Inlet Ozone Research Articles

Methane emission abatement by Pd-ion-exchanged zeolite 13X with ozone

The performance of 3 wt% Pd-ion-exchanged zeolite 13X for methane emission abatement under various parameters including reaction temperature (295–435 °C), inlet ozone concentration (0–4 vol%), space velocity (12 500–62 400 h−1) and inlet methane concentration (200 and 1400 ppm) were investigated. Without zeolite, gas phase reaction among methane, air and ozone gave 1–11% of methane conversion at 295–435 °C. The presence of inlet ozone (1.1–4 vol%) to the zeolite 13X system enhanced methane removal efficiency by 24–56%, giving an overall performance of 93% in this low temperature range. There existed a range of reaction temperatures where methane conversion was most enhanced by ozone in the zeolite system. Without ozone, methane oxidation showed an activation energy of 136 kJ mol−1. This was reduced to 116 kJ mol−1 by using 4 vol% of ozone. The enhanced methane removal efficiency was attributed to the decomposition of ozone to form atomic oxygen reacting with adsorbed methane. Higher percentage methane conversion was observed at lower space velocities under various inlet ozone concentrations. As the inlet ozone and methane concentration increased, the methane removal efficiency was limited by the number of available active sites in the zeolite, which governs the amount of adsorbed methane and atomic oxygen available for subsequent reactions. The system can be used for energy efficient green house gas and industrial effluent treatment.

Stimulative Effects of Ozone on a Biofilter Treating Gaseous Chlorobenzene

Recalcitrant volatile organic compounds with low biodegradabilities pose challenges for biofiltration technologies. In this study, the effects and mechanism of adding ozone on the performance of a biofilter were investigated. A biofilter treating chlorobenzene was set up and operated continuously for 265 days under different inlet ozone concentrations. Results showed that ozone below 120 mg m(-3) could notably enhance the biofilter performance. The average chlorobenzene removal efficiency increased from 40 to 70% and then to 90% while the inlet ozone concentration rose from 0 to 40 mg m(-3) and 120 mg m(-3). Reducing ozone concentration resulted in a decrease in removal efficiency from 90 to 40%. Further analysis indicated that the thickness and extra-cellular polymer substance content of the biofilm were remarkably reduced while inlet ozone concentration was gradually increased. Meanwhile, the specific surface areas of the filter bed were found to increase from 784 to 820 and 880 m(2) m(-3). A respiratory quinone profile showed that the dominant quinone shifted from ubiquinone-8 to menaquinone-9(H(2)) after ozone was added. This indicated that some Gram-positive bacteria with thick cell wall became the dominant species under ozone compression.

Catalytic decomposition of low level ozone with gold nanoparticles supported on activated carbon

Highly dispersed gold nanoparticles were supported on coal-based activated carbon (AC) by a sol immobilization method and were used to investigate their catalytic activity for low-level ozone decomposition at ambient temperature. Nitrogen adsorption-desorption, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts before and after ozone decomposition. The results showed that the supported gold nanoparticles prepared with microwave heating were much smaller and more uniformly dispersed on the activated carbon than those prepared with traditional conduction heating, exhibiting higher catalytic activity for ozone decomposition. The pH values of gold precursor solution significantly influenced the catalytic activity of supported gold for ozone decomposition, and the best pH value was 8. In the case of space velocity of 120000 h−1, inlet ozone concentration of 50 mg/m3, and relative humidity of 45%, the Au/AC catalyst maintained the ozone removal ratio at 90.7% after 2500 min. After being used for ozone decomposition, the surface carbon of the catalyst was partly oxidized and the oxygen content increased accordingly, while its specific surface area and pore volume only decreased a little. Ozone was mainly catalytically decomposed by the gold nanoparticles supported on the activated carbon.

