The sorption behavior of traces Sr(II) toward β-Ca3(PO4)2 (TCP) depending on the concentration of the cation, pH, and concentrations of humic acids (HA) in the solution was studied. Thermodynamic analysis of the solubility of TCP (1) was performed taking into account the formation of Ca(OH)2 (CH, 2), Ca(H2PO4)2 (MCPA, 3), CaHPO4·2H2O (DCPD, 4), Ca5(PO4)3OH (hydroxyapatite, OHAp, 5), and Ca2P2O7 (DCPP, 6). It was shown that, depending on the pH of the solution, the main equilibrium phases with the solution are phases 4 and 5. X-ray diffraction analysis, Raman spectroscopy, and 31P NMR data of the phase (1) samples after contact with a solution of 0.01 M NaNO3 for about 10 days showed the presence of only the phase 1. The solubility of 1 regarding the concentration of Ca2+, PO43– ions and the stoichiometric ratio (Ca/P) in solutions, depending on pH, correspond to the presence of surface phases 4 or 5. The model of surface complexation in the Henry region adequately describes the mechanism of Sr(II) sorption by the surface phase 5 on TCP particles in the form of the SrHPO40 complex. The formation of the HA complex of Sr(II) in solution does not affect distribution coefficient Kd(Sr) in the range of HA concentrations of 0–150 mg/L due to the competitive effect of hydrogen phosphate ions on strontium complexes.

By the methods of thermodynamic modeling, sorption diagnostics, analysis of particle zeta-potential, and UV-Vis spectrometry the equilibrium conditions of sorption interaction of CrO42–, MoO42–, WO42–, SeO32– oxygen anions in the region of chemical stability of Al2O3||C composite have been analyzed. The anion sorption isotherms are shown to follow the Langmuir model for a monoenergetic sorbent. The Henry region is observed at concentrations less than 1 μM. According to the established mechanism of surface complexation, the value of anions protonation constant (K1) in the investigated pH range determines the sorption activity of the composite to these anions. This explains the correlation found between the ratio of parameters of acid–base sites Al–O–, Al–HO0, and Al–OH2+ of composite KM(1,2) and the protonation constant of anion K1. It is shown that the Al2O3||C composite concentrates from dilute solutions both cations of d-, f-elements and oxygen anions of d-elements with the value of log Kd [mL/g] > 4, thereby exhibiting the properties of collective action sorbent.

For the closed system (Sigma): Zn (2+) - NH (3,aq) - NH (3,gas) , H+-OH--N-2,N-gas, experimental data on the change in the concentration of in the composition of the ammonia complex Zn(NH3)(2+)(4) in solution, colloidal particles Zn(OH)(2)/ZnO in solution and growing film on the reactor walls are presented depending on the synthesis time, zinc concentration and synthesis temperature Ts in the range of 50 -99 degrees C. It has been established that up to 95 degrees C the ion-molecular growth of Zn(OH)(2)/ZnO clusters in solution (Sigma) proceeds in a diffusion-controlled mode of homogeneous growth until reaching of their critical size. Further growth of ther critical clusters is followed by aggregation and coalescence of critical sized clusters into microcrystals with the formation of a film on a glass substrate of various morphologies. The solubility of such a film is determined by the size of critical clusters, which preserves in the growing polycrystal in the form of coherent scattering region (CSR). With an increase in the synthesis temperature to 99 degrees C, the aggregation mechanism is replaced by a faster diffusion-controlled attachment of Zn (II) ammonia complex to the end surface of the growing microcrystals simultaneously in colloid solution and in the film.

The review analyzes research over the past 20−25 years in the field of physical chemistry of complexation of humic acids with cations, including radionuclides, in aqueous solutions. Problems have been identified in describing the reactivity of humate complexes with consideration for the objective complexity of the chemical nature of humic acids as one of the main classes of natural organic matter. The main methods of modeling complexation with humic acids, experimental methods for separating humate complexes and unbound cations (ultrafiltration, dialysis, etc.), and direct instrumental (electrochemical and spectroscopic) methods for detecting complexes were considered. Attention was also paid to the practical aspect of using humic acids for the treatment of natural water and wastewater to remove pollutants—heavy metals and radionuclides. Published data on the sorption capacity of humic acids of various origins in relation to heavy metal cations and quantitative data characterizing the stability of humate complexes were analyzed.

