Volume 59, Nº 5 (2023)

The study investigated the physicochemical and adsorption characteristics of a micro-mesoporous carbon adsorbent obtained from wood waste by a thermochemical method with respect to the processes of the accumulation of liquefied natural gas vapors in long-term storage systems. X-ray diffraction analysis of the adsorbent showed that, as a result of synthesis of the adsorbent, its structure was an amorphous carbon phase, without signs of graphite-like phases characteristic of coal obtained from other types of raw materials. In turn, the developed porous structure of the adsorbent is represented by both micro- and mesopores, with a wide size distribution: the total pore volume was about 1.7 cm3/g. The sorption characteristics of the adsorbent at temperatures of 111.7–160 K and pressures up to 0.6 MPa were calculated based on the linearity of experimental isotherms at T from 303 to 333 K and the contribution from adsorption on the surface of mesopores in the monolayer and the capillary condensation effect (CCE). Based on sorption data, it is shown that the presence of mesopores has a predominant effect on the adsorption accumulation efficiency due to the contribution of CCE, providing an active capacity of cryogenic sorption accumulators at a level of 450 m3(NTP)/m3.

Technologies of membrane-based gas separation can be integrated into existing industrial processes for low-temperature helium recovery from natural gas at the stages of crude helium separation from the N2/He mixture and its purification. The effectiveness of these processes is most affected by the properties of the materials from which the membrane is made. Due to their unique properties, metal-organic framework are promising materials for use in gas separation. In the present work, both the Monte Carlo and equilibrium molecular dynamics methods were employed to examine the temperature dependence of membrane selectivity and nitrogen permeability for separation of an equimolar mixture of N2 and He by a HKUST-1-based membrane at a pressure drop of 0.1, 0.3, and 1 MPa. It was shown that the selection of optimal temperature conditions made it possible to obtain a significant increase in membrane selectivity and permeability for nitrogen compared to corresponding parameters at room temperature.

In the present study, the possibility of using a strong-base fibrous material FIBAN A-1 (Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus, Belarus) as a sorbent to remove tryptophan from aqueous solutions is investigated. The capacity characteristics of the anion exchangers in the form of granules and fibers containing quaternary ammonium bases as functional groups with respect to the chosen amino acid are analyzed. The influence of the pH of the medium on the sorption of amino indolylpropanoic acid onto the A-1 fiber is determined. IR spectroscopy confirms the fact of the fixation of amino acids from solutions with pH ~5.0–5.5 due to the charge exchange of the zwitterion by the OH groups of the sorbent. The specific features of both the equilibrium and kinetics of tryptophan sorption from solutions with a pH close to the isoelectric point are studied. Based on the analysis of the isotherms of sorption of the amino acid at different temperatures, a monomolecular mechanism of the sorptive sorption process and its endothermic character are established. The kinetic characteristics of tryptophan sorption indicate a significant contribution of external diffusion to the velocity of the investigated process.

This work studied bulk catalysts for hydrogenation processes of a carbonyl group that have similar compositions and contain copper, zinc, aluminum, and oxygen but were obtained by different methods, such as calcination of a mixture of salts followed by reduction in a hydrogen flow and alkalinization of metal alloys. The effect of the chemical composition and synthesis conditions of such copper-containing catalysts on their surface morphology and textural properties has been studied. The levels of adsorption of hydrogen on the studied catalysts are obtained by combined simultaneous thermal analysis–mass spectrometry. The presence of individual forms of adsorbed hydrogen with different metal–hydrogen bond energies is shown. An explanation for the difference in the adsorption properties relative to hydrogen is provided.

Layered double zinc and aluminum hydroxide modified with hexacyanoferrate(II) ions was synthesized for the first time by reverse deposition. The obtained samples were studied by X-ray phase analysis, scanning electron microscopy, and low-temperature nitrogen adsorption, and their sorption characteristics with respect to uranium U(VI) were studied. The sorption capacity for the modified material under static conditions, determined by the Langmuir equation, was qmax
l = 156.70 ± 12.38 mg/g (at phase ratio V/m = 1000 mL/g, in a monocomponent solution of uranyl nitrate UO2(NO3)2 at a temperature T = 25°C and sorption time t = 24 h). Layered double zinc and aluminum hydroxide modified with hexacyanoferrate(II) ions is a promising sorbent for purification of liquid media from uranium U(VI) due to its high capacity and specific surface area, the possibility of effective use in a wide range of pH [4, 10], and low cost.

This work presents the results of a study of the physical-chemical properties of gold nanoparticles (NP) prepared in reverse micellar solutions (RMS) using various ion reduction methods, including self-assembly (SA). The spectra of the electron plasmon resonance of the Au NP in the visible region (λmax ~ 530 nm) and in the UV region of the spectrum (λmax ~ 200–220 nm) were recorded by UV–Vis spectrophotometry. In the present work, the kinetics of the primary stages of the formation of Au NPs in RMS using various synthesis methods, including SA, has been studied. Based on the results we obtained, an explanation has been provided for the effect of oxygen (aerobic conditions) on the primary stages of the formation of Au NPs using chemical (Chem) synthesis in the presence of the flavonoid quercetin, and radiation-chemical (RadChem) one based on interaction with intermediate particles of water radiolysis. The formation of Au NPs with optical absorption bands in the UV region and the visible region of the spectrum has been corroborated by the results of electron microscopy.

Mo–(Y, Zr)–Si–B coatings were obtained by direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS) using composite targets of MoSi2 + 10% MoB and (MoSi2 + 10% MoB) + 20% ZrB2, with the Y segments located in their erosion zone with a total area of 5 and 10 cm2. The structure and composition of the coatings were studied by scanning and transmission electron microscopy, glow discharge optical emission spectroscopy, and XRD. The hardness, elastic modulus, elastic recovery, adhesive strength, and resistance of the coatings to abrasive wear and cyclic impact loading were determined. The oxidation resistance and thermal stability were estimated by heating the coatings to a maximum temperature of 1000°C in a muffle furnace and in a transmission electron microscope column, respectively. It has been established that the Mo–Si–B coating contains the h-MoSi2 phase with preferred orientation in the [110] direction and crystallite size of 75 nm. Alloying of Zr and Y coatings, as well as the transition from DCMS to HIPIMS mode, contributed to the suppression of preferential growth of crystallites, increasing their dispersity and the volume fraction of the amorphous phase, which led to an increase in the crack resistance and adhesive strength of the coatings. The HIPIMS method in coating deposition caused an increase in the hardness and elastic modulus by 10%; resistance to cyclical impact, by 60%; and abrasive resistance, by 20%; it also increased oxidation resistance up to 20%. Mo–Y–Zr–Si–B coatings with the optimal composition demonstrated high thermal stability; the main structural component is the hexagonal phase h-MoSi2; it remained in the temperature range of 20–1000°C and also resulted in a more than ninefold increased oxidation resistance of the Mo substrate at 1000°C.

An analysis of the nanostructure morphology of ionic carboxyl-containing phthalocyanine and tetrasodium salt of Cu(II)-phthalocyanine-tetrasulphonic acid in the structure of latex polymers is carried out using optical and quasi-optical methods: optical microscopy, atomic-force microscopy (AFM), and fluorescence and Raman spectroscopy. The variety of shapes and sizes of the phthalocyanine nanostructures localized in the interparticle space of the latex polymers is analyzed, which determines the difference in their photochemical properties.