Ozone Partial Pressure Research Articles

Partial-pressure measurement of atmospheric-pressure binary gas using two pressure gauges

We investigated a new method to measure the partial pressure of a binary gas system at near-atmospheric pressure conditions. The method utilizes two types of vacuum gauges, a capacitance manometer and a quartz friction pressure gauge. The partial pressure of the binary gas can be estimated by measuring the impedance change with a quartz friction pressure gauge, which depends on both viscosity and total pressure of a binary gas, and considering the total pressure change as measured by a capacitance manometer. We applied this method to measure the partial pressure of ozone in an ozone–oxygen gas mixture. The results suggested that the new method allows a partial-pressure measurement of ozone with an accuracy of Δp =0.2 kPa , close to atmospheric pressure. The advantages of the new method include compact size, high safety standards when measuring highly reactive gases, and the allowance for in-line monitoring.

Vertical ozone and temperature distributions above Santa Maria, Brazil (1996–1998)

Atmospheric soundings (troposphere and lower stratosphere) to measure ozone and meteorological profiles have been made at the Southern Space Observatory in Santa Maria, Brazil (29° S, 53° W) since 1996. In this paper a first analysis of the ozone profiles is presented from 1996 to 1998. Average ozone and temperature profiles are presented, and a comparison of total ozone obtained by integration of ozonesonde profiles with TOMS total ozone observations is performed. It is observed that ozone partial pressure has an average peak of about 128 μhPa, around 25 km. The minimum average temperature is about −70 °C around 16–17 km (tropopause). Total ozone integrated by soundings differs by about −6.63 ± 6.32% and −6.44 ± 4.73% in comparison with the total ozone measured by TOMS, using constant mixing ratio and McPeters climatology integration methods, respectively. Integrated tropospheric ozone represents about 12% (31 DU) of the total ozone, with minimum of 9% in March and maximum of 15% on October, while stratospheric ozone has a minimum in May and maximum in September. Around 50% of the soundings show a secondary ozone peak in the troposphere, mainly in November and January.

04/00524 Integrated IAO model for prediction of VOC emissions from building material: Haghighat, F. and Huang, H. Building and Environment, 2003, 38, (8), 1007–1017.

The oxidation of the organic substrate present in wastewaters generated in wine distilleries (“wine vinasses”) is studied by both an ozonation process and by an aerobic activated sludge system. The ozonation process is conducted in a subsequent first discontinuous and a second continuous periods. Values are reported of the organic matter removal, measured as chemical oxygen demand (COD) (5–25.2%) and as total aromatic compounds content (16.8–51.4%). The influences of the inlet ozone partial pressure, the hydraulic retention time in the reactor and the presence of UV radiation and H2O2 in addition to ozone are established. Approximate kinetic studies are conducted for both periods which lead to the evaluation of the apparent rate constants for the substrate decomposition 216 l/(mol O3 h) and 232 l/(g COD h), respectively. In the aerobic degradation by the activated sludge system, the evolution of the organic substrate and biomass are followed during both the discontinuous and continuous stages of the whole process, and COD removals from 31 to 85% are obtained for a hydraulic retention time between 24 and 72 h. For the first stage, a kinetic study is performed by using the Contois model, which applied to the experimental data provides the specific kinetic parameters: qmax=0.190 g COD/(g volatile suspended solids (VSS) h) and K1=6.48 g COD/g VSS. For the continuous period, the kinetic study carried out provides the specific rate constant for the substrate decomposition, q=0.027 g COD/(g VSS h).