Thermodynamic and experimental studies of Zn(OH)2/ZnO particle formation conditions in the model of closed system Zn2+-NH3,aq-NH3,gas-H+-OH--H2O-N2,g as (1), which often occurs in the process of synthesis of zinc oxide nanoparticles and films by chemical bath deposition (CBD) methods, were carried out. It was shown that the driving force for the formation and growth of Zn(OH)2/ZnO particles in the initially homo-geneous system (1) at 25 degrees C is the difference in the chemical potential of particles at the initial temperature (unsaturated system) and the synthesis temperature (supersaturated system). Using vibrational spectroscopy, X-ray phase and chemical analysis, diffuse light scattering and electrophoresis methods, it was found that the phase transformation of Zn(OH)2 into ZnO takes place in the region of 85 - 90 degrees C. The colloid-chemical trans-formation of Zn(NH3)2+ 4 ionic particles into colloidal polycrystals of Zn(OH)2/ZnO composition was established for the first time to be a staged process. The first stage of the process in the solution volume is localized at the gas nanobubble-solution interface as a result of rapid formation, growth and removal of gas nanobubbles from the solution. The interaction of positively charged Zn(OH)2 nanoparticles with the surface of larger negatively charged gas nanobubbles creates colloidal aggregates "bubble||surface film of hydroxide nanoparticles". Their adhesion forms an openwork foam-like structure of the colloid in the solution and in the film on the interfaces at the first stage of synthesis. After degassing of the electrolyte solution, the second stage develops, consisting of the nucleation and ionic-molecular growth of Zn(OH)2/ZnO particles from the supersaturated solution, their distribution between the solution and the electrolyte - reactor wall - air interfaces. The film growth at this stage is regulated by the difference in surface charges of the double electric layer of the interface and polycrystalline colloidal particles. In the solution and on the interface, columnar Zn(OH)2/ZnO structures grow as volumetric stars with conical hexagonal spikes.

The kinetics and mechanism of the electrochemical redox reaction of 3-(3,5-dimethilpirazole-1-yl)-6-R-1,2,4,5-tetrazines and their Cu(II), Co(II), and Ni(II) complexes were studied by voltammetry on glassy carbon electrodes in aqueous acetonitrile. The characteristics of electrode processes in the studied systems were determined.

Исследованы сорбционные свойства нового композита Al 2 O 3 ||C. Особенностью его макроскопической морфологии и структуры является сформированное в инертной атмосфере аморфное состояние оксида алюминия в химическом контакте с поверхностью графеноподобного углерода. Это определяет высокую химическую активность в водной среде композита на основе оксида алюминия (ОАК), сравнимую с активностью α-Al 2 O 3 или гиббсита Al(OH) 3 . Сорбционные свойства полученного композита по отношению к ионам La(III), Ce(III), U(VI) описаны в рамках модели поверхностного комплексообразования. Совпадение вычисленных из сорбционного эксперимента и литературных данных по величинам первой константы гидролиза катионов La(III), Ce(III), U(VI) доказывает адекватность выбранной сорбционной модели. Из модельного описания следует, что сорбционная активность композита вызвана более +высокой константой ( K 1a ) кислотной диссоциации -ОН 2 surf -групп (p K 1a = 3.9) поверхности аморфного ОАК и сортовыми коэффициентами распределения отдельных гидроксокомплексов исследованных катионов. Сорбция ионов композитом в растворе гуминовых кислот (ГК) полностью определяется параллельно протекающей реакцией конкурентной сорбции протонированных анионов ГК поверхностью аморфного ОАК в диапазоне концентрации ГК 10-200 мг/л. Al 2 O 3 ||C является эффективным сорбентом микроколичеств La(III), Ce(III), U(VI), их химических аналогов, а также гуминовой кислоты в природных и технологических растворах с низким солевым фоном.

The sorption properties of the new Al 2 O 3 ||C composite were studied. A feature of its macroscopic morphology and structure is the amorphous state of alumina generated in an inert atmosphere in chemical contact with the graphene-like carbon surface. This feature is shown to determine the high chemical activity of the alumina-based composite (AC) in an aqueous medium, which is comparable with the activity of α-Al 2 O 3 or gibbsite Al(OH) 3 . The sorption properties of the obtained composite towards La(III), Ce(III), U(VI) ions are described within the surface complexation model. The agreement between the values of the first hydrolysis constant of La(III), Ce(III), and U(VI) cations calculated from the sorption experiment and published data proves the adequacy of the chosen sorption model. It follows from simulation that the sorption activity of the composite is caused by a higher constant ( K 1a ) of the acid dissociation of –ОН 2 + surf groups (p K 1a = 3.9) of the amorphous AC surface and the partial distribution coefficients of individual hydroxo complexes of the studied cations. Sorption of ions by the composite in a solution of humic acids (HA) is completely determined by the parallel reaction of competitive sorption of protonated HA anions by the amorphous AC surface in the HA concentration range of 10–200 mg/L. Al 2 O 3 ||C is an effective sorbent for trace amounts of La(III), Ce(III), U(VI), their chemical analogs, and humic acid in natural and working solutions with a low salt background.

