Degree Of Oxidation Research Articles

Evaluation of Lipid Oxidation Characteristics in Salmon after Simulation of Cold Chain Interruption Using Rapid Evaporation Ionization Mass Spectrometry.

Temperature fluctuations occurring during the cold chain logistics of salmon contribute to lipid oxidation. This study aimed to simulate cold chain interruption through freeze-thaw operations and evaluate the lipidomics data from salmon samples subjected to different numbers of freeze-thaw cycles by using rapid evaporative ionization mass spectrometry (REIMS) combined with an intelligent surgical knife (iKnife). The results indicated significant differences in the relative abundance of characteristic ions among the samples (p < 0.05). A total of 34 ions with variable importance for the projection values ≥1 were identified as potential biomarkers, including m/z 719.4233 ([PCC36:5-NH(CH3)3]-), m/z 337.3134 ([FAC22:1]-), m/z 720.4666 ([PEC35:6-H]-), m/z 309.2780 ([FAC20:1]-), m/z 777.4985 ([PCC40:4-NH(CH3)3]-), m/z 745.4421 ([PCC38:6-NH(CH3)3]-/[PEC38:6-NH3]-), m/z 747.4665 ([PCC38:5-NH(CH3)3]-/[PEC38:5-NH3]-), etc. The degree of lipid oxidation was found to be associated with the number of freeze-thaw cycles, exhibiting the most significant alterations in the relative abundance of lipid ions in the 8T samples. Additionally, sensory evaluation by the CIE-L*a*b* method and volatile analysis by headspace solid-phase microextraction gas chromatography-mass spectrometry demonstrated significant differences (p < 0.05) in color and odor among the salmon samples, with a correlation to the number of freeze-thaw cycles. The primary compounds responsible for alterations in salmon odor were aldehydes with lower odor thresholds. In summary, the iKnife-REIMS method accurately differentiated salmon muscle tissues based on varying levels of lipid oxidation, thus expanding the application of REIMS.

Varying the degree of oxidation of graphite: effect of oxidation time and oxidant mass.

In this work, we employ a fast and less toxic modified Hummers' method to develop graphene oxide (GO) with varying degrees of oxidation and investigate the effect of the latter on the structure and the thermal properties of the synthesized materials. Two different key parameters, the time of the oxidation reaction and the mass of the oxidation agent, were systematically altered in order to fine tune the oxidation degree. All graphene oxides were characterized by a plethora of experimental techniques, like X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) as well as infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) for their structural, thermal and chemical identification. The results revealed that for a certain amount of oxidant, the time does not affect the final degree of oxidation of the materials, at least for the examined reaction times, because very similar structural patterns and thermal properties were obtained. At the same time, the oxygen-containing functional groups were found very similar. On the other hand, the degree of oxidation was found highly dependent on the mass of the oxidizing agent. XRD analysis showed a systematic increase of the interlayer distance of the synthesized GOs with the increase of the oxidant mass, whereas both the enthalpy of reduction and the % weight loss were increased. Moreover, XPS measurements provided a quantitative evaluation of the amount of carbon and oxygen in the materials; the increase of the oxidant mass led to a decrease of the total carbon content with the concurrent increase of the total oxygen amount.

Impact of doping on the mechanical properties of conjugated polymers.

Conjugated polymers exhibit a unique portfolio of electrical and electrochemical behavior, which - paired with the mechanical properties that are typical for macromolecules - make them intriguing candidates for a wide range of application areas from wearable electronics to bioelectronics. However, the degree of oxidation or reduction of the polymer can strongly impact the mechanical response and thus must be considered when designing flexible or stretchable devices. This tutorial review first explores how the chain architecture, processing as well as the resulting nano- and microstructure impact the rheological and mechanical properties. In addition, different methods for the mechanical characterization of thin films and bulk materials such as fibers are summarized. Then, the review discusses how chemical and electrochemical doping alter the mechanical properties in terms of stiffness and ductility. Finally, the mechanical response of (doped) conjugated polymers is discussed in the context of (1) organic photovoltaics, representing thin-film devices with a relatively low charge-carrier density, (2) organic thermoelectrics, where chemical doping is used to realize thin films or bulk materials with a high doping level, and (3) organic electrochemical transistors, where electrochemical doping allows high charge-carrier densities to be reached, albeit accompanied by significant swelling. In the future, chemical and electrochemical doping may not only allow modulation and optimization of the electrical and electrochemical behavior of conjugated polymers, but also facilitate the design of materials with a tunable mechanical response.

