Ozone Flow Research Articles

Catalytic Decomposition of Airborne Ozone by MnCO3 and its Mechanism

ABSTRACTOzone is an ubiquitous air pollutant. To develop a new kind of catalyst besides the usually used MnO2 for ozone decomposition, the sub-micrometer spherical MnCO3 was prepared via a facile co-precipitation method without additive agents at room temperature and characterized by XRD, BET, SEM, TGA, XPS and H2-TPR. As-prepared MnCO3 showed better catalytic activity for ozone decomposition than that of α-MnO2, which is frequently studied in the literature. Amorphous MnOx was found on the MnCO3 surface, and it further formed when MnCO3 was exposed to the ozone flow. The MnOx layer is regarded as the active component in the catalytic ozone decomposition and crystalline MnCO3 serves as the support-stabilizing MnOx surface phase. Then MnCO3 powder was supported on non-woven fabrics through a simple and low-cost impregnation method. The MnCO3-based non-woven fabrics exhibited 100% ozone conversion over 8 days at 25 °C with inlet ozone concentration 14 ppm and space velocity 42,000 h−1. This provides an alternative material for ozone-induced air cleaning.

Degradation of mixture of three pharmaceuticals by photocatalytic ozonation in the presence of TiO2/montmorillonite nanocomposite: Simultaneous determination and intermediates identification

This study addressed the simultaneous degradation of mixture of three pharmaceuticals including metronidazole (MET), ciprofloxacin (CIP) and acetaminophen (APAP) through the photocatalytic ozonation system. TiO2 nanoparticles were immobilized onto montmorillonite (MMT) support irradiated by UVA light in the presence of ozone. The samples were characterized by XRF, SEM, TEM, PL and N2 adsorption–desorption analysis. A rapid and sensitive chemometrics technique was then developed for the simultaneous determination of the three pharmaceuticals in their mixtures during the photocatalytic ozonation process. A UV–vis spectrophotometer was used for recording the absorption of the pharmaceuticals. The concentration of these pharmaceuticals was successfully determined using a PLS method, despite the severe overlap of their spectra. A central composite design (CCD) was utilized to analyze, model and optimize the effect of each operational parameter on multiple responses including MET degradation (Y1), CIP degradation (Y2) and APAP degradation (Y3). A multi response optimization approach based on a global desirability function (DF) of the factors was employed to simultaneously maximize the response factors. 25mgL−1 MET, 5mgL−1 CIP, 5mgL−1 APAP, 10Lh−1 ozone flow rate and a 15min of reaction time were found to be the ideal conditions at which the degradation of these pharmaceuticals could be simultaneously maximized (Y1=64.60%, Y2=80.58% and Y3=50.12%). Finally, the intermediate by–products of the drugs formed in the degradation process were identified using the GC–MS technique.

Photocatalytic ozonation of metronidazole by synthesized zinc oxide nanoparticles immobilized on montmorillonite

Abstract Released antibiotics in the aquatic environment have undesirable biological and ecotoxicological effects. In this work, photocatalytic ozonation process was used for removal of metronidazole (MET) as commonly used antibiotic from aqueous media. ZnO nanoparticles as an effective photocatalyst were immobilized on the surface of montmorillonite (MMT). The ZnO/MMT catalyst was characterized by X-ray diffraction (XRD), N2 adsorption/desorption, Fourier transform infrared (FT-IR), scanning electron microscope (SEM), and high resolution transmission electron microscope (HR-TEM). The ZnO/MMT activity was examined in the degradation of metronidazole under ozone bubbling and UV-A irradiation through photocatalytic ozonation process. The main influence factors on the photocatalytic ozonation activity such as ZnO/MMT dosage, pH, metronidazole initial concentration and ozone flow rate were studied. The results indicated that the MET removal efficiency was increased with increasing all the investigated factors except initial MMT concentration. The effect of organic and inorganic radical scavengers on the photocatalytic ozonation of MET was studied. Finally, several by products were identified by GC–MS analysis, which allowed to depict a possible mechanism for the MET degradation.

