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General increase of longevity in Ukraine and around the world along with the increasing number of women over 50 necessitates implementation of comprehensive scientifically based programs aimed to improve health and quality of life of this part of population. The aim of this review of international and Ukrainian studies was to investigate in depth hormone associated mechanisms of pathologic conditions formation in peri- and postmenopausal women. Materials and methods. Studies on association of climacteric symptoms and symptoms of dental pathology were analyzed. Results. Our literature review showed worse condition of dental health in menopausal women. The pres­ence of estrogen receptors in oral mucosa and salivary glands increases the risk of dental pathology when ovarian function diminishes. Gradual decrease of ovarian steroids in female body causes changes in oral microbiota and changes microbial landscape of periodontal pockets and effects local immunity. This causes increase of oral mucosa pathology such as glossodynia or burning mouth syndrome, lichen planus and angular cheilitis. It also causes the increase of periodontal diseases rate. Conclusions. Cross-disciplinary interaction of dentists and gynecologists-endocrinologists will provide possibilities to discover more common causes and pathogenic mechanisms of periodontal diseases and oral mucosa in menopausal women. This will provide possibilities for the development of comprehensive approach to diagnosis, treatment and prophylaxis.

In this paper, the effect of SnO2 impurity on the surface charge and adsorption properties of TiO2 samples is investigated. The experimental value of the zero charge point for TiO2 with 3%, 6% and 12% of SnO2 equals 3.53, 3.97 and 3.2, respectively. The adsorption activity of the samples was studied on model solutions of the anionic dye – Congo red. The maximum adsorption capacity (qexp) equals 24.6 mg/g for 3Sn/TiO2, 25.0 mg/g for 6Sn/TiO2 and 39.1 mg/g for 12Sn/TiO2. Langmuir, Freundlich, and Dubinin-Radushkevich models were used to describe the adsorption mechanism of Congo red dye on the surface of Sn/TiO2 samples. Based on the results of the studies of Congo red adsorption by the surface of titanium dioxide doped with Sn, all samples agree best with the Langmuir model. The correlation coefficients for the Langmuir isotherms are in the range of 0.9927 - 0.9996, while the values ​​of R2 for the Freundlich and Dubinin-Radushkevich isotherms are in the range of 0.721 - 0.8329 and 0.8283 - 0.9433, respectively. Experimental data obtained from adsorption isotherms show that the TiO2 sample containing 12% SnO2 is the most active. The best result of Congo red removal occurred at a concentration of Co = 5 mg/l (% of removed dye ≈ 83% for 12Sn/TiO2; 81% for 6Sn/TiO2 and 71% for 3Sn/TiO2). Therefore, the studied samples of TiO2 doped with SnO2 can be used as effective adsorbents of Congo red from aqueous solutions.

In this paper, the synthesis of spinel magnesium ferrite (MgFe2O4) nanoparticles is reported, along with its structural, magnetic and hyperthermic properties, which ensure them being effectively used in various fields. Firstly, magnesium ferrite was synthesized via sol-gel auto-combustion method, using honey as the reducing agent. The crystallite size was calculated via the Scherrer method, the modified Scherrer method, the Williamson-Hall method, and the size-strain plot (SSP) method. X-ray analysis was used to confirm the structure of the spinel. For morphological study of ferrite nanoparticles, scanning electron microscopy (SEM) was used. Finally, hyperthermic properties of magnesium ferrite were analyzed for potential usage in medicine. According to these results, spinel magnesium ferrite (MgFe2O4) nanoparticles proved to be suitable for destruction of cancer cells, as they can be heated to the desired temperature, which will increase the sensitivity of those cells.

The oxidative degradation of Rhodamine B dye under ultraviolet irradiation was studied. The degradation rate was measured with using of smartphone camera. Photocatalytic degradation of the Rhodamine B dye over the P25-TiO2 catalyst has been found to accelerate substantially in the presence of hydrogen peroxide. The relationship between the photocatalytic degradation rate and H2O2 concentration has been studied. The optimal concentration of H2O2 has been found to in the range of 10-25 mM. The proposed mixture of P25 photocatalyst and H2O2 oxidizer can be used to remove organic pollutions from industrial waste water.

A simple approach to test photocatalyst activity has been described. Photocatalytic degradation of a model dye was measured using a smartphone. The color changes were registered directly in the micro-photoreactor. The model dye Rhodamine B was degraded under UV irradiation (365 nm). The effect of H2O2 concentration and titanium dioxide photocatalyst dosage has been studied. Among three color systems, RGB, CIE L*a*b* and HSV, the first one proved to be the most suitable for the dye determination. The reference measurements were carried out with a UV-Vis spectrophotometer. Two smartphones and two tablets with different camera resolutions have been examined. The best calibration curve was obtained using a Samsung Galaxy A6 smartphone with a 16MP camera. The t-test has shown with 95 % confidence that there are no significant differences between the dye concentrations measured with the smartphone and spectrophotometer. The values of the relative standard deviation of the smartphone measurements were less than 0.5 %. Therefore, the proposed method for fast estimation of photocatalyst activity can be used in the control of advanced oxidation reactions.

