Вода і водоочисні технології. Науково-технічні вісті, № 2(36)
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Документ Відкритий доступ Modification methods to enhance the performance of TiO2 in photocatalysis(КПІ ім. Ігоря Сікорського; ТОВ «Українська водна спілка», 2023) Zhou, Z.; Dontsova, T. A.With industrial development and changes in human lifestyle, organic pollution has become an increasingly serious problem, posing a serious threat to the ecological environment and human health. As an emerging advanced oxidation process, titanium dioxide–based photocatalysis has shown unparalleled potential in solving environmental pollution problems due to its stable catalyst properties, mild reaction conditions, environmental friendliness and low cost. However, titanium dioxide is limited in its photocatalytic efficiency by the fact that it can only be excited by ultraviolet light, its carriers are easily compounded and its adsorption capacity is weak. In order to improve the photocatalytic degradation efficiency of organic pollutants, the properties of titanium dioxide can be enhanced by means of modification. This article mainly reviews several major modification methods and research progresses of semiconductor titanium dioxide materials for the degradation performance of organic pollutants in the environment, and focuses on the advantages of the new Metal Organic Frameworks/ titanium dioxide composite system in enhancing the degradation performance of organic pollutants. Finally, the application prospects and key issues of Metal Organic Frameworks/ titanium dioxide materials in photocatalytic treatment of organic pollution problems are presented.Документ Відкритий доступ 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.Документ Відкритий доступ Structure formation of iron-containing dispersions of organomontmorylonite(КПІ ім. Ігоря Сікорського; ТОВ «Українська водна спілка», 2023) Zhdaniuk, N. V.The aim of the work is to study the processes of structure formation of organomontmorillonite in iron-containing dispersions by studying the rheological and colloid-chemical properties of such systems. To modify the surface of montmorillonite, a cationic surface-active substance, a quaternary ammonium salt, hexadecyltriammonium bromide, was used. With the help of X-ray diffraction analysis, we confirmed the penetration of molecules of surface-active substances into the interlayer space of the mineral and its increase to 1.86 nm during the modification mineral surfactant/ cation exchange capacity (S/CEC)=1. The analysis of the results of rheological studies showed that the changes in the characteristics of montmorillonite dispersions depending on the concentration of surfactants are extreme and reach a maximum (6.7 Pa) at the degree of modification of the mineral S/CEC=0.3. The high values of ultimate shear stress confirm the formation of a continuous network between the mineral particles with an "edge–face" orientation. When the surfactant content in the system increases, the ultimate shear stress of the suspension gradually decreases and reaches practically zero values. These results lay the foundation for determining the optimal parameters for the synthesis of iron-containing dispersions based on organomontmorillonite. nZVI was obtained by its reduction on the solid surface of organomodified montmorillonite from a solution of iron(II) sulfate salt. X-ray diffraction data confirmed the fixation of nZVI on the surface of organophilized montmorillonite. Analysis of the results of rheological studies showed that changes in the characteristics of dispersions of iron-containing material based on organomontmorillonite depending on the content of nZVI are extreme and reach a maximum at (6.8 Pa) when the iron content in the sorbent is 0.01 mass fraction in the solid phase of the sorbent. When the content of nZVI is increased to 0.05 mass fraction of the solid phase of the sorbent, it is possible to obtain dispersions with high values of ultimate shear stress (3.3 Pa) and clearly expressed hysteresis loops, which indicates the formation of thixotropic structures and confirms the possibility of its use in permeable reaction barriers. Experimental data confirm that with an increase in the content of nZVI above 0.1 mass fraction in the samples, the ultimate stress and plastic viscosity decrease, which leads to the failure of the suspensions. These results lay foundation for determining the optimal parameters of sorbents synthesis and regulation of their properties by changing the hydrophilic-hydrophobic balance of source systems.Документ Відкритий доступ Photocatalytic activity of ZnO/TiO2 composites in circulating conditions(КПІ ім. Ігоря Сікорського; ТОВ «Українська водна спілка», 2023) Hutsul, K. R.; Ivanenko, I. M.The development of new efficient photocatalysts is an important task for solving problems related to the purification of water and air from organic pollution. Composite materials based on ZnO and TiO2 exhibit high photocatalytic activity, which makes them promising for this application. In this work, we present the synthesis and study of the photocatalytic activity of ZnO/TiO2 composites obtained by the method of intermediate hydroxide deposition. The synthesis was carried out on the surface of Evonik P25 TiO2 with three different mass ratios of ZnO to TiO2: 1:3, 1:1, and 3:1. The resulting composites were studied by X-ray diffraction (XRD), spectroscopy to determine the optical band gap, and subjected to photocatalytic decomposition under circulating conditions. It was confirmed by XRD that ZnO crystallizes in the wurtzite phase of hexagonal syngony, and TiO2 is contained in the form of two modifications: anatase and rutile. The effect of the mass ratio of ZnO to TiO2 on the optical band gap has been studied. The optical band gap of ZnO/TiO2 composites was determined using the Kubelka-Munk algorithm. For the composites (1)ZnO/TiO2 and (3)ZnO/TiO2, the bandgap was 3.22 eV, and the lowest value (2.99 eV) was obtained for the composite with an equal ratio of ZnO to TiO2 - (2)ZnO/TiO2. The photocatalytic activity of ZnO/TiO2 composites was studied under circulating conditions with congo red dye in the presence of four different composite weights: 0.2, 0.4, 0.6, and 2 g. The maximum efficiency of photocatalytic decomposition of the dye was observed for the composite with an equal ratio of ZnO to TiO2 at a dosage of 2 g of the composite per 0.075 g of dye. The synthesized ZnO/TiO2 composites exhibit high photocatalytic activity, which makes them promising materials for water and air purification from organic pollution. The optimum mass ratio of ZnO to TiO2 for the photocatalytic decomposition of congo red dye is 1:1.Документ Відкритий доступ Water purification from heavy metal ions using lime and PHMG(КПІ ім. Ігоря Сікорського; ТОВ «Українська водна спілка», 2023) Nyzhnyk, T. Y.The method of metal ions' chemical precipitation using polyhexamethylene guanidine (PHMG) and calcium oxide (CaO) was employed for extracting metal ions from concentrated solutions. The order of reagent introduction was found to be crucial in the extraction process, with the best extraction efficiency observed when PHMG was added to water before CaO. This order of addition facilitated the polyelectrolyte effect, resulting in the unfolded conformation of macromolecules and enhancing their interaction with metal ions in solution. Optimal dosage ranges were determined, coinciding with the concentration interval of the polyelectrolyte effect, which maximized the flocculation ability and complex formation of PHMG. The combined use of PHMG and CaO, along with variations in pH, achieved high degrees of metal ion removal (>99%) in a single stage of solution treatment, except for chromium (Cr3+) and cobalt (Co2+). The surface activity of PHMG and ability to transfer metal ions as metal-polymer complexes supported its use in the flotation method for extracting heavy metal ions from low-concentration aqueous solutions. The kinetics of PHMG and metal ion removal by flotation showed rapid binding of metal ions to polymer macromolecules, and regression equations were established to describe the kinetics. The residual concentrations of metal ions after flotation met regulatory sanitary and environmental requirements for wastewater and drinking water. A two-stage scheme for heavy metal ion extraction was developed, involving chemical precipitation and flotation extraction, with a pilot plant designed and manufactured for testing. During wastewater treatment in an electroplating production setting, metal ion concentrations that complied with regulatory standards were achieved.