E. E. Antipenko

The solubility of ozone in aqueous solutions of sulfuric, phosphoric, and perchloric acids

The solubility of ozone in pure water and aqueous solutions of sulfuric, phosphoric, and perchloric acids was determined at 20°C. An increase in the concentration of H3PO4 and HClO4 (to 14.8 and 9.5 M, respectively) caused a monotonic decrease in the solubility of ozone. The solubility of ozone in sulfuric acid was minimum at a 12 M concentration; the solubility then increased and, in 17.9 M H2SO4, reached almost the same value as in pure water. The ratio between the concentrations of O3 in solution and the gas phase was 0.276 in pure water, 0.122 in 12 M H2SO4, and 0.265 in 17.9 M H2SO4. The results obtained are compared with the available literature data.

The solubility of ozone and kinetics of its chemical reactions in aqueous solutions of sodium chloride

The solubility of ozone and the kinetics of its decomposition and interaction with chloride ions in a 1 M aqueous solution of NaCl at 20°C and pH 8.4–10.8 were studied. The ratio between the concentration of O3 in solution and the gas phase was found to be 0.16 at pH 8.4–9.8. The concentration of dissolved ozone decreased sharply as pH increased to 10.8 because of a substantial increase in the rate of its decomposition. It was observed for the first time that the interaction of O3 with Cl− in alkaline media resulted in the formation of ClO3− chlorate ions. The dependence of the rate of formation of ClO3− on pH was determined; its maximum value was found to be 9.6 × 10−6 mol l−1 min−1 at pH 10.0 and the concentration of ozone at the entrance of the reactor 30.0 g/m3. A spectrophotometric method for the determination of chlorate ions (concentrations 1 × 10−5−3 × 10−4 M) in aqueous solutions was suggested.

Formation of hydrogen polyoxides as constituents of peroxy radical condensate upon low-temperature interaction of hydrogen atoms with liquid ozone.

The composition of low-temperature condensates obtained by the reaction of hydrogen atoms with liquid ozone has been determined from the Raman spectra and data on the molar ratio of O2 to H2O2 in the decomposition products. The main constituents are hydrogen tetroxide H2O4, trioxide H2O3, and peroxide H2O2 in comparable amounts and also water H2O. The mechanism and quantitative kinetic model of their formation have been proposed. H2O4, H2O3, and H2O2 are formed in the diffusion-controlled reactions between OH and HO2 in the liquid ozone layer and stabilized by transfer to the solid phase. OH and HO2 radicals are generated via a sequence of the reactions initiated by the interaction H + O3(liq). The model adequately reproduces the properties of the real condensates.

Stoichiometry and Products of Ozone Reaction with Chloride Ion in an Acidic Medium

It is shown by means of direct spectrophotometry in the UV and visible ranges that the only product of the O3 reaction with Cl−(aq) in an acidic medium is molecular chlorine Cl2; in solutions, it is in equilibrium with the complex ion Cl3−. It is found that the consumption of one ozone molecule corresponds to the formation of one chlorine molecule. The stoichiometric equation for the reaction is obtained.

Erratum to: “Primary stage of the reaction between ozone and chloride ions in aqueous solution: Oxidation of chloride ions with ozone through the mechanism of oxygen atom transfer”

Relying on experimental data on products and the kinetic features of the complex reaction between O3 and Cl−(aq), we establish that the primary stage of the reaction proceeds via a mechanism in which an oxygen atom is transferred from an ozone molecule to a chloride ion. Analyzing the thermodynamic parameters of the primary stage, we conclude that a long-lived intermediate complex of a chloride ion and ozone is initially formed. The mechanism of acid catalysis in the reaction between O3 and Cl−(aq) is described as the formation of a protonated intermediate complex, HO3Cl, in the acidic medium and its rapid decomposition toward the formation of products.

Primary stage of the reaction between ozone and chloride ions in aqueous solution: Can chloride ion oxidation by ozone proceed via electron transfer mechanism?

It is found that chloride-ion oxidation by ozone via electron transfer mechanism does not occur due to its extremely high endoergicity and negligibly low rate. It is concluded that all processes supposedly associated with this reaction, particularly ozone decomposition in sodium chloride solution initiated by Cl· atoms, do not take place either. It is shown that experimental data on the products and kinetic regularities of the interaction of O3 with Cl− contradict the assumption that the electron transfer reaction is its primary stage. In fact, chloride-ion oxidation by ozone proceeds via the mechanism of oxygen atom transfer. It is noted that in order to estimate the possibility of using an ozonated physiological saline in medicine, the formation of chloride-ion oxidation products and ozonation byproducts must be taken into account.

Photometric determination of chlorine in a gas flow in the presence of ozone

A method was proposed for the determination of chlorine in a gas mixture containing ozone. The method is based on passing the mixture before absorption with a potassium iodide solution through a furnace, where the ozone is decomposed. The concentration of chlorine at the outlet of the furnace is determined photometrically.

Synthesis of peroxy-radical condensates from mixtures of H2+O2

One of the methods for the synthesis of peroxy-radical condensates is the condensation at liquid nitrogen temperature of an H2+O2 mixture dissociated in an electrical discharge at low pressure. Peroxy-radical condensates are thought to contain substantial quantities of higher hydrogen peroxides H2O3 and H2O4. The present work investigates the influence of experimental parameters on the synthesis of peroxy-radical condensates from an H2+O2 mixture, analyses the relevant literature, and recommends the optimal experimental conditions for the synthesis. The synthesis is carried out in a U-tube electrical discharge reactor (inner diameter ∼15 mm), immersed in liquid nitrogen, at rather low pressure (0.5–1 Torr). The maximum conversion of initial O2 into higher hydrogen peroxides was observed at a composition of initial gas mixture of 66.7% H2 + 33.3% O2.

The kinetics of reaction between permanganate and chlorine ions in acid solutions

The reaction between MnO4− and Cl− was studied in acid media at room temperature and ionic strength 1 M. The stoichiometric equation of the reaction has the form MnO4− + 8H+ + 4Cl− = Mn3+ + 2Cl2 + 4H2O. The reaction proceeds in two stages. At the first stage, permanganate ions are consumed to produce one Cl2 molecule per MnO4− ion. At the second stage, the second Cl2 molecule and the final MnO4− reduction product (trivalent manganese) are formed. The first stage is a reaction first-order in MnO4− and second-order in H+ and Cl−; its rate constant is (9.8 ± 0.6) × 10−2l4/(mol4 min). An analysis of the literature data leads to a value of 18–20 kcal/mol for its activation energy.

The oxidation of chlorine ions under the joint action of ozone and permanganate ions

The oxidation of chlorine ions in the system O3 + MnO4− + H+ + Cl− with the formation of Cl2 in the gas phase was studied. The phenomenon of transfer catalysis of the reaction between O3 and Cl− by the MnO4− ion was observed (the products of the reduction of MnO4− by the chlorine ion are oxidized by ozone to recover MnO4−). The rate of the formation of Cl2 in the O3 + MnO4− + H+ + Cl− system was higher than the sum of the corresponding rates in the oxidation of Cl− by O3 and MnO4− separately. A scheme explaining the trends observed experimentally for the formation of Cl2 and changes in MnO4− concentration was suggested. The formation of MnO4− in the oxidation of Mn3+ with ozone in acid media was studied.