TiO2-based nanomaterials are attracting much attention in many areas, such as photocatalysis, photoelectricity, probing, electrochromism, photochromism, etc. They are widely used in paints, polymers, sunscreens, and toothpaste. There are various ways of synthesis that affect the size, shape, and crystallinity of TiO2 nanoparticles. The main methods of obtaining titanium dioxide (with the structure of anatase, rutile or brookite) in the form of spheres, rods, fibers, and tubes include: sol-gel technology, hydrothermal and solvothermal methods, microwave method involving high-frequency electromagnetic waves, template method, electrodeposition, a sonochemical method using ultrasound, chemical and physical vapor deposition, "green" methods, etc. This literature review presents modern scientific results on the production of TiO2 nanoparticles by various methods.

Blue-colored ceramic nanopigments with the composition of CoAl2O4 were synthesized by solution combustion method using glycine (CoAl2O4-Gly), poly(vinyl alcohol) (CoAl2O4-PVA) and urea (CoAl2O4-Urea) as reductants and fuels. The morphology and chemical composition of the nanopigments were studied using SEM and EDS, respectively. The composition of the crystalline phase was examined using XRD. The crystallite sizes were calculated using the modified Scherrer method, Williamson-Hall method and size-strain plot method. Particles of the CoAl2O4-PVA sample have smaller crystallite sizes, whereas particles of the CoAl2O4-Urea sample have larger crystallite sizes. Thermal gravimetric analysis showed that thermal decomposition of cobalt(II) and aluminum nitrates is accompanied by the release of gases. As a result of material loosening, finely dispersed powders with high porosity were formed. FTIR-spectra of all the nanopigments contain absorption bands related to stretching vibrations of the Me-О bonds (400-700 cm−1). Stretching and deformation vibrations of water molecules are present as well. Color characteristics of the obtained nanopigments depend on the fuel used for the combustion synthesis. The pigment CoAl2O4-PVA has saturated blue-green color. The obtained spinel-type nanomaterials possess high suspension stability and can be used as pigments in ceramic technology.

Increased request for metal and metal oxide nanoparticles nanoparticles has led to their large-scale production using high-energy methods with various toxic solvents. This cause environmental contamination, thus eco-friendly “green” synthesis methods has become necessary. An alternative way to synthesize metal nanoparticles includes using bioresources, such as plants and plant products, bacteria, fungi, yeast, algae, etc. “Green” synthesis has low toxicity, is safe for human health and environment compared to other methods, meaning it is the best approach for obtaining metal and metal oxide nanoparticles. This review reveals 12 principles of “green” chemistry and examples of biological components suitable for “green” synthesis, as well as modern scientific research of eco-friendly synthesis methods of magnetic and metal nanoparticles. Particularly, using extracts of green tea, fruits, roots, leaves, etc., to obtain Fe3O4 NPs. The various precursors as egg white (albumen), leaf and fruit extracts, etc., can be used for the „green” synthesis of spinel magnetic NPs. “Green” nanoparticles are being widely used as antimicrobials, photocatalysts and adsorbents. “Green” magnetic nanoparticles demonstrate low toxicity and high biocompatibility, which allows for their biomedical application, especially for targeted drug delivery, contrast imaging and magnetic hyperthermia applications. The synthesis of silver, gold, platinum and palladium nanoparticles using extracts from fungi, red algae, fruits, etc., has been described.

In this study, hierarchical-structured Co3O4 nanocapsules and various rare earth metal (La, Nd, Gd, Sm)–doped Co3O4 materials were synthesized by a polymer-assisted combustion route. These rare earth metal–doped Co3O4 materials were tested as active electrode materials for high performance electrochemical supercapacitors. The Sm-Co3O4 electrode has shown an extraordinary electrochemical supercapacitor performance with high specific capacitance and exhibited a good cycling stability with the capacitance retention of 93.18% after 5000 cycles. The doping of rare earth metals in Co3O4 can reduce the charge transfer resistance and crystalline nature which are expected to improve the transfer of ions and electrons. Also, the large number of structural defects can promote the diffusion of electrolyte ion and electrochemical supercapacitance behavior. Furthermore, the antistructural modeling has shown that isovalent cation substitution leads to the formation of cation vacancies and interstitial defects, which enhance the electrochemical properties of doped Co3O4 materials.

