Inlet Ozone Research Articles

Physicochemical Investigations of Magnetite Persulfate Ozone Hybrid System for the Removal of Tartrazine Dye from Aqueous Solution

ABSTRACT This study involved the synthesis of magnetite nanoparticles by co-precipitation method. The synthesized nanoparticles were subsequently evaluated for their catalytic efficacy in the degradation and ozonation of tartrazine dye (TTD), employing sodium persulfate as a catalyst both in the presence and absence of ozone. The material characterization revealed that synthesized Fe3O4 nanoparticles were proven to have a crystalline structure by XRD. While spherical agglomerates with a flower-like morphology were revealed by the SEM, similarly FT-IR detected Fe – O – Fe and O – H bond vibrations, boosting surface area and catalytic activity. The degradation of the TTD was assessed in a laboratory-scale reactor, and its progress was monitored using UV-visible spectrophotometry. A comparative analysis of the two methods revealed that the catalytic ozonation demonstrated superior efficacy compared to the catalytic degradation, achieving a maximum degradation of 94.35% within 25 min of contact time. Optimal degradation parameters included a TTD concentration of 50 ppm, magnetite dosage of 0.75 g, persulfate concentration of 8 mm, and ozone inlet concentration of 5 g/L at pH 3. Evaluation of the degradation kinetics indicated the second-order kinetics model as the most appropriate, suggesting a physicochemical nature of the dye removal process. Furthermore, the study demonstrates enhanced efficiency in TTD decomposition compared to conventional methods.

Post-harvest quality of lettuce treated with ozonised water in a microbubble system

ABSTRACT This study aimed to determine the post-harvest quality of lettuce treated with ozonised water obtained in a microbubble system. The inlet ozone concentration was fixed at 3.5 mg L−1, which allowed obtaining 1.60 mg L−1 of ozone in the water. Six treatments were adopted: (i) control (untreated lettuce); (ii) ozonised water/5 min; (iii) ozonised water/10 min; (iv) oxygen/5 min; (v) oxygen/10 min; and (vi) chlorine/15 min. After the treatments, the samples were stored at 5°C and at a relative humidity of 80%. Microbiological and physicochemical analyses were performed immediately after ozonation (day 0) and after 3 and 6 days of storage. Reductions in the count of aerobic mesophiles and molds and yeasts were observed, immediately after the treatments with ozonised water. For the treatments ozonised water/5 min and ozonised water/10 min, the reductions of aerobic mesophiles were equal to 0.71 and 1.59 log reduction respectively, when compared to the control. Despite the significant increase in the leakage of electrolytes, especially when it was adopted exposure time to ozonated water of 10 min, it was considered that the conditions adopted favour the lettuce sanitation, without causing changes that make the product non-tradable.

Ozonation using a stainless-steel membrane contactor: Gas-liquid mass transfer and pharmaceuticals removal from secondary-treated municipal wastewater

A tubular porous stainless steel membrane contactor was characterized in terms of ozone-water mass transport, as well as its application in removing 23 pharmaceuticals (PhACs) detected in the secondary-treated municipal wastewater, under continuous mode operation. The volumetric mass transfer coefficient (KLa) was evaluated based on liquid flow rate, gas flow rate, and ozone gas concentration. The KLa values were substantially improved with an increment in liquid flow rate (1.6 times from 30 to 70 dm3 h−1) and gas flow rate (3.6 times from 0.30 to 0.85 Ndm3 min−1) due to the improved mixing in the gas-liquid interface. For the lowest liquid flow rate (30 dm3 h−1), the water phase boundary layer (82%) exhibited the major ozone transfer resistance, but it became almost comparable with membrane resistance for the highest liquid flow rate (70 dm3 h−1). Additionally, the influence of the specific ozone dose (0.39, 0.53, and 0.69 g O3 g DOC−1) and ozone inlet gas concentration (CO3,g,in = 27, 80, and 134 g Nm−3) were investigated in the elimination of 23 PhACs found in secondary-treated municipal wastewater. An ozone dose of 0.69 g O3 g DOC−1 and residence time of 60 s resulted in the removal of 12 out of the 23 compounds over 80%, while 17 compounds were abated above 60%. The elimination of PhACs was strongly correlated with kinetic reaction constants values with ozone and hydroxyl radicals (kO3 and kHO•), leading to a characteristic elimination pattern for each group of contaminants. This study demonstrates the high potential of membrane contactors as an appealing alternative for ozone-driven wastewater treatment.

