Browsing by Author "Frolova, Liliya A."

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Effect of Manganese Concentration and Calcination Temperature on Photochemical Properties of TiOF2/MnO(OH)
(MDPI AG, Basel, Switzerland, 2025) Sofronov, Dmytro; Frolova, Liliya A.; Rucki, Miroslaw; Mateychenko, Pavel; Baranov, Vyacheslav
ENG: The heterostructures TiOF2/(0.5–5 wt.%)MnO(OH) attract attention as potential catalysts for pollutant removal from water. In this paper, a novel synthesis route was proposed through the precipitation of MnO(OH) particles out of an alkaline solution on the TiOF2 particles. The formation of manganese oxyhydroxide was confirmed by X-ray diffraction analysis. The presence of manganese in proportions up to 1 wt.% recalculated to MnO(OH) did not affect the morphology of TiOF2/MnO(OH) particles. Higher concentrations of Mn caused the appearance of mostly spherical particles of dimensions ca. 100 nm. The effect of calcination temperatures 300–600 °C on the structure and photocatalytic activity of the particles was analyzed. It was found that calcination of the powder formed TiO2 phase with mainly anatase structure as well as Mn3O4. After calcination at 600 °C, the appearance of fluorine was detected, indicating the formation of fluorinated titanium dioxide. For higher manganese concentrations, the fluorine proportion in F-TiO2 samples decreased. Increased Mn content in TiOF2/MnO(OH) significantly improved its photocatalytic activity, shortening the degradation time and increasing the degradation degree of methylene blue (MB). However, an increase in the calcination temperature decreased the degradation degree of MB. It was found that the optimal concentration of MnO(OH) was 5 wt.%.
Influence of Synthesis pH on Structural, Dielectric and Magnetic Properties of MnFe2O4
(Oles Honchar Dnipro National University, Dnipro, 2025) Frolova, Liliya A.; Saltykov, Dmytro Yu.; Holub, Iryna V.; Bila, Оlena V.
ENG: Dispersed manganese ferrite particles were obtained by a combined co-precipitation method at different pH of the initial solution (7–12). The structural, morphological, optical and magnetic properties of the synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, and vibrational magnetometry. The XRD results showed that MnFe2O4 has a cubic spinel crystal structure with an average crystallite size of 14–65 nm. The presence of additional phases is observed at low pH and pH greater than 12. Ferritization significantly depends on pH, which affects the phase composition of the products and the size of the crystallites. In addition, with an increase in pH from 7 to 12, the percentage of microstresses and the density of dislocations decreases. The obtained MnFe2O4 samples exhibit ferrimagnetic properties, the highest saturation magnetization value of 56.8 Emu/g is achieved at pH 10. In addition, the coercive force changes from 5 to 50 Oe with increasing pH due to the increase in crystallite size.
Investigation of Structural, Magnetic, Optical, and Photocatalytic Properties of Fe/CoFe2O4 Composite
(MDPI AG, Basel, Switzerland, 2025) Frolova, Liliya A.; Protsenko, Vyacheslav S.; Butyrina, Tetiana E.
ENG: A Fe/CoFe2O4 nanocomposite was synthesized in one step by a hydrothermal method by processing the created iron and cobalt hydroxocomplexes. For precise characterization of the structure and morphology, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, and ultraviolet–visible diffuse reflectance spectroscopy (UV-vis-DRS) were used. It was found that the obtained samples have a pronounced spinel crystalline structure, with the presence of metallic iron. The crystal size was determined by various methods and was 93–104 nm. The saturation magnetization, determined from the hysteresis loop, was 189.24 Emu/g, and the force coefficient was 602 Oe. UV-vis-DRS studies showed a band gap of 2.1 eV. The photocatalytic degradation of ibuprofen, streptocide, furacilin, methylene blue, and tetracycline was investigated under the influence of UV radiation in the presence of a photocatalyst. It was confirmed that the rate of degradation of pollutants obeys pseudo-first-order kinetics. Analysis of the constant rate of reactions showed that in order of decreasing stability, pharmaceutical drugs can be dissolved as follows: ibuprofen → streptocide → furatsilin → methylene blue → tetracycline. It was found that the ratio of photocatalyst and hydrogen peroxide concentrations is important for the destruction of more stable pollutants. The effect of hydrogen peroxide and catalyst concentrations is extremely strong. For unstable compounds, the most influential factor is the duration of treatment.
PVA-CoFe2O4-Biochar Composites: Structure and Properties
(Oles Honchar Dnipro National University, Dnipro, 2025) Frolova, Liliya A.; Saltykov, Dmytro Yu.; Kushnerov, Oleksandr I.; Olkhov, Kostyantin V.; Nikitin, Maksim O.; Rodin, Dmytro O.
ENG: PVA-CoFe2O4-biochar composites were synthesized by a two-stage combined method. The resulting composites were characterized by X-ray diffraction, scanning electron microscopy, UV-visible absorption spectroscopy, vibrational magnetometry, and vector microwave analysis. The results of electron microscopy show that biochar has a block structure with large pores, so this structure can be used in the creation of composites. The magnetic properties depend on the content of cobalt ferrite in the composite. The results of the study of photocatalytic properties showed that the rate of destruction of methylene blue (MB) is 50–98% after 60 min of UV radiation. It was established that the reaction of photocatalytic decomposition of MB obeys pseudo-first-order kinetics. Among these catalysts, biochar showed the highest rate constant of 0.085 min−1, PVA/CoFe2O4-biochar composites – 0.05 min−1. When studying the absorption of electromagnetic radiation in the radar range from 8 GHz to 12 GHz by PVA/CoFe 2O4- biochar composites, it was found that with an increase in the ratio of CoFe2O4-bichar components to 0.67 wt. parts CoFe2O4, the absorption losses of the composite reach –14.15 dB/mm at a frequency of 8 GHz and –12.37 dB at a frequency of 12 GHz.
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.
Study of the Influence of Synthesis Parameters on the Structural and Magnetic Properties of Cobalt Ferrite
(Oles Gonchar Dnipro National University, Dnipro, 2024) Frolova, Liliya A.; Sknar, Irina V.
ENG: The synthesis of cobalt ferrite by plasma chemical method was studied in the work. The influence of pH of the reaction medium, temperature and duration of treatment on magnetic properties, intensity of peaks on X-ray diffraction, average size of crystallites, value of dislocation density was determined using the central composite rotatable planning of the experiment, which is based on the results obtained by X-ray phase analysis, vibrational magnetometry, and electron microscopy. Statistical analysis made it possible to quantitatively assess the influence of the synthesis parameters on the selected response functions. The results showed that the pH of the reaction medium is the parameter that shows the greatest influence both on the growth of cobalt ferrite powder crystallites and on the magnetic properties of the samples obtained by the plasma chemical method.