Mesoporous titania samples modified by sodium arsenate to form arsenate functionalities were synthesized using titanium aqua complex [Ті(ОН2)6]3+·3Cl− and salt Na3AsO4 as precursors. The structure, morphology, and texture of the samples were characterized using XRD, IR spectroscopy, TG-DTA, TEM, and nitrogen adsorption methods. The adsorption properties of the samples located in the aqueous media were analyzed with respect to Sr(II) removal. The modified titania samples have a large specific surface area (up to 405 m2/g) and appropriate pore volume (up to 0.26 сm3/g) with a major contribution of mesopores. The maximum adsorption capacity of modified titania (with 4% of arsenate groups) towards Sr(II) is 262.9 mg/g. It is much smaller for unmodified titania (92.1 mg/g). The equilibrium adsorption isotherms were fitted using the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The results revealed that the adsorption equilibrium data match with the Langmuir isotherm model (R2 > 0.993) that corresponds to the localized adsorption onto uniform surface. The adsorption kinetics fitted well by the pseudo-second-order kinetic model. A possible adsorption mechanism was analyzed. Sr(II) removal can be attributed to = Ti(О2AsОOН) groups located at a mesopore surface of the adsorbents. The materials demonstrate the stability of the degree of the Sr(II) adsorption during ten cycles. Thus, arsenate-modified mesoporous titania could be considered as an effective adsorbent for Sr(II) removal from wastewater.

Color images taken by a smartphone camera were used to estimate the rate of advanced photo-oxidation reaction of Direct Red 23 (DR23) azo dye as a model organic pollutant. The red, green, blue color coordinates were tested to quantify the dye. Images of the reaction mixture were taken at specified intervals to obtain kinetic lines and reaction rate constants. Both the reaction rate constant and the final degree of degradation were plotted as functions of the photocatalyst dose and the concentration of H

Designing and fabrication of smart hybrid multifunctional materials for energy/fuel production and environmental detoxification is indeed of great significance for sustainable development. Herein, we synthesized a new well-structured S-scheme heterostructure Fe@TiO

Cobalt-zinc ferrite nanoparticles were synthesized using environmentally friendly approach with quince extract as a reducing agent. Crystal structure and morphology of the obtained materials were studied by XRD, SEM-EDS, Mössbauer and IR spectroscopy. The synthesized nanoparticles have a cubic spinel structure and crystallite size ranging from 5 to 9 nm. The infrared spectra contain characteristic absorption bands for the M

The magnesium-zinc ferrites Mg1-xZnxFe2O4 (x = 0…1) were studied as magnetic sorbents for environmental applications. Low-temperature Mossbauer spectroscopy was used to determine the distribution of magnesium and ferric ions in the spinel crystal lattice. The influence of Zn content on magnetic parameters was investigated on the basis of VSM data. As the molar ratio of zinc to magnesium increases from 0 to 1, the pHPZC value decreases from 10.5 to 8.9. Langmuir and Freundlich models were used to check whether single-layer or multi-layer adsorption occurs. The adsorption of Cr(VI) and Ni(II) ions is well fitted by the Langmuir equation. To check the physical or chemical nature of the sorption process, the Dubinin-Radushkevich equation was used. It was found that the processes of adsorption of Cr(VI) and Ni(II) ions are of a chemical nature. The best Cr(VI) ion adsorption capacity was found for the Mg0·2Zn0·8Fe2O4 sample (qe = 30.49 mg/g). The percentage of heavy metal removal by the mixed ferrite samples increases with increasing zinc content. The most effective sorbent for Ni(II) removal is the Mg0·4Zn0·6Fe2O4 sample (93.2%). Modeling the antistructure provides deeper insight into the mechanism of heavy metal adsorption. The obtained magnesium-zinc ferrites are promising magnetic adsorbents for removing chromate and nickel ions from the environment.

Designing and fabrication of smart hybrid multifunctional materials for energy/fuel production and environmental detoxification is indeed of great significance for sustainable development. Herein, we synthesized a new well-structured S-scheme heterostructure Fe@TiO2/Boron Carbon nitride (FT/BCN) with high performance tetracycline degradation and selective CO2 photo-reduction to CH4. Under visible light irradiation, 96.3% tetracycline was degraded in 60 min using best performing FT30/BCN sample with a high 83.2% total organic carbon removal in 2 h. The tetracycline degradation rate for FT30/BCN composite catalyst was ∼7 times than bare boron carbon nitride (BCN). The impact of reaction parameters as pH, presence of interfering electrolytes, light source and water matrix was also investigated. The FT30/BCN photocatalyst shows dramatic improvement in CO2 photoreduction as exhibited in 24.7 μmol g−1 h−1 CH4 and 2.4 μmol g−1 h−1 CO evolutions with optimal 91.1% CH4 selectivity. Pure BCN shows a poor 39.1% selectivity. Further, effect of alkali activation, CO2/H2O feed ratio, reducing agent and light source onto CH4 production and selectivity was also investigated. The CH4 evolution and selectivity was improved because of enhanced visible light absorption, high adsorption potential, charge carrier separation and high reducing power of photogenerated electrons induced by an effective S-scheme heterojunction between Fe@TiO2 and boron carbon nitride. An S-scheme (step-scheme) charge transfer mechanism is here operative both during tetracycline removal and CO2 reduction. The drug degradation route and photocatalytic mechanism for antibiotic removal and CO2 reduction was also predicted.

