Ozone Flow Research Articles

Degradation and decolorization of reactive red X-3B aqueous solution by ozone integrated with internal micro-electrolysis

Ozone integrated with internal micro-electrolysis (O 3/IE) was applied to electrochemically oxidize reactive red X-3B owing to its well-established synergetic effect in the present study. The final removal rates of color, COD, TOC and AOX were found to be 99%, 85%, 59%, and 74%, respectively, when the following optimal conditions were used: dyestuff concentration of 1 g/L with a pH of 9.0, a reaction temperature of 60 °C, 400 g of iron scraps with the diameter in the range of 0.9–2.0 mm and 10 g/h ozone flow rate. The dominant degradation mechanism of reactive red X-3B was elucidated by the addition of radical scavenger/enhancer. The results indicated that the formation of hydroxyl radicals in the presence of ozone was the major contributing factor in O 3/IE system.

Degradation of p-Toluenesulfonic Acid by Ozonation: Performance Optimization and Mechanism

This paper explored ozonation for the treatment of pharmaceutical wastewater and p-toluenesulfonic acid (PTSA) was selected as the model pharmaceutical intermediate. The results showed that the ozonation process is efficient for the degradation of PTSA both in concentration and COD removal. The mono factor results showed that 60L/h was a suitable ozone flow rate. There were sharp difference between acid condition and alkaline condition, under acidic conditions, the direct oxidation with molecular ozone is of primary importance, and under alkaline conditions the hydroxyl oxidation starts to dominate, and pH=12 was a suitable value. Further, intermediates of PTSA degradation were analyzed and the reaction mechanism was discussed.

Kinetics of oxidation-precipitation of cobalt(II) from solution by ozone

In order to precipitate cobalt(II) in cobalt chloride solution, a novel method using ozone as the precipitant for its strong oxidability was proposed. The results show that the precipitation reaction is diffusion-controlled. The main factors affecting the oxidation rate such as the stirring speed, solution temperature, ozone partial pressure, initial concentration and flow rate were investigated. The kinetics equation of each condition was established. The results indicate that the oxidation rate is independent of the initial concentration or solution temperature. The oxidation rate increases obviously with increasing the stirring speed. The linear relationship between ozone partial pressure or flow rate and oxidation rate is found.

Assessment and optimisation of VOC mass transfer enhancement by advanced oxidation process in a compact wet scrubber

Dimethyl disulphide (DMDS) removal was investigated in a compact scrubber (hydraulic residence time ≈20 ms), composed of a wire mesh packing structure where liquid and gas flow at co-current and high gas superficial velocity (>12 m s −1). In order to regenerate the scrubbing liquid and to maintain a driving force in the scrubber, ozone and hydrogen peroxide were added to water since they allow the generation of nonselective and highly reactive species, hydroxyl radicals HO . Three ways of reagent distribution were tested. The influence of several parameters (liquid flow rate(s), ozone flow rate, pH and reagent concentrations) was investigated. The best configuration was obtained when ozone is transferred in the scrubbing liquid before introduction at the top of the scrubber simultaneously with the hydrogen peroxide solution, allowing to generate hydroxyl radical in the scrubber. With this configuration, DMDS removal could be increased from 16% with water to 34% at the same gas and liquid flow rates in the scrubber showing the potentiality of advanced oxidation process.

Catalytic ozonation of dimethyl phthalate over cerium supported on activated carbon