Chitosan quaternary ammonium salt-oxidized sodium alginate-glycerol-calcium ion biobased self-healing hydrogels with excellent spontaneous repair performance.

Self-healing hydrogels have attracted wide attention because of their potential applications in various fields. However, the complex processes, environmental requirements, and insufficient functionality limit their practical application. Herein, we synthesized a chitosan quaternary ammonium salt-oxidized sodium alginate-glycerol-calcium ion (HACC-OSA-Gly-Ca2+) biobased hydrogel with a multi-network structure that exhibits excellent self-healing abilities. This was achieved by utilizing reversible dynamic imine bonding, electrostatic interactions, Ca2+ ions as crosslinking points, and hydrogen bonding. The oxidation of sodium alginate (SA) with sodium periodate was carried out to obtain oxidized sodium alginate (OSA) with varying oxidation degrees. The resulting OSAs were then introduced into a glycerol-water solvent system containing chitosan quaternary ammonium salt (HACC) and calcium chloride, and this reaction successfully prepared the biobased eco-friendly self-healing hydrogel. The impacts of the oxidation degree (OD) of OSA on the microscopic morphology, mechanical properties, viscoelastic properties, swelling properties, and self-healing properties of the corresponding synthetic hydrogels were investigated. The outcomes indicated that the optimal HACC-OSA-Gly-Ca2+ hydrogel possessed good mechanical properties, with a tensile stress of 0.0132 MPa and elongation at break of 551.38%. Furthermore, the multiple bond interactions led to a high self-healing ratio (100%), with an elongation at break of about 614.29%, and excellent adhesion ability (average peel strength of 6.38 kN m-1) on various substrates. Additionally, the composite hydrogels exhibited excellent water retention, thermal stability, and resilience, making them promising for various potential applications. Moreover, the properties of the composite hydrogels could be facilely and finely tuned by varying the oxidation degree of OSA and ratio of each component. Thus, the presented strategy could enrich the construction as well as application of biopolymer-based self-healing hydrogels.

Regioselective palladium-catalysed aerobic oxidation of dextran and its use as a bio-based binder in paperboard coatings.

The coatings industry is aiming to replace petrochemical-based binders in products such as paints and lacquers with bio-based alternatives. Native polysaccharide additives are already used, especially as adhesives, and here we show the use of oxidised dextran as a bio-based binder additive. Linear dextran with a molecular weight of 6 kDa was aerobically oxidised in water at the C3-position of its glucose units, catalysed by [(neocuproine)PdOAc]2(OTf)2. The resulting keto-dextran with different oxidation degrees was studied using adipic dihydrazide as a crosslinker in combination with the commercial petrochemical-based binder Joncryl®. Coating experiments show that part of the Joncryl® can be replaced by keto-dextran while maintaining the desired performance.

Investigating the room- and cryo-milling impact in lignocellulosic biomass and its consequence over pyrolysis and oxidative treatments

The lignocellulosic biomass recalcitrance is the uppermost factor for the utilization of this renewable resource. The development of new pre-treatments, addressed to enhance performance in lignocellulosic biomass conversion into biofuels, fine chemicals, and as potential sources of building blocks for materials, must be focus in two main areas: effectiveness (cost-effective and chemical effective) and green chemistry. In this research, a set of different biomass sources (farmer, harvested wild trees and secondary products) were studied to evaluate the high efficiency of the non-liquid nitrogen (LN) and LN-treated biomass samples’ planetary ball milling performance. The samples have been characterized by particle size distribution, thermogravimetric, FT-IR, statistical chemometric and chemical oxidation analysis. The results have shown a high level on the rupture of the crystallinity and depolymerization degrees of the cellulose and the lignin, for both, non-LN and LN-treated samples. The thermogravimetric analysis showed a clear diminishing in temperature degradation, and a larger amount of biomass degraded at lower temperature, as well as, a high chemical oxidation degree than not milled samples. Finally, the LN-treated samples even exhibited a lower degradation temperature, a larger amount of biomass degraded at lower temperature and a higher oxidation degree, than those non-LN milled.

