Ozone Partial Pressure Research Articles

OZONE TREATMENT OF METHYLENE BLUE IN AQUEOUS SOLUTIONS

The kinetics of ozonation of the sulfur dye Methylene Blue in aqueous solution is studied. The experiments have been carried out in a bubble column, using a single nozzle as gas sparger. The influence of the operating variables (initial concentration of Methylene Blue, ozone partial pressure, temperature and pH) on the oxidation process is established. A stoichiometric ratio of 3 moles of ozone consumed per mol of dye reacted is deduced. A reaction scheme based on the direct ozone attack to the dye is suggested, and it agrees with the found stoichiometry. The overall reaction orders and rate constants as a function of pH and temperature are determined following the film theory which is applied to the experimental data. The process develops in the fast pseudo mth order kinetic regime of absorption.

Evidence for vertical ozone redistribution since 1967

Long-term measurements of ozone concentration in the vicinity of the city of Berlin have been performed with ground-based Dobson spectrophotometers and balloon borne systems. The respective experiments cover the past 24 yr. All data have been re-evaluated and corrected towards uniform calibration standards, leading to the longest lasting European data set of total column density, altitude-dependent ozone partial pressures and the corresponding temperatures. Smoothing algorithms reveal significant longterm trends. The analysis shows an increase of ozone concentration within the middle stratosphere (below 31 km height) as well as in the troposphere over the past 24 yr. On the contrary, ongoing ozone depletion in the lower stratosphere became evident. The large scale vertical redistribution of atmospheric ozone in the troposphere and the lower stratosphere seems to be in agreement with model calculations and trend predictions that have their roots in changes of the chemical composition and the ozone photochemistry due to anthropogenically induced tracer gas concentrations.

The distribution and size of laminae of enhanced and depleted ozone in the lower stratosphere

A 25-year record of ozonesonde profiles from fourteen stations has been examined for the occurrence of thin layers of enhanced and depleted ozone. The layers, or laminae, occur primarily in spring in both hemispheres from polar to middle latitudes, with a maximum rate of occurrence at around 14km in altitude. Significant year to year variations are apparent at all latitudes. The average vertical extent of the laminae and the increase (or decrease) in ozone partial pressure inside them differ with latitude, altitude and season, appearing sharpest and deepest around 14km during spring.

Photosynthesis, Growth, and Yield Response of `Casselman' Plum to Various Ozone Partial Pressures during Orchard Establishment

Nursery stock of plum (Prunus salicina Lindel., `Casselman') was planted 1 Apr. 1988 in an experimental orchard at the Kearney Agricultural Center, Univ. of California, near Fresno. The trees were enclosed in open-top fumigation chambers on 1 May 1989 and exposed to three atmospheric ozone partial pressures (charcoal-filtered air, ambient air, and ambient air + ozone) from 8 May to 15 Nov. 1989 and from 9 Apr. to 9 Nov. 1990. Trees grown outside of chambers were used to assess chamber effects on tree performance. The mean 12-hour (0800-2000 hr Pacific Daylight Time) ozone partial pressures during the 2-year experimental period in the charcoal-filtered, ambient, ambient + ozone, and nonchamber treatments were 0.044, 0.059, 0.111, and 0.064 μPa·Pa-1 in 1989 and 0.038, 0.050, 0.090, and 0.050 pPa·Pa-1 in 1990, respectively. Leaf net CO2 assimilation rate of `Casselman' plum decreased with increasing atmospheric ozone partial pressure from the charcoal-filtered to ambient + ozone treatment. There was no difference in plum leaf net CO2 assimilation rate between the ambient chamber and nonchamber plots. Trees in the ambient + ozone treatment had greater leaf fall earlier in the growing season than those of the other treatments. Cross-sectional area growth of the trunk decreased with increasing atmospheric ozone partial pressures from the charcoal-filtered to ambient + ozone treatment. Yield of plum trees in 1990 was 8.8, 6.3, 5.5, and 5.5 kg/tree in the charcoal-filtered, ambient, ambient + ozone, and nonchamber treatments, respectively. Average fruit weight (grams/fruit) was not affected by atmospheric ozone partial pressure. Fruit count per tree decreased as atmospheric ozone partial pressure increased from the charcoal-filtered to ambient + ozone treatment. Decreases in leaf gas exchange and loss of leaf surface area were probable contributors to decreases in trunk cross-sectional area growth and yield of young `Casselman' plum trees during orchard establishment.