Numerical simulation of ozone concentration profile and flow characteristics in paddy bulks

Ozone has shown the potential to control stored product insect pests. The high reactivity of ozone leads to special problems when it passes though an organic medium such as stored grains. Thus, there is a need for a simulation study to understand the concentration profile and flow characteristics of ozone in stored paddy bulks as a function of time. Simulation of ozone concentration through the paddy grain bulks was explained by applying the principle of the law of conservation along with a continuity equation. A higher ozone concentration value was observed at regions near the ozone diffuser whereas a lower concentration value was observed at regions away from the ozone diffuser. The relative error between the experimental and predicted ozone concentration values for the entire bin geometry was less than 42.8%. The simulation model described a non-linear change of ozone concentration in stored paddy bulks. Results of this study provide a valuable source for estimating the parameters needed for effectively designing a storage bin for fumigation of paddy grains in a commercial scale continuous-flow ozone fumigation system. © 2017 Society of Chemical Industry.

Mineralization and biodegradability enhancement of Methyl Orange dye by an effective advanced oxidation process

An effective process for the oxidation of Methyl Orange dye (MO) was determined by comparing the mineralization efficiency between two advanced oxidation processes (AOPs) viz., ozonolysis and gamma radiolysis in presence and absence of an added inorganic salt potassium persulfate (K2S2O8). The effects of various operating parameters such as ozone flow rate and reaction temperature were optimized to achieve the best possible mineralization extent of MO by ozonolysis. The mineralization efficiency of MO was significantly enhanced during gamma radiolysis in presence of K2S2O8 (γ+K2S2O8) compared to in absence of K2S2O8. The presence of methyl group at the amine of phenyl ring assisted the mineralization of dye during γ+K2S2O8. The oxygen-equivalent chemical-oxidation capacities (OCC) of ozonolysis and γ+K2S2O8 for 75% mineralization of the dye solution were calculated as 7.008 and 0.0336kg equiv. O2 m−3, respectively which signifies that γ+K2S2O8 can be explored as an effective AOP. The non-biodegradable MO dye solution became biodegradable even after the dose of 0.5 kGy during γ+K2S2O8 compared to 1 kGy in absence of K2S2O8. The study concludes that a lower dose γ+K2S2O8 could be one of the efficient pretreatment steps before undergoing biological degradation of dye solution.

A review and investigation of the effect of nanophotocatalytic ozonation process for phenolic compound removal from real effluent of pulp and paper industry.

Phenol and its derivatives are the major environmental pollutants discharged from paper and pulp industries into water bodies. All these compounds and chlorinated phenolic compounds in particular are very toxic to fauna and flora, even at relatively low concentration. This study aimed to investigate the removal rate of phenolic compounds from the effluent of pulp and paper industries using a combination of ozonation and photocatalytic processes. Firstly, a certain volume from the effluent of paper and pulp industries containing certain phenol concentrations was obtained and fed into a prefabricated reactor at laboratory scale. Then, the combined and separate effects of zinc oxide dosage (ZnO), ozone flow rate (O3), and pH under ultra violet radiation for 30min were evaluated. The concentration of phenolic compounds and the produced ozone gas flow rate were measured by a spectrophotometry and iodometric method, respectively. The results showed that the phenolic removal rate increased at acidic PHs compared with alkaline PHs; it was also decreased with the increase in ZnO dosages. Furthermore, the highest phenolic compound's removal rate was 99% at the optimal condition (pH5, ZnO dosage of 0.1gL-1 at the 30min with UV-C illumination of 125W). Finally, Daphnia toxicity test showed that treated effluent was safe and met the standards to the extent that it can be discharged into the receiving waters. Graphical abstract ᅟ.

A coupled ozonation–electrooxidation treatment for removal of bisphenol A, nonylphenol and triclosan from wastewater sludge

Organic emerging micropollutants are persistent during the biological process used in treatment plants and have the tendency to accumulate in the sludge. Since a common method of final sludge disposal is the land application, there are potential risks associated with the presence of contaminants within the sludge. In this work, the removal efficiency of endocrine-disrupting chemicals, namely bisphenol A, nonylphenol and triclosan from sludge was investigated using ozonation and electrooxidation using boron-doped diamond electrodes. Both procedures were studied to determine the optimal conditions (pH, current density and ozone flow) for removing these chemicals in an hour. With the obtained conditions, a coupled system ozonation–electrooxidation was used with the goal to have better pollutant elimination. Results indicate that these compounds could be effectively removed by the coupled system; the diminutions were Bisphenol A 86%, nonylphenol 68% and triclosan 67%. Also improvements in the quality of aqueous phase were obtained, and for instance, the chemical oxygen demand, color and turbidity, were abated in 62, 61 and 66%, respectively. Moreover, an additional advantage of the coupled system is the absence of any secondary pollution.

