Efficiency Of Catalytic Ozonation Research Articles

Optimization of Carbon-Defect Engineering to Boost Catalytic Ozonation Efficiency of Single Fe─N4 Coordination Motif.

Carbon-defect engineering in single-atom metal-nitrogen-carbon (M─N─C) catalysts by straightforward and robust strategy, enhancing their catalytic activity for volatile organic compounds, and uncovering the carbon vacancy-catalytic activity relationship are meaningful but challenging. In this study, an iron-nitrogen-carbon (Fe─N─C) catalyst is intentionally designed through a carbon-thermal-diffusion strategy, exposing extensively the carbon-defective Fe─N4 sites within a micro-mesoporous carbon matrix. The optimization of Fe─N4 sites results in exceptional catalytic ozonation efficiency, surpassing that of intact Fe─N4 sites and commercial MnO2 by 10 and 312 times, respectively. Theoretical calculations and experimental data demonstrated that carbon-defect engineering induces selective cleavage of C─N bond neighboring the Fe─N4 motif. This induces an increase in non-uniform charges and Fermi density, leading to elevated energy levels at the center of Fe d-band. Compared to the intact atomic configuration, carbon-defective Fe─N4 site is more activated to strengthen the interaction with O3 and weaken the O─O bond, thereby reducing the barriers for highly active surface atomic oxygen (*O/*OO), ultimately achieving efficient oxidation of CH3 SH and its intermediates. This research not only offers a viable approach to enhance the catalytic ozonation activity of M─N─C but also advances the fundamental comprehension of how periphery carbon environment influences the characteristics and efficacy of M─N4 sites.

Excess sludge-based biochar loaded with manganese enhances catalytic ozonation efficiency for landfill leachate treatment

This study developed an efficient and stable landfill leachate treatment process, which was based on the combination of biochar catalytic ozonation and activated sludge technology for intensive treatment of landfill leachate, aiming to achieve the standard discharge of leachate. The focus is to investigate the effect of manganese loading on the physicochemical properties of biochar and the mechanism of its catalytic ozonation. It was found that more surface functional groups (CO, Mn–O, etc.) and defects (ID/IG = 1.27) were exposed via the change of original carbon structure by loading Mn, which is conducive to the generation of lattice oxygen. Meanwhile, generating different valence states of Mn metal can improve the redox properties and electron migration rate, and encourage the production of reactive oxygen species (ROS) during the reaction process and enhance the catalytic efficiency. The synergistic action of microorganisms, especially denitrifying bacteria, was found to play a key role in the degradation of nitrogenous pollutants during the activated sludge process. The concentration of NH+4-N was reduced from the initial 1087.03 ± 9.56 mg/L to 9.05 ± 1.91 mg/L, while COD was reduced from 2290 ± 14.14 mg/L to 86.5 ± 2.12 mg/L, with corresponding removal rates of 99.17% and 99.20%, respectively. This method offers high efficiency and stability, achieving discharge standards for leachate (GB16889-2008). The synergy between Mn-loaded biochar and microorganisms in the activated sludge is key to effective treatment. This study offers a new approach to solving the challenge of waste leachate treatment.

Upgrade of the biggest catalytic ozonation wastewater treatment plant in China: From pollution control to carbon reduction

