Russian Journal of Applied Chemistry最新文献

The physicochemical features of the solubilization of gossypol (GS) with polyivinylpyrrolidone (PVP) were studied. In contrast to the initial polyphenol, the solubilization product is a water-soluble supramolecular complex. As shown by IR spectroscopy, the complexation of PVP with GS occurs via hydrogen bonding between the carbonyl oxygen atom of the pyrrolidone ring of the polymer and hydroxyl proton of polyphenol. The relative viscosity of aqueous solutions of the supramolecular complex depends on its composition and passes through a minimum with the lowest value of the PVP : GS ratio close to 2 : 1. That is, at this component ratio, the structure of the complex in an aqueous medium is the most compact. The GS solubilization with PVP can be presented as adsorption of the polyphenol onto the polymer and can be described by the Langmuir monomolecular adsorption theory.

Addition polymerization of 3-methyl-3-phenylcyclopropene and 3,3-di(n-propyl)cyclopropene in the presence of a palladium complex containing an acyclic diaminocarbene ligand was studied. When activated with the organoborate (Na⁺[B(3,5-(CF₃)₂C₆H₃)₄]^–), such complex catalyzes the addition polymerization of substituted cyclopropenes. The polymerization occurs selectively without opening of the cyclopropane ring. The copolymerization of 3,3-di(n-propyl)cyclopropene with a monomer of the norbornene series (5-ethylidene-2-norbornene) was monitored by a decrease in the intensity of the characteristic signals in the ¹H NMR spectra of the corresponding monomers. The substituted cyclopropenes were found to be more active monomers than norbornenes in the addition polymerization. The addition homopolymers of 3-methyl-3-phenylcyclopropene and 3,3-di(n-propyl)cyclopropene were characterized by differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction.

The effect that introduction of cerium oxide into oxide systems based on chromium and silicon exerts on the catalytic properties of these systems in nonoxidative propane dehydrogenation in a flow-through system with a fixed catalyst bed was studied. The characteristics of the catalysts CrO_x–SiO₂ and CrO_x–CeO₂–SiO₂, both containing 9 wt % CrO_x assuming the Cr₂O₃ stoichiometry, were compared. The СеО₂ content of the ternary system was 52 wt %. The catalysts were characterized by X-ray diffraction analysis, scanning electron microscopy, Raman spectroscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, temperature-programmed reduction with hydrogen, and thermal analysis. In the initial period of the reaction, the catalyst containing CeO₂ demonstrated higher propane conversion at 500 and 550°С and higher deactivation rate compared to CrO_x–SiO₂. Both catalysts can be regenerated by treatment in an air stream at 550°С for 30 min. Cerium dioxide favors the reduction of chromium in high oxidation states to form active reaction sites, Cr³⁺ ions, ensures higher dispersity of the chromium oxides, and favors partial oxidation of coke deposits in the initial period of the catalyst operation.

The need for polyethylene terephthalate recycling is associated with the formation of significant amount of its waste, which should be reprocessed due to the growth of polymer production and consumption of plastic products used in light, chemical, medical industries, in mechanical engineering and instrument making. The main share of polyethylene terephthalate (PET) recycling processes is chemical methods through which various monomers are generated. After purification and modification of these monomers, valuable petrochemical raw materials can be yielded. The review describes the principles and mechanisms of polyethylene terephthalate degradation upon pyrolysis. The influence of the heating rate during pyrolysis (fast, slow), type of raw material (pure polymer, polymer waste), additives (modifiers, stabilizers, fire retardants), type of reactor in the process (horizontal, vertical, fixed bed reactor, fluidized bed reactor, conical tip reactor, rotating dc arc plasma reactor) is considered, as well as the effect of processing conditions such as temperature, amount of raw material, pressure, atmosphere, and presence of catalyst on the quantitative and qualitative composition of oxygen-containing compounds formed in the gas fraction, pyrolysis oil, and semi-coke. The influence of additives of various polymers in a mixture with polyethylene terephthalate on the formation of products (gas fraction, pyrolysis oil, and semi-coke), additives of plant biomass, and food waste is demonstrated. The effect of microwave radiation on the polyethylene terephthalate pyrolysis is considered.

The nature of cathodic polarization in an iridium-plating electrolyte based on a sulfamate solution of H₂[IrCl₆] was studied. Spectroscopic analysis shows that the iridium electrolyte contains binuclear oxygen-bridged Ir(III, IV) sulfamate complexes. The microstructure and distribution profiles of the iridium deposit in contacts of different diameters were studied. The structure of the iridium deposit is highly dispersed. The nonuniformity of the iridium deposit profile over the contact area and the dependence of the deposit thickness on the contact diameter can be reduced by varying the hydrodynamic conditions of the metal electroplating (stirring of the electrolyte with a magnetic stirrer or ultrasound) and by using electrochemical polarization. The Ir–GaAs contacts with the Schottky barrier are characterized by high quality of electrophysical parameters and good reproducibility of the volt–ampere characteristics. A decrease in the thickness of the iridium deposit and of the n-GaAs epitaxial layer leads to an increase in the barrier height of the rectifying Ir–GaAs contacts.