Application of ozone at low-pressure: Control of egg and larval phases of Zabrotes subfasciatus, inactivation of Aspergillus flavus and qualitative changes in bean grains

Ozone applied in a low-pressure system has been studied in packed grains. In the present study, we evaluated the effect of ozone applied at low-pressures for the control of egg and larval phases of Zabrotes subfasciatus and inactivation of Aspergillus flavus in beans and possible changes in product quality. Samples of 5.0 kg of beans packed in woven polypropylene bags were exposed to ozone in the hypobaric chamber of internal volume equal to 70 L. The application of ozone was preceded by the reduction of internal chamber pressure to 50000 Pa. The ozone was then injected until the chamber's internal pressure reached 100000 Pa. An inlet ozone concentration of 61.37 mg L−1 was applied in 1, 4, 7, and 10 injections and a flow rate of 1.0 L min−1. In the control treatment, oxygen was used. The ozonation of beans with 10 injections was efficient in controlling the egg and larval phases of Z. subfasciatus, reducing mass loss and inactivation of A. flavus in the grains. The increase in the number of injections increased the electrical conductivity of the beans. However, ozone did not affect the thousand-grain mass, percentage of whole grains after cooking, total soluble solids in the cooking broth, dimensions of the orthogonal axes of the grains, volume and length-width ratio of the cooked beans. The results suggest that the number of injections in the system at low-pressure is a determining factor for the concentration of ozone inside grain packages. In this system, the application of ozone adopting 10 injections is efficient in the control of Z. subfasciatus and in the inactivation of A. flavus, without affecting the quality of the beans.

Regeneration of coked catalysts via ozonation: Experimental study of diffusion–reaction mechanisms at pellet and reactor scales

This work focuses on regeneration of coked catalysts using ozonation as an alternative process to typical coke combustion with oxygen. Different samples of coked ZSM-5 zeolites obtained during catalytic pyrolysis of polyethylene at 450 °C were exposed to an ozone enriched stream in a fixed-bed reactor. The influence of main operating parameters (time of exposure, temperature, O3 inlet concentration and gas volumetric flowrate) were studied by evaluating coke removal efficiency and by observing regeneration behavior both at pellet and reactor scales. These experimental results led to a better insight of the diffusion–reaction phenomena occurring during the process. Diffusion limitations were illustrated thanks to an innovative method, the analytical acquisition of carbon radial profiles on catalyst pellets, while the apprehension and quantification of competing reactivity (thermal, catalytic and oxidation) gave a better understanding of the ozonation process. Time of exposure and temperature were found to significantly affect carbon removal efficiency, while inlet ozone concentration and flowrate influence were respectively moderate and null in the investigated range. Similarly to combustion, coke ozonation is driven by a balance between diffusion and reactivity, leading to the appearance of a mix of known regeneration regimes depending on the operating conditions: homogeneous and shrinking-core.

Response surface methodology (RSM) for optimizing ozone-assisted process parameters for formaldehyde removal.

Formaldehyde, a volatile organic compound (VOC), is one of the main gaseous pollutants from commercial cooking. The present study evaluated the effectiveness of a laboratory-scale ozone-assisted indirect plasma method for formaldehyde removal using response surface methodology (RSM). A dielectric barrier discharge (DBD) reactor was used for ozone generation. Inlet HCHO concentration, ozone concentration, and residence time were considered the design parameters, and formaldehyde removal efficiency (response 1) and energy yield (response 2) were considered response parameters. The optimized models showed a positive correlation between the predicted and experimental outcomes. Inlet ozone concentration, the most significant parameter in the removal efficiency model, represented a positive correlation with this response in most parts of the operating region. The optimal point with the highest desirability (i.e., D1 point) was obtained at the inlet HCHO concentration of 120ppm, inlet ozone concentration of 40ppm, and reaction time of 11.35s within the parameter ranges studied, resulting in 64% removal efficiency and 2.64g/kWh energy yield. At the point with the second highest desirability (D2), 100% removal efficiency along with 0.7g/kWh energy yield was achieved indicating the very good performance of the process. The indirect plasma approach used in this study presented a successful performance in terms of removal efficiency along with acceptable energy yield compared to other plasma-assisted processes reported in the literature. The results suggested that ozone-assisted indirect plasma treatment can be utilized as an efficient alternative method for formaldehyde removal in commercial kitchens, while efficiency or energy yield should be prioritized for optimizing operating conditions.

