Russian Journal of Physical Chemistry A最新文献

It was experimentally established that an increase in the temperature in the range of 20–90°C improves the parameters of Lu/Yb chromatographic separation on the Dowex 50WX8 cation exchanger with the α-HIBA eluent (0.125 M, pH 4.3). An increase in the temperature leads to a decrease in the height of the equivalent theoretical plate (HETP) from 7.7 to 0.6 mm for Yb and from 1.1 to 0.3 mm for Lu, to an increase in resolution between peaks from 0.6 to 1.7, and a change in Yb peak asymmetry from 2.1 to 0.4. The temperature dependences of the retention volumes are well described by the Van’t Hoff equation (R² = 0.99). The observed 1.8-fold peak broadening for Yb and 2.4-fold for Lu is accompanied by a decrease in the maximum yield in fractions from 14.4 to 5.5% for Lu and from 5 to 3% for Yb.

The processes of electrodeposition of tin–nickel alloys on 08kp steel from oxalate–ammonium electrolytes and the physicochemical properties of the coatings were investigated. It is shown that the electrodeposition proceeds with high polarization, in contrast to the process of deposition of tin–nickel alloys from a chloride–fluoride electrolyte. The highest corrosion rate (26 μA/cm²) corresponds to a sample with a coating obtained from the chloride–fluoride electrolyte. Low corrosion rate is observed for coatings of tin–nickel alloys with a low nickel content deposited from oxalate–ammonium electrolytes with the addition of the OS-20 preparation (1.2–5 μA/cm²). The influence of the ratio of alloy components on the chemical composition and microstructure of the coatings is demonstrated.

The authors present results from studying of the distribution of the activity of different products of thoron decay according to the size of aerosol particles in the nanometer range under conditions of long-term storage. Instrumental, methodological, and metrological features of studying the state of radioactive aerosol particles are considered.

The thermal stability of polymers based on oligoester(meth)acrylates (OCM-2, PEGDM-n (n = 210, 550, 750), PETA) as a function of the nature of the monomer, quinone concentration in the photoinitiating system, monomer conversion, and radical polymerization method is studied by thermogravimetric analysis. Of the studied polymers, polyPETA synthesized by sequential photo- and heat-curing exhibits the highest thermal stability. The other polymers have comparable thermal stability. It is shown that the polymer degradation temperature increases with an increase in monomer conversion and elongation of the polyethylene glycol linker. The effective activation energies for thermal degradation processes are calculated by the Friedman and Vyazovkin methods.

A lignosulfonate (LS) sample was modified by introducing zinc and iron(III) cations in it (ion exchange sorption). Associative and dissociative transformations of modified LSs in an aqueous environment were studied. The effects of the concentration (0.01–0.32 g/dm³) and nature of the counterion (Na⁺, H⁺, Zn²⁺, Fe³⁺) in LS on the variation of pH, specific and molar electric conductivity, size of LS associates, and their polydispersity, as well as the surface tension at the liquid–gas boundary, were revealed. Using the nanoprecipitation method, modified LS nanopowders with particle sizes of 40–250 nm were obtained. It is shown that the nature of the LS cation introduced in the polymer matrix has almost no effect on the morphology and size of the isolated nanostructures. The encapsulating effect of the obtained nanoassociates of modified LSs relative to the hydrophobic dye cerasine red was evaluated. It was found that the encapsulation efficiency increases with the growth of LS concentration and the charge introduced in the LS cation and amounts to 60–70%.

Samples in two ternary Cs₂O–Al₂O –SiO₂ and SrO–Al₂O₃–SiO₂ systems and in the quaternary Cs₂O–SrO–Al₂O₃–SiO₂ system were prepared using a solid-phase synthesis method from precursors obtained under hydrothermal conditions. Quantitative elemental analysis was performed by X-ray fluorescence spectroscopy, the phase content was determined by X-ray powder diffraction. A comparative stability analysis was carried out using thermogravimetry up to 1500°С. The melting temperature was determined by visual polythermal analysis using a high-temperature microscope. Significant difference in thermal stability of the samples depending on the Cs₂O content has been observed. Regardless of the ratio of Al₂O₃ : SiO₂, the samples with a Cs₂O content up to 10 mol % have the highest thermal stability, with their mass losses being less than 3%. Higher Cs₂O concentration increases the melting point: the samples with the least thermal stability due to the cesium vaporization show the highest liquidus temperature up to 1910°C.

We numerically simulate the diffusion deposition of submicron aerosol particles from a Stokes flow in model fine-fiber filters with account for their inertia. The calculations are performed using the Langevin dynamics method based on a flow field in a cell model with account for gas slip effect on the fibers. The dependences of fiber capture efficiency for finite-size particles on particle radius are calculated for different values of the Péclet and Stokes numbers. It is revealed that the position of the minimum in the dependence of capture efficiency on particle radius is not affected by the simultaneous consideration of diffusion and inertia.

Highly permeable polyphenylene sulfone (PPSU) hollow fiber membranes containing different amounts of chlorine and hydroxyl terminal groups in a weight-average molecular mass range of 65 000–80 200 g/mol have been developed. It has been shown that membranes formed from polymers with chlorine terminal groups exhibit a higher water permeance during filtration of up to 125 kg/(m² h atm). The effect of superheated steam on porous filtration membranes made of polysulfone (PSU) and PPSU has been first studied. It has been shown that the mechanical properties of the PSU membranes abruptly change during treatment with saturated steam at an exposure time of more than 180 h. At the same time, the elastic modulus of the PPSU membranes varies only slightly; this fact suggests that they exhibit high hydrolytic stability.

Direct carboxylation of terminal alkynes with C–H bond functionalization combined with the use of CO₂ is an efficient method for obtaining carboxylic acids. Direct carboxylation of phenylacetylene with carbon dioxide can proceed with high conversion of the substrate and selectivity of formation of the desired phenylpropiolic acid under the action of cesium carbonate and in the absence of heterogeneous catalysts regardless of the CO₂ pressure. The introduction of cesium carbonate in zeolite NaX makes it possible to obtain a recyclable system for carboxylation of phenylacetylene.

Porous carbon and silica, which can be used as inexpensive adsorbents for air purification to remove volatile organic compounds (VOCs) and for solvent recovery, can be co-produced from rice husk ash (RHA). These materials are attractive due to their well-developed micro- and mesoporous structure and modifiable surface properties. The effect of various types of modification of RHA-derived adsorbents on the adsorption kinetics of VOCs is still poorly understood. In this study, porous carbons are subjected to alkaline activation, activation in a nitrogen stream, and amination in an autoclave, while silica is modified with γ‑APTES. The effect of various types of modification on the adsorption kinetics of benzene vapors is studied by a set of methods: X-ray photoelectron spectroscopy (XPS), elemental analysis, low-temperature nitrogen adsorption, scanning electron microscopy, and laser diffraction of particle dispersions. Intraparticle diffusion rates and activation energies for adsorption/desorption processes are calculated. The dependence of diffusion rate on vapor pressure is measured for carbon subjected to alkaline activation in a nitrogen stream, which is the most promising adsorbent.