The regularities of adsorption and oxidation of several aromatic and heterocyclic nitrogen- and oxygen-containing hydrocarbons from their aqueous solutions on lead (IV) oxide have been studied. Methods of chemical and molecular mechanics, as well as a correlation approach based on the comparison of adsorption equilibrium with the electronic properties of the adsorbate were used for evaluation. The energies of the occupied orbitals were used as parameters of the correlation between the electronic and adsorption properties of organic molecules. The marginally controlled adsorption mechanism is postulated to interpret the observed correlations for the specific adsorption of organic compounds on low-band PbO2. As a result of the study, it was found that organic compounds adsorbed or oxidized to lead (IV) oxide are quite selective. The observed effects cannot be explained by differences in chemical composition or, for example, in the degree of hydrophilicity of the test compound. It is established that the regularities of adsorption, oxidation and structural transformations of organic surfactants of compounds on lead oxide can be explained from the same point of view on the basis of orbital interactions of their boundary orbitals. The possibility of gaining the total energy of a system with complete electron transfer from an organic molecule to a PbO2 cluster model has been studied.

The thermodynamic equilibrium in TiO 2 -SO 3 -H 2 O and TiO 2 -NaF-SO 3 -H 2 O systems is studied.It is shown that rutile can spontaneously dissolve in sulfuric acid solutions.However, rutile is considered as an inert component of the titanium-bearing raw material due to the inhibition of such reactions.The kinetic deceleration of rutile dissolution in sulfuric acid is explained by the lability of Ti(IV) cations and the specific features of the rutile crystal structure.The breaking of Ti-O-Ti bonds without additional deformations of the crystal lattice is suggested to be more beneficial when using smaller anions; thus, fluoride ions can be used to this end.The thermodynamic analysis of sulfate-fluoride leaching of titanium confirms an additional decrease in Gibbs energy values for the dissolution of rutile in sulfuric acid in the presence of fluoride ions.A reaction mechanism is proposed for the interaction of rutile with sulfuric acid.The mechanism includes the stage of substitution of oxygen ions on the rutile surface by fluoride ions and the stage of sulfate-acid decomposition of titanium dioxide in places of «defects» of the rutile surface.

PbO2-polyelectrolyte composite materials with a content of polyelectrolyte up to 13 wt% are formed by electrochemical deposition of PbO2, depending on the solution composition and the deposition conditions. Several assumptions concerning the mechanism of the formation of composites that taking into account the oxygen-containing species of lead non-fixed on the surface, located in the near-electrode zone have been proposed. The shape and size of the PbO2 crystals is altered by the presence of polyelectrolyte. The surface is more uniform and the crystals are smaller, there is not a pronounced crystallographic orientation, however the phase content remains practically the same as in the undoped sample. When using composite materials based on lead dioxide containing polyelectrolyte, selective changes in the overvoltage of oxygen evolution and electrochemical conversion of organic substances into aliphatic non-toxic compounds are observed. In this case, the electrocatalytic activity of composite materials depends on the nature and content of the polyelectrolyte additive in the oxide. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

The regularities of adsorption and oxidation of several aromatic and heterocyclic nitrogen- and oxygen-containing hydrocarbons from their aqueous solutions on lead (IV) oxide have been studied. Methods of chemical and molecular mechanics, as well as a correlation approach based on the comparison of adsorption equilibrium with the electronic properties of the adsorbate were used for evaluation. The energies of the occupied orbitals were used as parameters of the correlation between the electronic and adsorption properties of organic molecules. The marginally controlled adsorption mechanism is postulated to interpret the observed correlations for the specific adsorption of organic compounds on low-band PbO2. As a result of the study, it was found that organic compounds adsorbed or oxidized to lead (IV) oxide are quite selective. The observed effects cannot be explained by differences in chemical composition or, for example, in the degree of hydrophilicity of the test compound. It is established that the regularities of adsorption, oxidation and structural transformations of organic surfactants of compounds on lead oxide can be explained from the same point of view on the basis of orbital interactions of their boundary orbitals. The possibility of gaining the total energy of a system with complete electron transfer from an organic molecule to a PbO2 cluster model has been studied.

