Russian Journal of Applied Chemistry最新文献

The key step of the thermal decomposition of hypophosphites is disproportionation determining the phase composition and morphology of the final products. The distinctive features of the thermal decomposition of hypophosphites are the formation of polyphosphoric acid from ammonium hypophosphite and of red phosphorus from the metal hypophosphites. The thermal decomposition of hypophosphites in air is accompanied by large heat release.

Wastewater treatment to remove organic ecotoxicants is one the most important problems today. Scientists’ efforts throughout the world are focused on searching for effective and harmless technologies for the removal and/or complete degradation of organic pollutants. One of the solutions is the use of UV lamps in combination with various oxidants. UV irradiation is widely used in various branches of industry, especially in water treatment. Photolysis methods are environmentally clean and are included in handbooks of the best available technologies. Experiments performed in this study were aimed at revealing kinetic relationships of the photochemical degradation of dihydric phenols in aqueous solutions under the action of active species. All the processes were performed using a flow-through laboratory installation. A 9 W, 254 nm OSMAR special ozone-free bactericidal lamp (Finland) was chosen as a UV radiation source. The residence time of the model solution in the reactor was varied from 20 to 120 s. Quantitative determination of dihydric phenols was performed by the spectrophotometric method. Hydrogen peroxide (3% solution) and potassium persulfate were chosen as oxidizing additives. The potential of the UV radiation and oxidative treatment for efficient removal of dihydric phenols from water was evaluated. Photooxidation of pyrocatechol, resorcinol, and hydroquinone in aqueous solution in the presence of hydrogen peroxide and potassium persulfate was performed. The oxidants were taken in amount from stoichiometric to fivefold excess relative to the stoichiometry. The photochemical degradation of dihydric phenols can be performed with up to 99% efficiency. At the phenol : oxidant molar ratio of 1 : 5, the photooxidation rate increases by a factor of 3–5. The degradation involves the breakdown of the benzene ring, and the main degradation products of dihydric phenols are monobasic carboxylic acids and formaldehyde.

Hardened cement pastes made of ordinary Portland cement (OPC) and strontium aluminate (Sr₄Al₁₄O₂₅)-Sol were made using a water cement ratio of 0.257 weight by weight. Two pastes containing (Sr₄Al₁₄O₂₅)-Sol with 1 and 3% content by the weight of OPC were prepared. All pastes were cured for various time intervals within the range of 1 to 28 days. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), compressive strengths, and surface properties were studied and related as much as possible to the pore structure of the hardened pastes (1 and 3%). The addition of strontium aluminate to OPC results in an increase in the values of specific surface area and a decrease in values of average pore diameter of the hardened pastes (1 and 3%) as compared to the hardened neat cement pastes (OPC); this led to a higher value of compressive strengths of hardened cement pastes (Sr₄Al₁₄O₂₅)-Sol admixtire, especially at 1% addition.

In present work, a series of novel pyrazole cyclic polymer poly(1,3-diphenyl-1H-pyrazol-5-yl methacrylate)/montmorillonite based nanocomposites, [poly(DPMA/OMMT : 2-7wt%) were prepared by in situ polymerization technique. Organic-modifier was vinylbenzyldimethylhexadecyl ammonium chloride. The X-ray diffraction analysis (XRD) showed that the clay dispersion in the polymer matrix was exfoliated type for all nanocomposites. A positive change was observed between the reinforced clay ratio and the thermal stability of the nanocomposites from thermogravimetry (TGA). It was determined that the nanocomposite with 7 wt % clay content was approximately 34.9°C more thermally stable than the undoped polymer. Thermal kinetic analysis of the decomposition process of nanocomposites in a conversion range of 7–19% was evaluated from dynamic experiments by means of various kinetic models such Flynn–Wall–Ozawa, Kissinger, Coats–Redfern, Tang and Madhusudanan methods. Doping the organoclay into the pyrazole polymer increased the activation energy from 79.5 to 109.5 kJ/mol compared to pure polymer. The results obtained from kinetic methods showed that all nanocomposites proceed via the thermal decomposition mechanism, D₁, one-dimensional diffusion type deceleration mechanism.

Silylated Ti–SiO₂ (S–Ti–SiO₂) was prepared by the chemical vapor deposition of TiCl₄ and following hexamethyldisilazane (HMDS) on SiO₂. Its specific surface area and pore size are decreased compared with Ti-SiO₂ while it keeps highly dispersed Ti species with low coordination. More importantly, S–Ti–SiO₂ possesses higher hydrophobicity than Ti-SiO₂, which can explain the fact that it performs better than Ti-SiO₂ in catalytic epoxidation of soybean oil using 30% aqueous H₂O₂ as oxidant. The relative conversion to oxirane (RCO) of S–Ti–SiO₂ can reach 27% and the catalyst can be used 3 times under the best reaction conditions.

