O3 Conversion Research Articles

Synthesis Ag-Hollandite by mild route for highly efficient ozone decomposition

Catalytic ozone (O3) decomposition is a promising technology for curbing indoor O3 pollution, whereas its application is limited by the stability and moisture resistance of heterogeneous catalysts. Ag-Hollandite is a capable solution, but its facile synthesis still lacks systematic investigation. In this study, Ag-Hollandite catalysts were prepared using AgMnO4 as the precursor by reflux (AMO-Re), hydrothermal (AMO-HT), and homogeneous (AMO-HR) methods, respectively. The as-prepared samples showed excellent stability under moisture conditions, with the optimal one maintaining an O3 conversion rate of 99.19 % after 100 h. In the characterization results, Ramsdellite (R-MnO2) was identified as an intermediate species in the synthesis. AMO-HR exhibits higher activity due to enhanced active site exposure and weakened adsorption towards *OO species, while reduced surface hydroxyl content was a crucial factor for moisture resistance. This study aims to contribute insights for preparing catalysts by a facile method.

High-efficient M-NC single-atom catalysts for catalytic ozonation in water purification: Performance and mechanisms

Heterogeneous catalytic ozonation (HCO) holds promise in water purification but suffers from limited accessible metal sites, metal leaching, and unclear structure-activity relationships. This work reported M-NC (M=Co, Ni, Fe, and Mn) single-atom catalysts (SACs) with high atomic efficiency and minimal metal release. The new HCO systems, especially the Co-based system, exhibited impressive performance in various refractory contaminant removal, involving various reactive species generation, such as •OHads, •OHfree, *O, and 1O2. For sulfamethoxazole removal, the normalized kobs for Co-NC, Ni-NC, Fe-NC, and Mn-NC were determined as 13.53, 3.94, 3.55, and 4.13 min−1·mMmetal−1·g·m−2 correspondingly, attributed to the abundant acid sites, faster electron transfer, and lower energy required for O3 decomposition and conversion. The metal atoms and hydroxyl groups, individually serving as Lewis and Bronsted acid sites (LAS and BAS), were the primary centers for •OH generation and O3 adsorption. The relationships between active sites and both O3 utilization and •OH generation were found. LAS and BAS were responsible for O3 adsorption, while strong LAS facilitated O3 conversion into •OH. Theoretical calculations revealed the catalytic mechanisms involved O3→ *O→ *OO→ O3•−→ •OH. This work highlights the significance of SAC design for HCO and advances the understanding of atomic-level HCO behavior.

Efficient Ozone Elimination Over MnO2 via Double Moisture-Resistance Protection of Active Carbon and CeO2.

The widespread ozone (O3) pollution is extremely hazardous to human health and ecosystems. Catalytic decomposition into O2 is the most promising method to eliminate ambient O3, while the fast deactivation of catalysts under humid conditions remains the primary challenge for their application. Herein, we elaborately developed a splendidly active and stable Mn-based catalyst with double hydrophobic protection of active carbon (AC) and CeO2 (CeMn@AC), which possessed abundant interfacial oxygen vacancies and excellent desorption of peroxide intermediates (O22-). Under extremely humid (RH = 90%) conditions and a high space velocity of 1200 L h-1 g-1, the optimized CeMn@AC achieved nearly 100% O3 conversion (140 h) at 5 ppm, showing unprecedented catalytic activity and moisture resistance toward O3 decomposition. In situ DRIFTS and theory calculations confirmed that the exceptional moisture resistance of CeMn@AC was ascribed to the double protection effect of AC and CeO2, which cooperatively prevented the competitive adsorption of H2O molecules and their accumulation on the active sites of MnO2. AC provided a hydrophobic reaction environment, and CeO2 further alleviated moisture deterioration of the MnO2 particles exposed on the catalyst surface via the moisture-resistant oxygen vacancies of MnO2-CeO2 crystal boundaries. This work offers a simple and efficient strategy for designing moisture-resistant materials and facilitates the practical application of the O3 decomposition catalysts in various environments.