The method of iodometric determination of chlorates impurities in sodium hypochlorite solutions for medical and veterinary purposes was developed. This method does not require sophisticated equipment and can be implemented directly where the solutions are used. The method is based on the different rates of interaction of ClO- and ClO3- with iodide ions depending on the acidity of the medium. We have shown that blank titration is advisable to improve the accuracy of the determination of low concentrations of chlorates in the matrix of hypochlorite which is present in excess since in this case possible systematic errors due to the presence of oxidizing impurities in the reagents are prevented. To quantify the low concentrations of chlorates, we proposed to remove 85-95% of hypochlorite ions by means of reducing their excess with sodium sulfite at pH 10.5. The solution of sodium sulfite does not require standardization before each analysis in the proposed procedure. The possibility of quantitative determination of chlorate impurities in the range of 2-50mg/L in the presence of 50-500-fold excess of sodium hypochlorite with an error of 5% has been proved. The expanded uncertainty of chlorate determination did not exceed 0.6mg/L.

Difference in adsorption properties of Fe(III), Mo(VI) oxides and Fe(III) molybdate as a cause of high selectivity of methanol oxidation on iron molybdate catalyst

The effect of pressure in a plasma reactor on the synthesis of mixtures of H2O2 and ClO 2 - has been studied. The yield of oxidants, selectivity for chlorites, the rate of the process, and its energy consumption have been treated as optimization parameters. Functional dependences of the optimal time of the plasma treatment of NaCl solutions on the reactor pressure with respect to parameters, such as the process selectivity and chlorite yield, have been determined.

The influence of temperature on the characteristics of Ni(II)–Ti(IV) LDH was investigated in the work.Ni(II)–Ti(IV) layered double hydroxides were synthesized from a solution of Ni2+ and Ti4+ with the cationic ratio of Ni2+/Ti4+=5 by using three coprecipitation techniques: titration, coprecipitation at high supersaturation and homogeneous coprecipitation. The prepared samples were characterized by means of X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC).By means of XRD, it was revealed that all samples prepared using titration and coprecipitation at high supersaturation at 65 and 20 oC correspond to Ni-Ti LDH structure. Elevated temperature during sample preparation using titration and coprecipitation at high supersaturation did not have a significant effect on phase composition, but affected the crystallinity. According to XRD results, the sample prepared using homogeneous coprecipitation at 70 oC had a significant content of b-Ni(OH)2. Increasing the synthesis temperature to 80 oC has led to the almost complete disappearance of b-Ni(OH)2 reflections.By means of TGA and DSC, it was found that titration method leads to formation of samples with higher thermal stability than those prepared by high supersaturation. Elevated temperature and hydrothermal treatment leads to higher thermal stability of the samples. Samples prepared by homogeneous coprecipitation show complicated behavior during thermal decomposition, confirming the presence of cyanate ions in the interlayer gallery.

Nickel hydroxide is used an active substance for accumulators and supercapacitors, which are widely used as power sources for various electric devices and electronics. According to literature the formation of divalent metal hydroxides such as zinc and cadmium hydroxides(Zn(OH)2, Cd(OH)2) occurs in two stage: 1) precipitation of metal hydroxyl salt; 2) reaction of hydroxyl salt with hydroxyl groups with formation of metal hydroxide. Though the nickel hydroxyl nitrate is known, the information regarding its formation mechanism and composition is limited. Aim of the work was to establish the formation mechanism of nickel hydroxide from nitrate precursor and to establish the composition of formed precipitate. In order to achieve the set aim, the analysis of Ni(NO3)2—NaOH system has been carried out using combined method of conductometric and potentiometric titration. It had been established that process of nickel hydroxide formation from nitrate solution occurs in two stages: 1) precipitation of basic nickel nitrate; 2) transformation of basic nickel nitrate into hydroxide. It had been established that composition of primary precipitate correspond to the formula Ni(NO3)0.13(OH)1.87.