Catalytic ozonation is a widely used effective technology in advanced treatment for the removal of refractory organics from wastewater. However, it is also a highly energy-consuming technology, usually accounting for 30%∼40% of the total electricity consumption of a wastewater treatment plant (WWTP). The O3 consumption per unit of COD removed (g-O3/g-COD) is usually higher than 1.5 g-O3/g-COD, and the total carbon emission from catalytic ozonation is usually higher than 393.12 kgCO2 e/m3 of wastewater. In this study, we investigated an energy reduction strategy for the biggest catalytic ozonation WWTP, from laboratory-scale experimentation to corresponding engineering application. Laboratory-scale experiments showed that the mass transfer rate of dissolved O3 to the catalyst surface is crucial for COD removal efficiency. To improve the efficiency of catalytic ozonation, adding effluent backflow is a simple method that can enhance the removal of extracellular polymeric substances (EPS) from the catalyst surface and promote surface exposure. In the pilot-scale experiment (48 m3/d), when the backflow ratio increased from 0% to 100% (the optimal value), the proteins in EPS on the catalyst surface decreased significantly by 66.7%. The corresponding O3 consumption per unit of COD removed was reduced from 2.0 to 1.0 g-O3/g-COD. Furthermore, in the engineering application (52,000 m3/d) with a backflow ratio of 100%, the average effluent COD reduced from 52.0 to 43.3 mg/L, and the O3 consumption per unit of COD removed decreased from 0.98 to 0.69 g-O3/g-COD. In terms of carbon reduction, the indirect carbon emission reduction was approximately 3.0 × 103 t CO2 e/a. This study demonstrates the advantages of catalytic ozonation improvement and provides an engineering model of energy conversation and carbon emission reduction for over 35 similar WWTPs in China.

Catalytic ozonation of N-methyldiethanolamine over mixed oxides derived from Mg/Fe-LDH.

The aim of this study was to evaluate the efficiency of catalytic ozonation to increase the degradation of aqueous N-methyldiethanolamine (MDEA) solutions, using two lamellar double hydroxides, namely MgxFe-LDH with x = Mg/Fe = 2, 3, were synthesized by the simple and rapid co-precipitation method. Then, the obtained materials were calcined at 400 °C for 6 h. The calcined products were respectively designated as HTcMg2Fe and HTcMg3Fe, and characterized by powder X-ray diffraction (XRD), N2 physisorption (BET), Fourier transform infrared spectra (FT-IR), and scanning electron microscopy (SEM). The powders produced were used in the ozonation reaction to remove MDEA from aqueous solutions. Experimental results showed that the highest MDEA removal efficiency is in the catalytic ozonation process. Under the optimal conditions for heterogeneous catalytic ozonation of MDEA: initial concentration of 4 Wt% MDEA, 30 °C, catalyst mass of 30 mg/100 ml solution, and contact time of 60 min. The results showed the highest percentage of COD removal, which was up to 80.76% for HTcMg2Fe higher than that of HTcMg3Fe 80.36%.

The regulation of electron distribution on Fe Lewis acidic sites within silicon skeleton and its contribution to Ketoprofen ozonation

Lewis acid site was vital center for activating O3 during catalytic ozonation process. Herein, we proposed a strategy to enhance the Lewis acid strength of Fe-MCM-48 (FeM) by fluorination. Fluorinated Fe-MCM-48 (FFeM) exhibited the better catalytic ozonation efficiency towards Ketoprofen (KET), a kind of nonsteroidal anti-inflammatory drug. 87.4 % TOC removal was obtained by F2.5Fe0.8M/O3 process, but only 27.5 % and 52.7 % were found by sole ozonation and Fe0.8M/O3 processes, respectively. Comparative characterizations, experiments and DFT calculations showed that fluorinated FFeM was regular sphere with three dimensional duct channel and large SBET. Doping of F reduced particle size, implanted electron withdrawing Si-F group and formed the electron poor center around Fe atom, which enhanced Lewis acid strength of FFeM. Protonated hydroxyl groups on Lewis acid sites were the main active sites for O3 activation. Greater amount of O3 were absorbed on the surface of FFeM and the greater O3 utilization rate, •OH and •O2– generation rates were obtained by FFeM/O3 process. Common anions such as Cl−, SO42− and NO3– and Humic acids (HA) had little effect on KET removal but inhibited TOC removal in FFeM/O3 process. •OH, •O2– and Fe(IV) = O oxidation were accounted for KET degradation. 16 kinds of intermediates generated from KET degradation and 4 pathways were deduced.

