Кафедра технології нерганічних речовин та екології (КТНРтаЕ)

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Green Approach to the Synthesis of Gold Nanoparticles With Antimicrobial Activity Using Plant Extracts Based on a Deep Eutectic Solvent
(Ukrainian State University of Science and Technologies, 2025) Skіba, Marharyta I.; Skyba, Y. M.; Kovalenko, Ihor L.; Gnatko, Olena M.; Radkevych, T. O.; Vorobyova, V. I.
ENG: Gold nanoparticles were synthesized by reducing hydrogen tetrachloroaurate(III) trihydrate (HAuCl4⋅3H2O) using plant waste (banana peel) extracts obtained using a deep eutectic solvent (DES) based on choline chloride. It was demonstrated that the plant waste (banana peel) extract obtained by DES allows the synthesis of spherical gold nanoparticles (Au NPs), characterized by a maximum plasmon resonance absorption peak at approximately λ=540–560 nm, with an average nanoparticle size range of 31–68 nm with a zeta potential value of –33 to –36 mV, depending on the initial concentration of the precursor stabilizer used in the synthesis process. Choline chloride-based DES was used as a new alternative to conventional solvents for ultrasonic extraction of active substances from plant waste, in particular banana peel. Low-temperature eutectic solvents based on choline chloride were compared with glycerol and lactic acid in a ratio of 1:3 and water 10–30%. It was found that choline chloride and glycerol in a ratio of 1:3 with a water content of 30% are highly effective for the extraction of flavonoid compounds from plant waste (banana peel). The influence of extraction parameters, namely sample-to-solvent ratio and extraction time, on the content of extracted flavonoids and antioxidant activity of the extract was studied using the methods of determining antioxidant activity by ferric ion reduction (FRAP) and the ABTS test (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid). It was established that the extracted flavonoid content using DES is 222–521 mg/100 g. It was established that the sample-to-solvent ratio (1:45–1:80) and the extraction time of 10–30 min allow obtaining the antioxidant activity value of banana peel extracts, determined by the FRAP and ABTS methods: 20–60 mmol/l and 15–35 mmol/l. The gold nanoparticles obtained using DES extracts of banana peel showed higher antibacterial activity against E. coli compared to the DES extract of banana peel and non-sterilized gold nanoparticles
Leaching of Reduced Ilmenite Concentrate From the Samotkan Deposit Using Sulfuric Asid Solutions
(Ukrainian State University of Science and Technologies, Dnipro, 2025) Kozhura, O. V.; Tsybulya, E. O.; Kovalenko, Ihor L.
ENG: A strongly altered ilmenite concentrate from the Samotkan deposit was reduced with coal at 12000C for 4 hours, yielding a product in which 90% of iron was reduced to the metallic state. Iron was leached from the reduced ilmenite using 6–22% sulfuric acid solutions at temperatures of 20–700C for three hours. It was found that the leaching of metallic iron by acidic solutions proceeds rapidly in the initial period, following a firstorder reaction mechanism with an apparent activation energy of 40.2–42.6 kJ/mol, indicating kinetic control of the process. The reaction order with respect to hydrogen was determined to be 0.36–0.42. After approximately 57% of iron was extracted, the leaching mechanism changed, causing a sharp slowdown in the process. Laboratory modeling of a two-stage countercurrent process was conducted to produce synthetic rutile by leaching the reduced ilmenite with titanium white waste acid. By metering the feed of reduced ilmenite, the rapid iron dissolution stage can be utilized to regulate the acidity of the waste to a level of 3–5 g/L H2SO4 . The required level of impurity removal was achieved by exposing the partially leached reduced ilmenite to an excess of the initial 22% titanium white waste acid for 3 hours at 700C. Calcination of the solid residue at 8000C yielded synthetic rutile containing 92% TiO2 and 2.6% FeO. After the crystallization of iron sulfate, the residual slightly acidic solution, containing iron(II), aluminum, magnesium, and titanium(III) sulfates, was found to contain about 22–24 mg/L of scandium.
Reduction of Water Calcium Hardness in the Denitrifying Biofilter
(Taylor and Francis Ltd., United Kingdom, 2025) Borysov, Ivan A.; Kovalenko, Ihor L.; Gevod, Viktor S.; Frolova, Liliya A.
ENG: Sustainable development goals emphasize the need for cost-effective removal of nitrates from water of sources where there is no centralized tap water supply. This paper describes the properties of the carbonate system in the filtrate of the point of use handy submersible denitrifying biofilter. Device has a U-shaped design with open tops of both elbows and operates in displacement (piston) mode. These allows getting up to 5 liters of denitrified water daily in one gulp, reducing the concentration of nitrate ions in the water by 96-98% from its initial value of 3⋅10−3⁢𝑀−1.2⋅10−2⁢𝑀 and the water hardness to reduce depending of initial nitrate concentration. The denitrification process occurs with the consumption of ethyl alcohol as a bacterial food substrate injected to water and accompanies by the accumulation of alkaline bacterial exometabolites in the filtrate. During the microbiological transformation of 3⋅10−3⁢𝑀 nitrate ions into nitrogen gas, the filtrate enriches with 2.6⋅10−3⁢𝑀 bicarbonate ions and 3.9⋅10−4⁢𝑀 of hydroxyl ions. This results in a reduction of filtrate hardness from 3.75 mg-eq/L to 1.87 mg-eq/L when in contact with atmospheric air. Physical experiments and mathematical modeling verified the concentrations of carbonate components and calcium ions in both the initial and denitrified water.
Reliable and Accessible Point-of-use Water Denitrification System
(Ukrainian State University of Science and Technologies, Dnipro, 2025) Gevod, Viktor S.; Borysov, Ivan A.; Kovalenko, Ihor L.
ENG: This paper describes the design and operation of a reliable and accessible point-of-use water denitrification system. The system includes a U-shaped submersible denitrifying biofilter and a bubble-film extractor. The biofilter utilizes the combined actions of denitrifying, sulfate-reducing, and sulfur bacteria. Denitrifying bacteria convert nitrates into nitrogen gas and reduce the calcium hardness of water in proportion to the nitrate concentration. When the water is contaminated with both nitrates and sulfates and the bacterial community receives excess nutrients (ethanol), some sulfates are converted into hydrogen sulfide. This process facilitates the removal of heavy metal ions from the water in the form of hydrosulfides. When the sulfate-reducing bacteria produce excess hydrogen sulfide, the sulfur bacteria convert it into colloidal sulfur at the biofilter outlet. The bubble-film extractor removes colloidal sulfur, heavy metal hydrosulfides, calcium carbonate dispersions, and hydrogen sulfide from the filtrate. The system is user-friendly, requiring no special skills or knowledge for installation and maintenance. The proposed system demonstrates cost-effective denitrification and water polishing over long-term use.