Colloidal-chemical transformations accompanying the thermal degradation of a homogeneous aqueous solution of nickel(II) ammoniac complexes are investigated by thermodynamic and kinetic methods. A competitive growth mechanism of β-Ni(OH)2 nano- and microcrystals in the solution bulk and on the solution–solid interface is proved. The weight growth rate for each of the kinetic routes is controlled by the kinetics of the first-order homogeneous reaction of $${\text{Ni}}\left( {{\text{N}}{{{\text{H}}}_{{\text{3}}}}} \right)_{6}^{{2 + }}$$ degradation. The reason for the competitive weight gain of the sol and β-Ni(OH)2 film lies in the different activation energies for $${\text{Ni}}\left( {{\text{N}}{{{\text{H}}}_{{\text{3}}}}} \right)_{6}^{{2 + }}$$ conversion to sol microcrystals (131.0 ± 27.0 kJ/mol) and to the film (94.0 ± 24.0 kJ/mol). This gives rise to the existence of two different temperature areas where sol or film growth is preferable. At 70–75°C, the sol and film growth rates are equal. An interpretation of the temperature-dependent colloidal growth mechanism of Ni(OH)2 crystals is proposed. The influence of the morphology and thickness of β-Ni(OH)2 films on their optical band gap width, photocatalytic and electrical activities is determined.

According to the data of static method of sorption of trace amounts of Co(II) ions by the Termoksid-35 (T-35) sorbent in a chloride-acetate solution, the cobalt distribution coefficient Kd was calculated as a function of pH, concentration of humic acids (HA), and temperature. The distribution of the complexes Co2+, CoAc+, CoCl+, Co(OH)+, Co(OH)02, Co(OH)3– between the solution and the sorbent was modeled within the framework of the surface complexation concept. The found stability constants of the Co(OH)+ and Co(OH)20 complexes coincide with the thermodynamic values. In the presence of HA (10.0 mg/L), the best agreement between the model function of Kd–pH and the experimental data corresponds to the sorption of a complex with the composition Co(OH)A0, where A– is the anion of humic acids. It was concluded that T-35 can be used as a sorbent for removal of Co(II) radionuclides from industrial process at pH > 7 and natural water in the presence of humic acids.

A study of the accumulation of trace elements in the marsh frog Pelophylax ridibundus Pall . , 1771 in the heating zones of the cooling ponds of the Beloyarsk nuclear power plant and Reftinsk heating electric power plant has been carried out. For the entire set of data on the concentrations of elements in frogs, no statistically significant differences are found between the studied water bodies. Using the example of both water bodies, no differences in the accumulation of elements by males and females of amphibians are revealed. A significant correlation between the concentration of elements in adult frogs with their content in water and plankton is found. An excess of the maximum permissible concentrations of some elements in the water of both reservoirs, as well as an excess of the concentrations of a number of elements in frogs, compared with background values, are revealed.

The nanostructured Al2O3:nC composites with enhanced chemical activity and higher solubility of oxide in acids have been synthesized. For the synthesis, an organometallic precursor, produced by thermal treatment of a mixture of Al(NO3)(3)center dot 9H(2)O with ethylene glycol, was heated in helium atmosphere at 700-1100 degrees C. X-ray powder diffraction, selected-area electron diffraction and transmission electron microscopy revealed the formation of a homogeneous amorphous mass with indistinguishable boundaries between the oxide and carbon components at 700-1000 degrees C, while annealing at 1100 degrees C provoked the crystallization of gamma-Al2O3 nanoparticles, forming a clear Al2O3/carbon interface. This specific microstructure provides a high sorption affinity of the composite for La (III), Ce (III), U (VI) ions in aqueous solutions, which is significantly higher than that of microcrystalline aluminum oxides.

This paper is a continuation of our earlier work devoted to determining the orbit and mass of the star 61 Cyg and the changes in the photometric characteristics of its components. The purpose of this work has been to refine the orbital elements, estimate the masses, and search for possible manifestations of periodic components in deviations from the orbital motion. Observations on two instruments at the Pulkovo Observatory have been used in this work: the normal astrograph during 1895-1919 and the 26-inch refractor during 1957-2019, as well as the earliest micrometric measurements by V. Ya. (F.G.W.) Struve during 1819-1837. Relative positions of the components determined from observations with the normal astrograph during 1895-1999 are published for the first time. Because of its closeness to the Sun and the spectral class of the components K5V and K7V, 61 Cyg is regarded as a probable candidate parent star of an exoplanet. Because of the combined observations with the 26-inch refractor and the transformation of all the data to a unified system, a gap in the observations from the beginning of the twentieth century has been filled. The modern astrophysical parameters of this star together with data published in the Gaia DR2 survey have been used. To check the orbit, the radial orbital acceleration W has been calculated from our data and found to be in good agreement with the acceleration derived by other authors from spectral observations. Possible periodic deviations from the orbital motion of the star are also discussed.