Nitrogen promoted electron transfer to create highly active Cu2+ and Mn3+ sites for efficient catalytic ozonation of Ammonia over copper and nitrogen co-doped Cryptomelane-Type manganese oxide at ambient temperature

Eliminating ammonia (NH3) from high-humidity exhaust gases by catalytic oxidation is a great challenge, especially at low temperatures. Herein, Cu and N co-doped cryptomelane-type manganese oxide (Cu-N-OMS-2) catalysts with high active Cu2+ and Mn3+ sites were synthesized and tested for catalytic ozonation of NH3 at 30 °C. The optimal Cu0.05-N2-OMS-2 catalyst exhibited 93.8 % NH3 conversion, 91.7 % O3 conversion, and 92.1 % N2 selectivity when the relative humidity (RH) was 40 %, whereas OMS-2 only demonstrated 39.3 %, 44.0 % and 83.1 %. Additionally, NH3 and O3 conversion at high RH could be recovered with just a basic water-washing, indicating that Cu0.05-N2-OMS-2 catalyst possessed outstanding renewable properties. The results of characterization revealed that N doping increased the amount of Cu fixed on the catalyst surface and promoted the electron transfer from Cu to Mn, resulting in an increase in electron-poor Cu2+ and electron-rich Mn3+ in Cu-N-OMS-2. In dry conditions, the Mn3+ sites provided O3 with electrons to form adsorbed oxygen species and •O2–, which were essential for oxidation of adsorbed NH3. The electron-poor Cu2+ sites combined with H2O and O3 to form Cu-OH and •HO3, which facilitated the generation of •OH and •O2–, thereby improving the stability under humid conditions. This study provides a new theoretical guidance for the efficient removal of NH3 in industrial exhaust gases.

Enhancing C[sbnd]Cl bond cleavage and ozone conversion: Optimizing surface Co3+ and chemosorbed oxygen through polystyrene and dodecylamine modification

The activation of CCl bonds and the conversion of O3 are crucial for the degradation of chlorinated hydrocarbons through catalytic ozonation. This work constructed the surface active sites of Co3O4 with polystyrene (PS) and dodecylamine to enhance dichloromethane (DCM) removal and O3 conversion in photo-ozone catalysis simultaneously. The dodecylamine created active Co3+ on the catalyst surface, and the PS prevented the elimination of active Co3+ during calcination by forming CCoO. The O3 pre-treatment removed the deposited carbon to expose the active Co3+ and the chemisorbed oxygen. The surface Co3+ played a crucial role in cleaving the CCl bonds of DCM, and the chemosorbed oxygen facilitated the conversion of O3 into O. Moreover, the photogenerated holes oxidized the intermediates formed after the DCM dechlorination. The removal rate of DCM for the sample co-modified by PS and dodecylamine was 80.8 mg/(g‧h) under one sun irradiation, which was 2.2 times higher than that by Co3O4.

Crystal facet engineering of K-OMS-2 for active site identification in catalytic ozone decomposition

Manganese oxide catalysts (MnOx) are expected to be utilized to catalytic ozone (O3) decomposition to curb indoor O3 pollution. However, the accumulation of oxygen-containing species (*OO) on the active site (oxygen vacancy, Ov) of MnOx limits the practical application. Herein, α-MnO2 with exposed {100} (Mn-100), {110} (Mn-110), or {310} (Mn-310) facet was synthesized, respectively. Mn-110 has preferred performance and stability, maintaining 99.9 % O3 conversion after 8 h under 35 % RH. Experimental and theoretical results indicated that the Mn-100 facet owns lower Ov content and *OO adsorption energy, exhibiting the highest specific area normalized activity. Mn-310 has a higher vacancy content and enhanced *OO adsorption energy, which resulted in a rapid accumulation of *OO species. Mn-110 has a moderate Ov content and *OO adsorption and thus exhibits optimal activity. This study hopes to point out a new optimization strategy for MnOx catalysts.

