Oxidative destruction of anionite AV-17×8 using the Fenton reaction

The kinetic studies of AV-17×8 strongly basic anionite’s oxidative destruction using the Fenton reaction have been carried out. The effect of the process’s temperature and the concentration of catalysts of iron(II) sulfate or copper(II) sulfate on the oxidation of anion-exchange resin with hydrogen peroxide is estimated. With an increase in temperature in the range of 323–348 K, a regular increase in the effective rate constant of oxidative anionite destruction is observed when using iron(II) sulfate by 1.5 times, and when using copper(II) sulfate – by 22 times. It was found that the obtained values of the activation energy of the anion exchanger’s oxidation with the addition of copper(II) sulfate are 124.3–115.7 kJ/mol and are characteristic of the process proceeding in the kinetic region. The nature of the change in the surface morphology of the anionite granules in the process of oxidative decomposition has been revealed.

COMPLEX OF NICKEL (II) ION WITH TRYPTOPHAN AS A HOMOGENEOUS CATALYST IN THE DECOMPOSITION REACTION OF CUMENE HYDROPEROXIDE IN AQUEOUS SOLUTION

The formation of Ni2+:Tryptophan (Trp) 1:1 complex, which acts as a model catalyst for decomposition of cumene hydroperoxide (ROOH) in Ni2++Trp+ROOH+H2O system, has been confirmed via kinetic study in aqueous solution at pH>7. The kinetic expression of a single catalytic decomposition reaction of ROOH under the influence of [NiTrp]+ complex was brought out. The temperature dependence of the effective rate constant of ROOH decay (Keff=Kcat[Ni2+]0[Trp]0=const) in the temperature range from 323 to 343 K can be expressed by Arrhenius equation (Eeff is in kJ/mol): Keff=(1.87±0.02)·106exp[–(49.8±0.3)/RT], min –1.

SIMULTANEOUS ACTION OF CAVITATION AND INERT GASES ON THE WATER PURIFICATION FROM BACTERIAL CELLS

The simultaneous effect of cavitation and inert gases (argon and helium) on the process of microorganisms (MO) destruction has been studied. Sporogenic rod-shaped bacteria of the Bacillus cereus type were used for the study. The initial microbial load was 104 cells per 1 cm3 of test water. The volume of water for the study was 75 cm3. The source of the cavitation phenomenon was an ultrasonic generator with a frequency of 22 kHz. The gas was bubbled through the water system at a rate of 0.2 cm3/s throughout the duration of the process (2 h) with a total flow rate of 0.7 dm3/h. After every 30 min of simultaneous action of gas/cavitation, water samples were taken to determine the dynamics of the number of microorganisms (NM) from the time of water treatment. The change in the NM for each gas is given depending on the duration of the process and the initial number of cells per unit volume of water. To compare the effectiveness of the studied gases, the values of the effective rate constant of bacterial destruction (kd) were calculated according to the kinetic equation of the first-order reaction. According to the calculated kd values, the higher efficiency of bacterial destruction during argon bubbling under cavitation conditions was noted, in comparison with helium in similar experimental conditions. It is shown that kd(Ar/US) > kd(He/US). The efficiency of the process of water purification from pollutants of biological origin under cavitation conditions depends on the nature of the bubbled gas.

Water Splitting and Transport of Ions in Electromembrane System with Bilayer Ion-Exchange Membrane

Bilayer ion-exchange membranes are mainly used for separating single and multiply charged ions. It is well known that in membranes in which the layers have different charges of the ionogenic groups of the matrix, the limiting current decreases, and the water splitting reaction accelerates in comparison with monolayer (isotropic) ion-exchange membranes. We study samples of bilayer ion-exchange membranes with very thin cation-exchange layers deposited on an anion-exchange membrane-substrate in this work. It was revealed that in bilayer membranes, the limiting current’s value is determined by the properties of a thin surface film (modifying layer). A linear regularity of the dependence of the non-equilibrium effective rate constant of the water-splitting reaction on the resistance of the bipolar region, which is valid for both bilayer and bipolar membranes, has been revealed. It is shown that the introduction of the catalyst significantly reduces the water-splitting voltage, but reduces the selectivity of the membrane. It is possible to regulate the fluxes of salt ions and water splitting products (hydrogen and hydroxyl ions) by changing the current density. Such an ability makes it possible to conduct a controlled process of desalting electrolytes with simultaneous pH adjustment.