Purification of cork processing wastewaters by ozone, by activated sludge, and by their two sequential applications

Wastewaters generated in the cork processing industry were treated in continuous reactors by means of single treatments separately—a chemical ozonation and an activated sludge system—and then by both sequential processes—ozonation followed by aerobic degradation, and aerobic degradation followed by ozonation. The removals obtained in the ozonation alone were 12–54%, 65–81%, and 55–89% for the COD, total phenolics, and absorbance at 254 nm, respectively, while the consumed ozone yield ranged from 40% to 61%, and the biodegradability (BOD 5/COD) varied from an initial 0.60 to final values between 0.68 and 0.93. The optimum hydraulic retention time and ozone partial pressure were 3 h and 3 kPa, respectively. The stoichiometric ratio was 0.56 g of organic substrate degraded per g of ozone consumed, while the rate constants obtained for the ozone disappearance and for the organic matter degradation were 4490 L g COD −1 h −1 and 1970 L g O 3 −1 h −1 respectively. The presence of hydrogen peroxide or UV radiation in addition to ozone increased the values of organic matter removal as well as the stoichiometric ratio and the rate constants. The aerobic treatment by the activated sludge system yielded COD removals between 13% and 37% for hydraulic retention times between 24 and 96 h, and the Contois model gave values of q max=0.14 g COD g VSS −1 h −1 and K 1=22.6 g COD g VSS −1 for the main kinetic parameters. The sequential processes increased the substrate removal efficiencies in comparison with the individual processes. These enhancements were greater in the aerobic degradation–ozonation sequence than in the ozonation–aerobic degradation sequence.

Kinetics of the ozonation and aerobic biodegradation of wine vinasses in discontinuous and continuous processes

The oxidation of the organic substrate present in wastewaters generated in wine distilleries (“wine vinasses”) is studied by both an ozonation process and by an aerobic activated sludge system. The ozonation process is conducted in a subsequent first discontinuous and a second continuous periods. Values are reported of the organic matter removal, measured as chemical oxygen demand (COD) (5–25.2%) and as total aromatic compounds content (16.8–51.4%). The influences of the inlet ozone partial pressure, the hydraulic retention time in the reactor and the presence of UV radiation and H2O2 in addition to ozone are established. Approximate kinetic studies are conducted for both periods which lead to the evaluation of the apparent rate constants for the substrate decomposition 216l/(molO3h) and 232l/(gCODh), respectively. In the aerobic degradation by the activated sludge system, the evolution of the organic substrate and biomass are followed during both the discontinuous and continuous stages of the whole process, and COD removals from 31 to 85% are obtained for a hydraulic retention time between 24 and 72h. For the first stage, a kinetic study is performed by using the Contois model, which applied to the experimental data provides the specific kinetic parameters: qmax=0.190gCOD/(gvolatile suspended solids (VSS)h) and K1=6.48gCOD/gVSS. For the continuous period, the kinetic study carried out provides the specific rate constant for the substrate decomposition, q=0.027gCOD/(gVSSh).

A comparison between effects of solar proton events and of geomagnetic storms on the ozone profiles

Short-term variations along the ozone profiles (both in experimental and theoretical aspects) are discussed in the present work. Thus, a selected period of the major Solar Proton Event (SPE) of 14 July 2000, and the ensuing strong geomagnetic storm (K p=9o) with Sudden Storm Commencement (SSC) is investigated. This SPE is dubbed the “Bastille Event”, after the French national holiday. Ozone partial pressure measurements from the program Halogen Occultation Experiment (HALOE), realized by the Upper Atmosphere Research Satellite (LIARS) are used. The GOES-8 satellite obtains the data on high-energy protons. A statistical analysis of ozone and proton flux data is accomplished. The profiles of the stratospheric ozone in the above-mentioned selected period were constructed and the variations of the ozone density during the SPE with SSC were studied. A new model for the calculation of the ozone production rate (mol.cm −3.s −1) by relativistic and high-energy particles is applied. The method takes into account the law of particle energy transformation by penetration through the middle atmosphere. The ozone density increases in the height interval 15.5–18.5 km and decreases in the interval 24.5–35 km. Comparisons between experimental and theoretical ozone variations are made. On the basis of these comparisons and evaluations an interpretation of the possible mechanisms of stratospheric ozone response is given.

