Key Engineering Materials Vol. 850

Abstract: The effects on birch outer bark (BOB) ethanolic extractives’ chemical composition after recrystallization with C2–C5 alkanols were studied in this paper. Ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and 1-pentanol were used as solvents. The solubility of BOB extractives at the solvents boiling point was determined empirically. It was found that, with an increase of the boiling point of the solvents, the solubility of the extractives increased, reaching up to 486 g/L in 1pentanol at 142.2 °C. Recrystallization yields reached up to 67 wt% using 2-butanol and the purity of betulin up to 96 wt% using 2‐propanol as a solvent. Considering the yield of recrystallization, betulin content, boiling point of the solvent, solvent loss, toxicity and eco-friendliness of the solvent, ethanol was chosen to be the most suitable solvent for industrial scale purification of betulin in the BOB extractives. Using only one recrystallization step the content of betulin was increased by 20% — from 75 to 95 wt% and the yield of recrystallization was 32.1 g per liter of solvent.

Abstract: Synthesis or humification of humic substances (HSs) is the second widely applied organic compound transformation process after photosynthesis. Peat decomposition process results in a production of a HSs which has a high demand in agriculture, forestry, and gardening areas. Addition of the KOH is good option for environmental protection and K⁺ belongs to the nitrogen, potassium and phosphorous (NKP) mineral component. A homogenization process in a customize for commerce, where peat treatment technology was improved with the help of the cavitation effect. This effect was provided with the help of the high-speed mixer-disperser (HSMD) developed at Riga Technical University. Mechanical cavitation causes relatively high energy shifts from mechanical movement of cavitation causing elements to the liquid medium which causes efficient destruction of particles inside a suspension. Values of the peat particle diameter at 50 % in the cumulative distribution before and after 1, 2, and 3 homogenization cycles were measured in the present study. The aim of the present study was to find the optimal conditions (KOH concentration, cavitation cycles and reaction temperature) to produce potassium humate (K-HSs) regarding sustainable regenerative approach aspects. Cavitation treatment of the tested peat particle diameter at 50 % in the cumulative distribution (d₅₀) from 267 down to 129 µm; the peak in the size range from 160 up to 409 µm completely disappears and significantly decreases the number of Dalton’s which causes the more efficient formation of fulvic acid caused by increased concentration of carbonyl and carboxyl groups as compared with the conventional homogenization method.

Abstract: Diatomite or diatomaceous earth (DE) is one of materials which can be used as an adsorbent to treat heavy metal ions from waste water, even there are many factories used it to clean the water for drinking. However, natural DE (raw DE) has very low adsorption capacity because of low specific surface area. In this work, natural DE from Lam Dong province, Viet Nam was demagnetized to remove iron and activated by HCl solution for 90 minutes with concentration of 10% at room condition. Adsorbent capacity was evaluated using As solution and the results show that the activated diatomite has adsorption capacity three times higher than that of raw DE, and the specific surface area of activated diatomite was increased 47.5% with the main chemical composition of 90.8% SiO₂ and high porosity

Abstract: The extraction of copper (II) ions using di (2-ethylhexyl) phosphoric acid – based liquid membranes during a galvanostatic electrodialysis-electrolysis process was studied. Effects of the current density, copper (II) and hydrochloric acid concentration in the feed solution, carrier and admixture concentration in the liquid membrane, type of acid in the catholyte were studied, and the optimal conditions were determined. A practically complete removal of copper (II) from the feed solution containing 0.01 M CuCl₂ was achieved during 3.0 −4.0 h of electrodialysis. A possibility of effective transfer and electrodeposition of copper (II) from dilute solutions of sulfuric, hydrochloric, perchloric, nitric and acetic acids was shown. Adherent copper coatings with a fine-grained structure were obtained from dilute sulfuric acid solutions. A maximum stripping degree into the catholyte of 88 % and an electrodeposition degree of 73 % were achieved in the studied system.