REGULARITIES OF HYDROLYSIS OF ALUMINUM ACTIVATED BY Ga-In-Sn EUTECTIC ALLOY AND ZINC

Aluminum is a promising metal for creating energy-storing substances (ESS) on its basis for hydrogen evolution from water as a result of its of activating aluminum and providing it with the ability to react with water, special attention is paid to methods of alloying it with additions of low-melting metals and alloys, in particular, the eutectic alloy of gallium, indium and tin is perspective alloy for alloying aluminum and obtaining ESS, capable of releasing hydrogen from water without additional heating. The temperature at which stable interaction of aluminum activated by low-melting metals and alloys with water begins to be determined by the temperature at which alloying metals on the surface of aluminum crystallites become liquid. The melting point of the four-component Ga61In25Sn13Zn1 eutectic is about 3 °C, what is about 8 °C lower than the melting point of the Ga-In-Sn eutectic. Therefore, in this work, aluminum was activated by the eutectic alloy of gallium, indium and tin, as well as zinc, and the regularities of the hydrolysis of the obtained EAPs were investigated. Comparative volumetric determinations of hydrogen, which was released during the hydrolysis of 95 wt.% Al + 5 wt.% Ga-In-Sn eutectic and 92 wt.% Al + 5 wt.% Ga-In-Sn eutectic + 3 wt.% Zn alloys, showed that the introduction of zinc into activated aluminum led to a significant acceleration of hydrogen evolution from water at low temperatures (25 and 40 °C). The effective rate constants of hydrolysis of the zinc-doped alloy, calculated using the modified Prout-Tompkins equation, were 1.33, 1.75, 2.19, and 2.58 min-1 at temperatures of 25, 40, 55, and 70 °C, respectively. The effective activation energy of the process, calculated from the temperature dependence of the effective rate constant, was 12.6 kJ·mol-1, which indicates diffuse control of the hydrolysis rate. An analysis of the X-ray diffraction pattern of the products of the hydrolysis of 92 wt.% Al + 5 wt.% Ga-In-Sn eutectic + 3 wt.% Zn alloy at the temperature of 55 °C showed that they contain boehmite, baerite and small amounts of alloying metals.

The effect of ultrasound on the treatment of domestic wastewater from organic and biological contamination

The effectiveness of the uses of ultrasonic cavitation for wastewater treatment has been investigated. The influence of the gases of different nature (nitrogen, oxygen, air, mixture of nitrogen and oxygen gases in the ratio of 1:1) on the destruction of organic and biological contaminants has been carried out. It is confirmed that ultrasound cavitation increases the purification effect of gases. It is established that the deepest purification from organic contaminants was achieved by the common action of air with ultrasound, the degree of water purification from organic compounds being 80% and from biological contaminants – by the common action of nitrogen with ultrasound – the degree of water purification from biological compounds being 99,5%. The effective rate constant was calculated.

COMPOSITIONS BASED ON AQUEOUS SOLUTIONS OF CHITOSAN AND GLUTAR ALDEHYDE FOR EMBOLIZATION OF BLOOD VESSELS

The article investigates the aqueous solutions of food chitosan and glutaraldehyde to determine the feasibility of their use as components of an embolizing composition. It was shown on the basis of experimental flow curves, viscosity and velocity curves that test solutions have low viscosity and exhibit Newtonian flow behavior. The activation energy of viscous flow of the fluids was estimated in the temperature range of 25-37 °C within the Arrhenius - Frenkel - Eyring equation. It varies within a narrow range: 17-24 kJ/mol. When mixing the aqueous solutions of food chitosan and glutaraldehyde, chemical interaction of the solutes occurs. It is accompanied by an increase in viscosity and formation of a covalently crosslinked gel. Using a simple exponential equation the effective rate constant of the chemical process was calculated. It varies in a wide range: 1.9-82.7∙103 1/s. These values can be used when selecting an optimal region of food chitosan-glutaraldehyde ratios and concentrations of their aqueous solutions to generate embolizing agents. The conditions at which gel formation takes place over forty seconds were determined. Differential scanning calorimetry indicated a negligible thermal effect of food chitosan reaction with glutaraldehyde in the aqueous medium, which ensures no thermal burn during the formation of an embolus in the blood vessel in situ. As a result of the work elastic solid gels suitable for use as embolizing agents were obtained.

Antioxidant properties of derivatives of 3,4-dihydropyrimidin-2-one with sterically hindered phenolic substituent in heterocycle

In the processes of free-radical oxidation of organic compounds, the inhibitory action of the inhibitor is mainly due to either the breakdown of the reaction chains on its molecules, or the slowdown of the decomposition of intermediate hydroperoxides, or both at the same time. We analysed the inhibitory properties of 4-[3,5-di(tert-butyl)-4-hydroxyphenyl]-5-ethoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2-one (I) and 4-[4-methoxyphenyl]-5-ethoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2-one (II) gasometry and hydroperoxide decomposition methods. These compounds were obtained by the three-component Biginelli reaction. The decomposition of cumene hydroperoxide in dimethylformamide under these conditions is described by a first-order kinetics equation. The first compound significantly inhibits the decomposition of hydroperoxide. The dependence of the effective rate constant of the decomposition of cumene hydroperoxide on the first concentration is described by the equation: . The second compound also slows the decomposition of hydroperoxide, but much less than the first compound. Therefore, both the phenolic moiety and the urea moiety of the dihydropyrimidinone cycle take part in slowing the cumene hydroperoxide decomposition. Initiated oxidation of cumene happened at 343 K with the presence of the initiator azodiisobutyronitrile. The concentration of the first compound varied from 1,5·10-4 to 2,5·10-3 mol/l. With a concentration of the first compound 1,25·10-3 and 2,5·10-3 mol/l, the duration of the induction period exceeds 80 min. In the concentration range (1,5÷6,3)·10-4 mol/l the linear change in the duration of the induction period is observed. 4-[3,5-Di(tert-butyl)-4-hydroxyphenyl]-5-aminocarbonyl-6-methyl-3,4-dihydropyrimidin-2-one is a more effective inhibitor than the ionol due to the urea moiety of the dihydropyrimidinone cycle. Confirmation is the notable antioxidant activity of the second compound. In conclusion, 4- [3,5-di (tert-butyl)-4-hydroxyphenyl]-5-ethoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2-one is a bifunctional inhibitor.