Preparation of SnOx-MnOx@Al2O3 for Catalytic Ozonation of Phenol in Hypersaline Wastewater

ABSTRACT The catalytic ozonation process (COP) is an effective and advanced oxidation technology for the treatment of organic wastewater. However, high salinity has a negative impact on catalytic ozonation performance. In this work, tin oxide (SnOx) and manganese oxide (MnOx) doped γ-Al2O3 catalysts (SnOx-MnOx@Al2O3) were prepared by the incipient wetness impregnation method and characterized by SEM, XRD, BET, XRT, XPS and FT-IR techniques. The SnOx-MnOx@Al2O3 catalyst was applied to the catalytic ozonation of phenol in hypersaline wastewater, and the catalytic performance was evaluated by COD removal efficiency. When the mass ratio of MnOx to SnOx was 1:3, the pH was 7, the catalyst dosage was 40 g/L, the ozone dosage was 6 mg/(L·min), the NaCl concentration was 15 g/L and the COD removal efficiency of hypersaline phenol wastewater reached 93.8% after 240 min of catalytic ozonation treatment. Compared with the single ozonation process (SOP), the introduction of SnOx-MnOx@Al2O3 catalyst improved the COD removal efficiency by 32.3%. Cl− may quench surface •OH species and ozone to form Cl• and Cl2•− with low activity and high selectivity, resulting in the reduction of catalytic ozonation efficiency. The catalytic activity of the SnOx-MnOx@Al2O3 catalyst remained high after eight cycles. In conclusion, the SnOx-MnOx@Al2O3 catalytic ozonation system exhibits efficient and stable mineralization performance and is a promising strategy for the treatment of hypersaline organic wastewater.

Insights into mechanism of catalytic ozonation of cinnamyl alcohol over core–shell Fe3O4@SiO2@La2O3 catalyst

In this study, a magnetic Fe3O4@SiO2@La2O3 nano-catalyst with a core–shell structure was synthesized to improve the efficiency of catalytic ozonation of cinnamyl alcohol. The structure, morphology, and elemental composition of the catalyst were analyzed with the help of catalyst characterization methods. The mechanism of strengthened degradation efficiency and mineralization of cinnamyl alcohol in catalytic ozonation system in the existence of the catalyst were further discussed according to the analysis results. The results showed that the Fe3O4@SiO2@La2O3 catalyst can not only greatly improve the degradation of cinnamyl alcohol, but also has good reusability and stability. And its economic efficiency is relatively good. The degradation rate of cinnamyl alcohol could reach up to 99.8% at 30 min, and the COD could be removed by 28.5% at 60 min with the help of the catalyst. The degradation efficiency of cinnamyl alcohol by ozone oxidation alone was only 52.1% at 30 min, and the COD removal rate was only 24.2% at 60 min in the same experimental conditions. Besides, the possible degradation pathway and degradation mechanism of cinnamyl alcohol were proposed according to the intermediate products detected by gas chromatography-mass spectrometry.

Facilitated catalytic ozonation of atrazine over highly stabilized Zn-Al layered double oxides composites: efficacy and mechanism

ABSTRACT A series of Zn-Al Layered Double Oxides (ZnAl-LDO) composites were prepared by the hydrothermal and calcination method via employing the Zn-Al Layered Double Hydroxide (ZnAl-LDH) as the precursors in the present study. The structural properties and the catalytic ozonation activity of ZnrAl-T composites synthesized with different Zn/Al molar ratios and calcination temperatures were systematically investigated. Diversified characterizations were applied to analyze the phase structure and chemical composition of ZnrAl-T composites. As the calcination temperature increased, the layered ZnAl-LDH structure could be entirely destroyed and the crystallinity gradually improved. With the Zn/Al mole ratio of 4.0 and calcination temperature of 500°C, the Zn4Al-500 composite obtained the outstanding catalytic ozonation performance for atrazine (ATZ) degradation with the pseudo-first-order constant of 0.5080 min−1, which was 5 times more than that in O3 alone. Meanwhile, the ATZ degradation efficiency was gradually enhanced from 44.1% to 99.9% within 3.0 min when the solution pH ranged from 3.0 to 10.0. Besides, the Zn4Al-500 composite exhibited splendid stability over multiple reaction cycles. In addition, the radical scavenging test and electron spin resonance measurement demonstrated that superoxide radical and hydroxyl radical are the dominant reactive species in O3/Zn4Al-500 process. Moreover, nineteen and ten transformation products were detected in O3 alone and O3/Zn4Al-500 process, and possible degradation pathways of ATZ were further elucidated. Overall, the Zn4Al-500 composite would provide a potential alternative for pollutants removal due to its high catalytic ozonation efficiency, stability, and reusability.