Separation of cobalt and nickel by ozone oxidation

The utilization of ozone for the separation of cobalt from nickel sulfate was investigated by determining the oxidation rate for Co(II) and Ni(II) ions under various ozonation conditions at 60°C. The oxidation reaction was observed to follow a first order rate with respect to the ozone partial pressure of the O3-O2 mixture gas and to be promoted considerably by vigorous agitation. The oxidation rates were virtually constant down to a fairly low concentration of the oxidizable ions. Nickel ion was found to be oxidized more easily at lower pH in the mixed sulfate solutions than in solutions of a single sulfate. At pH 2.5–5.0, ozone oxidation seems to be effective to separate cobalt ions selectively from nickel sulfate solutions, due to the extremely slow oxidation of the nickel ion in comparison with cobalt.

Growth of YBa2Cu3O7−δ in pure ozone irradiated with ultraviolet light

Pure ozone has been successfully used as the source of reactive oxygen for in situ molecular beam epitaxy (MBE) growth of cuprate superconductor thin films. The thermally driven ozone-oxidation process is relatively inefficient, however, requiring high ozone partial pressures and leading in some cases to film nonuniformities. We show that pure ozone-oxidation during film deposition can be significantly enhanced by the additional use of ultraviolet (UV) irradiation. The UV energy produces excited-state O and O2 species from ozone via a chain-type mechanism, thereby increasing the ozone activity at least tenfold. In comparison to the film growth process relying solely on thermal ozone decomposition, it is possible to lower the ozone pressure by an order of magnitude while improving the quality of the superconducting films.

Photosynthesis and Growth Response of Almond to Increased Atmospheric Ozone Partial Pressures

AbstractUniform nursery stock of five almond cultivars [Prunus dulcis (Mill) D.A. Webb syn. P. amygdalus Batsch, ev. Butte, Carmel, Mission, Nonpareil, and Sonora] propagated on peach (P. domestica L. Batsch.) rootstock were exposed to three different atmospheric ozone (O3) partial pressures. The trees were planted in open‐top fumigation chambers on 19 Apr. 1989 at the University of California Kearny Agricultural Center located in the San Joaquin Valley of California. Exposures of the trees to three atmospheric O3 partial pressures (charcoal filtered air, ambient air, or ambient air + O3) lasted from 1 June to 2 Nov. 1989. The mean 12‐h [0800–2000 h Pacific Daylight Time (PDT)] O3 partial pressures measured in the open‐top chambers during the experimental period were 0.038, 0.060, and 0.112 µPa Pa−1 O3 in the charcoal filtered, ambient, and ambient + O3 treatments, respectively. Leaf net CO2 assimilation, trunk cross‐sectional area growth, and root, trunk, foliage, and total dry weight of Nonpareil were reduced by increased atmospheric O3 partial pressures. Mission was unaffected by O3 and Butte, Carmel, and Sonora were intermediate in their responses. Foliage of Nonpareil also abscised prematurely in the ambient and ambient + O3 treatments. The results indicate that there are almond cultivars that are sensitive to O3 exposure.