Electrochemical concentration cell (ECC) ozonesonde pump efficiency measurements and tests on the sensitivity to ozone of buffered and unbuffered ECC sensor cathode solutions

On the basis of extensive laboratory and field tests of electrochemical concentration cell (ECC) ozonesondes, a height‐dependent artifact in ozone profile measurements was found that is primarily due to side reactions of the phosphate buffers used in the “standard” 1% potassium iodide sensing solution. The influence of the buffers was revealed as a result of new, direct measurements of the ozonesonde pump flow rate efficiency made in an environmental chamber using an oil bubble flowmeter developed at National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL). The new flow rate measurements give pump efficiency correction factors that are 2 and 15% greater at 100 and 5 hPa, respectively, than those used in currently recommended procedures. Profile measurements using ozonesondes with differing ECC sensor solutions, on dual‐sonde balloons and experiments in a simulation chamber, show that the impact of the buffers is most pronounced above the ozone partial pressure maximum. The effect is about a 10–15% overmeasurement of ozone at an altitude of 30 km. Careful consideration must be given to the combination of the sensing solution composition and pump efficiency correction if representative ozone profiles are to be obtained from ozonesonde measurements.

Catalytic ozonation of oxalic acid in an aqueous TiO2 slurry reactor

The ozonation of oxalic acid has been carried out in an agitated slurry semibatch reactor where powdered TiO2 has been used as a catalyst. The presence of TiO2 catalyst significantly improved the ozonation rate of oxalic acid compared to the results from non-catalytic ozonation. For gas flow rates higher than 12lh−1 and agitation speed above 100rpm, the catalytic process rate was chemically controlled. The kinetic study led to a zero-order kinetics for both the non-catalytic and catalytic ozonations. These experimental findings were corroborated by a mechanism of reactions. This kinetics also supported experimental results at different temperatures, ozone partial pressure and mass of catalyst per slurry volume. At low gas flow rate, where both mass transfer and chemical reaction controlled the process rate, the external gas to liquid mass transfer coefficient was also determined.

Formation of oxygen structures by ozonation of carbonaceous materials prepared from cherry stones: II. Kinetic study

In this second part, the kinetics of the ozonation process of a char prepared from cherry stones (CS) is investigated. The char was obtained by heat treatment of CS at 600°C for 2 h in nitrogen. The effects of reaction time, partial pressure of ozone, and mass transport phenomena on the formation of oxygen complexes are studied. The surface chemistry of the samples was examined by FT-IR spectroscopy and the elemental chemical analysis was also determined for some samples. Results showed that the ozonation of the char led to oxygen chemisorption and to carbon gasification. The amount of oxygen complexes formed in the chemisorption stage (i.e., OH groups, CO structures, and ether structures) was found to be very sensitive to the increase in the ozonation time. The type of oxygen complexes was also time dependent. Ozonated products with relatively high concentrations of CO groups and ether structures were prepared by applying high ozone doses, whereas the formation of OH groups was favored at low ozone contents. The particle size did not influence the surface chemistry of the ozonated products. Only when the gas flow rate was lower than 40 l h −1, restrictions to ozone mass transport developed. For kinetics of the char ozonation process, a mechanism based on the Langmuir–Hinselwood adsorption–desorption model was proposed, and the intrinsic reaction rates were calculated as a function of ozonation temperature. The activation energy for the ozonation stage of the char was equal to 41.6 kJ mol −1.

Exploring polar stratospheric cloud and ozone minihole formation: The primary importance of synoptic‐scale flow perturbations