Polyacrylonitrile chromium(III) molybdate composite has been synthesized by mixing polyacrylonitrile into inorganic material chromium molybdate. The physicochemical properties of this material were determined using X-ray diffractometer system (XRD), infrared (IR) and thermal analysis (TGA and DTA). The adsorption studies were carried out under various parameters, such as pH, adsorbent dosage, contact time, and initial dye concentration. The experimental results show that the percentage of adsorption increases with an increase in the adsorbent dosage. The maximum adsorption occurred at the pH value of 2.45 The equilibrium uptake was increased with an increase in the initial dye concentration in solution. Adsorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The experimental isotherms data were analyzed using Langmuir and Freundlich isotherm equations. The best fit was obtained by the Langmuir model with high correlation coefficients (R² = 0.9976) with a maximum monolayer adsorption capacity of 11.38 mg/g.

Mercury metal ions are very toxic, the presence of this metal and its derivatives, which are harmful even in very small amounts to the health of all organisms, was found in the study area. The purpose of this study is determination and elimination of Hg (II) ions from drinking water and aqueous environments. Modified and activated carbon produced from local plantain bark has been considered to be suitable and environmentally friendly material for mercury (II) ions removal in water treatments. 85% phosphoric acid chemical activator was used, It is then heated to 450°C for 5 h to carry out carbonization. The absorbent was characterized by SEM. Removal was performed by passing water containing ions through a column containing the adsorbent The prepared adsorbent well removed mercury ions from the aqueous solution, measuring of concentration mercury ions in samples from the inlet and outlet of the column was performed by two different methods, spectrophotometric determination at 492 nm with dithizone and atomic absorption (equipped with cold vaper apparatus) spectroscopy CVAAS, the results were almost the same. The various parameters such as pH, with (6–8), contact time (0.5, 1, 2, and 3 h), concentrations of metal ions entering the system (0.25, 0.5, 0.75, and 1 ppm), and agitation speed were investigated on adsorption effect. The efficiency of this absorbent for removal of Hg (II) ions is 87%. It can be used several times, which shows that this is a good adsorbent for elimination of mercury ions of real samples such as drinking water and industrial wastewaters, due to its ease of use, low cost and relatively good performance. The elimination method is simple, sensitive, inexpensive, fast, usable and vital for the peoples in this area

The structure and surface properties of the industrial silicon trapping catalysts were characterized by XRF, XPS, XRD, NH₃-TPD and NMR. The silicon trapping mechanism of the industrial silicon trapping catalyst was discussed. The results showed that the silicon capacity reached 28.17% during this lifetime. The captured silicon mainly existed on the surface of the silicon trapping catalyst as amorphous silicon with abundant Q species including Si(OSi)₄, Si(OSi)₃(OX), Si(OSi)₂(OX)₂, and Si(OSi)(OX)₃, proving the silicon was caputured as the amorphous silicon bilayer deposition model. After silicon deposition, the pore properties of the silicon trapping catalyst changed greatly. Compared with the fresh catalyst, the specific surface area and pore volume of the spent industrial silicon trapping catalyst decreased by 49.17% and 22.92% respectively. The deposition of silicon leaded to the loss of acid sites and changed the interaction between the support and the active metal, which result in the reduction of the number of active metal species. This may explain how the deposited silicon is related to the deactivation of the hydrotreating catalysts.

This study describes the fabrication and characterization of nanocomposite hydrogel beads based on Cellulose and synthesized silver nanoparticles (Ag-NPs) prepared by insitu and exsitu methods. The silver nanoparticles were synthesized by reducing silver nitrate (AgNO₃) by Sodium borohydrate (NaBH₄). Cellulose/Ag-NPs hydrogel beads were prepared using calcium chloride as the cross-linker. The hydrogel beads were characterized using FTIR and XRD. Moreover, swelling property of the cellulose /Ag-NPs hydrogel beads was investigated. The Ag release profile of the hydrogels was obtained for the amount of Ag released using Atomic Absorption spectroscopy (AAS). The cumulative release of Ag-NPs was estimated by measuring the absorbance at 405 nm of samples obtained at various time intervals. The exsitu and insitu nanocomposite hydrogels showed greater swelling behavior in comparison with virgin cellulose hydrogel. Both insitu and exsitu cellulose/Ag-NPs presented good antibacterial activities against Escherichia coli and Bacillus and with maximum zones of inhibition 12 ± 2 mm more than the pristine cellulose hydrogel thereby, have great pharmacological potential and a suitable level of safety for use in the biological systems.

Plain carbon steel is the most important group of engineering alloys with a wide range of applications. Electroless Ni–P coating has been attracting extensive attention because it exhibits excellent wear and corrosion resistance for steel. The present study aims to steel coating with a nanocomposite of nickel-phosphorus-hexagonal boron nitride (Ni-P-hBN) and investigate the abrasion and corrosion resistance, and its adhesion to the substrate. For this purpose, the nickel-phosphorus electroless coating was used as a substrate, and hexagonal boron nitride nanoparticles as a modifier. The coating properties were investigated by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that boron nitride with 3 g/L concentration afforded the best coating performance with a friction coefficient of 0.19.