The study proposes two new TiO2 photocatalysts with excellent photocatalytic properties obtained by the reverse micelle (RM-TiO2) and low temperature (LT-TiO2) methods. The crystal structure and morphology of the obtained TiO2 samples were analyzed by X-ray diffraction, scanning electron microscopy and IR-spectroscopy. The chosen synthesis conditions lead to pure rutile modification. FTIR spectra of the obtained samples contain characteristic bands, attributed to stretching vibrations of Ti–O bonds and to deformation vibrations of Ti–OH bonds. The average crystallite sizes for RM-TiO2 and LT-TiO2 samples are 5.4 and 9 nm, respectively. SEM analysis showed that the RM-TiO2 consists of TiO2 particles, assembled into spherical aggregates, while LT-TiO2 consists of smaller aggregates and is mostly mesoporous. The BET surface areas of the RM-TiO2 and LT-TiO2 samples are 39 and 63 m2/g, respectively. The photocatalytic degradation of the Congo Red (CR), Methyl Orange (MO) and Direct Red 23 (DR23) dyes in water medium has been studied under UV LED irradiation with H2O2 as an auxiliary oxidant. Both the RM-TiO2 and LT-TiO2 samples are active photocatalysts. The optimal dosages are 1.5 and 0.5 g/L respectively. The maximum photodegradation efficiency of RM-TiO2 is observed when the concentration of H2O2 is 15 mM for CR, 5 mM for MO and 10 mM for DR23. The maximum photodegradation efficiency of LT-TiO2 is observed when the concentration of H2O2 is 10 mM for CR, 2.5 mM for MO and 1.5 mM for DR23. The boosting effect of H2O2 on the degradation efficiency can be explained by an increased generation of •OH radicals. The real-time monitoring of degradation kinetics has been performed using measurements of light reflected from TiO2 suspension. The proposed technique allows the use of small volume of solution and amount of photocatalyst. The synthesized rutile photocatalysts may be used for wastewater treatment.

A facile approach involving electrochemical deposition method was utilized to coat ITO substrate with zinc selenide thin films at different rare earth metal (Eu3+, Sm3+ and Gd3+) ions. The characteristics of deposited films were studied in relation with the doped metal ions. The structure of the coating was confirmed to be hexagonal wurtzite in (101) plane by X-ray analysis. The new antistructural modeling shows that the doping of ZnSe lattice by rare earth cations increases the concentration of the surface active centers such as $${\text{Gd}}_{{{\text{Zn}}}}^{\cdot },\,{\text{Eu}}_{{{\text{Zn}}}}^{\cdot },\,{\text{Sm}}_{{{\text{Zn}}}}^{\cdot },\,{\text{and}}\,{\text{V}^{\prime\prime}_{{\text{Zn}}}}$$, which are located in the cationic sublattice. XRD data revealed that the average crystallite size of ZnSe and ZnSe:Eu, ZnSe:Sm, and ZnSe:Gd was 63, 54, 47, and 49 nm, respectively. The morphological results by scanning electron microscopy indicate that the spherical-like structure with agglomeration of grains and a slight increase in the particle size. Energy dispersive X-ray, UV–Visible and photoluminescence spectroscopy were used to study the composition and optical properties of the films. A blue-shift was observed in ZnSe thin films. The bandgap energy of undoped ZnSe and ZnSe:Eu, ZnSe:Sm, and ZnSe:Gd were found to be 2.28, 2.44, 2.68 and 2.75 eV, respectively. Among the different coated films, the Gd3+ ion doped ZnSe thin film exhibited a lesser charge transfer resistance of 25.5 Ω as analyzed from the electrochemical impedance measurement. The photoelectrochemical studies reveal that the rate of photoinduced charge carriers was higher in Gd3+ ion doped thin film. The present studies suggested that the Gd3+ ion doped ZnSe thin film can be a promising material for electrochemical device applications.

The aim of this study is to investigate in-depth the effect of Co 2+ ions doping on ZnFe 2 O 4 nanoparticles in term of morphology, magnetic and optical properties. Zn 1-x Co x Fe 2 O 4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) powders were prepared by co-precipitation method. X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) confirmed the incorporation of Co 2+ ions within ZnFe 2 O 4 host lattice, and an increase of the crystallite size from 37 to 51 nm in agreement with TEM analysis. FTIR revealed a slight change in two main bands υ 1 and υ 2 in the frequency range of 400–4000 cm −1 , which caused by stretching vibrations at the A- and B-sites respectively. The elastic moduli such as stiffness constant, Young's modulus, rigidity modulus, bulk modulus, Poisson's ratio, wave velocity and Debye temperature have been calculated using FTIR data. VSM showed transformation of magnetic behavior from paramagnetic to ferromagnetic as a result of Co 2+ ions doping. With higher Co 2+ (x = 0.2 to x = 0.5) content, the saturation magnetization (Ms) increased rapidly from 5.7 emu/g to 82 emu/g respectively. The remanance magnetization (Mr) and coercivity (Hc) were influenced by Co 2+ content too and this was mainly related to the change in crystallite size. The optical band gap ( Eg ) of Co-Zn ferrite samples was determined by means of diffuse reflectance spectra. The optical band gap value estimated from Tauc plots was found to decrease from 1.89 to 1.31 eV with increasing Co 2+ content.

