S. D. Razumovskii

Mechanism and kinetics of the reaction of ozone with sodium chloride in aqueous solutions

It is shown experimentally that Cl− appreciably accelerates ozone decomposition in water (τ1/2 = 1.5 h versus 6 h in pure water). The decomposition of ozone in NaCl solutions includes the reversible reaction of ozone with the chloride ion (O3 + Cl− → O3− + Cl) as the key step, which is followed by the development of a chain reaction in which chain propagation is performed alternately by the chlorine atom Cl and its monoxide ClO. The current concentrations of the chlorine atom are rather low ([Cl] ∼ 10−14 mol/l). The overall process is satisfactorily described by a first-order rate law with respect to ozone. The decomposition of ozone in aqueous solutions of NaCl is not accompanied by the formation of products other than oxygen. In particular, no noticeable amounts of hypochlorites and chlorates are observed. This is particularly significant for medicinal applications of ozonized isotonic solutions.

Water-soluble polyketones and esters as the main stable products of ozonolysis of fullerene C60 solutions

Stable ozonolysis products of C60 solutions in CCl4, toluene, and hexane were studied by elemental analysis, HPLC, and UV and IR spectroscopy. Polyketones and esters were established for the first time to be the main stable products, whose content increased during the whole ozonolysis time (1 h). Epoxides C60On (n = 1—6) are accumulated within 1—3 min, and after 5 min of ozonolysis their concentration decreases to zero. Fullerene C60 disappears from the reaction solution due to its conversion to oxides and mechanical capturing of C60 by these oxides to form a precipitate. The oxidation of C60 is completed in the solid phase by the formation of the C60O16 oxide in which 9.68 O atoms fall on fullerene polyketones, 6 O atoms are attributed to esters, and 0.32 O atoms fall per epoxides. The optimum medium for preparation of the C60 oxides is CCl4 rather than traditional toluene, which reacts with ozone in the side reaction to form products containing active oxygen. The C60 cage is raptured during ozonolysis because of the C=C bond cleavage to form two C=O groups at the ends of the open hexagon. Ozonolysis of C60 solutions in CCl4 is efficient for synthesis of water-soluble fullerene oxides due to the high yield and solubility of polyketones and esters in water.

Kinetics and Stoichiometry of the Reaction of Ozone with Fullerene C60 in a CCl4 Solution

The stoichiometry (1 : 1) and the numerical value of the rate constant of the reaction of a fullerene with ozone (1.2 × 103 l mol–1 s–1) at 0°C were determined. A kinetic study of the reaction revealed the presence of an active impurity in high-purity samples. Suggestions as to the structure of this impurity were proposed based on the rate constant of its reaction with ozone. In contrast to simple aromatic compounds, the reaction of the fullerene with the first molecule of ozone dramatically (by several orders of magnitude) decreased the reactivity of the other C=C bonds in the molecule.

Nature of active intermediate particles formed during ozone-induced oxidation

139 Ozone as a representative of reactive oxygen spee cies (ROS) is one of the most toxic components of the atmosphere. A number of studies have shown that ozone is able to generate other ROS, including HO • , , H 2 O 2 , etc. [1, 2]. In some cases, these secondary ROS can be even more deleterious than the ozone molecules themselves. It is now generally recognized that proteins are among the main targets of ROS. Under the action of ROS, proteins undergo oxidative modifications, which disturb their structures and functions. Oxidationnmodified proteins accumulate in the course of aging, oxidative stress, and various diss eases [3]. It was shown that fibrinogen is 20 times more sensitive to oxidative modification than other major plasma proteins (albumin, immunoglobulins, transs ferrin, and ceruloplasmin) [4]. Therefore, fibrinogen, which accounts for approximately 4% of the total plasma proteins, is an easily vulnerable target for oxii dants. It was previously shown that a number of proteins (fibrinogen [5, 6], fibrinnstabilizing factor [7], bovine serum albumin [8], etc.) are involved in oxidative proo cesses under the influence of ozone. In studying the ozonization of fibrinogen, it was found that moderate oxidation leads to a decrease in the content of not only reactive groups (NH x , > SH, etc.), but also to a marked reduction in the content of СН 2 groups, whose reactivity compared to that of NH x and SHHgroups is smaller by 7 and 4 orders of magnitude, respectively [9]. This interesting feature of the reaction could not be attributed to the molecular reaction of ozone but, rather, was due to the action of an as yet unidentified secondary ROS and required further explanation. Since ozone in the liquid phase can form highly toxic secondary ROS, the discriminaa O 2 • − tion between the effects of the molecular oxidation and the free radical oxidation caused by the generation of free radicals under the influence of ozone during ozonation is one of the key problems in understanding the mechanism of oxidation of different biological tarr gets with ozone. In this study, we investigated this problem using fibrinogen as an example. The oxidation of fibrinogen under the action of ozone was performed as described previously [6]. The amount of ozone in the reactor varied from 5 × 10 –8 to 2 × 10 ⎯7 moles. The generation of hydroxyl radicals generated under the …

