Russian Journal of Applied Chemistry最新文献

Creating polymeric microbeads that can respond to stimuli and deliver drugs has various practical uses in the pharmaceutical industry. To address this need, we have developed a new type of pH-sensitive polymeric microbeads that can be used as carriers for drug delivery applications. The gelation method was used to create microbeads incorporated with reduced graphene oxide (rGO) for the controlled release of metronidazole using sodium alginate and locust bean gum. The synthesized rGO and microbeads were analyzed by FTIR, XRD, and SEM. In vitro release and swelling studies were performed at pH 7.4 and 2.0 at 37°C. The release kinetics and mechanism are analyzed by fitting the release data into various kinetics models. The antibacterial activity of the generated microbeads was tested against B. subtilis, L. acidophilus, and S. mutans. The results suggest that the developed microbeads may serve as effective carriers for antibacterial treatment.

Ionic liquid (IL) surfactants were prepared from 1-bromododecane and ethanolamines (2-dimethyl- and 2-diethylethanolamines) in an equimolar ratio to reveal how their oil-collecting and dispersing ability is influenced by the structure of the alkyl fragment. The surface activity of the substances synthesized was studied tensiometrically, and the electrical conductivity, conductometrically. The effect exerted on the colloid-chemical parameters of the surfactants by the replacement of the methyl fragment in the head group by the ethyl fragment is described. The relative oil-collecting and oil-dispersing ability of these substances was evaluated under laboratory conditions by the example of a thin oil film on the surface of waters with different levels of mineralization.

The possibility of preparing mixed Keggin-type heteropoly compounds by introducing catalytically active vanadium(V) atoms activated by the peroxide method into the framework of Mo- and W-containing heteropoly anions was demonstrated. The pretreatment of the required amount of vanadium(V) in the form of V₂O₅ with a concentrated H₂O₂ solution ensures a considerable decrease in the content of foreign ions in solutions of heteropoly compounds and in salts based on them. Incorporation of vanadium(V) atoms into the heteropoly anion framework with preservation of the structural integrity was proved by the example of acidic salts Cs_3.5H_0.5PMo₁₁VO₄₀, Cs_3.5H_0.5PW₁₁VO₄₀, and Cs_4.5H_0.5SiW₁₁VO₄₀. The textural characteristics of the target compounds were studied, their thermograms were recorded, and the phase composition was determined. High stability and low solubility of the Cs-containing salts in three cycles of hydrothermal treatment were demonstrated.

Pt- and Pd-containing catalysts based on the mesoporous aluminosilicate Al–HMS (Hexagonal Mesoporous Silica) with the Si/Al ratio of 10 were synthesized. The catalysts were tested in furfural hydrogenation in an aqueous medium at a hydrogen pressure of 1–5 MPa in the temperature interval 100–200°С. At 100°C, furfural transformed mainly into furfuryl alcohol, and at 200°С, into cyclopentanone (3 MPa of Н₂, 1 h). In the presence of the Pd/Al–HMS catalyst, the conversion and selectivity of formation of tetrahydrofurfuryl alcohol increased with an increase in the initial hydrogen pressure or in the catalyst concentration (100°С, 1 h). Pd/Al–HMS is more active in furfural hydrogenation in an aqueous medium: With this catalyst, virtually complete furfural conversion was reached in the temperature interval 150–200°С, whereas with Pt/Al–HMS the conversion did not exceed 23% (3 MPa of Н₂, 1 h).

Dielectric properties of a series of addition poly(5-n-alkylnorbornenes) (alkyl = ethyl, n-butyl, n-hexyl, n-decyl, and n-tetradecyl) were studied in a wide range of electric field frequencies (0.01–1 × 10⁶ Hz) and temperatures (form –100 to +100°С). The relative dielectric permittivity of these polymers varies from 1.97 to 2.31 at the field frequency of 1 MHz and temperature of 25°С. Addition poly(5-n-butyl-2-norbornene) has the minimal dielectric permittivity. The dielectric permittivity of the addition polymers in the glassy state remained virtually constant in the frequency and temperature ranges examined. All the polynorbornenes prepared exhibit low values of the dielectric loss (εʺ ~ 10^–3–10^–4) and dielectric loss tangent (tan δ ~ 10^–3–10^–4) in the major part of the frequency and temperature ranges examined. However, εʺ and tan δ of the polymers with long alkyl substituents (n-hexyl, n-decyl, and n-tetradecyl) considerably increased at low frequencies and high temperatures.

