Fluorine Content Research Articles

Atmospheric Pollution from a Storage of Tungsten–Molybdenum Ore Mining and Processing Wastes

Experimental studies of the surface atmosphere pollution with mining and processing wastes of tungsten–molybdenum ore were carried out using an equipment devised for collecting aerosols above the surface of sands. It has been established that toxic components formed during the decomposition of residual sulfide mineralization and products of interaction between acidic waters and rocks are transported with water vapor from the sands to the surface. The moisture condensed over the sands contains high concentrations of aluminum, fluorine, iron, silicon, manganese, zinc, and phosphorus. These elements form an atmospheric pollution halo over the technogenic sands and are further dispersed by air currents over neighboring areas. In winter, the snow cover is polluted over a vast territory due to wind dispersion of the aerosols. The halo of pollution extends over tens of square kilometers. A dependence was identified of qualitative and quantitative composition of the components polluting the snow cover on the storage time of the ore processing products. It is shown that some of the toxic elements pass into solution during snow melting from suspended solids, which are brought by wind from the territory where the soil cover is disturbed by mining.

Preparation and characterization of graphene-based fluorine doped tin dioxide thin films via spray pyrolysis technique

Abstract In this work, fluorine-doped tin oxide (FTO) and graphene/fluorine-doped (G-FTO) thin films were prepared using a low-cost spray pyrolysis method at a substrate temperature of 500 °C. For the FTOs, stannous chloride was dissolved in methanol and acetic acid to form the precursor solution. A 0.05 mole (M) of hydrofluoric acid was added to the precursor as an n-type impurity. The FTO thin film has an optical transmittance of 82% and electrical sheet resistance of 15 Ω/□. By meticulously integrating graphene into the optimal precursor solution of FTO, a significant improvement in the electrical conductivity of the prepared samples was achieved, leading to a reduction in the sheet resistance to 8 Ω/□ with a suitable optical transmittance of 79%. Structural, morphological, optical, and electrical properties of the prepared sample are investigated using X-ray diffraction, scanning electron microscope, UV spectroscopy, and four-point probe technique. The best performance of the FTO thin films is achieved utilizing 2.5 µmole/L of fluorine concentration at a substrate temperature of 500°C for a spraying exposer time of 20 min. The prepared sample has an electrical sheet resistance of 15 Ω/□, optical transmittance of 82%, and figure-of-merit of 91.2×10−4 Ω−1.The addition of 0.4 µmole/L of graphene to the optimum FTO samples enhances the performance by a remarkable reduction in the electrical the sheet resistance to 8 Ω/□ and an acceptable reduction in the optical transmittance of 79%. The overall value of the figure-of-merit increased to 118.3×10−4 Ω−1. The achieved results offer a high potential for adopting the prepared films for electronic and optoelectronic applications.

The influence of various factors on the transition of the fluorinated graphene wettability from superhydrophilicity to high hydrophobicity

The wettability of fluorographene has been experimentally and theoretically investigated. The obtained results of modeling the contact angle using molecular dynamics are consistent with the experiment. Fluorographene is a high-quality insulator. The 2D insulator may be used as the atomically thin tunnel barrier. The interaction of fluorographene with water results in the formation of hydroxyl groups. Properties of hydroxofluorographene G(OH)F or Cn(OH)yFx imply temperature antiferromagnetic ordering. Previously it was assumed that complete fluorination leads to high hydrophobicity. The authors of this paper have shown that prolonged fluorination, on the contrary, induces superhydrophilicity. The adsorption of hydrocarbons from the ambient air onto the fluorographene surface results in high hydrophobicity. The combined effect of adsorbed hydrocarbons and nano-micro texturing of the surface due to fluorination allows for the transition to superhydrophobicity. After long-term storage of fluorographene in the air for 6 months, the fluorine content (in contrast to other works) has decreased slightly (by less than 10 %). Fluorine is present at a temperature of 250–300 °C in a hydrogen atmosphere. Stable C1F8.5 complexes have been obtained for the first time as a result of the self-organization of dome-shaped surface structures during prolonged fluorination. It is assumed that part of the fluorine (C1F1) has a covalent or ionic bond, and the rest of the fluorine molecules are arranged in a closed framework surrounded by C atoms. Usually, complete fluorination of graphene leads to a ratio of C1Fn less than 1 (maximum value n = 1–1.1). Dome-shaped structures with an external carbon backbone may be used for gas storage. It is possible to control the properties of fluorographene and ensure the transition from superhydrophilicity to superhydrophobicity.