Harnessing the Antioxidative Potential of Dental Pulp Stem Cell-Conditioned Medium in Photopolymerized GelMA Hydrogels.

Gelatin methacryloyl (GelMA) stands out for its biocompatibility, tunability, and functionality, being often selected as a scaffolding material. However, the biological modulations induced by its photocrosslinking process on mesenchymal stem cells as well as stress mitigation measures remain insufficiently explored. By using GelMA of Good Manufacturing Practice (GMP) grade, this study aimed (a) to achieve a comprehensive understanding of the biological effects of photocrosslinking process with a specific focus on oxidative stress and (b) to develop a strategy to mitigate the adverse effects by employing conditioned medium (CM) by dental pulp stem cells (DPSCs). Following photocrosslinking, pathways related to oxidative phosphorylation and DNA repair were enriched in the presence of DPSC-CM carrying various antioxidants such as peroxiredoxin (PRDX) 1-6 and superoxide dismutase type 1 (SOD1), while the control samples exhibited enrichment in inflammatory signaling pathways. Incorporating DPSC-CM into the hydrogel notably reduced the degree of cellular oxidation caused by photocrosslinking and stress responses, resulting in improved cell viability, growth, motility, and osteogenic differentiation, as well as fewer apoptotic and senescent cells compared to those without DPSC-CM. The deteriorated biocompatibility of freshly crosslinked GelMA hydrogel was confirmed by the disrupted vasculature of chorioallantoic membranes in chicken embryos after implantation, which was prevented by DPSC-CM. In conclusion, this study demonstrates the robust antioxidative effects of DPSC-CM, mitigating the negative effect of GelMA photocrosslinking processes.

Graphitic nanoflakes modulate the structure and binding of human amylin.

Human amylin is an inherently disordered protein whose ability to form amyloid fibrils is linked to the onset of type II diabetes. Graphitic nanomaterials have potential in managing amyloid diseases as they can disrupt protein aggregation processes in biological settings, but optimising these materials to prevent fibrillation is challenging. Here, we employ bias-exchange molecular dynamics simulations to systematically study the structure and adsorption preferences of amylin on graphitic nanoflakes that vary in their physical dimensions and surface functionalisation. Our findings reveal that nanoflake size and surface oxidation both influence the structure and adsorption preferences of amylin. The purely hydrophobic substrate of pristine graphene (PG) nanoflakes encourages non-specific protein adsorption, leading to unrestricted lateral mobility once amylin adheres to the surface. Particularly on larger PG nanoflakes, this induces structural changes in amylin that may promote fibril formation, such as the loss of native helical content and an increase in β-sheet character. In contrast, oxidised graphene nanoflakes form hydrogen bonds between surface oxygen sites and amylin, and as such restricting protein mobility. Reduced graphene oxide (rGO) flakes, featuring lower amounts of surface oxidation, are amphiphilic and exhibit substantial regions of bare carbon which promote protein binding and reduced conformational flexibility, leading to conservation of the native structure of amylin. In comparison, graphene oxide (GO) nanoflakes, which are predominantly hydrophilic and have a high degree of surface oxidation, facilitate considerable protein structural variability, resulting in substantial contact area between the protein and GO, and subsequent protein unfolding. Our results indicate that tailoring the size, oxygen concentration and surface patterning of graphitic nanoflakes can lead to specific and robust protein binding, ultimately influencing the likelihood of fibril formation. These atomistic insights provide key design considerations for the development of graphitic nanoflakes that can modulate protein aggregation by sequestering protein monomers in the biological environment and inhibit conformational changes linked to amyloid fibril formation.