The cation distribution of the spinel system Zn1-xCoxFe2O4 (with x = 0; 0.1; 0.2; 0.3; 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; 1.0) has been investigated by means of X-ray diffraction (XRD), Mossbauer spectroscopy and Fourier transform infrared spectroscopy (FTIR). In the present work, ferrites were prepared by co-precipitation method. XRD diffraction patterns show that all compositions have a pure single-phase cubic spinel structure over the whole composition range. It is found that both the lattice parameter and the average crystallite size decrease with increasing Co2+ content; from 8.4392 to 8.3536 A and from 37 to 25 nm for ZnFe2O4 and CoFe2O4, respectively. Morphological observations (SEM, TEM) reveal that the crystallinity decreases significantly with increasing Co2+ content meanwhile the particle size becomes more uniform. The elemental compositional stoichiometry have been carried out by means of energy dispersive analysis (EDS). The force constants Kt and Ko for the two sites have been deduced from IR band frequencies and compared with the trend of bond lengths: KT increases (from 2.084 to 2.144 dyn/cm2) because the bond length MA-O decreases, while KO decreases (from 1.043 to 0.948 dyn/cm2) because the bond length MB-O increases with increasing Co2+ content. For the first time antistructural modeling of zinc-cobalt ferrites considered. It shown that the acceptor in crystall latice is tetrahedral iron FeA , while the donor is octahedral cobalt Сo B ′ . With increasing Co2+ content, the concentration of active centers in tetrahedral and octahedral sublattice of zinc-cobalt ferrites are increases. The nature of the active centers are affecting on the chemical, electrical, magnetic, optical and catalytic properties of ferrites.

У роботі досліджено вплив легування Sn на структуру та морфологію Sn-легованих зразків TiO2. Легований діоксид титану отримувався золь-гель методом з використанням аквакомплексу [Ti(OH2)6] 3+·3Cl- як прекурсору титану і SnCl4 як модифікатора. Структура і морфологія зразків досліджувалися методами Х-променевої дифрактометрії, ТЕМ аналізу, низькотемпературної порометрії, ІЧ та енергодисперсійної спектроскопії. Провідність Sn-легованих зразків ТіО2 вивчалася методом імпедансної спектроскопії. Встановлено, що Sn-леговані зразки діоксиду титану містять кристалічні фази анатазу і рутилу. Співвідношення анатаз/рутил залежить від вмісту Sn: збільшення вмісту Sn(IV) від 3 до 12 % (ваг.) зумовлює збільшення вмісту рутилу від 33,8 to 97,1 % (ваг.). Ріст вмісту Sn також призводить до зменшення параметра кристалічної ґратки а та збільшення параметра с. ТЕМ-методом виявлено наявність стрежневидних і голковидних частинок рутилу в Sn-легованих зразках ТіО2. Величина питомої поверхні для зразка 6Sn/TiO2 становить 290 м2/г. Усі зразки Sn-легованого діоксиду титану є мезопористими. Механізми структуроутворюючих процесів пояснюються присутністю в реакційному середовищі молекул Sn(OH)4·2H2O, які діють як центри нуклеації, росту та кристалізації для наночастинок рутилу. Збільшення вмісту Sn зумовлює також зменшення питомого опору досліджуваних матеріалів порівняно із нелегованим зразком діоксиду титану. The effect of Sn doping on the structure and morphology of Sn-doped TiO2 samples has been investigated. The doped titania has been obtained by sol-gel synthesis using titanium aquacomplex precursor [Ti(OH2)6] 3+·3Cl– and SnCl4 as a modifier. The structure and morphology of the samples have been studied through XRD analysis, TEM, low-temperature porometry, IR-spectroscopy, and EDS analysis. The conductivity of Sn-doped TiO2 samples has been investigated by impedance spectroscopy. It was shown that the Sn-doped titania samples contain both anatase and rutile phases. The anatase/rutile ratio depends on the Sn content: the increasing Sn (IV) content from 3 to 12 % (wt.) leads to an increase in rutile content from 33.8 to 97.1 % (wt.). An increase in Sn content causes a decrease in the lattice parameter a and an increase in the parameter c. The presence of rod-shaped and needle-like rutile particles in the Sn-doped TiO2 samples has been observed by TEM. The specific surface area for 6Sn/TiO2 reached 290 m2/g. All the Sn-doped titania samples belong to the mesoporous materials. The mechanism of structure-forming processes is explained by existing Sn(OH)4·2H2O molecules in the reaction medium, which act as the centers of nucleation, growth and crystallization for rutile nanoparticles. The increase in Sn content leads to a decrease in the specific resistance of the studied materials compared to the undoped titania sample.

