Materials Science Forum Vol. 1088

Abstract: The chemical composition, distribution, and abundance of physiological groups of bacteria in thermal waters and microbial mats formed in the Nachikinsky, Malkinsky, and Verkhne-Paratunsky springs were studied. The degree of accumulation of microelements and formation of minerals by microbial mats of Kamchatka’s thermal springs was also analyzed. The study shows that the waters are characterized by different chemical composition, temperature, and pH content. The thermal waters under study show a low composition and numbers of functional groups of bacteria with the predominance of thionic bacteria. Prevalence of saprophytic, thionic, sulfate-reducing, manganese-oxidizing, ammonifying and nitrifying microorganisms in microbial mats was registered. The relevance of formed microbial mats in the concentration of many heavy metals, alkaline and alkaline earth elements was shown. Thus, cobalt, vanadium, arsenic (Nachikinsky), beryllium, cobalt (Malkinsky), cobalt and scandium (Verkhne-Paratunsky) were most concentrated in microbial mats of Kamchatka’s hydrotherms. All studied microbial communities show the lowest accumulation of Li (1.17-2.22), Sr (2.11-2.79), Rb (2.61-3.12), Cs (2.88-2.98) and As (1.98-2.58). The formation of minerals was found in algo-bacterial mats: quartz, plagioclase, anorthite, calcite, and magnetite.

Abstract: The need to protect technogenic soils from contamination with heavy metal ions determines the relevance of the topic under study. The aim of the work is to thermodynamically substantiate the ability of gypsum and magnesia stone to neutralize heavy metal ions. Such properties of gypsum and magnesia stone can be called geoecological protection, and the substances themselves can be called mineral geoantidotes. The main method for substantiating geoecological protection properties is a thermodynamic assessment of the reactions of interaction between ions of heavy metals and mineral geoantidotes, as well as an assessment of the solubility product of substances formed during their interaction. As a result of the research, the values of changes in the Gibbs energy during the interaction of mineral geoantidotes and heavy metal ions have been determined; it has been shown that possible products of interaction reactions can be minerals similar to natural ones. Calculations have shown the possibility of reactions occurring under non-standard conditions (1 to 40°C). The experiments carried out made it possible to determine the geoecological protective capacity of gypsum and magnesia stone in non-standard conditions and showed the absence of dependence of the geoecological protective capacity on the ambient temperature in the range from 1 to 40°C. The materials of the article can be useful for the development of technological solutions to reduce harmful pollution by ions of heavy metals of technogenic soils using gypsum and magnesia stone.

Abstract: The results of laboratory studies on selection of reagents and optimal dose during treatment of low-mast water of Saratov reservoir with high permanganate oxidability are presented. Laboratory studies of purification of low-yield water with high permanganate oxidability by POHA coagulants «Aqua-Aurat 30», aluminum sulfate and flocculants Praestol 650, PAA and Magnofloc LT-20 are presented, which can provide maximum degree of water clarification, with minimum content of residual aluminum in drinking water and permanganate oxidability value. The obtained results of experimental studies on the coagulation of low-flow waters of the Saratov reservoir with high permanganate oxidation in the flood period showed that the maximum decrease in permanganate oxidation concentration is achieved by settling at an optimal dose of coagulant «Aqua-Aurat 30» – 8.0 mg/dm³ by Al₂O₃ and a dose of flocculant Praestol 650 – 0.3 mg/dm³. The value of residual aluminium in purified water is 0.03 mg/dm³.

Abstract: The unique VSEP (Vibratory Shear Enhanced Process) membrane separation technology is presented, which minimizes the negative effects of concentration polarization. The difference in technology lies in the vibration of the membrane surface. The result are several key technology benefits. All this significantly pushes the boundaries of using membrane methods and makes it possible to use membranes where it was previously impossible. In addition, the separation process does not normally require the use of antiscalant, Recovery rates and Flux are much higher than those of traditional membrane separation systems. The technology is already widely used in the world for many different industries.