First-principles study of F adsorption by TiN with its oxide surface in three-dimensional NAND flash memory

Three-dimensional (3D) NAND flash memory is a key technology in the field of mainstream memory solutions, which is primarily due to its extremely low bit cost. The architecture of 3D NAND, characterized by its vertically stacked design, substantially enhances the capacity of individual chips. This advancement is completely consistent with the demands for high-capacity data storage in contemporary environments, securing its widespread adoption in diverse application scenarios. As storage density increases, the complexity of process integration increases, bringing new challenges. The word lines in 3D NAND are typically filled by using gate replacement techniques, and compared with chemical vapor deposition (CVD), atomic layer deposition (ALD) is favored for its superior step-coverage, especially for depositing tungsten (W) at the gate. However, due to the complexity of the replacement gate deposition structure, fluorine (F) residues are found in the voids of the tungsten metal gate filling structure and diffuse into the surrounding structure under subsequent process conditions, corroding other films such as silicon oxide and degrading device performance and reliability. To alleviate the problem of fluorine attack, a thin layer of titanium nitride is usually deposited as a barrier layer before deposition of tungsten gate, which blocks the fluorine in the tungsten gate and prevents its diffusion into the oxide layer. Previously, there were studies to increase the ability to stop F diffusion by varying the thickness of the F blocking layer (TiN). However, increasing the thickness of TiN will further increase the complexity of high aspect ratio etching in the 3D NAND process, which will have adverse effect on subsequent processes. To further minimize the effect of fluorine erosion, residual fluorine elements can be removed by introducing annealing in the subsequent process flow. In the actual 3D NAND process, elemental fluorine (F) is adsorbed and accumulates on the TiN surface, and is further activated by subsequent high-temperature processes, leading to severe fluorine erosion. The delay between TiN deposition and subsequent processing steps is hypothesized to facilitate fluorine adsorption due to the oxidation of TiN. This work corroborates this hypothesis through first-principles calculations, and demonstrates the role of TiN oxidation in fluorine adsorption. In this work, we evaluate the effect of this oxidation on the fluorine-blocking effectiveness of the TiN barrier layer. We simulate the adsorption of fluorine-containing by-products on TiN and its oxides, providing theoretical insights into mitigating fluorine attack. The higher degree of oxidation of TiN is more likely to cause F adsorption, and Ti exposed surface TiN is more prone to oxidation, which is more likely to cause F adsorption in unoxidized condition and oxidized condition. Based on these insights, we implemente an ammonia purge treatment in 3D NAND manufacturing, which effectively minimizes fluorine attack, reducing the leakage probability of word line by 25% and wafer warpage by 43%.

Reasons for the low productivity of the Bashkirian stage oil deposits on the southwestern slope of the South Tatar arch

Oil deposits of the Bashkirian stage of low-amplitude uplifts on the southwestern slope of the South Tatar arch are considered. It has been established that in the sections of the Bashkirian stage, only the upper two oil deposits are potentially productive. The reservoir rocks are composed of leached packstone-grainstone. The oil productivity of the upper oil reservoir is determined by the intensity of leaching of carbonate rocks and the nature of oil saturation, while the lower one is determined by the degree of oxidation of oils and the manifestation of secondary mineralization. Oxidation of oil from the lower reservoir oil deposit is associated with the penetration of peripheral stratal water enriched with sulphate ions and magnesium ions. Deposition of diagenetic calcite, dolomite and gypsum-anhydrite aggregates in previously formed leaching caverns leads to a decrease in porosity and connectivity within reservoir layers. For low-amplitude uplifts, there is a tendency for oil productivity to decrease as the proportion of diagenetic mineralization increases.