The formation of polar stratospheric clouds (PSCs) is sometimes attributed to cooling induced by mountain waves. Some examples of PSCs explained by this mechanism are found in the literature. Other studies show that the cooling producing PSCs is of synoptic scale. In this paper we use data from Polar Ozone Aerosol Measurement (POAM) II and from TIROS Operational Vertical Sounder (TOVS) showing coincident occurrences of PSCs and ozone miniholes over the sea and land. Using European Centre for Medium‐Range Weather Forecasts (ECMWF) analyses, we show that when both PSCs and localized ozone minima appear, they are associated primarily with anticyclonic potential vorticity anomalies near the tropopause. The flow anomaly penetrates upward and downward, inducing an upward displacement of isentropic surfaces above and a downward displacement below, the upward and downward penetration being consistent with the deformation scale. These flow anomalies result in synoptic‐scale quasi‐adiabatic uplift through the lower stratosphere. The adiabatic cooling of the air masses creates the conditions for PSC formation. Coincidentally, the ozone partial pressure decreases, and the localized ozone minimum appears. Our purpose in this paper is to show that the primary PSC formation mechanism in the Arctic is the same as for minihole formation: synoptic‐scale dynamics. We show three multiday sequences of PSCs and localized ozone minima. We reveal the robustness of the PSC/dynamics link by showing multiyear, monthly statistics of POAM II PSC sighting fraction compared with PSC formation temperature and isentropic geopotential.

Advanced oxidation processes for the degradation of p‐hydroxybenzoic acid 1: Photo‐assisted ozonation

AbstractThe oxidation of p‐hydroxybenzoic acid in aqueous solution by UV radiation and by photo‐assisted ozonation (UV+O3) has been studied. The effects of temperature (10, 20, 30 and 40 °C), pH (2, 5, 7 and 9) and ozone partial pressure (0.10–0.38 kPa) on the conversion of p‐hydroxybenzoic acid were established. Experimental results indicated that the kinetics for both oxidation processes fit pseudo‐first‐order kinetics well. In the combined process, the overall kinetic rate constant was split into two components: direct oxidation by UV radiation (photolysis) and oxidation by free radicals (mainly OH·) generated in the system. The importance of these two reaction paths for each specific value of ozone partial pressure, temperature and pH was quantified. Lastly, a general expression is proposed for the reaction rate which takes into account the two reaction pathways and is a function of known operating variables.© 2001 Society of Chemical Industry

Oxidative precipitation of arsenic(III) with manganese(II) and iron(II) in dilute acidic solution by ozone

Oxidative precipitation using ozone has been examined for removal of arsenic with manganese from dilute acidic sulfate solution under the following conditions: the initial concentrations of arsenic(III) and arsenic(V)=1–100 mg/L, the initial mole ratio of Mn/As=10–100, pH=0.4–5.0 and temperature=15–80 °C. The oxidation–reduction potential (ORP) of the system was continuously measured to monitor the process of oxidation reactions. The O 3–O 2 gas mixture (ozone partial pressure=0.010–0.031 atm, feed rate=500 mL/min) was found to produce an adequately high potential to oxidize arsenic(III) and then manganese(II). By formation of manganese(III) arsenate and uptake of arsenic by manganese dioxide formed by ozone oxidation, arsenic entities are removed to a sufficiently low concentration to meet the regulation against arsenic contaminant level for industrial waste water in Japan (0.1 mg/L) in the pH range 1.0–3.0 at 25 °C, where coprecipitation with ferric hydroxide is not very effective to remove arsenic. Furthermore, coexistence of an appropriate amount of iron(II) promotes significantly removal of arsenic with manganese at pH below 3 by ozonation.

Depuración de las aguas de lavado de aceitunas negras mediante procesos biológico aerobio y de ozonización

The purification of black olive washed waters has been studied by an aerobic biological treatment, an ozonation process and by the combination of both sequential processes: ozone-biological and biological-ozone. Biodegradation experiments have been carried out modifying the initial substrate and biomass concentration. In the ozonation experiments, temperature, pH and ozone partial pressure has been varied. A kinetic study applying the Contois’model to the biological experimental data was performed. In the ozonation process, supposing a firsts-order kinetic reaction with respect to COD and ozone, the kinetic constant was determined. In both combined treatments, the previous stage improved the reaction rate of the second stage. For the purification of these wastewaters, an aerobic biological treatment followed by an ozonation process was the most effective sequence.