Degradation kinetics of p-nitrophenol ozonation in water

The degradation of p-nitrophenol with ozone in water has been studied. The influence of pH and ozone partial pressure on p-nitrophenol conversion has been observed. The kinetic regime of ozone absorption has been shown to be highly dependent on both variables. Thus, at pH 2 the kinetic regime corresponds to a slow reaction regardless of the ozone partial pressure applied. At pH 6.5 the absorption of ozone develops in the fast kinetic regime the reaction being of pseudo first-order with respect to ozone at ozone partial pressures lower than 500 Pa. Finally, at higher pH (8.5 and 12.4) and ozone partial pressures higher than 2000 Pa, the reaction becomes instantaneous. Under conditions of slow and instantaneous kinetic regimes the liquid phase volumetric mass transfer coefficient, k L a, was calculated. The results are in agreement with those obtained from the absorption of ozone in organic-free water at similar pHs. On the other hand, under the situation of fast pseudo first-order reaction the rate constant for the p-nitrophenol-ozone direct reaction was determined to be 4.5 × 10 6 M −1 s −1. The ozone decomposition reaction develops to some extent only at pH 12.4.

オゾン酸化で生成した二酸化マンガンの生成条件とその特性 ＭｎＯ２含有量，水分含有量および比表面積

The contents of manganese, water and sulfate ion, O/Mn mole ratio and BET specific surface area have been determined for the manganese dioxide produced by ozone oxidation in acidified sulfate solutions. The manganese dioxide was formed under the following ozonation conditions: the sulfuric acid concentration of the solution, 0.25 to 5.0mol/l and the temperature, 25.0 to 80.0°C, and the ozone partial pressure, 2.8×10-2 atm.The water content of the manganese dioxide was considerably reduced with a rise in the ozonation temperature and increased with an increase in the acid concentration.The O/Mn mole ratio or x in MnOX was almost constant at a high value around 1.98 over an acid concentration range up to 5.0mol/l and increased very marginally with a rising ozonation temperature.Similar features were determined in the chemical analyses for the manganese dioxide formed in solutions of similar composition to the electrolyte solution for zinc electrowinning.

I n s i t u growth of YBa2Cu3Ox thin films by reactive cosputtering

We have synthesized superconducting YBa2Cu3Ox thin films in situ using magnetron cosputtering with three metallic targets (Y, Ba, Cu). We present details of the sputtering chamber, as well as the growth conditions necessary to obtain superconducting films. We discuss the effects of oxygen and ozone partial pressure, differential pumping, O2–Ar plasma deposition and Ba–Cu alloy targets. We elaborate on our ozone condensing and delivery system. Finally, we describe the difficulties encountered with the deposition system and provide details of possible improvements.

オゾン酸化によって酸性硫酸塩溶液から析出した二酸化マンガンのＸ線回折に基づく特性化

Manganese dioxide was precipitated by ozone oxidation from acidified sulfate solutions of sulfuric acid concentration ranging from 0.25 to 5.0mol/l at temperature varying from 25 up to 80°C at an ozone partial pressure of the ozone-oxygen mixture gas of 2.8×10-2 atm. The precipitates were analyzed by X-ray diffraction using Cu-Ka line. The X-ray diffraction patterns consisted of the peaks indicating γ-MnO2, α-MnO2 or a mixture of the two, depending on the ozonation conditions. Based on the X-ray diffraction data for 52 MnO2 -samples, a diagram was constructed to represent the ozonation conditions, the temperature and the acid concentration, for the formation of the individual types of manganese dioxide. At each acid concentration above 1.0mol/l, γ-MnO2 was found to be an ozonation product below a border-temperature, where a mixture of γ-andα-MnO2was produced. The border-temperature was gradually descending as the acid concentration was increased. Manganese dioxide of a-type in stead of 7-type was produced in high temperature-acid concentration region.In the X-ray diffraction diagrams for 7-Mn02 formed under varying conditions, a rise in ozonation temperature led to increased intensity and slight shift toward higher angles of the peaks. And an increase in acid concentration gave rise to broadening of the diffraction peakes.It was also demonstrated in the X-ray diffraction diagrams that the formation of MnO2 by ozonation was not significantly affected by the presence of zinc sulfate in acidified sulfate solutions having similar composition as the electrolyte solution for zinc electrowinning.