Cobalt (II) ferrite-chromites CoCr2-xFexO4 (x = 0.0 ÷ 2.0, step is 0.2) with spinel structure have been synthesized using sol-gel method with citrate metal-polymer precursor. The relations between structural, morphological and catalytic properties of the mixed spinels have been studied. The CoCr2-xFexO4 powders were analyzed using X-ray diffraction analysis, Mossbauer spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive analysis and Brunauer–Emmett–Teller (BET) methods. The average crystallite size was calculated using the Williamson-Hall and size-strain plot methods. Increase of Fe content resulted in increase of the crystallite size from 10 nm (CoCr2O4) to 35 nm (CoFe2O4). Chromium ions were located mainly in octahedral sites, whereas the cobalt and ferric ions were distributed between the octahedral and tetrahedral sites. The lattice parameter was dependent mostly on the octahedral site radius. Superparamagnetic properties of the nanoparticles were described by two-level relaxation model. The samples with a high content of chromium (III) have highly porous structure. Porosity of the samples was decreased with increasing the Fe content. IR spectra contain two peaks corresponding to two characteristic sites in the cubic spinel structure. The mixed ferrite-chromite spinels have catalytic activity in decomposition of hydrogen peroxide. Rate of H2O2 decomposition in the presence of cobalt (II) ferrite-chromite NPs corresponds to the first-order kinetic model. Within 25 min, the decomposition degree is 76.6% with the most active CoFe2O4 sample. Catalytic activity of the samples depends on two factors: the specific surface area and the surface active sites. Antistructure modeling revealed that the tetrahedral Fe(III) sites have electron acceptor properties. The formed Fe(II) ions are active centers in the Fenton-like processes. Probably, the red-ox pairs Co2+/Co3+ in the spinel lattice promote catalytic activity due to acceleration of electron transfer. The spinel cobalt (II) ferrite-chromites are promising catalysts for oxidation of toxic organic impurities in wastewaters with using H2O2.

Mg–Zn ferrites with porous cavity structure were produced by sol-gel auto-combustion method utilizing a new mixture of dl -alanine and urea as an organic fuel-reductant. The influence of non-magnetic Zn ions content on the structural, morphological and adsorption characteristics of Mg–Zn NPs has been investigated. It was found that Zn effects the porosity of Mg–Zn ferrospinels. X-ray diffraction analysis confirmed the formation of cubic spinel phase and the crystallite size was calculated by the SSP method, W-H method and modified Scherrer formula. SEM observations revealed mesh-like microstructure with the presence of 1–2 μm macropores and agglomerated nanoparticles. The EDS spectra confirmed the desired chemical composition of ferrites powders. Mossbauer spectroscopy confirmed the valence state of cations and their distribution over the spinel sublattices. The adsorption characteristics of spinel compounds were studied on Congo Red dye removal. The appropriateness of Langmuir, Freundlich, and Dubinin-Radushkevich adsorption models were investigated and the parameters of all models were determined. The observed data fitted well by Langmuir model, indicating that the Congo Red adsorption occurred on a homogeneous surface and that the active surface centers possessed similar energy values. The Dubinin-Radushkevich isotherm model was utilized to calculate the free energy of Congo Red adsorption, i.e. setting in the range 7.81–22.4 kJ/mol and indicating that the Zn content affects the mechanism of Congo Red adsorption onto ferrite surfaces and the removal efficiency is enhanced with the rise in Zn content.

The fast growth in the anthropogenic activities, that involve a wide use of pharmaceuticals, has led to the appearance of new toxic and hazardous chemical compounds, called "emerging pollutants", which could cause unpredictable consequences to the ecosystems. The current review is focused on emerging pollutants occurring in food or air and include caffeine and nicotine, as well as on pharmaceuticals, in particular amoxicillin, and the concerns caused by its wide usage for medical purposes. This review, for the first time, analyzes and discusses the potential risks and implications of caffeine, nicotine and amoxicillin as emerging environmental pollutants, a field that remains underrepresented to date. Both caffeine and nicotine belong to life style compounds, while pharmaceutical amoxicillin is one of the very popular β-lactam antibiotics used to take care of human and animal infections. The review covers the toxic effect caused by caffeine, nicotine and amoxicillin on humans and animals and describes some of the main adsorbents utilized for their removal (e.g., grape stalk, tea waste, wheat grains, bentonite, activated carbon, acid and base modified grape slurry wastes, graphene oxides, modified graphene oxides, zeolites, etc.). The isotherm and kinetic models for the analysis of caffeine, nicotine and amoxicillin adsorption by different adsorbents are presented. The impact of pH, temperature, adsorbent dosage and thermodynamic studies were deeply analyzed. The review also discusses the mechanism of adsorption for the above-mentioned emerging pollutants, which includes π-π interaction, cation-π bonding, electron-donor and electron-acceptor forces, van der Waals forces, electrostatic interactions, etc. The present review has a potential value for chemists, ecologists, toxicologists, environmental engineers, and other professionals that are involved in environmental protection.