It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II) as a precursor instead of Fe(III). This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III) oxide impurities which are detrimental for the process selectivity. The system containing Fe(II) and Mo(VI) species in aqueous solution was investigated using UV–Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II)–Mo(VI) system: (i) formation of complexes between Fe(II) and molybdate(VI) ions, (ii) inner sphere oxidation of coordinated Fe(II) by Mo(VI) and (iii) decomposition of the Fe–Mo complexes to form scarcely soluble Fe(III) molybdate, Mo(VI) hydrous trioxide and molybdenum blue. Solid molybdoferrate(II) prepared by interaction of Fe(II) and Mo(VI) in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II) precursor was tested in methanol-to-formaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III).

In this work the thermodynamical solubility diagrams of zinc and titanium hydroxides were reviewed in order to determine the conditions for maximum degree of phase composition homogenization of precipitates. Experimental investigation of dependency of titanium peroxohydroxide solubility on solution acidity has been carried out and coprecipitation of zinc ions has been studied. It was concluded that precipitation by constant addition of mixed salts and base solutions into the mother liquor with constant acidity of pH∼8.5 allows maximizing homogenization of precipitate composition. Thermal treatment process of mixed zinc and titanium hydroxides coprecipitated with hydrogen peroxide was studied using thermogravimetric analysis, differential thermal analysis and X-ray diffraction methods. It was found that precipitates of co-precipitated mixtures of zinc and titanium hydroxides contained impurities of salts precursors of the Zn(NO3)2 and TiOCl2 at a level of 1%. The experimental data demonstrate the influence of hydrogen peroxide on crystal growth rate of the zinc titanate during thermal treatment. The temperature ranges and kinetic parameters of hydroxide mixture dehydration, decomposition of the titanium peroxohydroxide and precursor impurities were determined.

It was shown that the presence of titanium dioxide nanoparticles with an average size of 14 nm in methanesulfonate electrolytes leads to acceleration of the electrolytic deposition and crystallization of lead dioxide. It was established that the process results in the formation of PbO2–TiO2 nanocomposites the composition and structure of which depend on the composition of the suspension electrolyte and the hydrodynamic conditions of electrodeposition.

The molybdate intercalated layered double hydroxides can be potentially applied as catalysts for organic synthesis and oxidation. According to literature they are most commonly prepared using multi-stage methods such as anion-exchange and rehydration of calcinated LDH precursor. Aim of the work was to study a possibility of one-stage synthesis of molybdate-intercalated Ni-Ti LDH. To achieve the set-out aim, a sample of molybdate-intercalated Ni-Ti LDH has been prepared using one-step coprecipitation at high supersaturation at room temperature synthesis method: drop-wise introduction of nickel and titanium salts solution into solution of sodium hydroxide and ammonium heptamolybdate. The prepared sample was characterized by SEM, XRD, FTIR, TG-DTA and EDX. Hydrotalcite-like structure has been confirmed by results of XRD, FTIR and TG. The results of SEM have showed that sample morphology is constituted by spherical agglomerates. According to XRD results the prepared sample has rather low crystalinity. The results of TG-DTA showed that thermal decomposition of the sample occurs into two stages: 1) 90-180oC accompanied by an endothermic event and associated with loss of adsorbed and interlayer water; 2) 280-340oC accompanied by an endothermic event and associated with dehydroxilation brucite-like layered, transformation of LDH into LDO and, possibly, transformations in Ni-Ti-Mo-O system. Results of FTIR have confirmed successive intercalation of molybdate anion into interlayer space of Ni-Ti LDH. The results of FTIR also indicate presence of polymobdate forms. The results of EDX analysis showed molar ratio of Ni:Ti:Мо=1:0,19:0,22. The acquired results show the possibility of one-stage synthesis of molybdate intercalated Ni-Ti LDH.