Ozonation and Biodegradation Processes in Batch Reactors Treating Black Table Olives Washing Wastewaters

The decomposition of the organic substrate present in wastewaters from the washing stages in the black table olives industry is studied in batch reactors by means of several treatments: by ozonation processes, with ozone alone, and in combination with hydrogen peroxide and UV radiation; by aerobic biodegradation; and by the ozonation of the aerobically pretreated wastewaters. In the ozonation processes, the effect of the inlet ozone partial pressure on the substrate removal, biodegradability, and aromatic compounds content as well as the influence of the presence of H2O2 and UV radiation on the substrate removal is established. A kinetic study is conducted which leads to the evaluation of the kinetic constants for the substrate reduction and ozone disappearance. In the aerobic degradation treatment, the evolutions of the substrate and biomass are followed during the process, and a kinetic study is performed by using the Contois model, which applied to the experimental data provides the specific biokineti...

Electron Transfer Effects in Ozone Decomposition on Supported Manganese Oxide

Manganese oxide catalysts supported on Al2O3, ZrO2, TiO2, and SiO2 supports were used to study the effect of support on ozone decomposition kinetics. In-situ laser Raman spectroscopy, temperature-programmed oxygen desorption, surface area measurements, and extended and near-edge X-ray absorption fine structure (EXAFS and NEXAFS) showed that the manganese oxide was highly dispersed on the surface of the supports. The EXAFS spectra suggested that the manganese active centers on all of the surfaces were surrounded by five oxygen atoms. These metal centers were found to be of a monomeric type for the Al2O3-supported catalyst and multinuclear for the other supports. The NEXAFS spectra for the catalysts showed a chemical shift to lower energy, and an intensity change in the L-edge features which followed the trend Al2O3 > ZrO2 > TiO2 > SiO2. The trends provided insights into the positive role of available empty d-states required in the reduction step of a redox reaction. The catalysts were tested for their ozone decomposition reactivity and reaction rates were found to have a fractional order dependency (n < 1) with ozone partial pressure. The apparent activation energies for the reaction were found to be low (3−15 kJ/mol). The support was found to influence the desorption step (a reduction step) and this effect manifested itself in the preexponential factor of the rate constant for desorption. Trends for this preexponential factor correlated with the NEXAFS trends and reflected the ease of electron donation from the adsorbed species to the active center.

Ozone Decomposition over Manganese Oxide Supported on ZrO2 and TiO2: A Kinetic Study Using in Situ Laser Raman Spectroscopy

Ozone decomposition on ZrO2- and TiO2-supported manganese oxide was studied using in situ laser Raman spectroscopy along with simultaneous steady-state kinetic measurements. The Raman spectra showed the presence of an adsorbed peroxide species for both catalysts under reaction conditions. The experimental data were well represented by a nonuniform surface kinetic treatment that assumed that the activation energies of adsorption and desorption were linear functions of the surface coverage of the peroxide species. Steady-state reaction rates were monitored for varying ozone partial pressure (0.6–3 kPa) and temperature (293–343 K). The reaction order with respect to ozone partial pressure for the ZrO2-supported sample was 0.98 and that for the TiO2-supported sample was 0.85. At zero surface coverage of the peroxide species, the activation energy for adsorption was 6 and 7 kJ/mol for the ZrO2- and TiO2-supported catalysts, respectively. The activation energies for desorption at zero coverage were 62 and 44 kJ/mol, respectively, for the same catalysts. The difference in ozone decomposition activity for the catalysts was primarily due to the difference in desorption kinetic parameters.

Southern hemisphere winter ozone fluctuations

In this paper the relationship between ozone and atmospheric variability is explored over the southern hemisphere during the austral winter season, with special emphasis on synoptic transient fluctuations. The analysis of ozone tracks (or high-frequency ozone variability) shows that they have a significant correspondence with storm tracks at middle and high latitudes. Moreover, ozone tracks maximize over the Indian Ocean slightly downstream of the storm-track maximum, while over the Pacific region both ozone and storm tracks show decreased amplitudes. In particular, over southern South America (a region of climatological winter ozone minima and moderate to high ozone variability) the leading winter synoptic-scale variability mode was identified through a rotated extended empirical orthogonal function analysis applied to the meridional-wind perturbation at 300 hPa. The resulting mode is characterized by a baroclinic wave travelling eastward along subpolar latitudes, which maximizes near the tropopause level. Composite ozone fields based on this mode confirm, from a statistical point of view, the classical relationship between ridges (troughs) and minimum (maximum) ozone content. Furthermore, it is shown that dynamical processes in the upper troposphere and lower stratosphere associated with subpolar waves are responsible for the observed ozone distribution. This happens due to the barotropic equivalent vertical structure of the wave, together with the fact that ozone partial pressure maximizes near the level where the waves attain maximum amplitudes.