A simple “green” method for the synthesis of cobalt‑zinc ferrites nanoparticles has been proposed. XRD, SEM/EDX, TEM, Mossbauer and FTIR techniques have been applied to investigate structure and morphology of the obtained spinel ferrites. Analysis of the cation distribution showed that during the transition from cobalt ferrite to zinc ferrite the inversion degree of the Fe cations decreases from δ = 0.89 to δ = 0.00. IR spectra show the presence of characteristic peaks of the MA-O (at ~450 cm−1) and MB-O (at ~610 cm−1) vibrations as well as the vibrations of functional groups of the honey residuals. It was concluded that honey acts as reductant and stabilizer preventing agglomeration of the nanoparticles. The force constants of the tetrahedral and octahedral bonds have been calculated. Dependence of the Debye temperature on Zn content was also established for the first time: it is increased from 782 K to 805 K with Zn increasing. It was shown that the ZnFe2O4 sample exhibits the highest adsorption capacity (289 mg/g) towards lead cations. This result is explained in terms of surface acidity of the examined samples, estimated from the variations of the ionic-covalent bond parameter. The Langmuir, Freundlich and Dubinin-Radushkevich models were tested to evaluate the adsorption mechanism. The efficiency of heat release by the CoxZn1-xFe2O4 magnetic nanoparticles for magnetic hyperthermia was investigated as well. The registered induction heating curves depend on the Zn content in the CoxZn1-xFe2O4 samples. The sample with х(Zn) = 0.6 exhibits the maximal specific loss power equal to 2.56 W/g. The intrinsic loss power (ILP) value is 0.40, and is 2.7 times higher than the ILP value of commercial Fe3O4. The obtained ferrite materials can be, therefore, used in magnetic hyperthermia applications and Pb(II) adsorption.

Halloysite is a natural tubular mineral with unique properties. It can be used in a various fields of industries. The aim of current review is to describe the structural properties and methods of halloysite surface modification, what led to the extension of its application. The achievements of scientists over the last 10 years indicate that halloysite is a promising material for drug delivery, as polymer filler, as matrix for photocatalysts and adsorbents for environmental and biomedical applications. Particular attention is drawn to the magnetic nanocomposites of halloysite. The composites halloysite/metal oxides are excellent adsorbents and due to their magnetic properties can be easily separated from the treated solutions by using of external magnetic field. Magnetically controlled adsorbents can be synthesized by metal oxides incorporation into the halloysite structure due to the presence of aluminol and siloxane surface groups. Such composite systems have a high adsorption capacity and can be used for effective water purification from inorganic and organic pollutants. In addition, major problems and future prospects for halloysite composites using have been identified. This review provides the latest findings from researchers, which sheds light on future halloysite studies.

Nanostructured Zn-doped cobalt ferrites (Co1−xZnxFe2O4, where x ranges from 0.0 to 1.0 with a step of 0.1) were studied in order to elucidate the relation between their cationic distribution within the spinel sublattices and catalytic properties. The thermal transformation of the precursors (metal hydroxides) obtained through the hydroxide co-precipitation method was studied by DTA, TGA and FTIR. The thermal behavior of the precursors showed that cobalt ferrite was formed at a lower temperature (376 °C) in comparison to zinc ferrite (478 °C). FTIR analysis revealed vibrational bands around 400 cm−1 and 600 cm−1 related to (MO4)6− and (MO6)9− groups, respectively. The cationic distribution was determined from Mossbauer spectra analysis and the results showed that Zn ions occupy the A-sites, while Co and Fe ions are located in the A- and B-sites. The spectra indicate spinel magnetic ordering in samples with x = 0.0…0.5. The increase in Zn content influences the difference in the Pauling electronegativities, distances between magnetic ions (hopping length) and polaron radius of Co1−xZnxFe2O4 ferrites, inducing changes in the ionic bond strength for the A- and B-sites. Photoelectrochemical measurements demonstrated that the introduction of Zn2+ into the spinel structure modifies the ability of the materials to reduce O2. Whereas photoinduced reduction of dioxygen at CoFe2O4 competes successfully with anodic photocurrent generation (observed as a decrease of photocurrent), for ZnFe2O4 this process is negligible. The relation between the cationic distribution (analyzed in terms of antistructure modeling) and the catalytic activity of spinel ferrites was demonstrated for the example of the soot combustion process. It was shown that the octahedral cobalt centers exhibit a higher catalytic activity than the tetrahedral ones.