Ozone decomposition on transition-metal-atom anchored graphdiyne: Insights from computation and experiment

Transition-metal-atom anchored graphdiynes (TM@GDY, TM = Mn, Fe, Co, Ni and Cu) have already been synthesized and found applications in hydrogen evolution, nitrogen fixation and etc. By means of first-principle predictions and test experiments, we propose here that Fe@GDY and Co@GDY are efficient catalysts for the sustainable conversion of O3 to O2. These two catalysts can spontaneously chemisorb O3 with zero reaction barrier and have low O3 conversion barriers (0.31 eV and 0.19 eV, respectively). The O3 decomposition experiment in a continuous flow membrane reactor and electron paramagnetic resonance results verify that Fe@GDY and Co@GDY are efficient catalysts under humid conditions. Raman spectra prove the formation of the key Fe-O/Co-O and FeOO and CoOO intermediates. The hydrophobic nature of graphdiyne and the strongest chemisorption of O3 among tested ambient gases, make Fe@GDY and Co@GDY ideal catalysts under both dry and humid conditions. These findings would stimulate future explorations on metal anchored GDY-based catalysts for applications of toxic gas decomposition or fixation.

One-step synthesis of δ-MnO2 with rich defects for efficient ozone decomposition under humid conditions

The catalytic performance of manganese oxides (MnOx) for ozone (O3) decomposition is affected by moisture and stability, for which MnOx with abundant defects offers a promising solution. In this study, a simple and mild one-step synthesis route was developed for highly defective δ-MnO2 preparation. The optimal catalyst was operated at 35 % relative humidity (RH) for 12 h, and the O3 conversion maintained over 99 %. Characterizations revealed that the K+ insertion into the interlayers preserved a highly defective layered structure. Rich surface defects and grain boundaries facilitated the generation of oxygen vacancies and the migration of oxygen species, stabilizing the elimination of O3. In addition, a combination of characterization and experiments determined that physisorbed water is critical for inhibiting activity, and thus, weak physisorption of water on the catalyst represents excellent water resistance. This work aims to provide guidance and new insights into the design of stable and water-resistant MnOx catalysts.

A portable instrument for measurement of atmospheric Ox and NO2 based on cavity ring-down spectroscopy

Atmospheric Ox (nitrogen dioxide (NO2) + ozone (O3)) can better reflect the local and regional change characteristics of oxidants compared to O3 alone, so obtaining Ox accurately and rapidly is the basis for evaluating the O3 production rate. Furthermore, Ox has proved to be a more representative indicator and can serve as a reflection of pollution prevention efficacy. A portable instrument for measuring atmospheric Ox and NO2 based on cavity ring-down spectroscopy (Ox/NO2-CRDS) was developed in this work. The NO2 concentration is accurately measured according to its absorption characteristic at 407.86 nm. Ambient O3 is converted into NO2 by chemical titration of high concentrations of nitrogen oxide (NO), and the O3 conversion efficiencies obtained are nearly 99%. The detection limit of the Ox/NO2-CRDS system for Ox is 0.024 ppbv (0.1 s), and the overall uncertainty of the instrument is ± 6%. Moreover, the Kalman filtering technique was applied to improve the measurement accuracy of Ox/NO2-CRDS. The system was applied in a comprehensive field observation campaign at Hefei Science Island from 26 to 30 September 2022, and the time concentration series and change characteristics of Ox and NO2 were obtained for five days. The measured Ox concentrations were compared with those of two commercial instruments, and the consistency was good (R2 = 0.98), indicating that this system can be deployed to accurately and rapidly obtain the concentrations of atmospheric Ox and NO2. It will be a useful tool for assessing the atmospheric oxidation capacity and controlling O3 pollution.摘要大气Ox (二氧化氮(NO2)+臭氧(O3))相比于O3能够更好的反应区域氧化剂的变化特征, Ox也是反应大气污染防治效果的一个关键指标. 本研究基于腔衰荡光谱技术研发了一套大气Ox和NO2同步测量系统 (Ox/NO2-CRDS). NO2浓度是利用其在407.86 nm处的特征吸收获取, 环境大气的O3通过高浓度的NO被转化为NO2进行间接测量, O3转化效率高于99%, Ox/NO2-CRDS的系统探测限为0.024 ppbv (0.1 s), 系统总不确定度为± 6%. 该Ox/NO2-CRDS系统成功应用于2022年9月26日–30日的合肥市科学岛综合外场观测中, 获取了连续5天的NO2和Ox的时间浓度序列和变化特征, 并将Ox的测量结果与商业化的设备进行了对比验证, 二者具有较好的一致性 (R2 = 0.98), 表明Ox/NO2-CRDS能够被应用于大气Ox和NO2的高灵敏探测. 未来该系统也将会变成评估大气氧化性以及控制臭氧污染的重要工具.

