Effect of silver and copper ions on the decomposition of ozone in water

Features of the kinetics of ozone decomposition in water at pH 2 are studied depending on the concentration of silver and copper ions that are present. The existence of a critical concentration of metal ions (??3?6 × 10^?6 M) is established, below which ions slow the rate of ozone decomposition and above which the accelerate the process. It is concluded that the first region is due to the capture of hydroxyl and other radicals by metal ions, inhibiting the chain of ozone decomposition in water. A further increase in the concentration of ions leads to dominance of their direct interaction with molecules of ozone. A mechanism for the process is proposed and the rate constants of reaction of ozone with silver ions and copper are calculated (0.033 and 0.06 M^?1 s^?1, respectively).     

Numerical simulation of the kinetics of ozone decomposition in an aqueous solution

The kinetic scheme for ozone decomposition in an aqueous solution in a wide pH interval was proposed on the basis of the known literature data. The apparent first-order rate constant for ozone decomposition at pH 1–14 was calculated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1151–1156, June, 2008.     

The Role of Sulphate and Phosphate Ions in the Recovery of Benzoic Acid Self-Enhanced Ozonation in Water Containing Bromides

The ozonation of aromatic compounds in low-pH water is ineffective. In an acidic environment, the decomposition of ozone into hydroxyl radicals is limited and insufficient for the degradation of organic pollutants. Radical processes are also strongly inhibited by halogen ions present in the reaction medium, especially at low pH. It was shown that even under such unfavorable conditions, some compounds can initiate radical chain reactions leading to the formation of hydroxyl radicals, thus accelerating the ozonation process, which is referred to as so-called “self-enhanced ozonation”. This paper presents the effect of bromides on “self-enhanced ozonation” of benzoic acid (BA) at pH 2.5. It is the first report to fully and quantitatively describe this process. The presence of only 15 µM bromides in water inhibits ozone decomposition and completely blocks BA degradation. However, the effectiveness of this process can be regained by ozonation in the presence of phosphates or sulphate. The addition of these inorganic salts to the bromide-containing solution helps to recover ozone decomposition and BA degradation efficiency. As part of this research, the fractions of hydroxyl, sulphate and phosphate radicals reacting with benzoic acid and bromides were calculated.     

The solubility and kinetics of decomposition of ozone in aqueous solutions of nitrates

The influence of the concentration of NaNO₃ on the solubility of ozone in water was studied at 20, 30, and 40°C. The solubility coefficients of ozone were calculated, and the Henry constants and Sechenov coefficients determined. The Sechenov coefficients (K _c ) were found to decrease insignificantly as the temperature increased. The kinetics of dissolved O₃ transformations was analyzed. The decomposition of ozone was described by a pseudofirst-order equation with respect to salt concentration. The rate constant (k _c ) for the decomposition of ozone in the presence of NaNO₃ was found to be 3.5 × 10^?4 l mol^?1 s^?1.     

On the structure and bonding of first row transition metal ozone carbonyl hydrides

Model complexes of the general form M(CO)m(H)n(O3) (m = 1-5, n = 0 or 1) between ozone and the transition metals Ti to Cu were studied by density functional theory (DFT) calculations. The CDA charge decomposition method was used to analyze the interaction between the metal atom and the ozone ligand in terms of the traditional donation-back-donation mechanisms. Information about bond strengths was extracted from an analysis of the electron density in terms of the theory of atoms in molecules (AIM). The bonding in the ozone-metal complex was also studied within the NBO paradigm. Bond dissociation energies were calculated to be positive for all the complexes studied. Considering all the criteria employed in this study to analyze the interaction between the ozone and the transition metal, the Fe-complex is predicted to be the most stable, whereas the copper complex has the weakest metal-ozone interaction.     

Influence of the Outer Electrode Material on Ozone Generation in Corona Discharges

The effect of the outer electrode material on negative corona discharge current and the process of ozone formation have been studied in coaxial cylindrical system of electrodes fed by dry oxygen. Three materials (brass, duralumin, stainless steel) were tested in experiments. The probability coefficient of ozone decomposition was found be slightly higher compared with known data. The coefficient of probability of ozone decomposition is decreasing with the time of exposition of the metal surface to mixture of oxygen and ozone. The effect of the electrode material on the current voltage characteristic of the discharge was marginal. In contrast to this at average energy density η higher than 10 J/cm³ the ozone concentration is affected by material of the outer electrode. A strong influence of the temperature of metal electrode on the probability coefficient of ozone decomposition was illustrated from the decrease of the ozone production.     