Abstract: The adsorption of nickel (II) ions by natural zeolites of the Sokirnitskoe (Transcar-pathia, Ukraine) and Kholinskoye (Eastern Transbaikalia, Russia) deposits has been studied. According to X-ray phase analysis data, the zeolite-containing sample of the Sokirnitskoe deposit contains at least 75 wt. % clinoptilolite and impurity rock - quartz SiO₂. The sample of the Kholinskoye deposit consists of heulandite (not less than 75 wt. %), as well as an impurity rock - potassium spar KAlSi₃O₈. The assessment of the ad-sorption capacity of zeolites with respect to nickel (II) ions was carried out on the basis of the analysis of adsorption isotherms. The pH of the medium of the studied aqueous solutions was 5.5–5.8. The value of ad-sorption of nickel (II) ions by heulandite is twice that for clinoptilolite and amounts to 0.104 mmol/L. The adsorption of nickel (II) ions was investigated using the Langmuir, Freundlich and Dubinin-Radushkevich models. On the basis of the Dubinin-Radushkevich adsorption model, the values of the free energy of adsorption are determined. That indicates the physical nature of the interaction of the adsorptive and the adsorbent, in the case of the zeolite of the Sokirnitskoe deposit. It is shown that the adsorption of nickel (II) ions by the zeolite of the Kholinskoye deposit proceeds according to the ion-exchange mechanism. This explains the higher adsorption values of nickel (II) ions by this sample.

Abstract: Herein, silica nanoparticles (SiO₂ NPs) were synthesized from a waste product of the zirconium carbide facility (WPZF). Firstly, the WPZF was characterized by using physical and chemical methods like X-ray powder diffraction (XRD), field emission scanning electron microscope (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), and energy dispersive X-ray analysis (EDXA) methods. Then WPZF proceeded via chemical reagents to synthesize SiO₂ NPs by using the sol-gel method. Obtained SiO₂ NPs were characterized by using XRD, SEM, EDXA, and transmission electron microscopy (TEM) methods. The yield of SiO₂ NPs reached up to 96.5% and particles were spherical with a diameter of 20 ± 3 nm. Most importantly observed SiO₂ NPs in this procedure has an amorphous structure.

Abstract: The feasibility of determining the extent of damage in fibered concrete after being subjected to high temperatures, using non-destructive methods was investigated. The study was conducted on four concrete mixtures with different fiber types. The specimens underwent a curing process at 23 °C before being exposed to different high temperatures of 400 °C, 600 °C, and 800 °C. After cooling to ambient temperature, various non-destructive tests including ultrasonic pulse velocity testing (UPV), the resonance frequency test (RF), the dynamic modulus of elasticity (Ed), the thermal conductivity test (λ), and Schmid Rebound Hammer (SRH), were performed. To evaluate the sensitivity of non-destructive techniques to assess the damage of fiber-reinforced concrete, the Lemaitre coefficient was used as a variable to describe the extent of the damage. The results indicated that the highest damage levels were obtained through the modulus of elasticity technique regardless of the type of concrete mixture or temperature exposure. There was also a potential agreement found between thermal and ultrasonic methods in evaluating the thermal degradation of concrete.

Abstract: This article shows the results of the modulus of rupture test for concrete specimens added with PET fibers and also with polypropylene, with the objective of giving a second use to this waste through recycling, and its incorporation into concrete to improve its mechanical properties. The samples were tested with different fiber contents, and the results showed an increase in the modulus of rupture at 90 days with respect to a normal sample (1-3%). Specimens with PET and polypropylene fibers had a poor performance (<18%).

Abstract: Fixed platforms employed in oil & gas shallow waters industry are subjected to dynamic loads created by winds, waves and currents. However, such loads can produce fatigue damage, like localized cracking in the weld toes of T-welded connections of the submerged structures of fixed platforms. Therefore, to repair localized cracking, a technique that combines grinding and wet welding can be applied at the weld toes of submerged structural connections. Accordingly, in the present work it is presented a methodology to restore the fatigue life of T-welded connections fabricated with A36 plate steel. Consequently, T-welded connections samples were prepared and tested under intact, grinding and grinding-wet-welding repair conditions. For the repair conditions, the weld toes were grinded 6 mm and 10 mm, and wet welding was deposited to fill the grinded material in a hyperbaric chamber, which simulated 50 m, 70 m and 100 m water depths. Afterwards, the repaired connections were subjected to fatigue loads, and the S-N curves were measured for intact and repair conditions. Fatigue results showed that the combined repair technique was able to restore the fatigue life of T-welded connections for a maximum water depth of 50 m. Nonetheless, for water depths of 70 m and 100 m the fatigue life was smaller than for 50 m, but higher compared to the only grinding repair condition.