Wastewater recycling: Application of ozone based treatments to secondary effluents

A secondary effluent from a municipal wastewater plant has been treated by means of several processes based on the use of ozone. Application of O 3 as the only oxidising reagent is capable of halving the initial COD (35 ppm at a flowrate of 40 L h −1) with a roughly 40% of mineralization degree. The system O 3/H 2O 2 slightly enhances COD removal albeit it is capable of significantly increasing the mineralization level up to 70% (35 ppm of O 3 at a flowrate of 40 L h −1 in the presence of 0.01 M of H 2O 2). The combination of two commercial activated carbons and ozone did not improve the results obtained in the single ozonation process. However, the simultaneous application of ozone and UV radiation showed beneficial effects both in the COD removal rate and TOC conversion if compared to ozonation alone. The systems applied in this work can be acceptably modelled by empirical mathematical expressions based on the inlet ozone concentration, hydrogen peroxide concentration, COD, etc.

Catalytic Ozonation of Toluene Using Zeolite and MCM-41 Materials

The effects of passing ozone over different zeolite and MCM-41 materials to remove toluene were investigated. Different ozone-to-toluene ratios were used to evaluate the catalytic performance during ozonation. The micro- and meso-porous materials removed about 50% of the toluene via adsorption and another 20-40% was decomposed by ozonation, which was catalytically enhanced by the zeolite and MCM-41 materials. The catalytic reaction portion increased by using a higher ozone inlet concentration and it was further enhanced to around 50% with the use of more adsorbents or with longer residence times. Inside the porous structure of the material, ozone was either decomposed into active atomic oxygen for reactions or converted into oxygen for active site regeneration. The number of Lewis acid sites in the adsorbents for ozone decomposition and byproduct generation during the reactions limit the catalytic activities. Trace amounts of intermediates including aldehydes and organic acids were quantified in the ozonation process. A higher ozone inlet concentration helped to reduce intermediate species formation but it led to more residual ozone in the exhaust. The high adsorption capability of the zeolite and MCM-41 adsorbents could serve as reservoirs for suppressing the release of intermediate species to the exhaust.

Application of physical vapor deposition process to modify activated carbon fibers for ozone reduction

This study utilized the activated carbon fiber (ACF) modified with metal catalyst via physical vapor deposition (PVD) process (ACF/PVD) to diminish ozone. Furthermore, the ozone removal efficiency of ACF/PVD was compared with that of original ACF and ACF modified with metal catalyst via impregnation process (ACF/impregnation). In addition to the kinds of coated metal and the inlet ozone concentrations, the effects of the coating thickness and the reaction temperature on ACF/PVD for ozone removal were also examined. The results indicate that the ozone removal efficiency of ACF/PVD is better than that of original ACF and ACF/impregnation. The ozone removal efficiency of different metal-coated ACF/PVD in the superior order is gold (Au), and manganese (Mn). The increase of Au-coated thickness (3 nm to 80 nm) on ACF/PVD will enhance the ozone removal. However, when the Mn-coated thickness on ACF/PVD is larger than 15 nm, the ozone removal efficiency displays a declining trend. Furthermore, a higher reaction temperature will result in a better ozone removal of ACF/PVD and the original ACF.

도시화에 의한 야간 대기 냉각율 변화에 관한 연구

This work investigated the methodology to simultaneously optimize the ozone and relative humidity composition for the NO x degradation using soil biofilter. Experiments were made as a function of inlet ozone concentration (0~1,770 ppb) and relative humidity (38~81%). Factorial design (2 2 +3) and response surface methodology by central composite designs were used to examine the role of two factors and optimal response condition on NO x degradation. It was found that a second-order response surface model can properly interpret the experimental data with an R 2 -value of 0.9730 and F-value of 71.83, based on which the maximum NO x degradation was predicted up to 92.8% within our experimental conditions.

Comparison of different advanced oxidation processes (AOPs) in the presence of perovskites

The efficacy of the oxidation systems: O 3, UV radiation, O 3/UV radiation, O 3/perovskite, UV radiation/perovskite, O 3/UV radiation/perovskite, H 2O 2/UV radiation, H 2O 2/UV radiation/perovskite, has been investigated by using pyruvic acid as probe compound. Under the operating conditions used, the combination of UV radiation and hydrogen peroxide (with or without perovskites) leads to the fastest pyruvic acid removal while the best results in terms of mineralization degree are obtained when combining O 3/UV radiation/perovskite. The effect of the variables: inlet ozone (15–75 mg L −1) and initial pyruvic acid (10 −3 to 10 −2 M) concentrations, catalyst load (0.01–1.5 g L −1) and pH (2–9) was investigated for the photocatalytic ozonation. The most influencing parameter was the ozone concentration fed to the photoreactor. A zero order was observed for pyruvic acid concentration and close to zero for catalyst load. Some deactivation is observed after reusing the catalyst, likely due to leaching of the active phase.