LES study of the impact of moist thermals on the oxidative capacity of the atmosphere in southern West Africa

The hydroxyl radical (OH) is a highly reactive species and plays a key role in the oxidative capacity of the atmosphere. We explore the potential impact of a convective boundary layer on reconciling the calculation–measurement differences for OH reactivity (the inverse of OH lifetime) attributable to the segregation of OH and its reactants by thermals and the resulting modification of averaged reaction rates. The large-eddy simulation version of the Meso-NH model is used, coupled on-line with a detailed chemistry mechanism to simulate two contrasted biogenic and urban chemical regimes. In both environments, the top of the boundary layer is the region with the highest calculated segregation intensities but with the opposite sign. In the biogenic environment, the inhomogeneous mixing of isoprene and OH leads to a maximum decrease of 30 % of the mean reaction rate in this zone. In the anthropogenic case, the effective rate constant for OH reacting with aldehydes is 16 % higher than the averaged value. OH reactivity is always higher by 15 to 40 % inside thermals in comparison to their surroundings as a function of the chemical environment and time of the day. Since thermals occupy a small fraction of the simulated domain, the impact of turbulent motions on domain-averaged total OH reactivity reaches a maximum decrease of 9 % for the biogenic case and a maximum increase of 5 % for the anthropogenic case. Accounting for the segregation of air masses by turbulent motions in regional and global models may increase OH reactivity in urban environments but lower OH reactivity in biogenic environments. In both cases, segregation alone is insufficient for resolving the underestimation between observed and modeled OH reactivity.

Effective reaction rate on a heterogeneous surface

We examine the problem of prescribing the macroscale boundary condition to the solute convective–diffusive mass transport equation at a heterogeneous surface consisting of reactive circular disks distributed uniformly on a non-reactive surface. The reaction rate at the disks is characterized by a first-order kinetics. This problem was examined by Shah & Shaqfeh (J. Fluid Mech., vol. 782, 2015, pp. 260–299) who obtained the boundary condition in terms of an effective first-order rate constant, which they determined as a function of the Péclet number $Pe=\dot{\unicode[STIX]{x1D6FE}}a^{2}/D$, the fraction $\unicode[STIX]{x1D719}$ of the surface area occupied by the reactive disks and the non-dimensional reaction rate constant $K=ka/D$. Here, $a$ is the radius of the disks, $D$ is the solute diffusivity, $\dot{\unicode[STIX]{x1D6FE}}$ is the wall shear rate and $k$ is the first-order surface-reaction rate constant. Their analysis assumed that $Pe$ and $K$ are $O(1)$ while the ratio of the microscale $a$ to the macroscale $H$ is small. The macroscale transport process is convection–diffusion dominated under these conditions. We examine here the case when the non-dimensional numbers based on the macroscale $H$ are $O(1)$. In this limit the microscale transport problem is reaction rate dominated. We find that the boundary condition can be expressed in terms of an effective rate constant only up to $O(\unicode[STIX]{x1D716})$, where $\unicode[STIX]{x1D716}=a/H$. Higher-order expressions for the mass flux involve both the macroscopic concentration and its surface gradient. The $O(\unicode[STIX]{x1D716})$ microscale problem is relatively easy to solve as the convective effects are unimportant and it is possible to obtain analytical expressions for the effective rate constant as a function of $\unicode[STIX]{x1D719}$ for both periodic and random arrangement of the disks without having to solve the boundary integral equation as was done by Shah and Shaqfeh. The results thus obtained are shown to be in good agreement with those obtained numerically by Shah and Shaqfeh for $Pe=0$. In a separate study, Shah et al. (J. Fluid Mech., vol. 811, 2017, pp. 372–399) examined the inverse-geometry problem in which the disks are inert and the rest of the surface surrounding them is reactive. We show that the two problems are related when $Pe=0$ and $kH/D=O(1)$. Finally, a related problem of determining the current density at a surface consisting of an array of microelectrodes is also examined and the analytical results obtained for the current density are found to agree well with the computed values obtained by solving the integral equation numerically by Lucas et al. (SIAM J. Appl. Maths, vol. 57(6), 1997, pp. 1615–1638) over a wide range of parameters characterizing this problem.