Enhanced water resistance mechanism in Ag-Hollandite for catalytic ozone decomposition

Catalytic ozone (O3) decomposition at ambient temperature is an efficient method to mitigate O3 pollution. However, practical application is hindered by the poor water resistance of catalysts. Herein, Ag-Hollandite (Ag-HMO) with varying Ag+ content was synthesized. Catalysts with more Ag+ exhibited improved efficiency and water-resistance, with the optimal one maintaining 98% O3 conversion at 70% relative humidity (RH) within 8 h. Physicochemical characterizations revealed that Ag+ had entered the tunnel of OMS-2, facilitating oxygen species removal. Notably, enhanced H2O desorption and the complete inhibition of chemisorbed water formation on Ag-HMO were the primary reasons for its high-efficiency O3 conversion across a wide humidity range. The underlying mechanism arises from the charge redistribution induced by the Ag-O interaction within the tunnel, which reduces acidity and modulates hydrophilicity. This study aims to contribute insights for designing catalysts with higher water-resistance.

Co-doped cryptomelane-type manganese oxide in situ grown on a nickel foam substrate for high humidity ozone decomposition

Monolithic catalysts with excellent O3 catalytic decomposition performance were prepared by in situ loading of Co-doped KMn8O16 on the surface of nickel foam. The triple-layer structure with Co-doped KMn8O16/Ni6MnO8/Ni foam was grown spontaneously on the surface of nickel foam by tuning the molar ratio of KMnO4 to Co(NO3)2·6H2O precursors. Importantly, the formed Ni6MnO8 structure between KMn8O16 and nickel foam during in situ synthesis process effectively protected nickel foam from further etching, which significantly enhanced the reaction stability of catalyst. The optimum amount of Co doping in KMn8O16 was available when the molar ratio of Mn to Co species in the precursor solution was 2:1. And the Mn2Co1 catalyst had abundant oxygen vacancies and excellent hydrophobicity, thus creating outstanding O3 decomposition activity. The O3 conversion under dry conditions and relative humidity of 65%, 90% over a period of 5 hr was 100%, 94% and 80% with the space velocity of 28,000 hr−1, respectively. The in situ constructed Co-doped KMn8O16/Ni foam catalyst showed the advantages of low price and gradual applicability of the preparation process, which provided an opportunity for the design of monolithic catalyst for O3 catalytic decomposition.