Exploring the short and long-range order in connection with fluorine content in mixed anions copper hydroxyfluorides

Hydroxyl-rich (Cu-LF) and Fluorine-rich (Cu–HF) copper hydroxyfluorides Cu(OH)2-xFx (x = 0.4–0.5 and x = 0.9–1.5) were prepared by precipitation route followed by hydrothermal process where the starting pH and the HF molar content play a key role. Based on powder XRD and PDF analysis, long range and short order were evidenced with various Cu–O/F bondlengths illustrating the Jahn-teller distortion as well as the Cu–Cu intra-sheet and interslab interactions. Tuning the fluorine content allows chemical bonding modulation by antagonist effect, resulting for instance in the weakening of H bonding in the hydroxyl-rich compound. When the fluorine content increases, the average structures evolve from a disordered network with a random distribution of anions in the vicinity of Cu2+ in Cu-LF to a well ordered mixed anions phase where Cu(OH)3F3/Cu(OH)2F4/Cu(OH)5F distorted octahedra are close to C2h point group symmetry. Raman spectroscopy confirm the average structural features with the point group symmetry. One should outline in Cu–HF composition, stronger CuF3(OH)3 octahedron stiffness associated to a stretching O–H mode at lower frequency, synonymous of O–H bond weakening and consequently stronger hydrogen bonding in agreement with PDF analysis. UV–visible–NIR spectra show in Cu–HF hydroxyfluoride, an increase of the optical band gap of 0.6 eV and a decrease of Cu2+(3 d9) crystal field splitting of 0.1 eV in agreement with the larger fluorine content. However, the dxz-dyz orbital splitting increases of 0.2 eV in Cu–HF in good agreement with the C2h point group symmetry and the related distortion. Finally, whereas the hydroxyl-rich Cu-LF phase decomposes into CuO at T > 300 °C, the Fluorine rich Cu–HF compound lead at T > 320 °C to the formation of CuF2, Cu2O in addition to CuO. This unusual reduction process Cu2+ → Cu+ at low temperature is associated to the strengthening of Cu–O/F and Cu–Cu bonding in the basal plane of Cu(OH)3F3 distorted octahedron.

Petrogenesis and rare-metal mineralization of the Ririwai alkaline granitoids, north-central Nigeria: mineralogical and geochemical constraints