Insights into gas flow behavior in venturi aerator by CFD-PBM model and verification of its efficiency in sludge reduction through O3 aeration

The use of ozone has become a new direction in residual sludge reduction. In order to improve the mass transfer efficiency and utilization efficiency of ozone, the structure of the venturi aerator was optimized by simulating the gas flow behavior with the CFD-PBM model. The gas volume fraction slowly decreased as the inlet angle increased. Besides, the ratio of throat diameter and throat length gradually increased, increasing bubble crushing rate and breakup probability. The turbulent eddy dissipation decreased with increasing outlet angle and moved from the central region to the sidewall, reaching a maximum at the throat. Thus, the optimal parameters for the venturi aerator were determined to be an inlet angle of 15°, a ratio of throat diameter to throat length of 1 and an outlet angle of 3°. Regarding the sludge reduction effect, the sludge dissolution efficiency after treatment with an optimized venturi aerator and traditional disc aerator was 35.3 % and 28.6 %, respectively. When the ozone dosage was 100 mg/g·MLSS, the venturi aerator had a better effect on ozone utilization than the disc aerator. At an ozone inlet flow rate of 2 L/min, the mass transfer coefficient of ozone in a venturi aerator was higher than that of the disc aerator. This study demonstrates the operational feasibility of ozone combined with a venturi aerator to reduce residual sludge production.

Ozonation with Hydrogen Peroxide for Treating Wastewater from Industrial Potato Processing - a Preliminary Investigation

ABSTRACT Wastewater generated from agricultural activities and food production is a source of environmental pollution, and its treatment is a challenging technological issue. Ozone gas (O3), and the possibility of associating it with hydrogen peroxide (H2O2), has the potential to remove persistent organic compounds in effluents. In the present work, wastewater from industrial potato processing was characterized, and its treatment with ozone combined with hydrogen peroxide was assessed. The inlet ozone concentration and the flow rate were 84.5 mg L−1 and 62.5 mL min−1, respectively. The promising conditions of temperature, pH, and H2O2/O3 proportion were determined to reduce the chemical oxygen demand, turbidity, and color, according to a central composite rotatable design. The H2O2/O3 proportions were 0.1, 0.3, 0.5, and 0.6. Additionally, the response variables were evaluated as a function of the ozone and hydrogen peroxide treatment time for up to 24 h. The conditions obtained for treating wastewater from industrial potato processing were the following: temperature = 25°C; pH = 3.0, and H2O2/O3 proportion = 0.1. For the water quality parameters adopted, the combination of ozone and hydrogen peroxide was effective at removing color and turbidity. The chemical oxygen demand, color, and turbidity reduction stabilized after 1.16 h, with cumulative applied dosages of ozone and hydrogen peroxide equal to 380 mg L−1 and 35 mg L−1, respectively.

Investigation of photocatalytic-proxone process performance in the degradation of toluene and ethyl benzene from polluted air

In this study, toluene and ethylbenzene were degraded in the photocatalytic-proxone process using BiOI@NH2-MIL125(Ti)/Zeolite nanocomposite. The simultaneous presence of ozone and hydrogen peroxide is known as the proxone process. Nanocomposite Synthesis was carried out using the solvothermal method. Inlet airflow, ozone concentrations, H2O2 concentrations, relative humidity, and initial pollutants concentrations were studied. The nanocomposite was successfully synthesized based on FT-IR, BET, XRD, FESEM, EDS element mapping, UV–Vis spectra and TEM analysis. A flow rate of 0.1 L min−1, 0.3 mg min−1 of ozone, 150 ppm of hydrogen peroxide, 45% relative humidity, and 50 ppmv of pollutants were found to be optimal operating conditions. Both pollutants were degraded in excess of 95% under these conditions. For toluene and ethylbenzene, the synergistic of mechanisms effect coefficients were 1.56 and 1.76, respectively. It remained above 95% efficiency 7 times in the hybrid process and had good stability. Photocatalytic-proxone processes were evaluated for stability over 180 min. The remaining ozone levels in the process was insignificant (0.01 mg min−1). The CO2 and CO production in the photocatalytic-proxone process were 58.4, 5.7 ppm for toluene and 53.7, and 5.5 ppm for ethylbenzene respectively. Oxygen gas promoted and nitrogen gas had an inhibitory effect on the effective removal of pollutants. During the pollutants oxidation, various organic intermediates were identified.