Ozonation of C.I. Reactive Black 5 and Indigo

The ozone transfer for the ozonation of the azo dye Reactive Black 5 (RB5) and indigo was investigated using a bubble column at semi-batch conditions. The results were analyzed by applying film theory and surface renewal theory. The ozonation of both dyes was so fast that an instantaneous reaction directly at the bubble surface can be assumed. The ozone balance in the gas phase was used to determine the volumetric mass transfer coefficient kLa and the enhancement factor E. Besides the measured concentrations, temperature and pressure only the Henry coefficient was required for the determination of kLa and E. By varying the ozone inlet and the dye concentration the reaction regime was identified. The Hatta number Ha which requires uncertain parameters did not have to be determined.

Advanced oxidation process–biological system for wastewater containing a recalcitrant pollutant

Two advanced oxidation processes (AOPs), ozonation and photo-Fenton, combined with a pilot aerobic biological reactor at field scale were employed for the treatment of industrial non-biodegradable saline wastewater (TOC around 200 mgL(-1)) containing a biorecalcitrant compound, alpha-methylphenylglycine (MPG), at a concentration of 500 mgL(-1). Ozonation experiments were performed in a 50-L reactor with constant inlet ozone of 21.9 g m(-3). Solar photo-Fenton tests were carried out in a 75-L pilot plant made up of four compound parabolic collector (CPC) units. The catalyst concentration employed in this system was 20 mgL(-1) of Fe2+ and the H2O2 concentration was kept in the range of 200-500mgL(-1). Complete degradation of MPG was attained after 1,020 min of ozone treatment, while only 195 min were required for photo-Fenton. Samples from different stages of both AOPs were taken for Zahn-Wellens biocompatibility tests. Biodegradability enhancement of the industrial saline wastewater was confirmed (>70% biodegradability). Biodegradable compounds generated during the preliminary oxidative processes were biologically mineralised in a 170-L aerobic immobilised biomass reactor (IBR). The global efficiency of both AOP/biological combined systems was 90% removal of an initial TOC of over 500 mgL(-1).

Water disinfection using the novel approach of ozone and a liquid whistle reactor

A novel approach of ozone treatment assisted by a liquid whistle reactor (LWR), which generates hydrodynamic cavitation, has been explored for water disinfection using a simulated effluent containing Escherichia coli ( E. coli), one of the dominant markers in faecal coliforms. A suspension having an E. coli concentration of approximately 10 8 to 10 9 CFU mL −1 was introduced into the LWR to examine the effect of hydrodynamic cavitation alone and in combination with ozone. Operating conditions of inlet pressure and ozone doses as well as time of ozonation for individual operation along with the combined operation have been varied with the aim of maximizing the extent of disinfection and arriving at an optimum strategy for treatment. It has been observed that nearly 75% disinfection can be achieved in about 3 h of treatment time using an optimized combination of hydrodynamic cavitation and ozonation. This combination has been found to be a cost-effective technique for achieving maximum disinfection compared to the individual operation of hydrodynamic cavitation (lower extent of disinfection) and ozonation (higher costs of treatment usually due to higher cost of ozone generation).

Dynamic Performance of Ozonation Treatment for Nonionic Surfactants (Polyoxyethylene Alkyl Ether) in a Bubble Column Reactor

The ozonation of a nonionic surfactant, Sannonic SS-90 (polyoxyethylene alkyl ether), which is one of polyoxyethylene nonionic surfactants, in water has been investigated using a bubble column. The effects of initial nonionic surfactant concentration, ozone gas flow rate, inlet ozone concentration in the gas-phase, liquid-phase temperature and hydrogen peroxide dose on decomposition of Sannonic SS-90 were systematically examined. The decomposition rate of Sannonic SS-90 decreased with the increase in the initial surfactant concentration and increased with increasing ozone flow rate and temperature. It was found that the rate of Sannonic SS-90 mineralization was weakly dependent on the gas-phase inlet ozone concentration in the range of the gas-phase inlet ozone concentration in this study. The oxidation rate increased with increasing concentration of H2O2, reached a maximum value and then decreased with further increasing of H2O2 concentration. The dynamic performance of the ozonation in a semi-batch bubble column was simulated using a mathematical model based on a tanks-in-series model. Reasonable agreement between the present experimental data and the simulated results was found.