Comparative study on heterogeneous and homogeneous catalytic ozonation efficiency in micropollutants' removal

Abstract Catalytic ozonation was applied for the removal of small concentrations (4 μM) of micropollutants benzotriazole, carbamazepine, p-CBA from aqueous solutions at pH 7. These compounds present different physicochemical characteristics and different kinetic rate constants, when reacting with ozone or hydroxyl radicals in the ranges of <0.15–3 × 105, 5.2 × 109, and 8.8 × 109 M−1s−1, respectively. Calcite was used as heterogeneous catalyst and its catalytic activity evaluated, by applying (and optimized) different experimental conditions (i.e., pH, temperature, ozone concentration), concerning the removal efficiency of p-CBA. Study of micropollutants' removal showed all examined organic compounds can be sufficiently removed by application of catalytic ozonation either by use of calcite, or by presence of Co(II) or Fe(II) (applied as homogeneous catalysts), while the optimum catalyst between them was found to be calcite. Carbamazepine with kO3 = 3 × 105 M−1s−1 can be easily removed, even by application of single ozonation, while benzotriazole and p-CBA resulted in 50% and 68.2% higher removal after application of catalytic ozonation within 3 min of oxidation reaction, due to acceleration of hydroxyl radicals' production by presence of calcite in the ozonation system. The contribution of hydroxyl radicals in removal of all three micropollutants was evaluated by extraction of Rct and f•OH parameters.

Synthesis of Nano Ag-La-Co Composite Metal Oxide for Degradation of RB 5 Dye Using Catalytic Ozonation Process

ABSTRACT Nanoscale composite metal oxide of Ag-La-Co was prepared by co-precipitation method for the treatment of Reactive Black 5 using catalytic ozonation process. Further, the catalyst was characterized by transmission electron microscope, X-ray powder diffraction (XRD), scanning electron microscope - energy dispersive X-ray (SEM-EDX) and Brunauer–Emmett–Teller (BET) surface area analyzer for clarity of the phenomenon. The factors such as amount of catalyst (0.2–1.2 g/L), solution pH (2, 7, and 12), initial dye concentration (100–1,000 mg/L), and ozone flow rate (30–60 LPH) were found to influence the process. The characterization results confirm the formation of the composite metal oxide of Ag-La-Co. The degradation efficiency of catalytic ozonation was 63% compared to 32% and 4% in ozonation without catalyst and adsorption on the catalyst, respectively. Furthermore, it was observed that a pseudo-first-order kinetics model fits well with the experimental data. In addition, the effect of tert-butyl alcohol, a hydroxyl radical scavenger, has been studied. Lastly, the repetitive use of the synthesized catalyst showed that even after three consecutive runs, the catalytic activity is not much degraded, and therefore, the degradation efficiency of the synthesized catalyst was comparatively high; about 95% of Total Organic Carbon (TOC) removal was achieved at solution pH 7, amount of catalyst 1 g/L, reaction time 80 min, and ozone flow rate 30 LPH, indicating an economically viable option for industrial wastewater treatment.