Surface characteristics of phenolic resin coatings

Phenolic resins are commonly used as polymer binders for metal, paper and mineral wool substrates. For such applications, mechanical, adhesive and thermal properties are considered most important, and the effect of synthesis and structural parameters on such end-use characteristics are well-documented. However, surface characteristics of cured phenolic resins can be equally relevant and are often overlooked. Widely used resins are phenol-urea-formaldehyde (PUF) and phenol-formaldehyde (PF). It is believed that the inherent chemistry and curing procedure of these resins result in coatings with distinct surface properties and wettability. To gain more insight into surface characteristics such as morphology, chemical composition and wettability of cured PUF and PF resins, different binder formulations were applied on glass substrates and subsequently characterised by Scanning Electron Microscopy (SEM), Contact Angle Goniometry (CAG) and X-Ray Photoelectron Spectroscopy (XPS). The effect of catalyst, chemical composition and curing conditions on surface characteristics of various PUF and PF coatings were investigated. The curing temperature was found to have a strong influence on surface properties; curing at 200 °C yields a surface with varying degrees of oxidation, differences in linkages between phenolic and urea species, and a lower overall nitrogen content in case of urea-containing coatings, resulting in stronger fluctuations in water-wettability compared to surfaces hardened at lower temperatures.

Enhancing minority carrier lifetime in Ge: Insights from HF and HCl cleaning procedures

Efficiently passivating germanium (Ge) surfaces is crucial to reduce the unwanted recombination current in high-performance devices. Chemical surface cleaning is critical to remove surface contaminants and Ge oxides, ensuring effective surface passivation after dielectric deposition. However, Ge oxides can rapidly regrow upon air exposure. To understand the surface evolution after wet cleaning, we present a comprehensive study comparing HF and HCl deoxidation steps on p-type Ge surfaces and monitor the surface as a function of air exposure time. Distinct oxide regrowth dynamics are observed: HF-treated samples exhibit swift regrowth of all Ge oxide states, whereas HCl-treated Ge surfaces exhibit a lower concentration of low degrees of oxidation and slower or no regrowth of high oxide states even after 110 min of air exposure. In addition, the presence of Ge–Cl bonds induces different oxidation dynamics compared to the Ge–OH bonds resulting from HF cleaning. This leads to varying surface electronic band structures, with HF-treated Ge exhibiting a strong positive band bending (+0.20 eV). Conversely, HCl-treated samples display a lower band curvature (+0.07 eV), mostly due to the presence of Ge–Cl bonds on the Ge surface. During air exposure, the increased GeOx coverage significantly reduces the band bending after HF, while a constant band bending is observed after HCl. Finally, these factors induce a reduction in the surface recombination velocity after wet etching. Combining both chemical and field-induced passivation, HF-treated Ge without rinsing exceeds 800 μs.

Tailoring pyrene excimer luminescence via controlled sulfur oxidation

Manipulation of the oxidation degree of sulfur is carried out to synthesize sulfide-, sulfoxide- and sulfone-substituted pyrenes, fine-tune the electronic effect and stiffness of the molecules, and obtain optimal luminous efficiency of the excimers.

Electrolyte engineering for the mass exfoliation of graphene oxide across wide oxidation degrees

Herein, we report a two-step electrochemical approach encompassing pre-intercalation and post-exfoliation/oxidation, enabling the mass exfoliation of graphene oxide with customizable oxidation levels on a timescale of minutes.

LASER POLISHING OF ADDITIVELY MANUFACTURED TITANIUM ALLOY IN OPEN AIR ATMOSPHERE

Additive manufacturing has witnessed remarkable growth, transforming the production of intricate geometries. However, post-processing is often required to enhance surface quality and alleviate residual stresses in additively manufactured components. Laser polishing, an advanced technique, efficiently reduces surface roughness in metals. This study stands out by conducting laser polishing without protective gas in an open atmosphere. Results demonstrate that surface roughness can be improved by up to 50% under these conditions. Nevertheless, the process introduces a recast layer with significant oxidation due to atmospheric oxygen, leading to the formation of a Titanium Oxide layer and the development of surface microcracks. As oxidation increases, surface hardness also rises. Achieving high-quality surfaces for additively manufactured Ti alloys in an open atmosphere is attainable, provided vigilant monitoring of oxidation-related challenges. This study reveals the intricate relationship between laser polishing, surface characteristics, and the effects of open-air conditions on Ti-6Al-4V components.