Indoor secondary pollutants from cleaning product and air freshener use in the presence of ozone

This study investigated the formation of secondary pollutants resulting from household product use in the presence of ozone. Experiments were conducted in a 50-m 3 chamber simulating a residential room. The chamber was operated at conditions relevant to US residences in polluted areas during warm-weather seasons: an air exchange rate of 1.0 h −1 and an inlet ozone concentration of approximately 120 ppb, when included. Three products were used in separate experiments. An orange oil-based degreaser and a pine oil-based general-purpose cleaner were used for surface cleaning applications. A plug-in scented-oil air freshener (AFR) was operated for several days. Cleaning products were applied realistically with quantities scaled to simulate residential use rates. Concentrations of organic gases and secondary organic aerosol from the terpene-containing consumer products were measured with and without ozone introduction. In the absence of reactive chemicals, the chamber ozone level was approximately 60 ppb. Ozone was substantially consumed following cleaning product use, mainly by homogeneous reaction. For the AFR, ozone consumption was weaker and heterogeneous reaction with sorbed AFR-constituent VOCs was of similar magnitude to homogeneous reaction with continuously emitted constituents. Formaldehyde generation resulted from product use with ozone present, increasing indoor levels by the order of 10 ppb. Cleaning product use in the presence of ozone generated substantial fine particle concentrations (more than 100 μg m −3) in some experiments. Ozone consumption and elevated hydroxyl radical concentrations persisted for 10–12 h following brief cleaning events, indicating that secondary pollutant production can persist for extended periods.

Process Integration: Continuous Anaerobic Digestion−Ozonation Treatment of Olive Mill Wastewater

The purification of the olive mill wastewaters (OMW) is investigated by the combination of an anaerobic digestion, followed by an ozonation treatment. Continuous anaerobic digestion (CAD) was performed in a laboratory-scale bioreactor at constant hydraulic retention time and influent organic substrate concentration. Chemical oxygen demand (COD), total polyphenolic compounds (TP), methane production, pH, total volatile fatty acids (VFA), and alkalinity were analyzed daily. The COD removal and methane yield coefficient were 81% and 295 L CH4/kg COD, respectively. A kinetic study is performed using the Monod model, which, when applied to the experimental data, provides the specific kinetic constant of this model. Effluent from CAD was submitted in an ozonation stage, where the temperature and inlet ozone partial pressure were varied. COD, total aromatic compounds (A), and TP removals were established. An approximate kinetic study for design purpose was developed, which leads to evaluation of the apparent kin...

Perovskite catalytic ozonation of pyruvic acid in water: Operating conditions influence and kinetics

The catalytic ozonation of pyruvic acid in the presence of the perovskite LaTi0.15Cu0.85O3 has been carried out. Typical operating parameters like ozone inlet concentration, catalyst dosage, protons concentration (below 0.01M) and temperature (below 303K) exert a positive influence on the pyruvic acid depletion rate. Regarding the pyruvic acid concentration, a zero kinetic order holds for most of experiments. Under the conditions applied, the process is controlled by the chemical reaction. Acetic and oxalic acids are the only intermediates formed with a higher selectivity towards the former (above 90–95%). The similarities between experimental total organic carbon (TOC) and calculated from the contributions of remaining pyruvic acid and formed acetic and oxalic acids corroborate the previous statement. The activity of the catalyst is enhanced after the first usage. Thereafter, four consecutive reutilisations of the catalyst indicate the high stability of the solid. The process is acceptably simulated by a Langmuir–Hinshelwood kinetic expression derived from adsorption of ozone and pyruvic acid onto different active sites.