Ozonation of aqueous solutions of resorcinol and phloroglucinol. 3. Instantaneous kinetic regime

The ozonation of resorcinol and phloroglucinol in water is carried out at ozone partial pressures higher than 1700 Pa,1-20 °C, and pH 7 and 8.5. AT these conditions the kinetic regime of absorptionis found to be instantaneous. This fact allows the determination of the volumetric mass-transfert coefficient k L a of the system. Values of k L a obtained in this way are in good agreement with others deduced from other chemicals methods.

Kinetics of the reaction between ozone and MCPA

The kinetics of the reaction between ozone and aqueous solutions of 4-chloro-2-methylphenoxyacetic acid (MCPA) has been investigated from gas absorption experiments in a semi-continuous reactor. They were conducted modifying the gas flow rate, agitation speed, ozone partial pressure, initial pesticide concentration, temperature and pH. The liquid mass transfer coefficient, the interfacial area and the stoichiometric ratio between ozone and MCPA were evaluated. A model based on the film theory was used to analyse the experimental data and to determine the rate constant and the kinetic regime. The results obtained support a second order overall reaction, the rate constants being well correlated by the expression: k = 9377 exp (− 3276/RT) [ OH −] 0.008

The Use of Surface Renewal and Eddy Diffusivity Theories in the Ozonation of a THM Precursor: 1,3-Cyclohexanedione

Abstract Kinetic equations derived from surface renewal and eddy diffusivity theories for fast and instantaneous kinetic regimes of absorption have been applied to the results of the ozonation of 1,3-cyclohexanedione (CYC) in water. This has allowed the determination of the rate constant of the direct reaction of ozone with CYC and the liquid phase volumetric mass transfer coefficient of the system. The results obtained are close to those reported in the preceding paper (SOTELO et al., 1991) when using the film theory. However, the ozone partial pressure necessary to reach the instantaneous kinetic regime is higher for the case of the theories applied in this work.

Kinetic Regime Changes in the Ozonation of 1,3-Cyclohexanedione in Aqueous Solutions

Abstract The reaction between ozone and 1,3-cyclohexanedione in aqueous solutions at different pH was investigated from the point of view of the film theory. The rate of ozone absorption is accompanied by a second order irreversible reaction with 1,3-cyclohexanedione. The kinetic regime of absorption was found to change from fast (the reaction being of pseudo first order) to instantaneous, according to the ozone partial pressure applied. The former kinetic regime allows the determination of the reaction rate constant, while the latter leads to the volumetric mass transfer coefficient of the system.

Lamination in ozone profiles in the lower stratosphere

AbstractA survey of the distribution and scale of layers of enhanced and depleted ozone in the lower stratosphere was conducted over the altitude range 9.5–21.5 km using data recorded by balloon‐borne sondes released at various sites around the world.The results show clearly that lamination is primarily a winter‐spring phenomenon from subtropical to polar regions in both hemispheres, and seems to be linked to the presence of the polar vortex. A peak altitude of occurrence was found near 14 km. The interannual fluctuations in lamina abundance were found to be extremely large, varying at high latitudes by as much as a factor of three.Both the mean vertical thickness of the laminae and the associated rise or fall in ozone partial pressure within them vary progressively with latitude, season and altitude.

Liquid-phase ozonation of cyclohexanol catalyzed by cobalt(III) acetylacetonate

The results of the liquid-phase oxidation of cyclohexanol using ozone as main oxidant and cobalt(III) acetylacetonate as catalyst are presented with two major aims: to determine the effect of several parameters (ozone partial pressure, catalyst concentration, and temperature) on the reaction rate and product distribution, and to show a kinetic study together with a reaction mechanism that justifies the main products obtained

In situ growth of high temperature superconductor thin films with evaporation techniques using an ozone jet

