Key Engineering Materials Vol. 1027

Abstract: This study focuses on the development and application of a novel copper hexacyanoferrate/graphitic carbon nitride composite (CuHCF/g-C₃N₄), synthesized using urea as a precursor, for the electrochemical adsorption of radioactive cesium-137 (¹³⁷Cs) from wastewater generated by washing electric arc furnace dust (EAFD). The CuHCF/g-C₃N₄-urea composite was prepared via an ultrasonication method to enhance its electrochemical and adsorption properties, resulting in a porous, high-surface-area material with improved electron transfer capabilities. Characterization through SEM-EDS, XRD, BET and BJH confirmed the composite’s structure and the successful integration of CuHCF within the g-C₃N₄ matrix, while BET analysis showed an enhanced surface area conducive to improved adsorption efficiency. Key parameters, including electrolyte concentration, potential range, and scan rate, were optimized to maximize adsorption efficiency. The material demonstrated excellent ¹³⁷Cs removal performance, with an efficiency greater than 50% within 250 cycles using the electrochemical method. These findings highlight the potential of CuHCF/g-C₃N₄-urea as an efficient material for the removal of radioactive cesium in industrial wastewater, offering a promising approach for sustainable environmental clean-up.

Abstract: The article deals with the peculiarities of the process of clay particle aggregation when coagulant and flocculant are introduced, as well as the regularity of formation and deposition of the formed flocs. The studies were carried out on a model suspension of bentonite clay with a concentration of 1-10 g/l. In the course of the study, the regularities of aggregate formation in the process of coagulation; the combined action of coagulants and flocculants, as well as the destruction of flocs under the influence of mechanical action were determined, and theoretical ideas were formed regarding the models of the process and the structure of the formed aggregates. It was found that the aggregation of fine particles has optimal ratios of both the concentration of the solid phase and the ratio of flocculant to the solid phase, at which the maximum rate of particle settling is observed. The optimum concentration for this type of clay, at which the maximum flocculation rate is observed, was 4-6 g/l. At other optimum concentrations, a slowdown in floc settling is observed due to the lack of formation of a spherical structure at low concentrations and compressed settling at higher concentrations. To intensify the sedimentation of loose flocs, it was proposed to introduce additional mineral lime particles with a particle size of 20-40 μm, which increase the weight of flocs and accelerate their sedimentation.

Abstract: This study presents the synthesis of carbon composites based on iron powder and hydrolysis lignin, both with and without the addition of oleic acid. The synthesized composites were characterized using X-ray diffraction, gas adsorption-desorption porosimetry, and magnetometry. In addition, the adsorption performance of the composites toward methylene blue and congo red dyes from aqueous solutions was investigated. It was found that the addition of oleic acid does not significantly alter the structural or magnetic properties of the synthesized composite. However, it does affect the composition of oxygen-containing surface groups on the carbon. Analysis of the adsorption isotherms revealed that the carbon composite synthesized with oleic acid is nearly equally effective in adsorbing both methylene blue and congo red dyes. Isotherm modeling demonstrated that the synthesized composites adsorb both dyes via a physisorption mechanism.

Abstract: Concrete is one of the most common building materials in the world, the production of which is associated with large energy costs, as well as greenhouse gas emissions, which negatively affect the planet’s ecosystem. Replacing OPC (ordinary Portland cement) with GPMs (geopolymer materials) makes it possible to reduce this impact significantly. Another advantage of GPMs compared to OPC is that during the production of geopolymers, various production wastes are mainly recycled. This work is devoted to the study of the possibility of regulating the properties of GPMs using FA (fly ash) – waste from the TPPs (thermal power plants) of Georgia. Various methods of ash activation have been developed, which makes it possible to optimize the properties of GPMs obtained on its basis. We intend is to optimize the properties of the GPMs using different FA activation approaches, which will make it possible to improve the physical-mechanical properties of the binder.

Abstract: Metakaolin is in great demand worldwide as a highly active pozzolanic additive to Portland cement. The use of metakaolin helps to increase the density, water resistance, and mechanical strength of Portland cement, which makes it possible to reduce the consumption of clinker – the most energy-intensive and expensive component of cement/concrete. Usually, metakaolin is obtained by thermal processing of kaolin clays at a temperature of 600–850°C. Kaolin clay reserves in the world are strictly limited. Kaolin clays have not been identified in Georgia. However, there are kaolinized clays, which are distinguished by a lower Al₂O₃ content compared to kaolin clays. The purpose of this work is to study the possibility of obtaining a highly active pozzolanic additive – metakaolin based on kaolinized clays of Georgia and regulation of the parameters of their synthesis. It is proved that the addition of fly ash to kaolinized clay allows reducing the temperature of heat treatment and obtaining a highly effective pozzolanic additive to cement.