Catalytic ozonation of phenol enhanced by mesoporous MnO2 prepared through nanocasting method with SBA-15 as template

Abstract A mesoporous MnO2 (M-MnO2) was prepared by nanocasting method with SBA-15 as the hard template, and was investigated as an ozonation catalyst. The composition and morphology of the as-prepared MnO2 were characterized using X-ray diffraction analysis, transmission electron microscopy and surface area analysis. The ordered nanorods with high surface area (100 m2g−1) helped the mass transport and the active sites exposed, and thus enhanced the efficiency of catalytic ozonation. The adsorption capacity of M-MnO2 on phenol was about 8 times as high as that of the control MnO2 (C-MnO2) calculated by the Langmuir adsorption model(10.47 mgg−1vs 1.20 mgg−1). Hydroxyl radical was identified as the main reactive oxygen species, and the hydroxyl radical yield from M-MnO2 is about 2-fold enhanced compared with that from C-MnO2. Benefiting from the high mass transport and abundant active sites exposed, the TOC removal of phenol catalyzed by M-MnO2 (35%) was much better than that by C-MnO2(27%)in 30 minutes.

Evaluation the Efficiency of Catalytic Ozonation by Magnetic Nanoparticles TiO2/Fe3O4 in Removal of Ceftazide Antibiotic from Aqueous Solutions

Evaluation the Efficiency of Catalytic Ozonation by Magnetic Nanoparticles TiO2/Fe3O4 in Removal of Ceftazide Antibiotic from Aqueous Solutions

Complementary Bifunctional Unique Properties of (α,β)‐PbO Nanoparticles for Efficient Catalysis and Adsorption for Water Remediation

AbstractLead oxides (PbO) of same chemical composition, but different crystallographic properties have been developed for complementary catalytic ozonation (designated by [PbO]a) and adsorption (designated by [PbO]b) of a model dye, reactive red–120 (RR‐120) with highest possible efficiency beyond the state‐of‐the‐art of individual processes. The highest extent of decolouration (∼99% after 4 min) with 1.77×10−2 s−1 and mineralization (50% after 15 min) of RR‐120 at pH 10.5 was achieved by ozonation using 0.5 g/L catalyst [PbO]a consisting major fraction of α‐PbO phase (α‐PbO: β‐PbO∼4:1) in its crystal structure. Minimum adsorption of RR‐120 (∼7%) on catalyst's surface [PbO]a led to higher accessibility of O3 to free catalyst surface sites and helped to achieve highest efficiency of catalytic ozonation. On the other hand, adsorbent [PbO]b mainly consisting of β‐PbO phase (α‐PbO: β‐PbO∼1:4) with a fractional coexistence of α‐PbO phase showed excellent adsorption of RR‐120 (571 mg/g at 320 K) at pH 7.5, but it showed inferior efficiency in catalytic ozonation. Both the materials were found to be reusable and environmentally acceptable.

The Function of Surface Hydroxyl Groups of Incorporated Alumina on Catalytic Ozonation of Heavy Oil Produced Water

ABSTRACTγ-Al2O3 was incorporated with SiO2 and used as carrier to support Ni and Cu oxides for catalytic ozonation of heavy oil produced water. The change of catalytic activity was in accordance with that of surface hydroxyl density after incorporation or reuse of catalysts. Nitrogen adsorption and X-ray power diffraction analysis indicated that the specific surface area decreased and the mineral phase and crystal structure of metal oxides unchanged after incorporation. The results confirmed that the neutral surface hydroxyl groups of the carrier were the active sites during catalytic ozonation. Increasing of surface hydroxyl could be another way of improving the catalytic efficiency of catalytic ozonation.