The discharge of wastewater without proper treatment gives rise to environmental problems. One of the ways to solve them is photocatalytic decomposition of organic pollutants in wastewater. This method attracts researchers’ attention as being simple and cheap. Powdered semiconductor oxide materials exhibiting good adsorption properties toward organic compounds, photochemical stability, and nontoxicity are mainly used as photocatalysts. Tin(IV), titanium(IV), zinc(II), and cerium(IV) oxides exhibit such properties. The possibility of using as photocatalysts thin-film materials, which can be readily separated from the treated water, has been demonstrated recently. In addition, it is known that heterostructures enhance the photocatalytic activity of the material, in particular, by decreasing the bandgap, which allows more efficient absorption of visible light by the substance. This study compares the optical properties of the SnO₂, CeO₂, and CeO₂/SnO₂ thin-film materials on quartz supports. The materials were prepared by the sol–gel method from film-forming solutions based on cerium(III) nitrate and/or tin(IV) chloride with salicylic acid. The film thickness and refractive index were studied by ellipsometry, and the transmittance was examined by spectrophotometry. The photocatalytic properties of CeO₂/SnO₂ thin-film materials were demonstrated in the model reaction of the decomposition of an organic dye, Methylene Blue, under UV irradiation (312 nm) in the daylight and in the dark. Films with the CeO₂/SnO₂ heterostructure having the thickness of 124 nm, refractive index of 1.33, and transmittance higher than 70% in the wavelength range 440–1000 nm absorb the visible light more efficiently than the SnO₂ and CeO₂ thin-film materials do. The photocatalytic activity of CeO₂/SnO₂ films under UV irradiation in the daylight is higher than that under UV irradiation in the dark. The amount of Methylene Blue decomposing under UV irradiation in the daylight is 1.2 times larger than that decomposing under UV irradiation for the same time in the dark.

The photocatalytic activity of iron-containing metal–ceramic composites based on silicon nitride modified with semiconductor tantalum oxo compounds in oxidative degradation of diclofenac (DCF) was studied. The composites were synthesized by autowave combustion of ferrosilicoaluminum with different additions (5, 10, 15 wt %) of tantalum metal in a nitrogen atmosphere. The phase composition was determined by X-ray diffraction and IR spectroscopy, and the content of elements in local surface areas was quantitatively evaluated by electron microprobe analysis. The activity of composites under the conditions of heterogeneous photocatalysis, heterogeneous photocatalysis combined with photo-Fenton and Peroxone processes under UV irradiation, and catalytic ozonation under UV and visible light irradiation was studied. The combination of heterogeneous photocatalysis and Peroxone process is the most effective. The Lаngmuir–Hinshelwood scheme was applied to elucidate the mechanism of DCF photocatalytic degradation.

This review article explores the potential of lignin as a sustainable alternative to conventional petroleum-based adhesives. Conventional adhesives derived from petroleum sources have been widely used in industrial, medical, and household applications. However, the depletion of petroleum resources and environmental and human health concerns have prompted the search for bio-based and environmentally friendly alternatives. Lignin, a biodegradable substance abundant in nature, has emerged as a promising substitute due to its non-toxic nature, three-dimensional structure, and functional groups. Replacing the chemicals used in conventional adhesives with lignin can reduce production costs, and the resulting adhesives exhibit decreased toxicity. Furthermore, lignin can be combined with biobased materials to create bio-based adhesives. This article provides an overview of lignin extraction methods, explores the diverse applications of lignin in various industries, discusses chemical modifications of lignin, and specifically focuses on the production of lignin-based adhesives. Finally, the challenges associated with lignin-based adhesive production are addressed.

This study reports the hydrothermal synthesis of hierarchical aluminum phosphate molecular sieves doped with V, Cu, Fe, and Ni. The catalysts were characterized by XRD, SEM, EDS, XPS, NH₃-TPD, and N₂ adsorption-desorption from the perspectives of structure, morphology, acidity pore size, etc., which confirmed that the metals successfully infiltrated the molecular sieve skeleton. The synthesized D-MeAPO-5 molecular sieve was applied to the oxidation of benzene to the preparation of phenol. It was found that the catalytic effect of the D-VAPO-5 molecular sieve was superior to other catalysts. The conversion rate of benzene and selectivity of phenol were 27.0% and 80.4%, respectively, indicating that the activation ability of the C-H bond on the V-benzene ring was stronger. For optimal experimental design, the response surface method was carried out using D-VAPO-5 as the catalyst and phenol yield as the response value. In addition, a quadratic model was established for four influencing factors and phenol yield, and the significance of the factors was found to be as follows: reaction temperature>H₂O₂ dosage>catalyst dosage>reaction time.

The goal of this investigation effort was to organize activated carbon from olive stone through by 0.01 M D₂EHPA. The adsorption ability of carbon with cadmium and zinc existed also studied. Focuses of metals were examined through using flame atomic absorption spectrophotometry. The factors that disturb the adsorption, such as contact time, acid concentration, solid liquid ratio, RPM, and temperature, have been considered and enhanced conditions were determined. The results showed that the maximum adsorption capacities of carbon were found to Cd²⁺ and Zn²⁺with 28.0 and 22.17 mg/g, respectively. The Langmuir adsorption model might be used to clarify the adsorption isotherm with the pseudo-second order and The Cd²⁺ and Zn²⁺sorption process onto the olive stone (OS) occurred spontaneously (­–ΔG), in an exothermic nature (–ΔH), and with increased non randomness (–ΔS).