Highly c-disordered birnessite with abundant out-of-layer oxygen vacancies for enhanced ozone catalytic decomposition

Ozone pollution has long been a hazard to human health and ecosystems. Manganese oxides have been intensively investigated for O3 decomposition, but improving the catalytic activity and stability of MnOx remains challenging. Herein, hexagonal birnessites with varying degrees of c-disordering were synthesized and showed strikingly different catalytic activities. As the degree of c-disordering increase, the highly disordered birnessite (HDB) possessed the highest content of oxygen vacancies (VO) and thus demonstrated the superior catalytic activity. The HDB remained a high O3 conversion efficiency of 96% even after reaction for 24 h at a high space velocity of 600,000 mL·g−1·h−1 and under the relative humidity of 50%. At the same time, HDB could be easily regenerated after heating for 1 h at 200 °C under air atmosphere. We found two different types of VO (the in-layer VO and the out-of-layer VO) on the c-disordered birnessites, and the out-of-layer VO was more stable than the in-layer VO. The out-of-layer VO was beneficial to desorption of the intermediate O22– and reduced the competitive adsorption of H2O, which accounted for the enhanced catalytic stability of HDB. This work may provide guidance for the VO engineering in metal oxides toward the catalytic purification of waste gases.

Catalytic ozonation of methylethylketone over porous Mn–Cu/HZSM-5

The catalytic ozonation of methylethylketone (MEK) was performed at the room temperature (25 °C) using the synthesized Mn and Cu-loaded zeolite (ZSM-5, SiO2/Al2O3 = 80) catalysts. The ZSM-5 zeolite was used as a porous support material due to the large surface area and high capacity for adsorption of volatile organic compounds. Since Mn and Cu-loaded zeolite catalysts were effective for the catalytic ozonation of VOCs such as MEK, according to the loaded concentration of Mn and Cu, there are four types of metal loaded ZSM5 catalysts synthesized [5 wt% Mn/ZSM-5, 5 wt% Cu/ZSM-5, 5 wt% Mn-1 wt% Cu/ZSM-5 (5Mn1CuZSM), and 5 wt% Cu-1 wt% Mn/ZSM-5]. The catalytic efficiency for the removal of MEK and ozonation using the different catalysts was also studied. Based on various experimental analysis processes, the characteristics of the synthesized catalysts were explored and the removal efficiencies of MEK and O3 together with the COx concentration generated from the destruction of MEK and O3 were explored. The results for the decomposition of MEK and O3 at the room temperature indicated that the Mn dominant ZSM-5 catalysts showed better efficiency for the conversion of MEK and O3. The 5 wt% Mn/ZSM-5 outweighed the rest of them for the removal of MEK while the 5Mn1CuZSM showed the best catalytic reactivity for the conversion of O3 and the CO2 selectivity. It was ascertained that during the reaction time of catalyst and reactants of 120 min the Mn dominantly deposited bimetallic catalyst, 5Mn1CuZSM, was determined as the most effective for the removal of MEK and O3 due to the high capability of production of Mn3+ species and more available adsorbed oxygen sites compared to the other catalysts. Finally, the durability measurement for the 5Mn1CuZSM catalyst was performed together with the produced CO and CO2 concentration for 420 min.

High urban NOx triggers a substantial chemical downward flux of ozone.

Nitrogen oxides (NOx) play a central role in catalyzing tropospheric ozone formation. Nitrogen dioxide (NO2) has recently reemerged as a key target for air pollution control measures, and observational evidence points toward a limited understanding of ozone in high-NOx environments. A complete understanding of the mechanisms controlling the rapid atmospheric cycling between ozone (O3)-nitric oxide (NO)-NO2 in high-NOx regimes at the surface is therefore paramount but remains challenging because of competing dynamical and chemical effects. Here, we present long-term eddy covariance measurements of O3, NO, and NO2, over an urban area, that allow disentangling important physical and chemical processes. When generalized, our findings suggest that the depositional O3 flux near the surface in urban environments is negligible compared to the flux caused by chemical conversion of O3. This leads to an underestimation of the Leighton ratio and is a key process for modulating urban NO2 mixing ratios. As a consequence, primary NO2 emissions have been significantly overestimated.