Ozone as an alternative fumigant for controlling Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) in cowpea beans

This study aimed to characterize the reaction kinetics of ozone gas in cowpea beans, to determine its insecticidal activity against Callosobruchus maculatus adult insects, and to assess grain quality after ozonation. Samples of 3.0 kg of cowpea beans were exposed to ozone gas at inlet concentrations of 500, 1,500, 2,500, and 3500 μg L−1, at a specific flow rate of 0.5 L min−1 kg−1 of grains. Moisture content, cooking time, germination percentage, and electric conductivity of the grains were analyzed. Grain quality was evaluated after exposure to the gas for periods corresponding to the lethal time to 95% of the insects (LT95), at each ozone concentration. The cowpea samples exposed to ozone at the inlet concentrations of 500, 1,500, 2,500, and 3500 μg L−1 got saturated with the gas after 45.18, 20.11, 16.86, and 14.70 min, respectively. The first-order kinetic model provided the best fit to the ozone decay data in cowpea beans. The average half-life of ozone in the grains was 6.88 ± 0.48 min. The estimated lethal times at the inlet ozone concentrations of 500, 1,500, 2,500, and 3500 μg L−1 were 777.27, 133.27, 84.29, and 52.33 min (LT50), and 1698.00, 331.20, 157.07, and 84.40 min (LT95), respectively. Callosobruchus maculatus adult progeny declined as the exposure time increased, at all inlet ozone concentrations. Cowpea bean quality did not change after ozone exposure, except for the electric conductivity, which differed between the grains exposed to ozone and those to atmospheric air. The results of this study indicate that ozone gas controls C. maculatus effectively and, in general, does not change the quality of cowpea beans at the inlet concentrations and exposure times appraised.

Bezafibrate removal by coupling ozonation and photocatalysis: Effect of experimental conditions

The pseudo-first order rate constants of bezafibrate (BZF) degradation by photocatalytic ozonation (PCO) in the presence of commercial TiO2, P25, were studied under different experimental conditions. Removal percentage of BZF was positively affected by the increase of ozone inlet concentration and catalyst amount, while initial pollutant concentration presented a negative influence. In addition to the importance of catalyst during BZF removal, its presence plays a crucial role in terms of mineralisation level, achieving a significant degradation of the intermediates in a short period of reaction. The BZF was mainly removed by direct reaction with molecular O3, regardless of the experimental conditions. In addition to the higher affinity of direct O3 reactions to remove BZF and the first by-products at pH 4.4, the adsorption capacity is enhanced due to BZF deprotonated form (pH > pKa) and the catalyst surface positively charged (pH < pHpzc).The estimated pseudo-first order rate constant revealed that BZF degradation is more inhibited by humic acid, especially at high concentrations, than tert-butanol, suggesting that HO radicals are not the main responsible for BZF decay.

Removal of Aqueous Para-Aminobenzoic Acid Using a Compartmental Electro-Peroxone Process

The presence of emerging contaminant para-aminobenzoic acid (PABA) in the aquatic environment or drinking water has the potential to harm the aquatic ecosystem and human health. In this work, the removal of aqueous PABA by a compartmental electro-peroxone (E-peroxone) process was systematically investigated from the kinetic and mechanism viewpoints. The results suggest that single electrolysis or ozonation was inefficient in PABA elimination, and the combined E-peroxone yielded synergistic target pollutant degradation. Compared to the conventional E-peroxone oxidation, the sequential cathodic reactions, followed by anodic oxidations, improved the PABA removal efficiency from ~63.6% to ~89.5% at a 10-min treatment, and the corresponding pseudo first-order kinetic reaction rate constant increased from ~1.6 × 10−3 to ~3.6 × 10−3 s−1. Moreover, the response surface methodology (RSM) analysis indicated that the appropriate increase of inlet ozone concentration, applied current density, initial solution pH value, and solution temperature could accelerate the PABA degradation, while the excess of these operational parameters would have a negative effect on the treatment efficiency. The comparation tests revealed that the coupling of electrolysis and ozonation could synergistically produce hydroxyl radicals (HO•) and the separation of cathodic reactions and anodic oxidations further promoted the HO• generation, which was responsible for the enhancement of PABA elimination in the compartmental E-peroxone process. These observations imply that the compartmental E-peroxone process has the potential for aqueous micropollutants elimination, and the reaction conditions that favor the reactive oxygen species generation are critical for the treatment efficiency.