Southern hemisphere winter ozone fluctuations

AbstractIn this paper the relationship between ozone and atmospheric variability is explored over the southern hemisphere during the austral winter season, with special emphasis on synoptic transient fluctuations.The analysis of ozone tracks (or high‐frequency ozone variability) shows that they have a significant correspondence with storm tracks at middle and high latitudes. Moreover, ozone tracks maximize over the Indian Ocean slightly downstream of the storm‐track maximum, while over the Pacific region both ozone and storm tracks show decreased amplitudes.In particular, over southern South America (a region of climatological winter ozone minima and moderate to high ozone variability) the leading winter synoptic‐scale variability mode was identified through a rotated extended empirical orthogonal function analysis applied to the meridional‐wind perturbation at 300 hPa. The resulting mode is characterized by a baroclinic wave travelling eastward along subpolar latitudes, which maximizes near the tropopause level. Composite ozone fields based on this mode confirm, from a statistical point of view, the classical relationship between ridges (troughs) and minimum (maximum) ozone content. Furthermore, it is shown that dynamical processes in the upper troposphere and lower stratosphere associated with subpolar waves are responsible for the observed ozone distribution. This happens due to the barotropic equivalent vertical structure of the wave, together with the fact that ozone partial pressure maximizes near the level where the waves attain maximum amplitudes.

Wine vinasses treatments by ozone and an activated sludge system in continuous reactors

In this work wine vinasses have been treated separately by means of a chemical ozonation and a biological aerobic degradation in an activated sludge system, and later by means of a combined process which consisted of an aerobic pretreatment followed by an ozonation treatment, in continuous reactors in all cases. In the ozonation experiments, the hydraulic retention time and the ozone partial pressure were varied leading to substrate removals in the range 4.4–16%, with increases in this removal when both operating variables were increased. A kinetic study, which combines mixed flow reactor model for the liquid phase and plug flow reactor model for the gas phase, allows to determine the rate constant for the ozone reaction and the consumption ratio, which are kO3 = 3.6 l/(g COD · h) and b = 22.5 g COD degraded/mol O3 consumed. The aerobic degradation experiments were conducted in the activated sludge system with variations in the retention time and influent organic substrate concentration in the wastewater. A modified Contois model applied to the experimental results leads to the determination of the kinetic parameters of that model: K1 = 5.43 l/g VSS and qmax = 6.29 g COD/(g VSS · h). Finally, the combined process reveals an improvement in the efficiency of the ozonation stage due to the previous aerobic treatment with increases in the substrate removal reached and in the rate constant obtained, the last one being kO3 = 5.6 l/(g COD · h).

Ozone remediation of some phenol compounds present in food processing wastewater

Aqueous ozonation of four phenolic compounds (gallic acid, tyrosol, (+)‐catechin and p‐hydroxybenzoic acid) has been carried out in a semibatch reactor. The influence of the presence of free radical scavengers (t‐BuOH), inlet ozone partial pressure and pH has been investigated in aqueous solution using high concentrations of the phenolic substances (up to 3 g L‐1), typically found in wastewater from food related industries. In all cases, the ozone dose fed to the reactor exerted a positive influence on the ozonation rate. In addition, ozonation rates of p‐hydroxybenzoic acid and tyrosol increased when pH was also increased. In most cases, no significant effect was observed in the ozonation of gallic acid and (+)‐catechin when pH was increased from 2 to 7. The removal mechanism of studied phenols was exclusively due to their reaction with molecular ozone.