Catalysts based on Ru and Pd nanoparticles on mesoporous hybrid supports consisting of mesoporous phenol–formaldehyde polymers and silica were synthesized. The catalysts were tested in furfural hydrogenation at 150–250°С and hydrogen pressure of 3 MPa. In furfural hydrogenation in the presence of the Pd catalyst, the yield of tetrahydrofurfuryl alcohol was 99% when performing the reaction in ethanol, whereas the Ru catalyst showed high selectivity with respect to cyclopentanone (80%) in furfural hydrogenation in water. The hybrid catalysts exhibit higher activity than the polymer analogs.

The possibility of recovering Rh, Ru, and Pd from nitric and hydrochloric acid solutions with Fe₄[Fe(CN)₆]₃ was examined. The conditions for practically complete recovery of the sum of platinum group metals from nitric acid solutions at the acid concentrations in the interval 1–5 M were determined. From hydrochloric acid solutions, Rh and Ru can be recovered at the acid concentration of 0.1–0.5 М. Pd is completely recovered from both 1–5 M nitric and 1–5 M hydrochloric acid solutions. From simulated spent nuclear fuel reprocessing solutions, Cs, Mo, and Zr are recovered to different extents jointly with Rh, Ru, and Pd. The Rh and Ru sorption isotherms are described by the Langmuir equation. The Pd sorption isotherm has a nonstandard two-step shape. Fe₄[Fe(CN)₆]₃ can be recommended for recovering platinum metals from process solutions, including those from reprocessing of spent nuclear fuel and spent catalysts.

In this study, the effects of artificial neural networks on CO₂ adsorption on several types of rice husk activated carbon samples are investigated. Using conventional approach, the eight activated carbon samples are examined for carbon dioxide adsorption at 298 K and up to 1 bar pressure. The influence of altered training/validating ratios, various data initiation points, various training algorithms and number of neurons necessary for an artificial neural network model were investigated using ANN modelling. The work can give useful information on the effects of each of the investigated factors, which are crucial in ANN modelling and training techniques. The results may be used to create an optimum activated carbon, improved applications of gas and oil purification that plan to use artificial intelligence modelling in their evaluations.

CeO₂–MnO_x mixed oxides supported on different carriers (ZSM-5, TiO₂, and SAPO-34) were prepared by the sol-gel combustion method and evaluated for the selective catalytic reduction of NO with NH₃. The physicochemical properties of the samples were determined by using XRD, TEM, N₂ adsorption (BET method), H₂-TPR, and NH₃-TPD. The Ce–Mn/TiO₂ exhibited a higher NO conversion than Ce–Mn/ZSM-5 in the 100-200°C temperature range, but the NO conversion of Ce–Mn/ZSM-5 increases with reaction temperature (being the N₂ selectivity close to 100%) whereas, for Ce–Mn/TiO₂, the N₂ selectivity extremely decreases. The reducibility and surface acidity of samples seems to explain the catalytic performance. Thus, although the reducibility of Ce–Mn/ZSM-5 and Ce–Mn/TiO₂ was similar, the large number of surface acid sites of Ce–Mn/ZSM-5 could be a plausible reason for its excellent SCR activity. In fact, the superior SCR activity of Ce–Mn/ZSM-5 (94% NO conversion and 95% N₂ selectivity at 300°C) is related to the presence of well-dispersed Ce–Mn mixed oxide nanoparticles, high reducibility, and a large number of surface acid sites.

In this study, the anticorrosive properties of a series of sodium methyl ester sulfonate anionic surfactants on a carbon steel were estimated for an oilfield injection water collected from a well of Hassi R’Mel region—Algeria, known as Baremian water, and are compared to those of sodium dodecyl sulfate. This class of surfactants was synthesized from fatty acids by a photochemical process and present good physico-chemical properties and good biodegradability. The inhibition performance was evaluated by weight loss and electrochemical techniques: linear polarization resistance and electrochemical impedance spectroscopy. The results showed that these surfactants are good inhibitors; the inhibition efficiency increases with increasing concentration surfactants. In addition, the increase of chain length surfactants leads to the best inhibition efficiency for sodium sulfo palmityl methyl ester surfactant with 95.27, 98.20, and 95% via weight loss, linear polarization resistance and electrochemical impedance spectroscopy, respectively. Scanning electron microscopy–Energy dispersive X-ray allowed the visualization of a good adhesion of the protective deposit formed by the surfactants on the carbon steel surface including the elements presents on this surface as sodium and sulfur. The adsorption of these surfactants shows the maximum adherence to the Langmuir model and the values of Gibbs free energy of adsorption indicated that the inhibitor molecules are physically adsorb onto the metal surface.