Intensification of Ozone Mass Transfer and Generation of Hydroxyl Radicals by Ceramic Membrane

ABSTRACT The strengthening ability of ozone to treat the reverse osmosis concentrate (ROC) of landfill leachate is a crucial issue. From the standpoint of coupling intensification, a ceramic membrane/ozone (CM/O3) system was developed to improve the oxidation performance of ozone. The results showed that CM/O3 system could significantly improve the ozone concentration and the generation of hydroxyl radicals (·OH) when compared to the traditional O3 bubble system. The reaction condition, such as inlet ozone concentration and ozone flow, ceramic membrane pore size, transmembrane pressure, and temperature on the concentration of ozone in the liquid phase and the formation of ·OH, has been considered. Experimental results showed that the concentration of ozone and OH in the liquid increased with the increase in the inlet ozone concentration and ozone flow. Moreover, a certain degree of reduction in membrane pores was facilitated to intensify the mass transfer of ozone. The increase of pressure was able to raise the concentration of ozone. However, there was a slight effect on ·OH concentration. As for the temperature, a low-temperature situation was conducive to strengthen ozone dissolution. In terms of the generation of ·OH, a high-temperature situation was a better favorable environment. In order to evaluate the performance of the reactor system, three treatment processes (CM/O3, CM alone and O3 alone) were compared to treat ROC. In the CM/O3 system, the final removal efficiency of Chemical Oxygen Demand (COD) was 81.9%, and the final removal efficiency of Total Organic Carbon (TOC) was 62.6%.

Physiological Quality of Corn Seeds Treated with Gaseous Ozone

ABSTRACT The objective of this study was to evaluate the effect of gaseous ozone on the physiological quality of corn seeds with different initial germination percentages. Seeds with initial germination percentages of 54.0% (low physiological quality) and 86.0% (high physiological quality) were used. Samples of 0.12 kg of seeds were exposed to different combinations of inlet ozone concentrations (10 and 30 mg L−1) and exposure times (0, 30, 60, 90, and 120 min). A flow rate of 1.0 L min−1 was used at a temperature of 25 °C. The percentage of germination, shoot, root, and seedling lengths, germination velocity index, and electrical conductivity were analyzed. Univariate and multivariate analysis were used for data analysis. Seeds with low initial germination percentage showed increase of 1.6 to 1.8 times in germination percentage and approximately 1.2 times in length of the seedlings when the inlet ozone concentration was 10 mg L−1 and the exposure times were 30 and 120 min. Regarding seeds of high physiological quality, there was an increase in the germination velocity index of 1.1 to 1.2 times in ozonated seeds at 10 mg L−1, compared to the non-ozonated seeds. According to the multivariate analysis, the inlet ozone concentration of 10 mg L−1 associated with exposure times of 30 and 120 min showed similar results for seeds with low initial germination percentage. Based on the obtained results, we concluded that regardless the initial corn seeds quality, the recommended treatment is made by the combination of inlet ozone concentration of 10 mg L−1 and exposure time of 30 min. Also, greater benefits are obtained from the application of ozone gas in corn seeds of low initial physiological quality. The ozonation proved to be a promising technique for seed treatment since it increased germination percentage and shoot and seedling lengths.

