WATER AND WATER PURIFICATION TECHNOLOGIES. SCIENTIFIC AND TECHNICAL NEWS

SNO2/ZNO POWDERS AND THIN FILMS FOR H2 AND NO2 MONITORING IN WATER TREATMENT PLANTS

Yevheniia Yuzupkina — 2024-12-26

Water treatment plants often use technologies associated with the emission of various gases. These can be anaerobic digestion processes, various methods of converting waste from wastewater treatment plants into valuable resources such as biogas. Increasingly, in order to comply with the principles of a circular economy, in to water purification additional processes such as electrolysis are carried out to obtain green hydrogen. Sometimes the preparation of drinking water itself requires a clean gas environment. Metal oxide semiconductor (MOS) gas sensors are used to monitor air at water objects and treatment plants. The work is devoted to studying the properties of SnO₂/ZnO powders and thin films with different molar ratios for monitoring hydrogen and nitrogen (IV) oxide. To characterize SnO₂/ZnO powders, X-ray phase and X-ray structural analyses were performed, diffuse reflection spectra were obtained in the UV-visible range, the band gap energy was calculated, and porosity and specific surface area were determined. Powder diffraction patterns were obtained for which the crystallite size was determined depending on the SnO₂/ZnO molar ratio. The band gap values range from 3.0 to 3.49 eV depending on the crystallite size. The most developed porous structure is 63.2 m²/g in a powder with 60% SnO₂, in which the average pore size is about 8.5 nm_.. To study the response of the synthesized thin films to hydrogen and nitrogen (IV) oxide, impedance spectroscopy was performed in a closed system without access to moisture at room temperature under the influence of ultraviolet radiation. The highest response value to NO₂ is observed for the film with a molar ratio of SnO₂ to ZnO as 4 to 1 (80%/20%), which is at the level of 2.12. The highest response to hydrogen is 2.42 and corresponds to a sensitive material consisting of 100% SnO₂.

ACID-BASE PROPERTIES OF NATURAL AND ACTIVATED ZEOLITES AND THEIR COMPOSITES

Viktor Kurylenko — 2024-12-26

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.

METHODOLOGY FOR DETERMINING THE EFFICIENCY OF OXYGEN REDUCING AGENTS IN AQUEOUS COOLANT

Serhii Kontsevoi — 2024-12-26

In heat exchange systems where water is isolated from air, preventing oxygen corrosion primarily involves removing dissolved oxygen. For circulating water systems, chemical reduction of oxygen is the preferred method, with reducing agent effectiveness traditionally evaluated through various physical and chemical methods in industrial and laboratory settings. The article also presents the rationale for the need to dose oxygen reducing agents in heat supply systems where damage to heat exchangers for consumers’ hot water supply is possible. We present a widely accessible technique for chemical laboratories to determine reducing agent effectiveness by measuring its concentration before and after heating water to a specified temperature in the isolated reactor with a sample material from the heat exchange system. The presence or absence of corrosion products in the water sample after heating without air contact serves as a qualitative indicator. Using an autoclave reactor at 70°C, we observed reduction efficiencies of 75% without catalyst and 98% with catalyst (Co²⁺, 0.01 mg/dm³) for Steel 3 samples. For Steel 40 samples, efficiencies were 85% and 99%, respectively. Corrosion products were detected in water after heating without catalyst but were absent when catalyst was present. While catalyst concentration was selected based on literature data, our proposed method allows determination of minimum effective concentrations for known catalysts and facilitates investigation of novel oxygen reducing agents and their catalysts at water temperatures up to 190°C and beyond. This approach builds upon a previously developed method using the same laboratory equipment, which determines safe water composition to prevent calcium carbonate formation during heating. The methodology presented here will require adaptation to evaluate the effectiveness of corrosion inhibitors based on film-forming substances.

BIOCHEMICAL TREATMENT OF WASTEWATER FROM CANNING COMPANIES FOR BIOGAS AND DIGESTATE PRODUCTION

Natalia Bublienko — 2024-12-26

Canneries are a powerful source of wastewater. Wastewater is produced at various stages of the technological process and is contaminated with carbohydrates, proteins, fats, etc. Often, such wastewater is not treated or discharged into natural reservoirs incompletely treated. It is advisable to use methane fermentation. This biotechnological process will contribute to the removal of pollutants from sewage. At the same time, biofuel and biofertilizer are also produced. Therefore, research on methane fermentation of cannery effluents to obtain biogas (alternative biofuel) and digestate (plant growth stimulator) is relevant. The purpose of the work is to study the methane fermentation of cannery effluents with the production of biogas and digestate. The work's task is to study the process of methane fermentation of cannery effluents, determine the intensity of gas generation, study the stimulating effect of digestate on plant seeds. The initial COD of the effluents is 4200 mg O₂/dm³, pH 6.8. The research was carried out in a periodic regime, the loading dose was 30 %. Methane fermentation caused a high efficiency of wastewater treatment. The final value of the COD of the effluents was 500 mg O₂/dm³. The cleaning efficiency is 88.1 %. The intensity of biogas release was high. Recorded biogas formation of 4 dm³ from 1 dm³ of wastewater. The amount of biogas in terms of the amount of initial pollution: 0.95 dm³/g of COD_start. The amount of biogas in terms of the amount of fermented pollution: 1.08 dm^3/g of COD_ferm. Biogas had a high methane content – 65 – 68 %. Such biogas is used as an alternative biofuel. There is a clear classical interdependence between the reduction of sewage pollution and the release of biogas. Digestate is a valuable fertilizer and seed biostimulator. When seeds were treated with a digestate solution, the growth of roots (by 20 – 27 %), stems (by 21 – 30 %) was accelerated. Germination energy increased by 24.8 % compared to the control experiment.

ECOLOGICAL AND HYGIENIC MONITORING OF LITHIUM IN WATERS FOR VARIOUS PURPOSES IN UKRAINE AND APPROACHES TO POST-TREATMENT

Iryna Andrusyshyna — 2024-12-26

The technological revolution is transforming global demand for resources, shifting the focus from traditional energy sources like oil and gas to metals such as lithium, cobalt, and nickel. Lithium, now dubbed "white oil", is critical for powering devices and vehicles, as lithium-ion batteries are foundational in consumer electronics and electric vehicles. Historically, lithium's primary application was in the glass and ceramics industries, with secondary uses in optics and electronics. However, demand has increased substantially in recent years due to advancements in energy storage technology. The environmental impacts of lithium extraction are significant, raising levels of heavy metals like arsenic in nearby surface waters. Traditional extraction methods create evaporation ponds that lead to environmental risks, potentially releasing lithium and other metals into the ecosystem. Environmental monitoring has shown elevated lithium concentrations in contaminated industrial sites and mining runoff areas, often exceeding safe drinking water limits. Current U.S. guidelines from the EPA focus on safe recycling practices for lithium-ion batteries, but regulatory frameworks are lacking in other regions, including Ukraine. In Europe, lithium battery producers are required to incorporate recycling costs into their products, with Germany opening a lithium processing facility to support local demand and decrease reliance on imports. In Ukraine, significant lithium reserves exist, potentially among the largest in Europe, though official regulation for lithium energy storage management is lacking. Given lithium’s toxic effects at high doses — such as impacts on the gastrointestinal tract, kidneys, and nervous system — further environmental monitoring and risk assessment are crucial for sustainable development and public health protection.