Kinetics and stoichiometry of the reaction between ozone and C70 fullerene in CCl4

The kinetics and stoichiometry of the reaction between C70 fullerene and ozone have been studied. The reaction obeys a bimolecular rate law. The stoichiometric coefficients of the reaction are 1: 12 to 1: 22, depending on reaction conditions. The rate constant at 22°C is 5 × 104 l mol−1 s−1 for the first stage of fullerene conversion and (0.8–0.6) × 104 l mol−1 s−1 for the subsequent stages. Since the stages differ in terms of reaction rate, the original C70 molecules are first involved in the reaction, whereas, at the subsequent stages, all molecules are involved with equal probabilities, irrespective of the number of preceding reaction events in which they have participated.

Kinetics of phenol oxidation with ozone in a thin layer on a solid surface

Ozone has been reacted with phenol in thin supported layers, and the dynamics of this reaction has been investigated. The stoichiometry of this reaction coincides with the stoichiometry of the same reaction in solution. Specific reaction rate (β) has been determined for various phenol conversions. The effective rate constant of the reaction, estimated by extrapolating β to zero reaction time, is significantly higher than the rate constant of the reaction in solution. The reaction between ozone and phenol is diffusion-controlled. The reaction products form a barrier layer, which protects the deeper phenol layers against ozone. The barrier layer is as thick as 8–15 phenol monolayers.

Effect of cavitational disintegration of surplus activated sludge on methane generation in the process of anaerobic conversion

The effect of mechanical pretreatment of surplus activated sludge from the wastewater treatment facilities of a plant producing chips (LLC “Frito Lay Manufacturing,” Kashira, Moscow oblast) in a cavitation disintegrator on methane generation in the process of anaerobic conversion is investigated. In laboratory conditions, cavitation disintegration pretreatment of the activated sludge results in a two- to sixfold increase in the transfer of various types of organic materials from the cell suspension into the aqueous phase. It is demonstrated that cavitation pretreatment of the activated sludge makes it possible to produce 31% extra methane as compared to the amount produced from the original sludge.

On the mechanism of the reaction between ozone and alcohols: Ozonation kinetics of butanol-1 and its esters in CCl4

The ozonation kinetics of butanol-1, tributyl borate, butyl acetate, and butyl trichloroacetate was studied in the temperature range from −20 to 45°C. The reactivity of the α-methylene group of the n-butyl moiety decreases in going from the alcohol to its trichloroacetic ester. In butyl trichloroacetate, this group is deactivated to such an extent that the kinetic parameters of the ozonation of this ester are comparable to the parameters observed earlier for n-butane. This decrease in reactivity is due the fact that the preexponential factor in the rate constant of the initial formation of an ozone-substrate complex decreases on passing from the alcohol to its esters. The activation energy of this process is constant within the error of data processing. It is concluded that the high reactivity of alcohols toward ozone is due to the initial formation of the ozone-substrate complex involving the hydroxyl group of the latter.

Cathode Materials for Hybrid Supercapacitors Based on Ozonated Reduced Graphene Oxide

A carbon material capable of reversible electrochemical oxidation and reduction with relatively high electrical conductivity was prepared by ozonation of thermally reduced graphene oxide. The specific discharge energy for such materials used in lithium ion electrochemical cell cathodes with non-aqueous electrolytes (LP-71) can reach 540 W h/kg at 40 mA/g current, while the average specific discharge power is 11.5 kW/kg at 5 A/g current. The specific charge after 2500 charge/discharge cycles at 5 A/g current was at a level of 93% of the initial value. The obtained materials appear promising for the design of new electricity storage systems.

Effect of free radical oxidation on the structure and function of plasma fibrin-stabilizing factor

Plasma fibrin-stabilizing factor (pFXIII) is a heterosubunit protein, the main function of which is the covalent stabilization of the fibrin matrix. This paper examines the ozone-induced free radical oxidation of plasma fibrin-stabilizing factor at different stages of its enzymatic activation. Electrophoretic data on the accumulation of γ-γ-dimers and α-polymers in the formation of stabilized fibrin suggests that a reduction in the enzymatic activity of FXIIIa is largely dependent on the stage of activation of pFXIII at which the oxidation is carried out. The results of UV, IR, and Raman spectroscopy measurements suggests that the oxidation of the amino acid residues of the polypeptide chains of pFXIII primarily affects cyclic, cysteine, and cystine groups and leads to the formation of oxidation products, being accompanied by the disruption of the protein secondary structure. Dynamic light scattering measurements revealed a loosening of the protein structure in the course of free radical oxidation. Spin label EPR spectroscopy data are suggestive of a change in the pFXIII conformation as a result of oxidative modification. Possible reasons for the different sensitivity of pFXIII to oxidative modification in the process of enzymatic activation are discussed. It is presumed that FXIII-B2 regulatory subunits function as scavenges of reactive oxygen species, thereby protecting FXIII-A2 catalytic subunits from oxidation.