ABSTRACT The Ririwai anorogenic alkaline complex harbours extensive rare metal (Nb-Zr-Sn-Zn) mineralization. However, uncertainty still surrounds their origin and magmatic-hydrothermal processes responsible for their rare metal mineralization. The complex is composed of peralkaline arfvedsonite ± albite-bearing granites, mildly peralkaline fayalite-bearing granite porphyries, and weakly peraluminous biotite-bearing granites, all of which show diagnostic A1-type characteristics. Zircon U-Pb dating reveals emplacement ages between 181.4 ± 0.81 and 188.6 ± 7 Ma for the three rock units. Sm-Nd and Pb isotopes (εNd (t) = –0.6 to −5.4, 206Pb/204Pb = 17.68–17.93) constrained the Ririwai A-type granites to represent highly fractionated products of enriched mantle-derived magmas. Mass-balance modelling suggests that magma evolution was fuelled by extensive fractional crystallization of 50 ~ 60 vol.% K-feldspar, 30 ~ 35 vol% fayalite, 5 ~ 10 vol.% amphibole, and ~ 5 vol.% apatite under reduced and water-undersaturated (ΔFMQ = –1.55; logfo2 = –18.63; H2O = <2.0 wt.%) conditions and assimilation of ~ 50 vol.% crust. Whole rock and amphibole compositions revealed an increasing degree of fractionation from the fayalite-bearing granite porphyries through biotite-bearing granites to the arfvedsonite ± albite-bearing granites. This extended fractionation at the late stage of magma differentiation, facilitated by fluorine dissolution and concentration of excess HFSE and REE as alkali-fluorocomplexes in the fluorine-rich silicate melt, allowed the accumulation of economic rare metal pyrochlore and columbite mineralizations in the highly fractionated arfvedsonite± albite- and biotite-bearing granites, respectively. Nonetheless, the metasomatic reaction rim textures around the magmatic pyrochlore, coupled with the M-type lanthanide tetrad effect (TE1,3 >1.10) indicate the subsequent effect of hydrothermal processes. Tectonically, reactivated shear fractures and transcurrent faults following lithospheric stresses in a transtensional regime allowed magma uprising and emplacement of A-type granites in the Ririwai complex.

Siloxane‐containing polyimide films with high heat resistance and low dielectric constant

AbstractA series of siloxane‐containing polyimide films (PIS) were prepared by copolymerising with rigid aromatic dianhydride, siloxane diamines and six different aromatic diamines. The effects of siloxane structures, fluorine and imide content, rigid or flexible segment on the heat resistance, moisture absorption, dielectric performance, mechanical and bonding properties were systematically studied. The results show that PIS films maintain good heat resistance with Tg between 292 and 420°C and 5% weight loss temperature higher than 500°C. The moisture absorption and dielectric constant can be significantly reduced due to the presence of siloxanes and fluorinated groups, with the absorption rate as low as 1.2% and dielectric constant of 2.85 at 1 MHz. When measured at 10 GHz, the dielectric constant ranges from 3.10 to 3.50, and dielectric loss varies from 0.0059 to 0.0098. The PIS‐6 film has the best comprehensive performance due to the low imide content, introduction of trifluoromethyl and ether bonds. The peeling strength of bonding PIS‐6 film with a copper foil can reach 9.2 N/cm. It is proven that siloxane‐containing PIS films with high heat resistance, low dielectric and outstanding adhesion are achieved, which can be applied for flexible integrated circuit boards, high‐frequency electronics and microelectronics fields.

Tuning fluorine content of fluorinated graphene by an ionothermal synthesis method for achieving excellent tribological behaviors

Fluorinated graphene (FG) has been an excellent lubricant additive due to its wider layer spacing and weaker interlayer forces, and FG with different fluorine content can exhibit different tribological performance. Herein, an ionothermal synthesis method was provided to prepare FG nanosheets with different fluorine content. Under the dual function of the ionic liquids ([C16C1im][Br]) and the temperature, the [C16C1im][Br] can work well as both an intercalation agent and polar catalyst, thus achieving tuning fluorine content of FG. Surprisingly, due to the chemical stability of [C16C1im][Br], the [C16C1im][Br] used in the exfoliated process of FG can be recycled and reused at least 5 times and still remain favorable exfoliation effect. Moreover, it can be obtained that friction coefficient and wear track width are reduced by 53.1 % and 52.8 % through adding FG nanosheets into PAO4 oil, the function generated by breaking of C–F bonds can form an adsorbed film on the friction surface, thus offering a synergistic lubricant mechanism with formation of FG tribo-film. Therefore, the FG dispersed into PAO4 oil can greatly enhance the tribological behaviors during the friction process.