Cerium supported on activated carbon (Ce/AC), which was prepared by dipping method, was employed to degrade dimethyl phthalate (DMP) in water. The mineral matter present in the activated carbon positively contributes to its activity to enhance DMP ozonation process. A higher dipping Ce(NO 3) 3 concentration and calcination process increase its microporous volume and surface area, and decreases its exterior surface area. The catalytic activity reaches optimal when 0.2% (w/w) cerium is deposited on activated carbon. Ce/AC catalyst was characterized by XRD, SEM and BET. The presence of either activated carbon or Ce/AC catalyst considerably improves their degradation and mineralization in the ozonation of DMP. During the ozonation (50 mg/h ozone flow rate) of a 30 mg/L DMP (initial pH 5.0) with the presence of Ce/AC catalyst, TOC removal rate reaches 68% at 60 min oxidation time, 48% using activated carbon as catalyst, only 22% with ozonation alone. The presence of tert-butanol (a well known OH radical scavenger) strongly inhibits DMP degradation by activated carbon or Ce/AC catalytic ozonation. TOC removal rate follows the second-order kinetics model well. In the ozonation of DMP with 50 mg/h ozone flow rate, its mineralization rate constant with the presence of Ce/AC catalyst is 2.5 times higher than that of activated carbon, 7.5 times higher than that of O 3 alone. Ce/AC catalyst shows the better catalytic activity and stability based on 780 min sequential reaction in the ozonation of DMP. Ce/AC was a promising catalyst for ozonizing organic pollutants in the aqueous solution.

Decolorization of direct dye in textile wastewater by ozonization in a semi-batch bubble column reactor

Decolorization of wastewater containing direct dye (Sirius Blue SBRR) by ozonization was studied in an attempt to abate pollution caused by textile dyeing houses and dye-producing plants. The decolorization process of the direct dye was carried out by bubbling ozone at the bottom of a bubble column reactor containing the dye solution. The effect of dye concentration, ozone dose, ozone-air flow rate and solution pH on the rate of decolorization was studied. The reaction rate was followed by measuring the dye concentration at different times of the decolorization process. The rate of dye oxidation was found to increase with increasing ozone concentration in the air-ozone and to decrease with increasing the dye concentration. The rate of dye oxidation increases with increasing the air–ozone flow rate and solution pH, reaches a maximum and then decreases with a further increase in the air–ozone flow rate. The results with the direct dyestuff wastewater showed that decolorization was remarkable under the basic condition of pH 12. A large amount of bubbles was formed at a high ozone–air flow rate. After 26 min of ozone treatment, decolorization was completed. From these results, the ozone treatment of the dyestuff wastewater in decolorization was excellent.

Analysis of regional meteorology and surface ozone during the TexAQS II field program and an evaluation of the NMM‐CMAQ and WRF‐Chem air quality models

This study examines meteorological conditions associated with regional surface ozone using data collected during the summer Second Texas Air Quality Experiment, and the ability of the Nonhydrostatic Mesoscale Model–Community Multi‐scale Air Quality Model (NMM‐CMAQ) and the Weather Research and Forecast (WRF) model coupled with Chemistry (WRF‐Chem) models to simulate the observed meteorology and surface ozone. The surface ozone data consist of 118 sites that are part of the U.S. Environmental Protection Agency Aerometric Information Retrieval Now (AIRNow) network, while the meteorological data came from a network of eleven 915‐MHz wind profilers with RASS temperatures and supporting surface meteorological stations. High and low 8‐h maximum ozone occurrences most frequently develop as regional events, with similar ozone concentration patterns across all of east Texas, allowing for a separate analysis of high‐ and low‐ozone day conditions. The ability of the NMM‐CMAQ and WRF‐Chem models to simulate the meteorologically distinct high‐ and low‐ozone events is analyzed. Histograms of surface ozone show that both the NMM‐CMAQ and WRF‐Chem models underpredict the full range found in the observations. For low ozone values, the analysis indicates that the models have a positive bias because of too large of an ozone inflow boundary condition value over the Gulf of Mexico. In contrast, the models have a negative bias for very high ozone values that occur mostly in Houston and Dallas, which suggests that the urban emissions and/or chemistry is misrepresented in the models.