Ozone as a Fungicidal and Detoxifying Agent to Maize Contaminated with Fumonisins

ABSTRACT The objective of this work was to evaluate the effectiveness of ozone in the control of fungi and the degradation of fumonisins in maize and possible effects on the chemical composition of the product. Two cultivars of hybrid maize (30F53H and AS1581 PRO) were used. Initially, the saturation process of the porous medium with ozone was studied. The incidence of Fusarium verticillioides, Penicillium spp. and Aspergillus flavus; the suitability of ozone to detoxify grains contaminated by fumonisins and possible qualitative changes in the product were evaluated. Ozone was applied at an inlet ozone concentration of 13.5 mg L−1 and flow rate of 1.0 L min−1, in five exposure periods (0, 12, 24, 36, 48 and 60 h). The estimated daily intake of FB by horses from grains subjected to ozonation was obtained. For the hybrid AS1581PRO, the estimated saturation time and concentration were equivalent to 67.34 min and 5.91 mg L−1, respectively. With regard to the hybrid 30F53H, the saturation time and concentration were 41.74 min and 8.72 mg L−1, respectively. Ozone was an effective fungicidal agent. The use of a concentration of 13.5 mg L−1 over a 24 h-treatment led to a reduction of 81.2 and 86.2% in the concentrations of fumonisin B1 and fumonisin B2, respectively. The estimated daily intake of fumonisins was reduced to 17.21 µg kg−1 BW per day, corresponding to half of the acceptable daily intake for equines. Ozone did not affect the chemical composition of the grain. Ozone is effective in controlling fungi and as a detoxifying agent in maize contaminated by fumonisins.

Control of Listeria monocytogenes in Refrigerated Ozonated Water

ABSTRACT The present work aimed at the effectiveness of ozonated water in the control of Listeria monocytogenes, adopting different combinations of pH, contact time, and storage time under refrigeration. To obtain ozonated water, the dose applied was 21 mg L−1 min−1, for 15 min. Samples of 1.0 L of water were ozonated at the inlet ozone concentration of 21 mg L−1 and a flow rate of 1.0 L min−1. The initial concentrations of ozone dissolved in water were equal to 5.81 mg L−1 at pH 4.0, 5.20 mg L−1, at pH 7.0, and 7.20 mg L−1 at pH 8.2. Samples of ozonated water with different initial pHs were used and stored at 7℃ for up to 24 h. The storage times of the ozonated water under refrigeration were 0, 6, 12, 18, and 24 h. The contact times of L. monocytogenes with ozonated water were 3.0 and 6.0 min. Ozone decomposition kinetics was evaluated. Ozonated water stored at 7℃ proved effective in controlling L. monocytogenes, especially in water pH values of 7.0 and 8.2. The initial pH of the water affects the effectiveness of ozonated water regarding the control of L. monocytogenes. The sharp reduction in ozone concentration was observed in water with pH 4.0, with a half-life of 13 min. For pHs of 7.0 and 8.2, the half-lives were 65 and 45 min, respectively. It is viable to use ozonated water stored at 7℃, for up to 24 h, to inactivate L. monocytogenes, when adopting initial pHs of 7.0 and 8.2, adjusted with sodium bicarbonate.

Impact of green and white roofs on air handler filters and indoor ventilation air

Rooftop surfaces near building outdoor air intakes may contribute to the mass loading on filters and compounds emitted to ventilation air downstream of the filter. In laboratory analyses, we characterized microbial composition, primary volatile organic compound (VOC) emissions, ozone removal rates, and VOC emissions in the presence of ozone on filters collected from air handlers located on the green and white roof sections of a big-box retail store. Total DNA masses per area of filter were 26.3 ± 11.9 ng cm−2 and 6.3 ± 6.5 ng cm−2 for green and white roof filters respectively, with higher mass observed in winter compared to the fall season. Of eight VOCs quantified at constant 23 °C and 50% RH across both seasons, fluxes of m/z 33.02 (putatively attributed to methanol) dominated VOC emissions for green, 10.96 ± 3.09 μmol m−2 hr−1, white, 12.02 ± 3.41 μmol m−2 hr−1, and unused filters, 5.64 ± 1.08 μmol m−2 hr−1. Ozone removal across all filters varied from 3.5% ± 2.8%–14% ± 2.8%, depending on temperature and RH condition. Fluxes of eight quantified VOCs were lower in the presence of ozone, apart from m/z 69.07 (putatively attributed to isoprene), where the presence of ~180 ppb inlet ozone resulted in increased fluxes by a factor of ~2.4. A steady-state mass balance predicted increases in ventilation air methanol levels by green roof filters ranging 0.10 μg m−3 to 19.44 μg m−3, depending on filter face velocity and filter geometry.

Removal of volatile organic compounds (VOCs) from waste air stream using ozone assisted zinc oxide (ZnO) nanoparticles coated on zeolite.