Modern state of research in the field of physical chemistry of the complexation of humic acids with cations, including radio nuclides, in aqueous solutions is considered. Quantitative data characterizing the stability of humate complexes, theoretical approaches to their determination, and problems encountered in describing the reactivity of humate complexes are analyzed with consideration for the objective complexity of the chemical nature of humic acids as one of the main classes of natural humic substances.

By X-ray diffraction analysis and Raman spectroscopy, we studied samples of fine-grained graphite MPG-7 with detected chemical and structural defects. We determined the effect of structural and chemical defects on the micro- and macrostructure of graphite and estimated its crystallinity depending on the type of defects detected.

kinetic model of the mass transfer of a microcomponent in the simplest competitive system from the sorbed state (A) into a solution (B) and then into a sorbent (C) in accordance with the scheme A ⇄ B ⇄ C was formulated within the framework of competitive sorption statics. The kinetic equations were solved numerically. The influence exerted by the weight of competing sorbents А and С and by the degree of reversibility of linear reactions on the nonequilibrium decontamination factor Kdec(t) was determined. The time in which the equilibrium decontamination factor is attained for the model of chemical sorption kinetics was estimated from the experimental data on the rate constants of direct and reverse heterogeneous reactions and on the distribution coefficients of Cs(I) in the SiO2 (A)–CsCl solution (B)–Prussian Blue (C) system.

Problems of choosing a model for describing empirical sorption data in a system consisting of an energetically nonuniform sorbent and a chemically uniform sorbate in the case when the distribution of energetically nonuniform sorption sites in the material is unknown a priori are considered. The advantages and drawbacks of choosing a sorption model adequate to the experimental data on the basis of analysis of variance are analyzed taking into account the estimated boundaries of the minimum necessary accuracy of the primary experimental data. Statistical methods do not always allow unambiguous choice of an adequate model because of limited accuracy of the experimental data. In such cases, the check of the physicochemical consequences of the model is the best argument in favor of its adequacy.

The variability of the components A and B of the visual binary system 61 Cyg is analyzed. The observations were made on the normal astrograph of the Pulkovo Observatory from 1956 through 1982 (a total of 296 brightness estimates). A search was undertaken for the periods of the variability of both components of the system with independent application of two periodogram analysis techniques: a sinusoidal approximation and the traditional Scargle method. As a comparison, the complete photometric series including all 296 values of the stellar magnitude and the yearly averages (27 values) were analyzed. This yielded a reliable value of about 15 years for the period of both components and a period of 8.5-9 years for the component 61 Cyg B that coincides with the 9.1-year period of the coronal and chromospheric activity discovered in 1978 by Wilson. 61 Cyg A was also found to have a less significant period of about 6 years, which coincides, to within the limits of accuracy, with a period of 7.5±1.7 years of the coronal and chromospheric activity previously noted by Hempelmann. Yet another less significant period of about 4 years of unknown origin was observed for 61 Cyg B. This may be the second harmonic of the fundamental period. We assume that the low accuracy of the estimated periods may be related to their instability owing to the complicated multicomponent character of the observed variability. A period of about 15 years detected for both components A and B may be related to astroclimatic or instrumental effects.

Iron and carbon doped nanostructured titanium dioxide with different morphology of aggregates was synthesized using the developed precursor technique. Glycolate of the general composition Ti1-xFex(OCH2CH2O)(2-x/2) (0 <= x <= 0.1) was used as a precursor. The synthesized samples of the compositions Ti1-xFexO2, Ti1-xFexO(2-x/2)-yCy and Ti1-xFexO(2-x/2)-yCy:nC were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet and visible absorption spectroscopy, as well as by vibration and X-ray photoelectron spectroscopy methods. In addition, they were tested as photocatalysts in the hydroquinone oxidation reaction under ultraviolet and visible irradiation. It is established that the insertion of iron into the structure of carbon-doped anatase (TiO2-yCy) suppresses its photocatalytic activity in the visible range of the spectrum, but leads to no change under ultraviolet irradiation. Globular samples of Ti1-xFexO(2-x/2)-yCy containing no more than 2.5 at% Fe show the maximum photocatalytic activity. To clarify the reasons for the observed complex dependence of photocatalytic activity on the concentration of the dopant first-principles, calculations of the electronic band structure and optical absorption of anatase doped with iron and carbon are performed and discussed.