Coupling GEOS-CHEM with a regional air pollution model for Greece

The sensitivity of regional air quality modeling simulations to boundary conditions over Greece is investigated, for various synoptic conditions. For this purpose, a global to mesoscale model-chain is developed and applied, coupling the individual models' simulations. The global chemical transport model GEOS-CHEM, applied in a one-way nested procedure, is used to drive the regional UAM-V chemical dispersion model with time-varying lateral and top boundary conditions. The results of the coupling procedure are compared with the MINOS campaign measurements at Finokalia (Southern Greece) during the period from 1 to 16 August 2001 which is mainly characterized by an interchange of two synoptic types, High-Low and Long Wave trough. The comparison between the simulation results and the measurements reveals that the coupling procedure captures satisfactorily the range of observed CO concentrations at the southern part of Greece. The most severe deviations are observed under strongly variable atmospheric circulation, when no distinct synoptic circulation is allowed to be established in the area. Regarding O 3, the highest, though underestimated, surface concentrations are simulated under Long Wave trough conditions due to the influence of the ozone inflow predicted by GEOS-CHEM at the western boundary of the innermost domain and/or under enhanced NOy emissions arriving at Finokalia from urban and ships plumes.

Influence parameters in the ozonation of phenol wastewater treatment using bubble column reactor under continuous circulation

The ozonation of phenol wastewater treatment system has been investigated with effective mass transfer between gas and liquid phase in a bubble column reactor. The designed bubble column reactor was investigated for increasing the rate of mass transfer of ozone, the rate of oxidation of phenol in the solution, the solubility and decomposition rate of ozone in the distilled water were also studied at different flow rates. The decomposition rate constants were calculated based on pseudo first order kinetics. The oxidation of phenol was investigated in order to provide the overall reaction rate constant for the reaction between ozone and phenol at 25 °C. The influence of the operating parameters like initial phenol concentration, ozone flow rate and pH for the destruction of phenol by ozonation were studied. The pseudo first order rate constant was depending on the initial concentration of phenol solution. A comparison of TOC removal percentage between bubble column reactor and bubble diffuser using ozonation were reported.

Ozone-initiated disinfection kinetics of Escherichia coli in water

The effect of ozonation on the rate of disinfection of Escherichia coli was investigated as a function of ozone concentration, ozonation duration and flow rates. Ozone was generated in situ using Corona discharge method using compressed oxygen stream and depending on the oxygen flux the ozone concentrations ranged from 0.91–4.72 mg/L. The rate of disinfection of all the three microbes followed pseudo–first-order kinetics with respect to the microbe count and first order with respect to ozone concentration. The influence of pH and temperature the aqueous systems on the rate of ozone initiated disinfection of the microbe was investigated. The inactivation was faster at lower pH than at basic pH. Molecular ozone is found more effective in disinfection than hydroxyl radicals. Two reported mechanisms for antimicrobial activity of ozone in water systems from the literature are discussed. Based on the experimental findings a probable rate law and mechanism are proposed. Ozonation of natural waters significantly decreased the BOD levels of the control and microbe contaminated waters.

Ozone Killer by UV-Light Irradiation for Reduced Pressure and High Concentration Ozone Gas

We have developed a high efficiency ozone killer for reduced pressure and high concentration ozone using ultra-violet (UV) light irradiation to ozone gas. The highly concentrated ozone gas (∼100%) of 30-110 Pa with a flow rate of 50 sccm† can be decomposed to the concentration as low as 5% by UV light (200 nm-300 nm, 15 mW/cm2) irradiation. However, the residual ozone gas concentration increases the supplied ozone flow rate, since ozone molecule must stay in the ozone killer to absorb a UV photon. The photo-type ozone killer can be practically applied to actual processes by optimizing the dimension of the killer for a given pressure and gas flow rate.

Identification and Climatology of Cut‐off Lows near the Tropopause

Cut-off low pressure systems (COLs) are defined as closed lows in the upper troposphere that have become completely detached from the main westerly current. These slow-moving systems often affect the weather conditions at the earth's surface and also work as a mechanism of mass transfer between the stratosphere and the troposphere, playing a significant role in the net flow of tropospheric ozone. In the first part of this work we provide a comprehensive summary of results obtained in previous studies of COLs. Following this, we present three long-term climatologies of COLs. The first two climatologies are based on the conceptual model of a COL, using European Centre for Medium-range Weather Forecasts (ECMWF) analyses (1958-2002) and National Centers for Environmental Prediction-National Center for Atmospheric Research (1948-2006) reanalysis data sets. The third climatology uses a different method of detection, which is based on using potential vorticity as the physical parameter of diagnosis. This approach was applied only to the ECMWF reanalysis data. The final part of the paper is devoted to comparing results obtained by these different climatologies in terms of areas of preferential occurrence, life span, and seasonal cycle. Despite some key differences, the three climatologies agree in terms of the main areas of COL occurrence, namely (1) southwestern Europe, (2) the eastern north Pacific coast, and (3) the north China-Siberian region. However, it is also shown that the detection of these areas of main COL occurrence, as obtained using the potential vorticity approach, depends on the level of isentropic analysis used.