The release of volatile organic compounds (VOCs) from stationary and mobile sources increases the concentration of these pollutants in the environment. These compounds have the potential to cause adverse effects on human health and the environment. The adoption of management and engineering procedures to control the emission of these pollutants to the air has become essential. The aim of this study was to use an advanced oxidation process namely the catalytic ozonation to reduce the concentration of these pollutants in industrial output. In this experimental study, the catalytic ozonation process in the presence of ZnO nanoparticles coated on zeolite media was used in a laboratory scale to treat the air contaminated with BTEX compounds as indicators of VOCs. For this purpose, First the nanocomposites were synthesized based on chemical co-precipitation method. SEM, XRD, BET and FT-IR analyses were performed to investigate the characteristics of nanocomposites. The variables including initial concentrations of BTEX (50-200ppm), polluted air flow rate (5-20l/h), humidity (0-75%) and ozone dose (0.25-1g/h) were investigated. The concentration of BTEX compounds was measured by the Gas Chromatography (GC) technique according to the NIOSH 1501 manual. The results of SEM, XRD, BET and FT-IR analyses showed the proper synthesis of nanocomposites. According to the laboratory results, the optimal conditions of the process were found to be as follows: the initial concentration of pollutants equal to 50ppm, inlet air flow rate of 5l/h, relative air humidity of 25-35%, and inlet ozone concentration equal to 1g/h. Under these conditions, the removal efficiency of the compounds: benzene, toluene, ethylbenzene and xylene were obtained 98, 96, 92 and 91%, respectively. Simple ozonation and adsorption processes were less efficient than catalytic ozonation. This process had the ability to reduce the concentration of BTEX compounds to standard level.

Ozonation of quinoa seeds (Chenopodium quinoa Willd.): saturation and decomposition kinetics of ozone and physiological quality of seeds

Ozonation has been evaluated as an alternative method for seed treatment. In this context, the goal of this study was to evaluate the saturation process and kinetics of decomposition of ozone in a porous medium composed of quinoa BRS Syetetuba and possible changes in seed quality. Ozone concentration and saturation time in the porous medium and half-life were determined by adopting an inlet ozone concentration of 885 ppm and a flow rate of 5.0 L min-1 at 25 °C. The ozonation periods adopted were 0, 30, 60, 90, and 120 min. Regarding the physiological quality of the seeds, the germination percentage, germination speed index, electrical conductivity, and length of the shoot, root, and normal seedlings were analyzed. At the inlet ozone concentration of 885 ppm and a flow rate of 5.0 L min-1, the saturation concentration and saturation time in the porous medium composed of quinoa were 522.5 ppm and 12.0 min, respectively. The half-life of ozone in the porous medium was 6.08 min at 25 °C. Under these conditions, ozonation did not affect the physiological quality of quinoa BRS Syetetuba seeds for up to 120 min.

Simulation and optimization of the removal of toluene in air by ozonation with a catalytic open-cell foam

A heterogeneous catalyst, composed of an open-cell glass foam support impregnated with zerovalent ruthenium nanoparticles (loading around 0.1 wt.%), was used to remove toluene in air by catalytic ozonation. Experiments with lab-designed 2−6 cm length and 1.6 cm diameter catalysts were performed. A model based on the Langmuir–Hinshelwood mechanism, coupled with mass transfer limitations and including competitive effects between toluene and ozone, was designed. It accurately fits experimental data gathered at various temperatures (30−90 °C), gas velocities (0.0025−0.017 m s−1) and inlet ozone concentrations (6.4–11.2 g m−3). The removal of ozone and toluene was mainly ruled by the ozone concentration at low concentrations while the adsorption competition becomes significant at high ozone concentrations.Predictive simulations, at 1.0 g m−3 inlet toluene concentration, were compared in terms of investment cost, operating cost and process performances. The results highlighted the complexity of the process, which involves antagonist aims between toluene removal and the design of a compact and energy-efficient reactor. With the best operating conditions (90 °C and 46 g m−3 ozone inlet concentration), the removal of toluene reached 88% (removal rate of 0.25 g m−3 s−1) with a high ozone degradation (97%) in a moderate reactor length of 0.11 m. These good performances associated to the low cost of the catalyst’s synthesis make it an efficient alternative for the removal of pollutants from air.