Перегляд за Автор "Kurylenko, V. S."

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    Acid-base properties of natural and activated zeolites and their composites
    (КПІ ім. Ігоря Сікорського ; ТОВ «Українська водна спілка», 2024) Kurylenko, V. S.; Yanushevska, O. I.
    This study investigates the acid-base surface characteristics of natural zeolite samples from the Sokyrnytsia deposit (Ukraine). The samples include untreated natural zeolite, its acid-activated form obtained by treatment with nitric acid (HNO3, 2 M) at 40 °C under continuous stirring for 4 hours, and zeolite modified with titanium dioxide, both in its natural and acid-activated forms. The acid-base properties of all zeolite forms and composites were studied using the Hammett indicator method, which involves the selective adsorption of acid-base indicators from solutions onto the surface of solid materials. Significant changes in the distribution of Brønsted acid and base sites on the surface of the investigated zeolite-based samples were observed. X-ray diffraction analysis of the acid-activated natural zeolite revealed that acid treatment induced only minor changes in the phase composition while preserving the crystalline structure of the zeolite compared to the untreated material. The influence of pH on fluoride ion removal efficiency by natural zeolite was also investigated to explain the changes in its surface acid-base properties following acid activation. To confirm the potential redistribution of the electronic configuration on the zeolite surface and the possible blocking of its adsorption properties, additional experiments were conducted on the adsorption removal and photocatalytic degradation of Congo Red dye from solutions using the acid-activated zeolite modified with titanium dioxide. The findings demonstrate the feasibility and practicality of utilizing cost-effective natural Ukrainian zeolites for the development of adsorbents and photocatalysts with tunable acid-base surface properties, which could offer competitive advantages in the removal of various pollutants from water.
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    Fluoride ions removal efficiency of natural/activated zeolite and bentonite sorbents
    (КПІ ім. Ігоря Сікорського; ТОВ «Українська водна спілка», 2023) Kurylenko, V. S.; Tolstopalova, N. M.; Obushenko, T. I.; Sanginova, O. V.; Dontsova, T. A.
    Addressing the health concern of fluoride ions contamination in water, that cause such deceases as dental and skeletal fluorosis, requires the development of effective adsorption materials for water treatment. Our research objective was to evaluate the adsorption properties and capacities of zeolite and bentonite, sourced from Ukrainian deposits, and their acid-activated forms in relation to fluoride ions and estimate fitting this data to various adsorption models. Characterization of natural and acid-activated zeolite and bentonite sorbents was performed through X-ray diffraction to determine the phase composition of these substances. Adsorption experiments were carried out at different initial fluoride ions concentrations (3, 5, 10 and 15 mg/l) and pH (3.7; 7.5). Acidification (changing pH from 7.5 to 3.7) increase adsorption capacity of natural zeolite and bentonite more than twice. It was found that natural zeolite removes fluoride ions at the level of 67 % at pH 3.7 and a high dosage of sorbent – 10 g/l and an initial concentration of fluoride ions – 5 mg/l, while its acid-activated form was more effective - the removal of fluoride ions is 86 % at a lower dosage of sorbent – 1 g/l. Similarly, natural bentonite demonstrated a maximum removal efficiency of 45 % at pH 3.7 and a dosage of sorbent – 10 g/l, and its acid-activated form allowed for the removal of fluoride ions of about 83 % at a dosage of sorbent – 2 g/l at the same fluoride ions concentration. It is shown that the Vagelar-Langmuir (VL) isotherm model is the most accurate for describing the process of fluoride ions adsorption by acid-activated forms of natural sorbents, where the R2 values are close to 0.999, indicating monolayer adsorption on homogeneous active centers. The obtained results indicate the greater efficiency of acid-activated forms of natural sorbents and the prospects of their use for the removal of fluoride ions from water.
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    Potential applications of tio2/natural zeolite composites for dye removal
    (КПІ ім. Ігоря Сікорського; ТОВ «Українська водна спілка», 2024) Kurylenko, V. S.; Dontsova, T. A
    Water pollution by organic dyes is a critical environmental issue that requires innovative and effective solutions. Photocatalytic materials based on titanium dioxide (TiO2) can effectively degrade these pollutants; however, their use in suspension form has several drawbacks, such as the difficulty of separation and limited reusability. To overcome these limitations, the use of composites is promising, as they simplify the separation of TiO2 after the reaction. The aim of this study is to modify natural Ukrainian zeolite and its acid-activated form with TiO2 nanoparticles and to determine their photocatalytic activity towards anionic dyes. TiO2/zeolite composites were synthesized by depositing titanium (IV) oxide nanoparticles onto natural zeolite and its acid-activated form, followed by thermal treatment at 500 °C. Characterization of the composites showed that the acid-activated composite achieved a specific surface area of 173.8 m²/g compared to 34.5 m²/g for the natural composite. The photocatalytic activity of the composites was evaluated by the degradation of the anionic dye Congo Red (10 mg/L) under ultraviolet irradiation. The results showed that the acid-activated zeolite modified with TiO2 nanoparticles achieved a Congo Red degradation efficiency of 65.6% after 30 minutes of ultraviolet exposure, which is 12% higher compared to the natural zeolite modified with TiO2 under the same conditions. The adsorption efficiency for Congo Red was 33.8%. This indicates that the composite not only facilitates the photocatalytic degradation of the dye but also contributes to its adsorption, enhancing the overall removal efficiency. Thus, the use of inexpensive natural zeolite as a TiO2 carrier, especially in its acid-activated form, not only simplifies the subsequent separation of the photocatalyst from the purified water but also maintains the photocatalytic efficiency in degrading anionic dyes. The enhanced surface properties and structural characteristics of the acid-activated composite make it highly effective for practical applications. This makes such composites promising candidates for application in industrial wastewater treatment systems, where economic feasibility, operational simplicity, and environmental safety are primary criteria.