The kinetics of ozone decomposition in water,the influence of pH and temperature

The influence of pH on the kinetics of ozone decomposition in water was studied. Over the pH range 1–8, the kinetics was well described by a second-order reaction equation. Starting with approximately pH 3, the pH dependence of the logarithm of the constant at 19°C corresponded to the equation logk= −2.66 + (0.49 ± 0.03)pH. The activation energy of ozone decomposition was found to be 76.0 ± 8.3 kJ/mol.     

Effect of composition and structure of cobalt(II) complexes with oxyaldiminopropylaerosils on their catalytic activity in the decomposition of ozone

The composition, structure, and catalytic activity in low-temperature ozone decomposition were described for cobalt(II) complexes with oxyaldiminopropyl ligands achored to aerosil A-300 differing in the nature and position of the benzene ring substituent. The effect of the geometry of the coordination unit and electronic effects of the benzene ring substituents on the catalytic activity of the cobalt(II) complexes in ozone decomposition were established.     

高湿度条件下分解高浓度O3催化剂的研究

Ｏ3 (臭氧 )具有极强的氧化能力 ,因此被广泛地用于水和空气的除臭、杀菌以及染料废水的脱色、ＣＯＤ的去除及芳香族有机物的降解[1,2 ] 。但Ｏ3 是一种毒性物质 ,处理过程中剩余的Ｏ3 排放到空气中会造成环境污染。目前 ,处理含Ｏ3 尾气的方法主要有活性炭吸附法、药液吸收法、高温热解法和催化分解法[1] ,其中催化分解法不仅有高的分解率 ,而且满足长期稳定、安全、经济等要求 ,是较为理想的Ｏ3 分解方法。催化分解法使用的催化剂主要有含Ｍｎ催化剂、含Ｔｉ催化剂和过渡金属催化剂等。各种催化剂在低湿度条件下的催化性能都比较好 ,但在…     

The influence of phosphates on the decomposition of ozone in water: Chain process inhibition

The addition of phosphates was found to decrease the rate of the decomposition of ozone in water; they accepted hydroxyl radicals and thereby inhibited chain ozone decomposition. The presence of phosphates decreased the order of the reaction from second for pure water to one-and-a-half. The rate constants for ozone decomposition in the presence of various phosphate concentrations increased as pH grew from 4 to 9.     

Treatment of Soot by Dielectric Barrier Discharges and Ozone

The results of the presented special treatment method indicate a soot decomposition mechanism due to long-living species like ozone and a multistage process between diesel soot and ozone. Measurements inside a dielectric barrier discharge (DBD) and measurements with ozone externally generated show a strong dependence of the decomposition rate on the temperature. In addition the temperature dependence of the lifetime of ozone up to 180°C and the oxidation of carbonmonoxide to carbondioxide were investigated.     

Kinetics and mechanism of the reactions of ozone with guaiacol,veratrol, and veratrol derivatives

The kinetics of the reactions of ozone with compounds modeling structural lignin fragments, viz., phenol, guaiacol, veratrol, veratric aldehyde, and veratric alcohol, was studied. The reaction rate constants were calculated using the mass transfer model for the chemical reaction based on the film theory. The rate constants of the reactions of ozone with compounds of the veratryl series were calculated by the Hammett equation. The major ozonation products of the studied compounds were determined by HPLC. The ozonation mechanism was proposed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 276–281, February, 2008.     

Decomposition of linear dodecylbenzenesulfonate by simultaneous treatment with ozone and ultraviolet irradiation: rapid disappearance of formed mutagens.