Copper recovery from reverberatory furnace flue dust

In this study, leaching of reverberatory furnace dust at Sarcheshmeh was investigated in H2SO4-O3 medium. Response surface methodology based on central composite face-centered design (RSM-CCF) was applied to optimize the operating parameters. The optimal conditions to achieve the principle objectives of maximizing copper dissolution and minimizing iron dissolution from dust were identified to be a temperature of 30°C, a leaching time of 3h, an initial pH of 0.5, a pulp density of 20%, and an ozone flow rate of 1g/h. Under the optimum conditions, the copper and iron concentrations in the leaching solution were found to be 27.11 and 0.90g/L, respectively. The results showed that selective copper extraction from the dust could be achieved using sulfuric acid and ozone.

Enhanced Removal of COD and Color in Paper-making Wastewater by Ozonation Catalyzed by Fe Supported on Activated Carbon

After biological treatment, pulp and paper mill effluent still may contain large amounts of recalcitrant organic pollutants that need to be further treated. In this study, Fe supported on activated carbon (Fe@AC) was prepared and used as a catalyst in the catalytic ozonation of pulp and paper mill effluent. The activity of this catalyst was studied in terms of color and chemical oxygen demand (COD) removal efficiencies. Results showed that the COD removal rate was increased by 21% in the presence of the Fe@AC catalyst. After 60 min of ozonation (3g/h ozone flow rate) of the pulp and paper mill effluent (initial COD 360 mg/L), COD removal rates reached 56% in the presence of Fe@AC, 43% using AC as catalyst, and only 35% with ozonation alone. Ozone alone can achieve satisfactory color removal results. Owing to the scavenging effect of carbonate and bicarbonate ions towards hydroxyl radicals, the COD removal rate in Fe/AC catalytic ozonation of the effluent was strongly inhibited in the presence of these two ions. The COD removal rate followed the pseudo-second-order kinetics model well. The COD removal rate constant in the Fe@AC/O3 process was about 1.6 times higher than that of the AC/O3 process, and approximately 2.1 times higher than that of ozone alone.

Degradation of 2,4-dichlorophenol using combined approach based on ultrasound, ozone and catalyst

The present work investigates the application of ultrasound and ozone operated individually and in combination with catalyst (ZnO and CuO) for establishing the possible synergistic effects for the degradation of 2,4-dichlorophenol. The dependency of extent of degradation on the operating parameters like temperature (over the range of 30–36°C), initial pH (3–9), catalyst as ZnO (loading of 0.025–0.15g/L) and CuO (loading of 0.02–0.1g/L) and initial concentration of 2,4-DCP (20–50ppm) has been established to maximize the efficacy of ultrasound (US) induced degradation. Using only US, the maximum degradation of 2,4-DCP obtained was 28.85% under optimized conditions of initial concentration as 20ppm, pH of 5 and temperature of 34°C. Study of effect of ozone flow rate for approach of only ozone revealed that maximum degradation was obtained at 400mg/h ozone flow rate. The combined approaches such as US+O3, US+ZnO, US+CuO, O3+ZnO, O3+CuO, US+O3+ZnO and US+O3+CuO have been subsequently investigated under optimized conditions and observed to be more efficient as compared to individual approaches. The maximum extent of degradation for the combined operation of US+O3 (400mg/h)+ZnO (0.1g/L) and US+O3 (400mg/h)+CuO (0.08g/L) has been obtained as 95.66% and 97.03% respectively. The degradation products of 2,4-DCP have been identified using GC–MS analysis and the toxicity analysis has also been performed based on the anti-microbial activity test (agar-well diffusion method) for the different treatment strategies. The present work has conclusively established that the combined approach of US+O3+CuO was the most efficient treatment scheme resulting in near complete degradation of 2,4-DCP with production of less toxic intermediates.

The application of activated carbon modified by ozone treatment for energy storage

Activated carbon modified by ozone treatment was examined. The process was carried out in a glass reactor under a continuous flow of ozone through a bed of activated carbon for 15, 30, 60, 120, and 240 min. The modified and unmodified carbon materials were characterized by Raman spectroscopy and observed by scanning electron microscopy (SEM). Thermogravimetric analysis was used to estimate the presence of oxygen groups in the carbon structure. The surface area and pore size distribution were examined by nitrogen adsorption method at 77 K. Moreover, Fourier transform infrared (FTIR) spectroscopy was used to estimate the functional groups of modified activated carbon. The carbon content was estimated using the elemental analysis. The process of ozonation increases oxygen functionalities, thus the activated carbon was tested as electrodes for an electrochemical capacitor. The performance of an electrochemical capacitor was estimated by selected alternating (AC) and direct current (DC) methods in 1 M H2SO4, 1 M Na2SO4, and 6 M KOH electrolytes.