The sizes of colloid particles and aggregate stability of nitrate and methanesulfonate suspension electrolytes used for obtaining of PbO2-TiO2 composite materials were investigated. It is found, that TiO2 colloid solutions at the presence of the big surpluses of plumbum ions and acids are inclined to fast aggregation. The same effect results also introduction in electrolytes of the sodium dodecylsulfate additives. It was established that the adsorption of sodium dodecylsulfate on the TiO2 powder had a weak specific nature, as evidenced by the low value of the energy of adsorption interaction. As a result of the conducted researches it was established that aggregately stable suspension electrolytes may be derived from sols of titanium dioxide, which are formed by the hydrolysis of titanium isopropylate. Optimum conditions of obtaining of electrolytes with high aggregative stability were determined: pH similar to 1, concentration Pb(II) salt - 0,1 M, the size of particles TiO2 sol - no more than 14 nm.

The sizes of colloid particles and aggregate stability of nitrate and methanesulfonate suspension electrolytes used for obtaining of PbO2–TiO2composite materials were investigated. It is found, that TiO2colloid solutions at the presence of the big surpluses of plumbum ions and acids are inclined to fast aggregation. The same effect results also introduction in electrolytes of the sodium dodecylsulfate additives. It was established that the adsorption of sodium dodecylsulfate on the TiO2 powder had a weak specific nature, as evidenced by the low value of the energy of adsorption interaction. As a result of the conducted researches it was established that aggregately stable suspension electrolytes may be derived from sols of titanium dioxide, which are formed by the hydrolysis of titanium isopropylate. Optimum conditions of obtaining of electrolytes with high aggregative stability were determined: рН ~ 1, concentration Pb(II) salt – 0.1 M, the size of particles TiO2 sol – no more than 14 nm.a

Thermodynamics and kinetics of decomposition of iron molybdate in soda solutions was studied in order to optimize the molybdenum recovery conditions. The leaching was performed in a model circulating reactor with a stationary solid phase. An equation for the rate of the heterogeneous process was derived for the first time. In this equation, the concentration of the leaching reagent is functionally related to the conversion of the solid reagent. Factors of the optimizing effect of the molybdenum leaching process are considered. The optimal size of raw material particles is determined by the ratio between the leaching and suspension filtration rates. As the concentration of the soda solution is raised, it is necessary to take into account, in addition to the positive effect that consists in the increasing decomposition rate of iron molybdate, the possible quality deterioration of the target product due to the accumulation of the iron impurity in this product.

Theoretical and practical results of the treatment of water and aqueous solutions by low-temperature nonequilibrium contact plasma are considered. It is shown that the liquid medium in the process of plasma treatment or thereafter undergoes significant structural and physical-chemical transformations, the use of which opens up new horizons in the modernization or improvement of technological processes to replace out-of-dated or obsolete ones.

Методами термического анализа исследованы образцы молибдата железа, полученные смешением растворов гептамолибдата аммония и нитрата железа. Определены температурные диапазоны и кинетические параметры процессов дегидратации, разложения примесей и топохимической реакции между оксидами железа и молибдена. Разработана математическая модель процесса термической обработки. Получены данные о содержании компонентов твердой фазы в зависимости от температуры и продолжительности прокаливания.

Теоретически и экспериментально изучена возможность получения осадков молибдата железа(III) в смеси с триоксидом молибдена с минимальным содержанием примеси оксида железа. Образцы осадков изучены методами ИК-спектроскопии, термического, рентгенофазового и рентгенофлуоресцентного анализа. Показано, что осаждение способом непрерывной кристаллизации при постоянной кислотности маточного раствора (рН 1) позволяет получать осадки с примесью Fe2O3 до 2%.