Catalytic Ozonation Of Organic Pollutants Research Articles

Surface Mn-O3* complex-mediated nonradical electron transfer for boosting catalytic ozonation of organic pollutants

As initial and important reactive species, surface O3 complexes are rarely investigated in catalytic ozonation, which might be one cause of dispute in mechanistic understanding. Herein, In-situ DRIFTS and premixing-standing experiments confirmed the generation of long-lived Mn-O3* complexes upon O3 adsorption on surface Lewis acid sites of α-MnO2. In α-MnO2/O3 system, the oxidation rate of various pollutants showed a good linear correlation with their redox potentials, as well as the energy gap between the pollutants and Mn-O3* complexes. Joint catalytic mechanism experiments and density functional theory calculations revealed that the oxidation of pollutants was boosted mainly because there was fast nonradical intermolecular electron transfer from the HOMO of pollutants to the LUMO of Mn-O3* complexes. This study illustrates the significance of surface Mn-O3* complex in catalytic ozonation and discloses an efficient nonradical catalytic ozonation process that is resistant to pH fluctuation and matrix interference.

CeO2-modified monolithic ceramic foams for efficient catalytic ozonation of refractory organic pollutants in a continuous-flow reactor

The monolithic catalyst of CeO2-loaded ceramic foam for the catalytic ozonation of organic pollutants operated in a continuous-flow mode was developed, achieving effective TOC removal of organic pollutants and high utilization efficiency of ozone.

MgAl2O4 incorporated catalytic ceramic membrane for catalytic ozonation of organic pollutants

Heterogeneous catalytic ozonation (HCO) is a promising technology for organic pollutants removal in wastewater treatment owing to the generation of powerful but short-lived hydroxyl radicals (HO·). Herein, we incorporate MgAl2O4 catalysts on the surface of ceramic membrane pores (MgAl membrane) to enhance HO· utilization and promote pollutant degradation under spatial confinement. The MgAl catalytic membrane achieved a removal efficiency of 74.0% for ibuprofen (5 mg/L) with 68.8% total organic carbon (TOC) removal, and the pollutant removal efficiency maintained over 67% in 25 h. Electron paramagnetic resonance (EPR) and scavenging experiments revealed that HO· played the dominant role in pollutant degradation. The catalyst surface hydroxyl groups were identified as active sites to effectively generate HO· via ozone decomposition. This work provides a viable strategy to achieve efficient pollutant degradation in wastewater treatment under spatial confinement in a membrane configuration.

Controllable synthesis of substitutional and interstitial nitrogen-doped ceria: The effects of doping sites on enhanced catalytic ozonation of organic pollutants

Nitrogen doping sites greatly affected the electronic structure of catalysts. However, identification of nitrogen doping sites in CeO2 and their effects on catalytic ozonation have never been addressed. Herein, nitrogen was selectively doped at substitutional (Ns) or interstitial sites (Ni) in CeO2 by simply controlling the heat treatment conditions. The obtained NCe2–400 with 100% Ni significantly enhanced the elimination of sulfamethoxazole to 93.7 ± 1.9% within 30 min at the initial solution pH of 6.2. The first-order rate constant reached 8.77 × 10−2 min−1, 2.1 and 4.1 times that of 50.1%Ns-doped CeO2 and ozonation, respectively. The experimental and DFT calculation results demonstrate that compared to Ns, Ni favors the formation of oxygen vacancies (OVs). Both Ni and OVs significantly decreased the energy barrier of the adsorption and activation of ozone. This study provides a simple site-tunable N-doping method and gains a new insight into the roles of Ni and Ns in catalytic ozonation.

