. The crystal structure, morphology and composition of Mn₂O₃ microsheets, MnO particles, Mn₃N₂/MnO/C composite particles and Mn₃N₂/C rods were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS). MnO particles, Mn₃N₂/MnO/C composite particles and Mn₃N₂/C rods were explored as the anode materials for Li-ion batteries. Compared with MnO particles and Mn₃N₂/C rods electrodes, the capacity of Mn₃N₂/MnO/C composite particles electrode is the highest, and the discharge capacity retained 583 mA h g^–1 at a current density of 100 mA g^–1 after 300 cycles. More importantly, the synthetic strategy may be extended to synthesis of other metal oxides and metal nitrides composites as anode materials for Li-ion batteries.

Solubilization with pluronic F-127 gave water-soluble forms of hydrophobic photosensitizers—steroid derivatives of pyropheophorbide a. Solubilization was performed by evaporating the chloroform co-solutions of photosensitizer and pluronic (triple block copolymer of ethylene and propylene oxide) and subsequently dissolving the resulting dry residue in water. The concentration ratios of modified pyropheophorbide–pluronic at which the photosensitizer completely passed into the aqueous phase were determined. Among the starting hydrophobic photosensitizers, pyropheophorbide–dihydrotestosterone possessed the highest activity in photosensitized oxidation of anthracene with singlet oxygen in chloroform, while after solubilization, pyropheophorbide–testosterone was most active in the test (for photodynamic therapy) oxidation of tryptophan in aqueous solutions.

The maximum adsorption capacity of bovine brain galactocerebroside on samples of silicalite-1 synthesized on solid supports (in powder form and applied to glass) is determined. It changes in the range of 6 to 27 mg/g, depending on the accessibility of adsorbent pores for lipid molecules. IR spectroscopy data show that the lipid molecules are oriented with carbohydrate fragments facing the adsorbent surface. It is established that adsorption of protein molecules (BSA and hemoglobin) occurs predominantly on the lipid, and only partially on the free outer surface of the silicalite. It is concluded that adsorption alters the parameters of the porous structure.

The spectral and kinetic characteristics of short-lived triplet exciplexes, formed by quenching the triplet state of acceptor 2,6-diphenyl-1,4-benzoquione (Q) with electron donors 1,4-diazabicyclo[2.2.2]octane and triphenylamine, are studied. The elementary events of the reaction are investigated in vitro in different solvents (toluene, dibutyl phthalate, tetrahydrofuran, and acetonitrile). Quenching the quinone (Q) triplet with amine in low-polarity solvents gives rise to short-lived complexes with complete charge transfer.

The thermodynamic parameters (ΔH, ΔG, and ΔS) of the micellization of hexadecyltrimethylammonium bromide (CTAB) in aqueous solutions of 1-pentanol at 298.15 and 313.15 K are measured via micelle destruction. Critical micelle concentrations CMC 1 and CMC 2 at different concentrations of pentanol are determined. It is found that adding pentanol to a solution at 313.15 K does not affect the entropy of micelle formation, which is ΔS in pure water. A linear compensation relationship between the ΔH and ΔG values is revealed. It is shown that the entropy of a solution at 298.15 K falls upon adding pentanol, and the compensation relationship between the ΔH and ΔS values is in this case similar to the one obtained upon varying the temperature of a solution.