Degradation of 2,4,6-trichlorophenol in synthetic wastewater by catalytic ozonation using alumina supported nickel oxides

This research aimed to investigate the efficiency of catalytic ozonation on degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in synthetic wastewater. Nickel oxide doped on alumina support (NiO/Al2O3) was used as heterogeneous catalyst. Three independent variables including TCP concentration, pH, and dosage of catalysts were investigated. The results showed that efficiency on degradation of 2,4,6-TCP by using ozonation alone was 64.36% at an initial TCP concentration of 75 mg/L, pH of 4 (not adjusted), and contact time of 40 min. Degradation reaction followed the first order kinetic pattern with an apparent rate constant (kapp) of 0.025 min−1. As the pH increased to 12, the 2,4,6-TCP removal efficiency of sole ozonation increased up to 89.65%. Catalytic ozonation using NiO/Al2O3 as catalyst at a dosage of 5 g /L (equivalent to 0.25 g Ni/L) provided 2,4,6-TCP removal efficiency of 83.44% with an apparent rate constant of 0.044 min−1. Within a pH range of 4–12, the 2,4,6-TCP removal efficiencies of catalytic ozonation with NiO/Al2O3 catalyst were consistent at 84.30–86.58%. After 4 cycles of use, the 2,4,6-TCP removal efficiency reduced from 94.36% to 84.81%.

An Optimization Study of Cobalt Supported on Activated Carbon for the Catalytic Ozonation of Oxalic Acid: Effect of Operating Parameters and Synergetic Combination

ABSTRACTIn this study, new heterogeneous cobalt (Co) catalysts supported on activated carbon (Co/AC) were developed using a wetness impregnation process. The effect of preparation conditions on catalyst characteristics was examined. This work focused on two key parameters: the impregnation rate and the calcination atmosphere (temperature and time). Different catalysts were prepared by varying the Co loading on AC. Various catalysts were characterized by means of nitrogen sorptiometry at 77K, Boehm and pHpzc analysis. It was found that the catalyst properties and the functional surface groups were affected by the operating conditions. The best surface area was 997.5 m2/g obtained when the activated carbon was impregnated with 5% Co loading and calcined at 350°C for 2 h. The effects of parameters, such as cobalt loading, pH, catalyst dose, and ozone dose, were explored on oxalic acid removal (OA). Results show that the use of Co/AC for heterogeneous catalytic ozonation enhanced the degradation efficiency of oxalic acid (OA) significantly compared with simple ozonation and O3/AC. The main results indicate that the optimum catalytic activity was observed when 5% (wt/wt) of Co was supported on AC reaching a catalytic ozonation efficiency of 95%. The results of total organic carbon removal of 91% were achieved at optimum conditions.

Mineralization of Recalcitrant Organic Pollutants in Pulp and Paper Mill Wastewaters through Ozonation Catalyzed by Cu-Ce Supported on Al2O3

There has been great interest in developing cost-effective and high-performance catalysts for the ozonation treatment of biologically refractory wastewaters. This study developed a novel copper-cerium oxide supported alumina (Cu-Ce/Al2O3) catalyst for the catalytic ozonation of pulp and paper mill wastewater. The evenly distributed composite metal oxides on the surface of catalysts evidently improved the catalytic degradation efficiency. The Cu-Ce/Al2O3/O3 process increased the total organic carbon (TOC) removal by 6.5%, 9.5%, 24.5%, and 35.5%, compared with Ce/Al2O3/O3, Cu/Al2O3/O3, Al2O3/O3, and ozone alone processes, respectively. The enhanced catalytic ozonation efficiency was mainly ascribed to an increased hydroxyl radical (·OH)-mediated ozonation, both in the bulk solution and on the surface of catalysts. The surface hydroxyl groups (-OHs) of Al2O3 along with the deposited Cu-Ce oxides greatly enhanced the catalytic performance. This work illustrated potential applications of Cu-Ce/Al2O3 catalyzed ozonation for the advanced treatment of biologically recalcitrant wastewaters.