Salinization of shallow groundwater in the Jiaokou Irrigation District and associated secondary environmental challenges

Understanding groundwater salinization of irrigation areas and related secondary environmental challenges is important for ensuring sustainable development. However, the mechanism under which groundwater salinization forms under the influence of long-term anthropogenic activities remains unclear. Therefore, this study analyzed the spatiotemporal variation in groundwater salinization and the underlying mechanism, and discussed the secondary environmental challenges in an irrigation area. The Jiaokou Irrigation District, North China, was adopted as a case study. The results showed a slight downward trend in groundwater salinity over the past two decades at a rate of 0.0229 g/L/y. Higher groundwater salinity was observed in areas with shallow groundwater depth. This correlation was mainly attributed to evaporative concentration, with secondary processes including natural weathering, depth of water-table, and fertilizer leaching. Drainage ditches may reduce groundwater salinity. Groundwater was transformed from freshwater to salt water and then to brackish water during the runoff process. The former transformation is mainly related to evaporation and fertilization. The latter transformation could be related to the inverse relationship between the distance to the Wei River and sediment permeability, with sediment permeability positively related to groundwater flow and leading to the discharge of salt into the Wei River. The secondary environmental challenges related to groundwater salinization in irrigation areas, mainly manifested in deterioration of irrigation water quality, soil salinization, and increased fluorine concentration. This study can act as a theoretical and practical reference for the development and utilization of water resources, ecological protection, and soil salinization in typical irrigation districts.

Enhancing oil repellency of electron beam‐grafted polyethylene terephthalate fabric with 2‐(perfluorohexyl) ethyl acrylate monomer via pre‐irradiation

AbstractElectron beam (EB)‐induced graft polymerization is advantageous for the surface modification of fabrics. We investigated the effect of monomer concentration and the addition of alkyl groups on the oil repellency of polyethylene terephthalate (PET) fabrics treated with monomers containing fluoroalkyl groups through EB‐induced graft polymerization via pre‐irradiation. We use 2‐(perfluorohexyl) ethyl acrylate (FEA) and stearyl acrylate (SA(C18)) with long alkyl chains as vinyl monomers to induce reaction with radicals generated from EB irradiation. The weight gain and surface morphology of the PET fabrics change with the FEA monomer concentration. The uniformity of the EB‐grafted PET fabric surface is determined at low monomer solution concentrations. Results of X‐ray photoelectron spectroscopy analysis show that adding 0.1 mol/L of FEA monomer to the EB‐grafted PET fabric yields the highest dodecane contact angle of 93.4° and a surface fluorine concentration of 39.8%. The addition of SA(C18) monomer to the FEA monomer decreases the dodecane contact angle by 77.5° and yields a surface fluorine concentration of 19.1%. EB graft polymerization via pre‐irradiation results in a uniformly treated surface, and stable oil repellency is achieved when using solely the FEA monomer at a lower monomer concentration than that used in a similar irradiation method reportedly previously.

Influence of CaF2 on the spectroscopic studies of Dy–Eu co-doped fluoroborate glass for lighting applications

To investigate novel glass materials applicable to W-LED, we designed and prepared a series of glasses with varying compositions. The compositions of the glasses were (64-x)B2O3–15Al2O3–10Na2O–10Bi2O3-xCaF2-0.5Dy2O3-0.5Eu2O3 (x = 0, 5, 10, 15, 20, 25). The glasses were synthesized using the melting quenching method. The effect of CaF2 on the structural feature of fluoroborate glass was studied by infrared spectroscopy analyses. Determination of fluorine content in glass by 19F NMR inversion spectroscopy. The absorbance of glass increased as the CaF2 content increased in the visible and ultraviolet light ranges. The optical band gap of the prepared glasses was obtained from the absorption spectrum, which confirmed the existence of nonbridging oxygen (NBO) in the glass network structure. The fluorescence lifetime of the glass increases with increasing CaF2 content, and the quantum yield of the glass first increases and then decreases. In addition, fluoroborate glass had a lower Urbach energy, indicating that its network structure was relatively uniform and stable. In contrast, the increase in Urbach energy is due to the substitution of CaF2, leading to more defects. By adjusting the excitation wavelength and CaF2 content, the color temperature (1598–3346 K) and color rendering index (36–63) of fluoroborate glass can be effectively adjusted. These results show that the prepared Dy/Eu co-doped fluoroborate glasses have a potential application in white lighting.