Abatement of 4-Chlorophenol in Aqueous Phase by Ozonation Coupled with a Sequencing Batch Biofilm Reactor (SBBR)

The aim of this work was to assess the mineralization of 100 and 200 mg L−1 4-chlorophenol (4-CP) solutions by ozonation-biological treatment. The results show that starting from a 4-CP initial concentration from 100 to 500 mg L−1 and using an ozone flow rate of 5.44 and 7.57 g h−1, 4-CP was completely removed. A kinetic constant around 9·10−2 min−1 was calculated for the ozone direct attack. The biodegradability (BOD5/COD) of the pre-ozonated solutions increased from 0 until a range between 0.2–0.37. The combination of the ozonation and aerobic biological treatment in an aerobic sequencing batch biofilm reactor (SBBR) gave an abatement of more than 90% of the initial TOC.

Ozonation of tannery effluent for removal of cod and color

Ozonation of leather dye effluent for removal of color and COD reduction covering wide range in operating parameters forms the scope of the present work. The influence of parameters such as influent pH, ozone flow rate and initial effluent concentration on ozonation efficiency has been critically examined. It has been observed from the present investigation that a maximum of COD removal efficiency of 92% has been achieved under optimum operating conditions. Further the biodegradability index of the tannery effluent has increased from an initial value of 0.18 to 0.49 during ozonation indicating favorable adaptation of ozonation as a primer to the biochemical technique to enhance the efficiency of biochemical treatment.

Removal of Congo red from textile wastewater by ozonation

Congo red, which has a complex molecular structure with various diazo aromatic groups, is widely used in textile industry as an anionic dye. The purpose of this study was to investigate the degradation of Congo red in laboratory solution which had the chemical properties of the rinse waters of textile manufacturing dye-houses and the samples with Congo red alone wastewater by ozonation and to optimize the reaction parameters such as pH and time which influence the efficiencies of total organic carbon, total kjeldahl nitrogen and chemical oxygen demand removal. Ozonation of Congo red dye were carried out in a semi-batch reactor with constant ozone flow rate and concentration of 23 mL/sec and 13.6 mg/L, respectively. Decolorization was complete within a few minutes of ozonation possibly due to the cleavage of chromophore groups. It was observed that its structural destruction occurs predominantly at higher pHs. The reduction of chemical oxygen demand and destruction of the dye was more than 60 % and 42 %, respectively. Total kjeldahl nitrogen removal was accompanied by slight changes in nitrogen oxides. It can be deduced from the experimental results that: (a) the mineralization is very weak; (b) the reaction follows the indirect mechanism; i.e., the interaction of hydroxyl radicals with the dye and (c) the nitrification is rather predominant. Biological oxygen demand is declined in simulated alkalic and neutral samples respectively. At 13.6 mg O 3 /L, the biological oxygen demand levels were significantly enhanced. This might be attributable to the enhancement of its biodegradation at alkaline pHs.

Catalytic ozonation of p-chlorobenzoic acid by activated carbon and nickel supported activated carbon prepared from petroleum coke

The aim of this research was to investigate catalytic activity of petroleum coke, activated carbon (AC) prepared from this material, Ni supported catalyst on activated carbon (Ni/AC) in the ozonation of aqueous phase p-chlorobenzoic acid ( p-CBA). Activated carbon and Ni/AC catalyst were characterized by XRD and SEM. The presence of petroleum coke did not improve the degradation of p-CBA compared to ozonation alone, but it was advantageous for p-CBA mineralization (total organic carbon, TOC, reduction), indicating the generation of highly oxidant species ( OH) in the medium. The presence of either activated carbon or Ni/AC considerably improves TOC removal during p-CBA ozonation. Ni/AC catalyst shows the better catalytic activity and stability based on five repeated tests during p-CBA ozonation. During the ozonation (50 mg/h ozone flow rate) of a 10 mg/L p-CBA (pH 4.31), it can be more mineralized in the presence of Ni/AC catalyst (5.0 g/L), TOC removal rate is over 60% in 60 min, 43% using activated carbon as catalyst, only 30% with ozonation alone.