The decomposition products and mutagenic activity in Salmonella typhimurium strains TA98, TA100 and TA104 in the presence and absence of S9 mix of linear dodecylbenzenesulfonate (DBS) in aqueous solution after ozone treatment alone or simultaneous treatment with ozone and ultraviolet (UV) irradiation (ozone/UV treatment) were investigated. The decomposed DBS solutions after these treatments for 4 h were mutagenic for strains TA98, TA100 and TA104 both with and without S9 mix, but this mutagenicity disappeared rapidly during further ozone/UV treatment. Mutagenicity of the decomposed solution of DBS, however, was not substantially decreased by treatment with ozone alone. Formaldehyde and glyoxal were identified as the decomposition products of DBS in water by high-performance liquid chromatography after treatment with 2,4-dinitrophenylhydrazine. Although these two compounds were mutagenic for strain TA104 both with and without S9 mix, they disappeared after further ozone/UV treatment but not after ozone treatment alone. These results indicate that ozone/UV treatment is an effective procedure for purifying drinking water.     

The overall reaction process of ozone with methacrolein and isoprene in the condensed phase

The reaction of isoprene and methacrolein with ozone was investigated at different stages in the condensed phase at temperatures from 15 to 265 K by IR spectroscopy. The results revealed the following overall reaction process: the generation of primary ozonide (POZ), then its decomposition, and finally conversion into secondary ozonide (SOZ), which supported the Criegee mechanism. In the POZ and SOZ of isoprene, ozone cyclo-added preferentially to the double-bond that is not substituted by the methyl group. For methacrolein, the mainly detected SOZ is claimed to be MACSII formed by recombination of the intermediate CH(2)OO radical with aldehyde carbonyl of methylglyoxal in stead of the ketone carbonyl group. Theoretical calculations were performed at the B3LYP//MP2/6-311++G (2d, 2p) level to analyze the resulting spectrum. The good agreement between the calculated infrared spectra of POZ and SOZ and the experimental spectra supports the above-described findings.     

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 (τ_1/2 = 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.     

Interaction of silver nanoparticles with ozone in aqueous solution

The interaction between ozone and silver nanoparticles stabilized with sodium polyphosphate is studied in aqueous solutions. The process of ozone decomposition is established to have a chain character. The oxidation of one silver atom initiates the decomposition of about three ozone molecules. The stability of colloidal silver decreases upon the oxidation, which leads to its partial aggregation.     

The evaluation of time variation global warming effects, TWPA and CWP, for CFC alternatives

Evaluations methods of global warming are presented by considering the direct warming effect of chemical compounds and of decomposed compounds, warming effect due to the formation of troposphere ozone, and the cooling effect due to the decomposition of stratosphere ozone. It is easy to take account the stabilization of global warming gases concentration in the atmosphere, as those methods can conduct the time variations analysis. The methods are named Total Warming Prediction Analysis (TWPA) and Composite Warming Potential (CWP). The evaluation of Mobile Air Conditioning refrigerant is presented as an example of application of our method.     

Performance of an Ozone Decomposition Catalyst in Hybrid Plasma Reactors for Volatile Organic Compound Removal

In order to enhance the energy efficiency of nonthermal plasma methods for volatile organic compound decomposition in a catalyst-hybrid plasma reactor, we used a Cu–Cr catalyst to dissociate ozone into active atomic oxygen species at low temperatures. We investigated the conditions necessary to obtain the synergetic effect in single-stage and two-stage combinations. The ozone decomposition catalyst was not effective for the reaction under plasma discharge in the single-stage combination. In the two-stage combination, the efficiency increased by increasing the amount of catalyst. Although the propensity of catalysts for active oxygen species formation from ozone decomposition is important for optimizing the reaction efficiency, the surface area is even more important. We conclude that ozone decomposition catalysts are more effective in the two-stage combination compared to the single-stage.     

Ozone decomposition in concentrated aqueous solutions of salts

Effect of high concentrations of electrolytes (Na₂SO₄, NaCl, and NaNO₃) on the rate of ozone decomposition in water was studied. The conversion kinetics of O₃ dissolved in these solutions was analyzed. The rate constants of ozone decomposition were determined.     

臭氧层的化学破坏及其对策

臭氧层的化学破坏是人类的重大环境问题。本文对臭氧层的形成，作用，臭氧层破坏的后果，破坏臭氧层的物质及作用机制和保护臭氧层的对策作了探讨。