Hydrophobic-oleophobic polyurethane with mechanical reinforcement: Synthesized by thiol-ene click chemistry

Polyurethane (PU) is a universal polymer material with excellent performance, widely used as foam materials, adhesives, coatings, rubber, etc. Nevertheless, the considerable presence of ester and ether bonds in the polyurethane backbone, combined with the hydrophilic –OH group located at the end of molecular chain, renders it intrinsically hydrophilic. This inherent hydrophilicity presents substantial constraints on its potential utilization in flexible electronic displays, wearable electronic devices, and various other fields. It is a great challenge for hydrophobic polyurethane to simultaneously achieve mechanical reinforcement. Herein, the fluorinated chain extenders were introduced into PU, which not only resulted in low surface energy but also improved the surface roughness through the microphase separation due to the difference in the solubility parameters between the fluorine-containing side chain and the main chain. The long-chain perfluorinated extender was achieved via thiol-ene click chemistry, thus regulating the fluorine content by adjusting the amount of chain extender. The low surface energy and high roughness, developed by microphase separation, make the DFX-PU films exhibit excellent hydrophobicity (120°) and oleophobicity (121°). Additionally, the fluorine-containing side chains aggregate to form physical cross-linking points, reinforcing the mechanical properties of the film. When the fluorine-containing chain extender accounted for 10% (DF0.5-PU), the PU film showed the best mechanical properties. Compared with the control group, tensile strength is enhanced by 165%, the toughness is increased by 287%, and the elongation-at-break was improved by 156%.

Effect of fluorine content in layered double hydroxide catalyzing oxygen evolution

Layered double hydroxides (LDHs) have been extensively studied in OER owing to their unique advantages. The mechanism of the effect of NH4F, a common and essential structural guide in the synthesis of LDH, on LDH is relatively ambiguous. Therefore, the solvothermal process synthesized a series of FeCoNi LDHs with different fluorine contents. Physical and chemical characterizations show that the fluorine content regulates the synthesis process, morphology, and electronic structure of the catalysts. The optimal catalyst required 196 mV overpotential to reach 10 mA cm-2, with a Tafel slope of 22 mV dec-1, and stable operation at a current density of 100 mA cm-2 for more than 120 h. XPS analysis demonstrated that the F- ions leached gradually during the OER reaction, promoting the formation of high-valent intermediates at the Co active site to enhance the catalyst activity. This work contributes to the subsequent study of LDH modification and NH4F.

Effects of titanium fluoride on caries inhibition and elemental distribution in the tooth structure: Comparisons with sodium fluoride at the same fluoride concentration and pH values

Titanium fluoride (TiF4) reduces mineral loss and lesion depth more effectively than sodium fluoride (NaF). However, the pH values of TiF4 and NaF solutions are different. This study aimed to evaluate the effects of TiF4 solution on the inhibition of demineralization and elemental distribution in root dentin in comparison with NaF solution at the same pH and fluoride concentrations. This study was conducted using 0.5% TiF4 or 0.675% NaF solution adjusted to pH 5 or pH 7. Bovine dentin specimens of 200 [Formula: see text]m thickness were subjected to pH cycling (pH 4.5 and 7.0; 6 cycles/day; simulated oral conditions) for eight weeks to prepare artificial carious dentin. During this cycle, the specimens were soaked in each solution once a week for 5 min. The control group involved no fluoride application during the test period. After cycling, the demineralization depth was measured and the calcium, fluorine, and titanium distributions were analyzed and calculated using an in-air micro-proton-induced X-ray emission (PIXE)/proton-induced gamma emission (PIGE) system at TIARA. At pH 7, TiF4 solution yielded a lower lesion depth than the NaF solution. The NaF solution at pH 7 showed lower fluorine concentration than that with the other fluoride solutions. Thus, TiF4 is more effective in inhibiting demineralization than NaF in a solution adjusted to pH 7. Moreover, the presence of titanium may strengthen the tooth structure.