The effect of Zn-doping in CoFe2O4 nanoparticles (NPs) through chemical co-precipitation route was investigated in term of structural, optical, and magnetic properties. Both XRD and FTIR analyses confirm the formation of cubic spinel phase, where the crystallite size changes with Zn content from 46 to 77 nm. The Scherrer method, Williamson-Hall (W-H) analysis, and size-strain plot method (SSPM) were used to study of crystallite sizes. The TEM results were in good agreement with the results of the SSP method. SEM observations reveal agglomeration of fine spherical-like particles. The optical band gap energy determined from diffuse reflectance spectroscopy (DRS) varies increases from 1.17 to 1.3 eV. Magnetization field loops reveal a ferromagnetic behavior with lower hysteresis loop for higher Zn content. The magnetic properties are remarkably influenced with Zn doping; saturation magnetization (Ms) increases then decreases while both coercivity (HC) and remanent magnetization (Mr) decrease continuously, which was associated with preferential site occupancy and the change in particle size.

A magnetic core-shell adsorbent was synthesized by immobilization of titanium dioxide nanoclusters on the cobalt ferrite nanoparticles. The synthesis was carried out using a modified Pechini sol-gel method with citric acid and ethylene glycol as chelating agents. The structure and morphology of reference TiO2, pristine CoFe2O4 and resulting nanocomposite CoFe2O4@TiO2 were thoroughly characterized using XRD, XRF, BET, SEM, IR spectroscopy and Mossbauer spectroscopy. The obtained spectral data indicate that a shift of electron density from titanium to oxygen atoms takes place. Antistructure modeling suggests that some titanium atoms are entered into the CoFe2O4 spinel structure resulting in defects of crystalline structure. In this way additional adsorption centers arise. The adsorption efficiency of the CoFe2O4@TiO2 nanocomposite was found to be more than twice as high as compared to TiO2 and CoFe2O4 alone. The observed synergistic effect is associated just with the formation of distorted titania nanocrystals. The obtained magnetic nanoadsorbent proved to be efficient in water purification from dichromate anions (83% removal) and Congo Red dye (61% removal).

In this study, para-aminobenzoic acid functionalized activated carbon (PABA@AC) was successfully synthesized and applied as an adsorbent for removal of malachite green dye (MG) from aqueous system. For characterization of the prepared PABA@AC composite, (FT-IR), (SEM) and (EDX) were used. Impact of many parameters such as pH, amount of PABA@AC composite (m), contact time (t), temperature (T), initial MG concentrations (Co) upon MG adsorption using PABA@AC was investigated to estimate the optimum parameter conditions for adsorption. The results showed that the optimized parameter values of pH solution, contact time, adsorbent dose, and temperature were 7, 240 min, 30 mg and 25 °C, correspondingly. The isotherm adsorption and kinetic studies showed that the adsorption process was well fitted to Langmuir isotherm and Pseudo-first-order kinetic models, respectively. The maximum MG adsorption capacity was 66.87 mg/g by Langmuir model. The thermodynamic studies showed that the adsorption process was exothermic and spontaneous.

This review is devoted to the study of the adsorption behavior of uranium(VI) using titanium dioxide based sorbents. Uranium pollution of groundwater, soil and rocks is a big problem due to the long-term toxicity of uranium compounds. Waste uranium is a by-product of the enrichment process used in the production of atomic energy, and the danger associated with this is due to the radioactivity of uranium and its toxicity as a heavy metal. The mechanisms of uranium adsorption by titania adsorbents are presented here, depending on the various environmental conditions, as well as the kinetics of adsorption. The influence of the structural characteristics of the sorbents on the adsorption behavior of uranium is depicted. Surface chemistry and sorption activity of titanium dioxide were reviewed. Examples of new advanced sorbents with nanometer dispersion are described and the parameters of adsorption isotherms are also presented. One of the practical tasks of this analytical review is to obtain information for modeling the behavior of uranium in the water/adsorbent system due to anthropogenic pollution.

On the basis of X-ray diffraction and mass spectrometric analysis of carrier γ-Al2O3 and catalysts CuCl2/CuCl on its surface, the chemical structure of the active centers of two types oxidative chlorination catalysts applied and permeated type of industrial brands "Harshow" and "MEDС-B" was investigated. On the basis of quantum-mechanical theory of the crystal, field complexes were detected by the presence of CuCl2 cation stoichiometry and structure of the proposed model crystal quasichemical industrial catalyst permeated type MEDС-B for oxidative chlorination of ethylene. On the basis of quantum-mechanical calculations, we propose a new mechanism of catalysis crystal quasichemical oxidative chlorination of ethylene reaction for the catalysts of this type (MEDС-B) and confirmed the possibility of such a mechanism after the analysis of mass spectrometric studies of the active phase (H2 [CuCl4]) catalyst oxidative chlorination of ethylene. The possibility of the formation of atomic and molecular chlorine on the oxidative chlorination of ethylene catalyst surface during Deacon reaction was displaying, which may react with ethylene to produce 1,2-dichloroethane. For the active phase (H [CuCl2]), catalyst offered another model of the metal complex catalyst oxidative chlorination of ethylene deposited type (firm 'Harshow,' USA) and the mechanism of catalysis of oxidative chlorination of ethylene with this catalyst.