Chemical characterization of sunflower oil oxidized by UV and ozone with different degrees of oxidation and study of their antimicrobial action

Oxidation by the action of ozone takes place at high rates and involves the reaction of ozone molecules with fatty acid double bonds followed by the formation of stable oxidation products with biological activity. In the present work, a comparative study on sunflower oil oxidized by ultraviolet (UV) light and ozone was carried out. This study involved the chemical characterization of sunflower oil oxidized by UV irradiation and ozonation, in addition to assessing the germicidal activity of oxidized oils obtained under various conditions. The results indicated that under the conditions studied, the increase in the dose of UV irradiation did not produce significant changes in the level of oxidation of the oil. Ozonation promoted the formation of oxygenated compounds at higher rates, increasing in concentration as the applied dosage of ozone increased. The germicidal activity of the oils behaved similarly, with considerably higher activity found in the ozonized oils.

Main minerals of the Araxá alkali-carbonatite complex, Minas Gerais State, Brazil

The Araxá alkali-carbonatitic complex is a significant source of niobium and phosphate and accounts for approximately 75% of global niobium production. The complex contains magmatic niobium ore minerals, such as natrium-pyrochlore and calcium-pyrochlore, and hydrothermal niobium ore minerals in the form of kenopyrochlore and natrium-pyrochlore. The magmatic micas in the complex are tetraferriphlogopites that exhibit Mg-rich cores surrounded by one or two rims of tetraferriphlogopites formed by hydrothermal alteration. These rims have lower IVAl and Mg apfu (atom per formula unit) values but higher IVFe3+ and Fe2+ contents than the original phlogopite. Microphlogopitite dikes that formed during several episodes of magmatism between 83.48 and 77.4 Ma contain tetraferriphlogopites, phlogopite, eastonite, biotite, and annite-siderophyllite. These micas exhibit variations in Mg2+ and Fe2+ concentrations owing to the magmatic differentiation and subsequent hydrothermal alteration, resulting in rims with higher Mg and lower Fe2+ concentrations than the mica core. The Araxá complex also contains magmatic magnetite that has been further altered by hydrothermal processes, resulting in the formation of ilmenite and the oxidation and crystallization of titaniferous hematite. Magnetite within the microphlogopitites displays variations in the concentrations of Fe3+ and Ti, likely owing to the timing of the intrusion of the microphlogopitites into the Araxá complex. The degree of oxidation of the oxidized ilmenite of the Araxá complex varies based on the intrusions, which occurred before or during hydrothermal activity. Apatite is concentrated in carbonatites, which form a ring around the core of the complex, and disseminated in phlogopite-rich rocks hosting norsethite carbonatite veins in the center of the complex. The apatite in the core rocks exhibits complex zonation with unexpected changes in Ca, P, and Sr concentrations. Apatite in the carbonatite ring was generated during the differentiation of the carbonatite magma, whereas that in the core rocks exsolved from the phosphorus-saturated carbonatite magma (in press). The carbonate minerals dolomite, norsethite, and calcite exhibit compositions grouped around their end-members, suggesting that they formed during different stages of magmatic source differentiation. Strontium differentiation occurs in the magmas corresponding to each endmember, and carbocernaite is exsolved from the Sr-saturated crystals, thus forming micro-inclusions in some carbonate crystals that have been displaced by late-magmatic hydrothermal fluids.

Microstructural Evolution of High-Entropy Intermetallic Compounds during Detonation Spraying

This study aims at investigating the feasibility of depositing quality coatings from various high-entropy intermetallic compounds (HEICs) using detonation spraying (DS). Four different HEIC coatings, namely (NbTaVCrTi)Al3, (NbTaVNiFe)Al3, (NbTaVZrHf)Al3, and (FeNiCoCrMn)(MoCr), were prepared by DS on low alloy steel substrates. The HEIC powders were first prepared by arc melting followed by ball milling and then used as reinforcement particles to deposit HEIC coatings. Elemental segregation was observed for all the as-cast samples. Powders with average particle sizes of about ~25 µm for (NbTaVCrTi)Al3, ~22 µm for (NbTaVNiFe)Al3, ~34 µm for (NbTaVZrHf)Al3, and ~18 µm for (FeNiCoCrMn)(MoCr) were obtained. (NbTaVCrTi)Al3, (NbTaVNiFe)Al3, and (NbTaVZrHf)Al3 HEICs exhibited a nearly single D022 (TaAl3 type) structure, while (FeNiCoCrMn)(MoCr) exhibited a single D8b (FeCr type) structure. Dense coatings consisted of a lamellar microstructure and sound bonding with the substrate, and low porosity was obtained for all the samples. Crystal structures of the HEIC samples were highly retained during DS, whereas all the samples underwent some degree of oxidation. Microhardness values of 745 HV for (NbTaVCrTi)Al3, 753 HV for (NbTaVNiFe)Al3, and 862 HV for (NbTaVZrHf)Al3 were obtained, which are significantly higher than the microhardness of the substrate (~140 HV). Among all the samples, (FeNiCoCrMn)(MoCr) exhibited the highest microhardness values of about 1047 HV.