Synthesis, Characterization, and Environmental Applications of Novel Per-Fluorinated Organic Polymers with Azo- and Azomethine-Based Linkers via Nucleophilic Aromatic Substitution.

This study reports on the synthesis and characterization of novel perfluorinated organic polymers with azo- and azomethine-based linkers using nucleophilic aromatic substitution. The polymers were synthesized via the incorporation of decafluorobiphenyl and hexafluorobenzene linkers with diphenols in the basic medium. The variation in the linkers allowed the synthesis of polymers with different fluorine and nitrogen contents. The rich fluorine polymers were slightly soluble in THF and have shown molecular weights ranging from 4886 to 11,948 g/mol. All polymers exhibit thermal stability in the range of 350-500 °C, which can be attributed to their structural geometry, elemental contents, branching, and cross-linking. For instance, the cross-linked polymers with high nitrogen content, DAB-Z-1h and DAB-Z-1O, are more stable than azomethine-based polymers. The cross-linking was characterized by porosity measurements. The azo-based polymer exhibited the highest surface area of 770 m2/g with a pore volume of 0.35 cm3/g, while the open-chain azomethine-based polymer revealed the lowest surface area of 285 m2/g with a pore volume of 0.0872 cm3/g. Porous structures with varied hydrophobicities were investigated as adsorbents for separating water-benzene and water-phenol mixtures and selectively binding methane/carbon dioxide gases from the air. The most hydrophobic polymers containing the decafluorbiphenyl linker were suitable for benzene separation, while the best methane uptake values were 6.14 and 3.46 mg/g for DAB-Z-1O and DAB-A-1O, respectively. On the other hand, DAB-Z-1h, with the highest surface area and being rich in nitrogen sites, has recorded the highest CO2 uptake at 298 K (17.25 mg/g).

Geochemical and geochronological evolution of the UHT granulites from the Eastern Ghats Mobile Belt, India: implications from F-OH substitution in biotite, thermal events and cooling age

ABSTRACT The thin lenses and bands of ultra-high temperature (UHT) granulites with diagnostic sapphirine and quartz in contact are occasionally found on the western flank of the Eastern Ghats Mobile Belt (EGMB), which inherits the suturing and over-thrusting signatures of the EGMB with the Greater Indian Landmass (GIL). The mineral biotite contains an abnormally high fluorine concentration, as revealed by the geochemical examination of these granulites from the research area (Kothuru), which was caused by the F-OH substitution to withstand extreme thermal metamorphic conditions. The geochemical results from the multi-element spider diagram and the Harker’s variation diagram with primitive-mantle normalization also show an enrichment of light rare earth elements and large-ion lithophile elements over depleted heavy rare earth elements and high-field strength elements. An evolutionary history has been established for the high-grade rocks that were subjected to ultra-high temperature metamorphism, based on the geochemical signatures of the examined granulites. The use of isotopic K-Ar cooling ages and electron microprobe monazite chemical ages of the thermal episodes, which act as useful tools to explain the time and span of the polycyclic metamorphic terrane, is another significant component of the current work. Numerous researchers have attempted to estimate the thermal episodes in various areas of the Eastern Ghats Mobile Belt, but their cooling ages are still poorly understood. Consequently, two thermal episodes that happened at 842 Ma and 637 Ma ago, as well as a cooling age of about 448 Ma that marked the quick exhumation of the high-grade rocks under study, have been recorded in the current investigation. The association between the Greater Indian Landmass and Eastern Antarctica during the existence of the Rodinian supercontinent has been established by recorded geochronological events.