Fe-Mn bi-metallic oxides loaded on granular activated carbon to enhance dye removal by catalytic ozonation.

A Fe-Mn bi-metallic oxide supported on granular activated carbon (Fe-Mn GAC) has been fabricated by an impregnation-desiccation method and tested in the catalytic ozonation of methyl orange (MO) degradation and mineralization. X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy characterizations revealed that Fe-Mn oxides were successfully loaded and uniformly distributed on the GAC, and nitrogen adsorption isotherms showed that the supported GAC retained a large surface area and a high pore volume compared with the pristine GAC. The catalytic activity was systematically assessed by monitoring the MO removal efficiencies at different operational parameters, such as catalyst dosage, initial solution pH, and ozone flow rate. The Fe-Mn GAC exhibited better catalytic activity relative to ozone alone and GAC alone, improving the TOC removal by 24.5 and 11.5% and COD removal by 13.6 and 7.3%, respectively. The reusability of the hybrid was examined over five consecutive cyclic treatments. The Fe-Mn GAC catalytic activity was only a slight loss in the cycles, showing good stability. The addition of Na2CO3 as hydroxyl radicals (•OH) scavengers proved that the catalytic ozonation mechanism was the enhanced generation of •OH by the Fe-Mn GAC. The above results render the Fe-Mn GAC an industrially promising candidate for catalytic ozonation of dye contaminant removal.

Degradation of p-nitrophenol (PNP) in aqueous solution by a micro-size Fe0/O3 process (mFe0/O3): Optimization, kinetic, performance and mechanism

A micro-size Fe0/O3 process (mFe0/O3) was setup to degrade p-nitrophenol (PNP) in aqueous solution, and its key operational parameters (i.e., initial pH, ozone flow rate, and Fe0 dosage) were optimized by the semibatch experiments, respectively. Under the optimal conditions, COD removal efficiency (89.5%) obtained by the mFe0/O3 process was about two times of the sum (44.8%) of COD removal obtained by Fe0 alone and O3 alone. The results suggest that the synergetic effect between O3 and Fe0 in the mFe0/O3 process played a vital role in the degradation of PNP. In addition, treatment efficiency of the mFe0/O3 process also was much higher than some of the present technologies (e.g., Fe0/air process, MnO2/O3 and Al2O3/O3), which confirm the superiority of the mFe0/O3 process. Furthermore, the degradation mechanism and pathway of PNP was proposed according to the analysis results of UV–vis, FTIR, IC and GC–MS. According to the present literature and analysis data of SEM, EDS and XRD analysis, it can be concluded that the high-efficient mFe0/O3 process was mainly resulted from the combination of homogeneous or heterogeneous catalytic ozonation, Fenton-like reaction, adsorption and precipitate. Therefore, the mFe0/O3 process was a promising technology for the refractory industrial wastewater.

COD and Color Removal from Real Dyeing Wastewater by Ozonation

ABSTRACT: Ozonation of real dye wastewater for removal of color and COD reduction covering a 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 92.5% has been achieved under optimum operating conditions (pH=11; ozone flow rate: 6×10−3 m3/minute). Further the biodegradability index of the dye 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.

Intensification of depolymerization of polyacrylic acid solution using different approaches based on ultrasound and solar irradiation with intensification studies

Depolymerization of polyacrylic acid (PAA) as sodium salt has been investigated using ultrasonic and solar irradiations with process intensification studies based on combination with hydrogen peroxide (H2O2) and ozone (O3). Effect of solar intensity, ozone flow and ultrasonic power dissipation on the extent of viscosity reduction has been investigated for individual treatment approaches. The combined approaches such as US+solar, solar+O3, solar+H2O2, US+H2O2 and US+O3 have been subsequently investigated under optimum conditions and established to be more efficient as compared to individual approaches. Approach based on US (60W)+solar+H2O2 (0.01%) resulted in the maximum extent of viscosity reduction as 98.97% in 35min whereas operation of solar+H2O2 (0.01%), US (60W), H2O2 (0.3%) and solar irradiation resulted in about 98.08%, 90.13%, 8.91% and 90.77% intrinsic viscosity reduction in 60min respectively. Approach of US (60W)+solar+ozone (400mg/h flow rate) resulted in extent of viscosity reduction as 99.47% in 35min whereas only ozone (400mg/h flow rate), ozone (400mg/h flow rate)+US (60W) and ozone (400mg/h flow rate)+solar resulted in 69.04%, 98.97% and 98.51% reduction in 60min, 55min and 55min respectively. The chemical identity of the treated polymer using combined approaches was also characterized using FTIR (Fourier transform infrared) spectra and it was established that no significant structural changes were obtained during the treatment. Overall, it can be said that the combination technique based on US and solar irradiations in the presence of hydrogen peroxide is the best approach for the depolymerization of PAA solution.