In English

The equilibrium and spatial structure of the polycyclic aromatic hydrocarbon C96H24, chosen as a model of the graphene plane, as well as the systems obtained from it by removing the diatomic molecule C2 (C94H24) and then replacing four carbon atoms with four nitrogen atoms (C90N4H24) have been studied by the DFT method (B3LYP) in the 6-31G** basis using Grimme corrections to account for dispersion interactions. In the same approximation, the energetics of the formation of a complex of an iron atom in zero oxidation degree (Fe0) with C90N4H24 ([C90N4H24Fe]0) in the square planar field of the ligand has been studied. The types of molecular orbitals of the ligand, which correspond to the symmetry of the atomic d-orbitals of the Fe atom, have been determined. Interaction diagrams of the d-orbitals of the Fe atom with some molecular orbitals of the ligand C90N4H24 of the corresponding symmetry are constructed. It is concluded that the binding of the transition metal atom on the double vacancy of the graphene plane can be rationally described based on the local symmetry of the coordination center and molecular orbitals of the ligand and the formed complex.

Investigation of the solid oxidizer effect on the metal geotechnology efficiency

Purpose. The research is aimed at increasing the useful component content in a pregnant solution during in-situ leaching (ISL) using a solid oxidizer and increasing the ferric iron concentration in the leaching solution based on laboratory research. Methods. Laboratory research is performed on a specially developed model electrolyzer for obtaining comparative data on divalent iron oxidation to trivalent iron and the change in the useful component content in a pregnant solution. Firstly, tests are conducted with a basic leaching solution, then on the oxidation of the leaching solution with a solid oxidizer in the form of a lead dioxide plate. Tests are conducted by changing sulphuric acid concentration within 5-50 g/l, amount of divalent iron ions in the solution from 0.5 up to 4.0 g, lead dioxide plate surface area from 19 to 76 cm2. The leaching time is up to 10 hours. Findings. The results of laboratory research on determining the oxidation degree of divalent iron ions and change in the oxidation-reduction potential (ORP) depending on the sulphuric acid concentration and on the initial concentration of divalent iron ions in the initial solution are presented. With a change in the sulphuric acid concentration from 5 to 50 g/l, the oxidation value of divalent iron ions increases from 26.5 to 96.5%, and with an increase in the initial solution concentration of divalent iron, the oxidation degree of divalent iron naturally decreases from 95.2 to 58.8%. In the initial leaching solution, the divalent solution concentration is 312 mg/l, and that of the trivalent solution is 288 mg/l. After oxidation with a solid oxidizer, the divalent and trivalent iron concentrations are 56 and 392 mg/l, respectively. In the course of further laboratory research using core materials from a uranium deposit, it has been revealed that when leaching with a basic solution, the uranium content in the pregnant solution is 19.36 mg/l, and when leaching with a solution after oxidation with a solid oxidizer, it is 27.9 mg/l, which is by 8.54 mg/l more. Originality. New dependences have been determined of the oxidation degree of divalent iron ions to trivalent one on the sulphuric acid concentration and on the initial concentration of divalent iron ions, as well as the useful component content in the pregnant solution on the leaching time when using a solid oxidizer. Practical implications. Using of a solid oxidizer, it is possible to increase the trivalent iron concentration in the leaching solution and the useful component content in the pregnant solution compared with the basic technology, thereby reducing the time of mining uranium reserves. Proposed technology is environmentally friendly, with low capital costs.