Enhanced catalytic performance and reduced by-products emission on plasma catalytic oxidation of high-concentration toluene using Mn-Fe/rGO catalysts

High-concentration toluene is refractory to mineralize and must be controlled. The synergistic catalytic degradation of toluene with dielectric barrier discharge (DBD) results in the creation of large quantities of O3 and NOx. In this study, reduced graphene (rGO)-based catalysts with Mn and Fe (Mn-Fe/rGO) were recommendable. The effect of Mn-Fe/rGO catalysts on DBD oxidation of toluene was studied by changing Mn-Fe molar ratios and total loading. We investigated the performance of Mn-Fe/rGO catalysts on DBD oxidation of toluene by varying the Mn-Fe molar ratios and the total loading. The Mn-Fe molar ratio was 3:1, loading was 10 wt%, maximum toluene conversion was 85%, and COx selectivity was as high as 69.8%. When energy density (ED) was 598.25 J/L and toluene concentration was 657.14 mg/m3, toluene conversion, COx selectivity, O3 conversion, NO2 conversion, and NO conversion were 85.6%, 68.9%, 82.5%, 68.2%, and 64.3%, respectively. Analyzing the gas chromatography-mass spectrometric (GC-MS) data and determining the tail gas mechanism, it was found that toluene ring-opening was synergistic between active substances and Mn-Fe/rGO catalysts. Ferromanganites not only promoted the ring-opening degradation of toluene, but also had a positive effect on O3 conversion and NOX conversion. They consume aldehydes and NOX, produce O·and N·, and thus facilitate the mineralization process. This study provides new insights into plasma catalytic oxidation of high-concentration organic pollutants.

Enhanced sludge dewaterability via ozonation catalyzed by sludge derived biochar loaded with MnFe2O4: Performance and mechanism investigation

In order to develop an efficient and environmental-friendly alternative for enhancing dewatering performance of waste activated sludge (WAS), the sludge derived biochar loaded with MnFe2O4 (MnFe2O4@SBC) was firstly prepared for catalyzing ozonation of sludge. The optimal condition was determined to be pH = 6, O3 dosage = 60 mg/g VS and MnFe2O4@SBC dosage = 600 mg/g VS, under which the capillary suction time (CST) and specific resistance to filtration (SRF) of WAS declined from 98.3 ± 1.0 s and 1.1 ± 0.03 × 1014 m/kg to 18.3 ± 0.8 s and 0.32 ± 0.03 × 1014 m/kg, respectively. The water content (Wc wt.%) of sludge cake declined from 87.1 ± 0.98% to 68.1 ± 0.87%. The mechanism for enhanced dewatering performance of WAS by MnFe2O4@SBC was systematically clarified. Firstly, the circulation of valence states for Fe and Mn on the surface of MnFe2O4@SBC was found promoting the conversion of O3 into highly active free radicals and the generation of hydroxyl radicals (·OH). Secondly, the density functional theory (DFT) calculation firstly manifested that O3 molecules were easier to be activated and dissociated into ·OH groups on the surface of MnFe2O4 phase. With the above promotion of ·OH generation, the inner part of sludge flocs especially the protein in extra-cellular polymers (ECPS) was destructed strongly, with significant release of bound water and the decrease in water bound energy. The organic biopolymers with negative charges were diminished followed by the increased zeta potential and enlarged particle size, resulting in the enhanced dewatering performance of WAS. This study illustrated the rationality and validity of the new strategy for enhanced sludge dewatering in both practice and theory, shedding light on the further development of sludge dewatering technology.

Promotional effect of surface fluorine on TiO2: Catalytic conversion of O3 and H2O2 into ·OH and ·O2− radicals for high-efficiency NO oxidation

Inducing radicals for low-temperature NO oxidation is considered to be one of the most efficient methods. In the present study, it was proposed that catalytic conversion of O3 and H2O2 on F/TiO2 (surface fluorine of TiO2) into multiple radicals for high-efficiency NO oxidation, which excessed 96% under the molar ratio of O3/NO = 0.5 and H2O2/NO = 4.36. A promotion mechanism was carefully discussed by experimental design and characterization analysis: F/TiO2 could greatly promote the deprotonation of H2O2 to form Ti-OOH species. Besides, surface fluorine was conducive to the adsorption of O3. Thus, F/TiO2 enhanced the reaction of Ti-OOH with O3 to generate ·OH and ·O2– radicals, which induced a high-efficiency NO oxidation. Finally, the effect of reaction temperature, H2O2 concentration, pH value, the concentration of CO, CO2 and SO2 were systematically investigated. The results revealed that this process exhibited a good stability and resistance of different gas composition, and had an industrial application prospect.