Abstract: Humic substances are the main component of soil organic matter and they actively interact with substances in soils, including pollutants. Humic acid-clay mineral composite materials can be considered as prospective and low-cost sorbents for contaminant removal. The aim of this study is to develop clay mineral and humic acid composite materials and to characterise their possible applications. For this research, montmorillonite, kaolinite and bentonite were saturated with three types of humic substances: technical humic acid from lignite, humic substances extracted from raised bog peat (Latvia) and technical K humate from lignite. Obtained sorbents were characterized using FTIR. The sorption was characterised according to the chosen clay mineral and humic acid type and concentration. Comparing the influence of clay minerals and humic substances on humic matter sorption, it has been found that the sorbed amount of humic substances depend on chosen humic substances and/or clay mineral. Obtained sorbents were used for sorption of chlorpromazine. Results indicate that the most perspective sorbents for chlorpromazine removal are bentonite and bentonite modified with humic acid. However, montmorillonite-humic composites also can be used for removal of chlorpromazine from water.

Abstract: In this study ZnO photocatalysts with different loading of Eu₂O₃ and Sm₂O₃ were prepared vie microwave-assisted hydrothermal method. The prepared samples were investigated by using XRD, SEM and BET analysis. The photocatalytic activity was determined by degradation of methylene blue (MB) under Osram Vitalux illumination. Prepared ZnO photocatalysts shown high photocatalytic activity under solar light simulated radiation. After 30 minute of irradiation more than 95 % of initial MB solution was degraded. The effect of pH and photocatalyst dosage was investigated. The reusability of photocatalysts was also studied.

Abstract: This work demonstrates that 5wt% gold catalysts supported on Al₂O₃ and TiO₂ nanopowders as well as on TiO₂ nanofibers are active in the 1,2-propanediol (1,2-PDO) oxidation to lactic acid. The influence of catalysts different parameters and reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. The best result was achieved using 5wt%Au/TiO₂ catalyst over the following oxidation parameters: c₀(1,2-PDO) = 0.3 mol/L, n (1,2-PDO)/n (Au) = 4000 mol/mol, p (O₂) = 6 bar, c₀(NaOH) = 2 mol/L, t = 60 °C: 1,2-propanediol conversion was 98 % and lactic acid selectivity 89 %.

Abstract: 1.25 – 5wt%Pt/Al₂O₃, 1.25 – 5wt%Pd/Al₂O₃, 1wt%Pd/TiO₂, 1 – 5wt%Pd/TiO₂-NF, 1.25wt%Pt+1.25wt%Pd/Al₂O₃, 5wt%Pt/SiO₂, 5wt%Pt/C catalysts were synthesised and tested in the selective oxidation of 1,2-propanediol by molecular oxygen. It was found that all catalysts were active in alkaline water solutions; lactic acid was obtained as the main product of the reaction. The conversion of 1,2-propandiol and the yield of lactic acid depended on the content of active metal in the catalysts. The most active for the oxidation of 1,2-propandiol were palladium-containing catalysts supported on TiO₂ nanofibers (Pd/TiO₂-NF). The highest 1,2-propanediol conversion (100 %) and lactic acid yield (96 %) were obtained using the 5wt%Pd/TiO₂-NF catalyst at the following oxidation parameters: c₀(1,2-propanediol) = 0.3 mol/L, P(O₂) = 1 atm, n (1,2-propanediol)/n (Pd) = 500 mol/mol, t = 60 °C, c₀(NaOH) = 1.5 mol/L.

Abstract: Several 2-substituted 4-nitrobenzoic acid (NBA) derivatives such as 2-chloro-4-nitrobenzoic acid (2C4NBA), 2-methyl-4-nitrobenzoic acid (2CH34NBA) and 2-hydroxy-4-nitrobenzoic acid (2OH4NBA) were selected as model compounds because of their availability and chemically similar structures, in which the different group/atom (R) does not significantly affect the dominant intermolecular interactions – hydrogen bonds formed by the carboxylic group [1]. Quantum chemical calculations of lattice and intermolecular interaction energy were carried out to identify possible factors, which could be, used in prediction of the formation of solid solutions (SS) in binary systems of chemically similar molecules, in this case - various nitrobenzoic acid derivatives. Meanwhile, crystallization experiments were used to determine the experimental information about formation of solid solutions. The obtained crystalline phases were characterized by combined use of powder X-ray diffraction (XRPD) and differential scanning calorimetry/thermogravimetry (DSC/TG) [2].