Earthworm toxicity during chemical oxidation of diesel‐contaminated sand

An ecotoxicity test with Eisenia fetida was performed to monitor the removal of diesel and toxicity variation during the ozonation process. The three-dimensional (3-D) cell test was introduced for the monitoring of the ozonation process, and the removal rate based on total petroleum hydrocarbons (TPHs) mass was about 95% near the ozone inlet ports. This high removal rate might be caused by the low soil organic matter (SOM) content and low water content of sand. The use of a fiber-optic transflection dip probe (FOTDP) demonstrated that more than half of the injected ozone was consumed by reactions with diesel or natural ozone-consuming materials. The earthworm toxicity test using Eisenia fetida demonstrated that diesel concentrations in soil exceeding 10,000 mg/kg caused a dose-dependent weight loss in earthworms and increased mortality. Toxic effects were reduced greatly or eliminated after ozonation, and the degradation products of the ozonation were not toxic to the earthworms at the concentrations tested. One specific result was that the sublethal test on the earthworm might be more sensitive for the evaluation of the quality of contaminated soil, for some samples, which did not result in mortality and produced an adverse effect on weight.

Photocatalytic degradation of toluene with ozone addition

The main goal of this study is to analyze the characteristics of photodegradation and photocatalytic activation experimentally with the major parameters such as air flow rate, inlet toluene concentration, ozone concentration, UV light and bead material, etc. In particular, the effects of transmissivity of UV radiation with TiO2 coated supporter (bead material) and void fraction (bead size) on the photocatalytic degradation are estimated for TiO2/UV and O3/TiO2/UV process. In results, the experiment shows that the UV light transmissivity of 5mm glass bead becomes much higher than that of 6.5 mm alumina bead in spite of lower void fraction inducing the higher photoactivation. The conversion of toluene represents about 96% during reaction time 420 min at the toluene concentration of 100 ppm and ozone concentration of 2.5 ppm, showing a conversion rate of ozone of 95% for O3/TiO2/UV process.

Application of an Experimental Design to Modeling of Ozone Bleaching Stage in TCF Processes

ABSTRACT An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequence using an ozone stage (Z) followed by a hydrogen peroxide stage (P). Ozone treatments were carried out at a laboratory scale with new automated equipment. The Z stage was modeled using a four-variable sequential statistical plan over the following ranges: 10–20 g o.d.p. mass pulp, 20–50 mg/L ozone inlet concentration, 80–220 LN h ozone flow, and 0.25–0.65% o.d.p. ozone dose. The influence of these variables on several pulp properties after the Z and P stages of the XZP sequence was examined. The models defined from the results obtained predicted, in the Z stage, variations in ISO brightness, viscosity, and kappa number of 74.6–85.6%, 496–876 mL/g, and 0.44–2.27, respectively. For the P stage, the models predicted variations in ISO brightness and viscosity of 84.2–92.7% and 568–857 mL/g respectively. It is possible to obtain bleached eucalyptus pulp of brightness over 89% ISO and viscosities over 800 mL/g. The variable most strongly influencing the pulp properties was found to be the ozone dose.

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).

Ozonation treatment of 2-nitrophenolic wastewater using a new gas-inducing reactor

Ozonation is a potential chemical process for the treatment of nitrophenolic wastewater. However, due to the low solubility and utilization rate of ozone, a conventional gas-inducing reactor for ozonation treatment has limited app-lication for treating phenolic wastewater. In this study, 2-nitrophenol wastewater ozonation was conducted in a new gas-inducing reactor that has been investigated in our laboratory over the past few years. The ozonation conducted in this reactor can be operated with a higher ozone utilization rate and lower power consumption than a conventional gas-liquid reactor. The ozone utilization rate increases with increasing pH value and can be maintained at over 95%. Kinetic studies show that a pseudo first-order reaction model derived from a two-film theory can describe the ozonation of 2-nitrophenol. Kinetic study of 2-nitrophenol ozonation shows that there are two stages in 2-nitrophenol ozonation. The observed rate constant in the second stage of 2-nitrophenol ozonation is higher than the first stage. A change in the 2-nitrophenol concentration is responsible for the change in the observed rate constant. Below pH 7, the oxidation rate of 2-nitrophenol increases with increasing pH and increasing ozone inlet concentration. This new gas-inducing reactor can improve the ozone utilization rate. The ozonation of 2-nitrophenol can be effectively conducted in this reactor.