Ozone Decomposition on Defective Graphene: Insights from Modeling

We propose via first-principles calculations that graphene tailored with specific structural or foreign-atom defects can be used as catalysts for O3 decomposition. Compared to the pristine graphene, we show that introduction of thermodynamically stable surface defects, that is, Stone-Wales, 555–777 divacancy or nitrogen atoms to graphene, can drastically lower the chemisorption energy barrier of O3. The ozonides once formed can evolve into epoxide or ketone-like intermediate structures on graphene, which assist in the sustainable conversion of O3 to O2. The minimal energy needed to complete the O3 decomposition cycle on different graphene substrates has the order of E555–777 (0.22 eV) < EN-doping (0.33 eV) < EStone-Wales (0.61 eV) < Epristine graphene (1.08 eV). As two most promising catalysts, 555–777 divacant and N-doped graphene shows a clear adsorption selectivity to O3 under the ambient conditions. N-doped graphene outperforms 555–777 divacant graphene at the stage of physisorption in that the former catalyst separates O3 from the ambient gases by a much larger adsorption energy. These results and conclusions are a pivotal and necessary step that should stimulate both the proof-of-principle experiments and the computational search of metal-free catalysts for O3 decomposition.

Catalytic degradation of caffeic acid by DBD plasma and Mn doped cobalt oxyhydroxide catalyst

In this study, caffeic acid (CA) was degraded by electrical discharge plasma combined with Mn doped CoOOH catalyst. Doping of Mn significantly improve the catalytic activity of CoOOH. CA degradation efficiency was 75.6% with dielectric barrier discharge treatment for 10 min, and it reached 97% using CoOOH as the catalyst at the same treatment time. CA was 100% degraded with only 8 min using Mn/CoOOH as the catalyst. The introduction of Mn into the lattice of CoOOH induced the formation of oxygen vacancy, causing part of coordinate number of Co decreased from 6 to 5, and thus produces unsaturated Co to be the Lewis acid sites. Lewis acid sites (unsaturated Co) could coordinate with O3 and H2O2 and break their chemical bonds to form O and –OH. Assisting in the conversion of O3 to ·OH was the main role of H2O2 in the catalytic process. The degradation products and pathway of CA were studied by three-dimensional fluorescence, liquid chromatograph-mass spectrometer and density functional theory calculations.

Nanometer CeO2 doped high silica ZSM-5 heterogeneous catalytic ozonation of sulfamethoxazole in water

A novel CeO2 doped high silica ZSM-5(CeO2@HSZSM-5) composite was originally fabricated via ammonia precipitation for the catalytic ozonation of sulfamethoxazole (SMX). Physicochemical properties have been investigated through electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, etc. The prepared nanometer CeO2@HSZSM-5 had a much higher specific surface (348–395 m2/g), a finer crystallite size (8.2–33.5 nm) and superior stability. Temperature-programmed desorption and reduction analysis revealed that the formed CeO2 nanoparticles on the surface of CeO2@HSZSM-5 could improve the reducibility of surface-capping oxygen, induce more oxygen vacancies and promote oxygen migration. CeO2@HSZSM-5 exhibited excellent catalytic performance for SMX mineralization in the pH range of environmental waters. The great enhancement of CeO2@HSZSM-5 catalytic activity was ascribed to the conversion of O3 into active oxygen involved in SMX mineralization, including .OH, O2.– and 1O2. This work provides a reference for the removal of pollutants by zeolite supported Ce catalytic ozonation process in water.