A study on simultaneous catalytic ozonation of Hg0 and NO using Mn–TiO2 catalyst at low flue gas temperatures

Mn–TiO2 catalysts were utilized as an ozonation catalyst for the first time to study the simultaneous catalytic ozonation of Hg0 and NO at low flue gas temperatures. BET, SEM–EDS, XRD, XPS, H2-TPR, NO x -TPD and Hg0-TPD were used to characterize the catalysts. The Mn–TiO2 catalyst, in which the molar content of metal Mn was 60%, exhibited the best catalytic activities of Hg0 and NO oxidation, compared with other Mn–TiO2 catalysts. It was found that within the range of experiment, the catalytic ozonation efficiency of Hg0 and NO was higher than that of ozonation or catalytic oxidation. The results also showed that the presence of NO gas inhibited the catalytic ozonation of elemental mercury, and the inhibition was enhanced with the NO inlet concentration, while few elemental mercury molecules did promote the catalytic ozonation of NO. The addition of H2O vapor promoted the catalytic ozonation of Hg0 and NO. In addition, 0.6Mn–TiO2 catalyst demonstrated a good TOS and cyclic stability. The catalytic ozonation of NO and Hg0 on Mn–TiO2 catalyst likely followed the Langmuir–Hinshelwood mechanism, where the hydroxyl radicals reacted with adjacently adsorbed NO molecules and elemental mercury on catalyst surface.

The efficiency of catalytic ozonation using carbosieve in xylene removal from waste air stream

Catalytic ozonation process (COP) is a new method of single ozonation process that has recently received considerable attention in air pollution control industry. The present study aimed to evaluate the efficiency of catalytic ozonation using carbosieve in xylene removal from the waste air stream. An experimental-laboratory study was conducted at the pilot scale, and the performance of carbosieve adsorbent system, simple ozonation, and catalytic ozonation was studied. A lab-scale pilot was designed and launched at the chemical laboratory of the Faculty of Health, Hamadan. Xylene liquid with purity of 99.5 was prepared from Merck (German) and carbosieve from Aldrich Co. (USA). The specific surface rate and the used catalyst size in this study were 972 m2/g and 1.8–2.3 mm, respectively. Results showed that by increasing xylene concentration in the beginning of the system, the time of bed saturation and adsorbent breakpoint decreased, and removal efficiency by ozone gas declined by increasing xylene concentrations in the reactor inlet from 20 to 200 ppm. The findings showed that the carbosieve breakpoint and saturation in catalytic ozonation can happen later from the absorbent carbosieve system alone. It seems that the catalytic ozonation was more efficient in xylene removal compared with absorbent carbosieve system and simple ozonation. The COP by carbosieve could be a promising alternative to conventional volatile organic compounds; removal systems are particularly toxic compounds from waste air stream. © 2017 Desalination Publications. All rights reserved.

Catalytic ozonation of chlorinated VOCs on ZSM-5 zeolites and alumina: Formation of chlorides

This study aims to understand the mechanisms and kinetics of chlorinated volatile organic chemicals (VOCs) removal during the catalytic ozonation process on γ-alumina and ZSM-5 zeolites. Both the H-ZSM-5 and Na-ZSM-5 types with different SiO2/Al2O3 ratios and counter ions (Z1000H:SiO2/Al2O3=1000, Z900Na:SiO2/Al2O3=900, Z25H:SiO2/Al2O3=25 and Z25Na:SiO2/Al2O3=25) were studied. In order to fully understand the mechanisms behind the catalytic processes, degradation of VOCs and chlorides formation were investigated during both ozonation alone and catalytic ozonation on alumina and zeolites. The effects of pH and hydroxyl radical scavengers on the efficiency of catalytic ozonation on alumina and zeolites were also studied. The results revealed that, as opposed to alumina, zeolites promoted decomposition of VOCs. Furthermore, the decomposition of chlorinated VOCs resulted in the generation of chlorides at significantly higher levels when compared with ozonation alone. The presence of hydroxyl radical scavengers had no significant effect on the removal rates of VOCs and the generation of chlorides in the presence of zeolites. It is therefore suggested that catalytic ozonation of organic VOCs on zeolites proceeds via a non-radical mechanism that involves reactions of molecular ozone with pollutants adsorbed on the surface of zeolites.