Interannual variations in total ozone fields at high latitudes of the Northern Hemisphere, November to March 1998–2005

Synoptic analysis of monthly and daily mean total ozone fields is carried out using ground-based (Roshydromet) and TOMS measurements. Large interannual changes in the evolution of the stratospheric polar vortex and the North Pacific anticyclone influence the formation and dynamics of the winter-spring ozone fields in the stratosphere of high northern latitudes. The analysis shows considerable variations in the direction of zonal ozone transport from the sector of ozone inflow from low latitudes and accumulation in the Far East depending on the winter polar stratosphere temperature and the quasi-biennial oscillation (QBO) phase. In years with the easterly QBO phase and the warm polar stratosphere, ozone at the end of winter is transported to northeastern Canada and Atlantic. In years with the easterly phase and cold polar stratosphere, ozone transport is directed to northern Eurasia. These characteristics will be verified on extensive observational data.

Growth of lithium silicate crystals inside porous silicon film and their exploitation for ozone detection

Silicon dioxide was formed by oxidizing porous silicon film and annealed, in a next step, at 920 °C with lithium nitrate embedded in its structure. These operations have produced the two lithium silicates, Li 2Si 2O 5 and Li 2SiO 3, as it has been confirmed by the X-ray diffraction measurements. At relative high temperature (230 °C), the experimental ionic conductivity of this achieved sample has doubled in presence of ozone flow. A comparison with other samples, prepared with varieties of metallic nitrates and by following the same experimental procedures as for the former one, has proved that the sample prepared with zirconium was also good for ozone detection.

Development and evaluation of a particle-bound reactive oxygen species generator

Identifying the most important sources and variability of source impact for particulate matter is essential to assessing their health impacts. A central hypothetical mechanism of how particles affect human health involves the generation of reactive oxygen radicals at target sites in situ. These could be generated via activation of cells by cell–particle interactions and by oxidative species present in particulate matter. However, prior studies have shown that there are reactive oxygen species (ROS) associated with ambient respirable particles. In order to assess the health effects of particle-bound oxidative species, a generator was developed to produce ROS-bearing model particles and deliver known, reproducible, and stable exposures to these model particles that could be used in toxicological studies. The generator was found to be capable of providing a stable throughput of these particles with an average ROS generation capability of 6.5 nmol of equivalent H 2 O 2 / m 3 of ( aerosol + ozone ) flow sampled. The development, characterization, and evaluation of the ROS-bearing particle generator is described.

Decolorization of C.I. Reactive Yellow 84 in Aqueous Solution by Electrocoagulation Enhanced with Ozone: Influence of Operating Conditions

We studied the use of a combination of electrocoagulation (EC) and ozonation for the decolorization of the azo dye, C.I. Reactive Yellow 84 (RY84). The effects of initial dye concentration, initial pH, current density, salt concentration, ozone flow rate, temperature and interelectrode distance on the decolorization of RY84 were investigated. The results showed that a synergistic effect was achieved by combining EC with ozone for the decolorization of RY84. Under the experimental conditions, the decolorization rate increased with an increase in current density. However, the decolorization rate decreased with an increase in initial dye concentration and salt concentration. The interelectrode distance did not substantially affect the decolorization rate. Other operating parameters such as initial pH, ozone flow rate and temperature had both positive and negative effects. Over 97% of the color decay was achieved within 10 min reaction time under reasonable experimental conditions. When the decolorization of RY84 was complete, the efficiency of removal of total organic carbon (TOC) was more than 85%.