Ozonation of Reactive Orange 122 Using La3+-Doped WO3/TiO2/Sep Photocatalyst

ABSTRACTLa3+/WO3/TiO2/sep composites have been prepared by the sol–gel method. The degradation of dye was studied under the influence of various operational parameters such as initial pH, amounts of catalyst, concentrations of the dye, and ozone flow rate. The mineralization of Reactive Orange 122 has been confirmed by chemical oxygen demand measurements. The color removal of dye was found to follow a pseudo–first-order kinetics. Maximum color and chemical oxygen demand removal were 99.9% and 90% respectively, at a dye concentration of 200 mg/L, ozone flow rate of 2.0 L/min., 0.05 g/L weight of catalyst, and pH of 6.9 in 4 h. In addition, the catalyst was characterized by X-ray diffraction spectra, Fourier-Transform Infrared Spectroscopy, scanning electron microscopy, and a transmission electron microscope. This work could be a good candidate as a practical application for photocatalytic dye degradation.

Ozonation optimization and modeling for treating diesel-contaminated water

The effect of ozonation on treatment of diesel-contaminated water was investigated on a laboratory scale. Factorial design and response surface methodology (RSM) were used to evaluate and optimize the effects of pH, ozone flow rate, and contact time on the treatment process. A Box–Behnken design was successfully applied for modeling and optimizing the removal of total petroleum hydrocarbons (TPHs). The results showed that ozonation is an efficient technique for removing diesel from aqueous solution. The determination coefficient (R2) was found to be 0.9437, indicating that the proposed model was capable of predicting the removal of TPHs by ozonation. The optimum values of experimental initial pH, degree of O3, and reaction time were 7.0, 1.5, and 35min, respectively, which could contribute to approximately 60% of TPH removal. This result is in good agreement with the predicted value of 57.28%.

피루브산의 오존산화반응에 미치는 TiO2첨가 및 UV 조사의 영향

Ozonation was investigated for its ability to remove pyruvic acid in a laboratory-scale batch reactor under various experimental conditions, including UV irradiation, TiO₂ addition, and variations in temperature. An ozone flow rate of 1.0 L min^-1 and a concentration of 75±5 mg L^-1 were maintained throughout the experiment, and pH, COD, and TOC were measured at 10 min intervals during a 60 min reaction. Our results confirmed that the combination of UV irradiation and photocatalytic TiO₂ in the ozonation reaction improved the removal efficiency of both COD and TOC in aqueous solution at 20℃. Pseudo first-order rate constants and activation energies were quantified based on the COD and TOC measurements. We observed that the O₃/UV, O₃/UV/TiO₂ system increased mineralization and reduced the activation energy (E_a) necessary for pyruvic acid decomposition.

Mineralization of ammunition wastewater by a micron-size Fe0/O3 process (mFe0/O3)

A micron-size Fe0/O3 process (mFe0/O3) was set up to mineralize the pollutants in ammunition wastewater, and its key operational parameters (e.g., initial pH, ozone flow rate, and mFe0 dosage) were optimized by the batch experiments, respectively.

Combination of electrocoagulation with advanced oxidation processes for the treatment of distillery industrial effluent

The treatment of distillery industrial effluent by means various combinations of electrocoagulation with Advanced Oxidation Processes (AOPs) such as ozonation, electrocoagulation, peroxi–electrocoagulation, photo–electrocoagulation, ozone–electrocoagulation and peroxi–photo–electrocoagulation process on the removal of percentage color, COD and energy consumption. The effects of various operating parameters such as ozone flow rate (5 to 15 LPM), initial effluent pH (2 to 10), current density (0.10 to 0.50A/dm2) and H2O2 concentration (50 to 500mg/L) on the removal of pollutant were studied in this study. Moreover comparison of all the processes in terms of color removal, COD removal and energy consumption was also carried out. The experimental results showed that100% of color and COD removal could be achieved by ozone–electrocoagulation process with an energy consumption of 5.7kWh/m3 within four hours of reaction time. The extent of color and COD removal was analyzed using a UV/vis spectrophotometer and closed reflux method.