Distinctive Features of the Major and Trace Element Composition of Biotite from Igneous Rocks Associated with Various Types of Mineralization on the Example of the Shakhtama Intrusive Complex (Eastern Transbaikalia)

This article presents data on the composition of biotite from igneous rocks of the Shakhtama complex, which are associated with various types of mineralization in Eastern Transbaikalia: Au-Cu-Fe-skarn, skarn-porphyry, Mo-porphyry, rare-metal–greisen, Au-polymetallic and Au-Bi. The major element and halogen contents were determined by EPMA. The content of trace elements was determined by means of LA-ICP-MS. As a result, the specific traits of the composition of the biotite of igneous rocks associated with specific types of mineralization of the Eastern Transbaikalia were determined. The biotites of rare-metal–greisen deposits are characterized by the maximum content of fluorine (&gt;2 wt. %) and low chlorine content (&lt;0.04 wt. %). In addition, such biotites are characterized by high XFe (&gt;0.47). Within Eastern Transbaikalia, igneous rocks developed at the Bystrinsky deposit are potentially ore-bearing for the “classic” porphyry type of mineralization. They have the highest values of IV(F/Cl) (4.9–7.1) and IV(F) (2–2.8) and the lowest values of Log(XMg/XFe) (0.1–0.4). The trace element composition clearly distinguishes biotites from rare-metal–greisen deposits and is identified by the highest contents (ppm) Ga &gt; 65, Li &gt; 600, Sn &gt; 20, Mn &gt; 2000, Cs &gt; 50, Zn &gt; 600. Biotites of Au-polymetallic and Au-Bi deposits occupy an average position between rare-metal–greisen and Mo-porphyry ones. Biotites of Mo-porphyry deposits differ in minimum values (ppm) of Sn &lt; 3, Zn &lt; 160, and low values of Li (150–290), V (290–440), and Ga (39–48). In general, the chemical composition of biotites shows that the degree of igneous rock fractionation of deposits increases in the series: porphyry–skarn–polymetallic–rare-metal.

Fate of fluorine in stratified samples from BGL gasifier at Hailar Chemical Plant, Inner Mongolia: An intermediate process perspective

This study investigated the fate of Fluorine (F) during the super high temperature (2000 °C) gasification process by analyzing 23 stratified samples inside the British Gas Lurgi (BGL) gasifier in production. Through sequential chemical extraction (SCEP), ion selective electrode (ISE), scanning electron microscope with energy dispersive spectrometer (SEM-EDS), high-resolution transmission electron microscope with energy dispersive spectrometer (HRTEM-EDS) and X-ray diffraction (XRD), this article complements the intermediate forms of transformation of F, in addition to the methods of deduction of the fate of F through input and output.Overall, the concentration of fluorine gradually decreases with increasing temperature and ≈1200 °C (14th layer) is the key temperature for its volatilisation. This may be related not only to the volatility of organic matter, but also to the significant contribution from the melting of a large amount of silicate and aluminosilicate minerals in the sample.In addition, the fluorine concentration remained stable from layer 14 to layer 27 (≈2000 °C), rather than continuing to evaporate, due to the formation of a new, stable mode of fluorine occurrence: Ca-P-F-Si minerals have been identified. The free and active SiO2, possibly derived from the melting of quartz and kaolinite, played a key role in preventing the melting of fluorapatite. The mechanism of formation of the new refractory materials (Ca-P-F-Si minerals) needs to be further validated by laboratory and computer simulations.

Efficient Mineralization of Fluoroelastomers Using Superheated Water in the Presence of Potassium Hydroxide.