High-quality YBa/sub 2/Cu/sub 3/O/sub 7/ thin films were grown in situ on various substrates (SrTiO/sub 3/, Al/sub 2/O/sub 3/, and Si) using MBE (molecular beam epitaxy) techniques and an ozone jet. The yttrium and copper are evaporated from electron-gun sources and the barium is evaporated from a Knudsen cell. All sources are controlled by a single mass spectrometer feedback system to obtain the correct fluxes at high partial ozone pressures. During deposition, the partial ozone pressure at the substrate position is estimated to be 10/sup -3/ -10/sup -2/ mbar. The substrate holder temperature is 700 degrees C. The real substrate temperature is estimated to be lower than 650 degrees C. The films are analyzed with R(T), X-ray diffraction, and RBS (Rutherford backscattering) measurements. Scanning electron microscope photographs are taken of the surface. The best film so far is grown on SrTiO/sub 3/ and has a T/sub c.onset/ of 88 K and a T/sub c0/ of 80 K. One 200-nm-thick film grown on bare silicon has a T/sub c.onset/ of 88 K and a T/sub c0/ of 60 K. This film shows negligible superconductor-substrate interactions according to the RBS measurements.

The effect of different atmospheric ozone partial pressures on photosynthesis and growth of nine fruit and nut tree species

Nursery stock of peach (Prunus persica L. Batsch, cv. O'Henry), nectarine (P. persica L. Batsch, cv. Fantasia), plum (P. salicina Lindel., cv. Casselman), apricot (P. armeniaca L., cv. Tilton), almond (P. dulcis Mill., cv. Nonpareil), prune (P. domestica L., cv. Improved French), cherry (P. avium L., cv. Bing), oriental pear (Pyrus pyrifolia Rehd., cv. 20th Century), and apple (Malus pumula Mill., cv. Granny Smith) were planted in open-top chambers on April 1, 1988 at the University of California's Kearney Agricultural Center located in the San Joaquin Valley (30 degrees 40' N 119 degrees 40' W). Trees were exposed to three atmospheric ozone partial pressures (charcoal-filtered air (C), ambient air (A), or ambient air + ozone (T)) from August 1 to November 17, 1988. The mean 12-h (0800 to 2000 h) ozone partial pressures measured in open-top chambers during the experimental period were 0.030, 0.051, and 0.117 microPa Pa(-1) in the C, A and T treatments, respectively. Leaf net CO(2) assimilation rate decreased linearly with increasing 12-h mean ozone partial pressure for the almond, plum, apricot, prune, pear, and apple cultivars. Stomatal conductances of apricot, apple, almond, and plum decreased linearly with increasing ozone partial pressure. Cross-sectional area relative growth rates of almond, plum, apricot, and pear decreased linearly with increasing ozone partial pressure. Net CO(2) assimilation rate, stomatal conductance, and trunk growth of cherry, peach and nectarine were unaffected by the ozone treatments. Reduced leaf gas exchange probably contributed to ozone-induced growth reduction of the susceptible species and cultivars. Several of the commercial fruit tree species and cultivars studied were relatively tolerant to the ozone treatments.

オゾンによるＭｎ｀２＋´の酸化

The oxidation of manganous ion by ozone has been investigated in sulfate solutions under the following conditions: the initial concentration of manganous ion. 0.4to2.0g/l; pH, 1.0 to 7.0; temperature, 25.0 to 80.0°C ozone partial pressure, 7.1×10-3 to 2.3×10-2 atm.1) The oxidation was found to be significantly promoted by an increase in an ozone partial pressure and a vigorous agitation.2) The oxidation reaction followed a zero order at pH below 4.5, the rates being virtually constant down to low concentration of Mn2+. The final product was determined to be MnO2 in this pH range.3) The reaction was found to proceed at pH lower than 4.5 according to the relationship.-d [Mn2+]/dt=κ[O3 (aq)][H+] -0.12 exp (-5000 (cal/mol)/RT)(mol/l/min)4) Mn2O3 as well as MnO2 was considered to take part in ozone oxidation at pH above 5.0, where the rates slightly decreased as the reaction proceeded.5) The oxidation was not remarkably promoted by a rise in temperature. A reduced reaction rate was observed at 80°C probably due to a reduced stability of ozone in the solution at elevated temperatures.