The mineralization of fluoroelastomers (FKMs) in superheated water in the presence of potassium hydroxide (KOH) was investigated with the aim of developing a methodology for recycling the fluorine element. Two FKMs-an "uncrosslinked FKM", representing a poly(vinylidene fluoride-co-hexafluoropropylene) (poly(VDF-co-HFP)) copolymer with a VDF/HFP molar ratio of 78/22 and a "crosslinked FKM" consisting of this copolymer (cured by peroxide) and carbon black-were treated. The fluorine content of these FKMs was efficiently transformed into F- ions in the reaction solution using low KOH concentrations (0.10-0.50 M) at 200-250 °C. When the uncrosslinked or crosslinked FKMs reacted with aqueous KOH (0.20 M) at a rather low temperature (200 °C) for 18 h, the fluorine content of these FKMs was completely mineralized (both F- yields were 100%). Although the crosslinked FKM contained carbon black, the fluorine mineralization of the FKM was not inhibited. The addition of Ca(OH)2 to the reaction solutions after the superheated water treatment at 250 °C for 6 h with aqueous KOH (0.50 M) led to the production of pure CaF2, identified using X-ray spectroscopy, with 100% and 93% yields for the uncrosslinked and crosslinked FKMs, respectively.

DYNAMICS AND CAUSES OF ENDEMIC HUMAN DISEASES IN UKRAINE

The article describes the dynamics and causes of endemic human diseases in Ukraine. According to the results of statistical data on the dynamics of indicators of anthropogenic and technogenic load on the surrounding natural environment, the ecological situation in Ukraine is a crisis. This leads to environmental pollution with substances dangerous to human health, deterioration of the Earth's ozone layer, and also contributes to the appearance of new chemical compounds and changes the quantitative composition of existing ones.&#x0D; Endemic diseases are those that are observed in people for a long time in a certain limited territory and are caused by natural and social conditions. The occurrence and risk of development of endemic diseases is determined by the action of environmental elements, anthropotechnogenic and social factors.&#x0D; The purpose of the study was to establish the dynamics and causes of endemic diseases in the population of Ukraine during 2017-2021. It was established that endemic caries, endemic fluorosis, endemic goiter, and water-nitrate methemoglobinemia were the most common endemic diseases of the population of Ukraine during the studied years. Among all identified endemic diseases, endemic caries was recorded most often among the population, methemoglobinemia was less common. The dynamics of occurrence of the above-mentioned endemic diseases among the population during 2017-2021 increased. The causes of the development of endemic caries are the insufficient content of fluorine in the consumed water (up to 0.5 mg/l), endemic fluorosis, on the contrary, the intake of fluorine in excessive amounts (over 1.5 mg/l). Endemic goiter develops due to a lack of iodine in consumed products and water, water-nitrate methemoglobinemia – due to an excess of nitrates over 50 mg/l. Endemic fluorosis, for the most part, is characteristic of the inhabitants of the mountainous regions of Ukraine and Poltava region, endemic goiter – for the Carpathian, Carpathian and Transnistrian-Danubian regions, endemic caries and water-nitrate methemoglobinemia – for all regions of Ukraine.

Dental health of first-year students of the Novgorod State University

Goal and objectives: to study the dental health of 1st year students of the Novgorod State University. Materials and methods: questionnaire, literature review, study of statistical data on the Russian Federation, India, Egypt, and Pakistan. An analysis of the dental health of first-year Russian and foreign students of the Yaroslav-the-Wise Novgorod State University was carried out, and factors influencing dental health were identified. Official reports on the condition and composition of tap water in the city of Veliky Novgorod and tap water in Egypt, India, and Pakistan were studied. The standards for the content of fluorine and iodine in tap water in Veliky Novgorod, Egypt, India, and Pakistan were analyzed. The influence of changing climatic conditions, quality of nutrition, and the presence of bad habits and stress on the development of dental diseases in students was considered. The World Health Organization’s global oral health status report for 2022 in the Russian Federation, Egypt, India, and Pakistan was analyzed. A survey among students of the Novgorod University was conducted in order to evaluate water in the Novgorod Region in comparison with their homeland; the survey included general health questions with an emphasis on oral hygiene. What paste, brush, and cleaning method students used when brushing their teeth, and if they visited the dentist. What dental problems they had before and what issues they have now. Conclusions: To provide recommendations on oral hygiene, the choice of oral hygiene items and products, the diet taking into account the fluorine and iodine content in the region, and daily routine.