Cation deviated stoichiometry Ca1.1ZrO3 perovskite as an efficient ozonation catalyst for m-cresol wastewater degradation

Highly efficient and stable catalysts for continuous catalytic ozonation of organic pollutants are of great significance in industrial applications. Perovskites have been seen as promising environmental catalysts because of their tunable defect structures and electronic properties. This work reports on A-site cation stoichiometry deviation as an effective engineering strategy to improve the crystallinity of perovskite CaZrO3, as well as its catalytic ozonation activity. High pure phase Ca1.1ZrO3 nanocrystals were successfully synthesized using a co-precipitation calcination method and evaluated as ozonation catalysts for m-cresol degradation. Surprisingly, Ca1.1ZrO3 exhibits a higher total organic carbon (TOC) removal rate, ozone utilization rate, and conversion rate of m-cresol than the stoichiometric of CaZrO3 and other conventional transition metal catalysts. In addition, Ca1.1ZrO3 shows an almost constant conversion rate of m-cresol (100%) and TOC removal rate (∼82%) during uninterrupted 100-h catalytic ozonation m-cresol degradation, demonstrating its excellent catalytic stability. These outstanding catalytic activity and stability toward ozonation are attributed to the synergistic meliorated oxygen octahedron structure, including Zr cation and contiguous coordinated oxygen, by introducing a non-stoichiometry defect into the perovskite. Thus, Ca1.1ZrO3 presents an advanced oxidation process of reactive oxygen species (·OH, O2·-, 1O2). These results were verified by in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, electron paramagnetic resonance, and density functional theory. This work strongly believes that Ca1.1ZrO3 can be an efficient, stable, and an economic catalyst for catalytic ozonation.

Bi-metal oxide-modified flat-sheet ceramic membranes for catalytic ozonation of organic pollutants in wastewater treatment

Ceramic membranes have a highly porous structure and a high surface area, which provide suitable support for heterogeneous catalytic oxidation. In this study, as effective catalysts for ozonation, Mg, Ce, and Mn oxides were coated by co-precipitation onto a flat-sheet ceramic membrane to produce two catalytic ceramic membranes (CCMs), namely an Mg-Ce membrane and an Mg-Mn membrane. This technique combines ceramic membrane filtration with catalytic ozonation for advanced water and wastewater treatment. The CCM characterization showed that the metal oxide catalysts were well coated on the membrane surface and inside the membrane pores. Compared with non-catalytic ozonation, catalytic ozonation with CCMs was more effective for the degradation and removal of organic pollutants, including a dye as a model pollutant in water and residual organics in secondary wastewater effluent. At the same ozone dosage for ozonation coupled with membrane filtration, the organic removal efficiency was increased from approximately 30% for the ceramic membrane without the catalyst coating to over 80% for the CCM with the catalyst coating. Membrane catalytic ozonation also resulted in effective membrane fouling control during ultrafiltration of the secondary effluent. Based on the hydroxyl (OH) quenching test, ozonation with CCMs produced more OH free radicals than ozonation alone, which led to enhanced organic degradation. Moreover, catalytic ozonation in the membrane reactor played an effective role in mitigation of membrane fouling. Ceramic membrane-based catalytic ozonation can be used for effective removal of toxic and persistent organic pollutants from water and wastewater.

Heterogeneous Catalytic Ozonation of Aqueous p-nitrophenol over MIL-100(Fe) Metal–Organic Framework

ABSTRACT Metal–organic frameworks have been extensively studied in catalysis owing to their unique physicochemical properties. However, this class of materials has not yet been directly applied to the catalytic ozonation of organic pollutants. In this study, MIL-100(Fe) was synthesized by a solvothermal method and characterized by powder X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, N2 adsorption–desorption and scanning electron microscopy. A range of reaction conditions such as pH, solute concentration and catalyst content were applied to investigate the catalytic activity of our MIL-100(Fe) sample for the ozonation of p-nitrophenol in water. According to the experimental results, at a neutral initial pH, the catalytic ozonation of p-nitrophenol proceeded mainly through radical reactions, whereas in the absence of the MIL-100(Fe) catalyst, ozone could react with p-nitrophenol via the direct reaction pathway. The catalyst achieved a conversion of up to 98% and chemical oxygen demand removal of up to 75%. Moreover, our MIL-100(Fe) catalyst retained this performance for seven cycles of operation, which offers potential applications for metal–organic frameworks as catalysts in wastewater treatment.

Nano- and macro-structured cerium oxide – Carbon nanotubes composites for the catalytic ozonation of organic pollutants in water

A novel methodology for the preparation of nanostructured layers of mechanically processed carbon nanotubes (CNT) on macro-structured supports was investigated as a means to prepare macro-structured composite catalysts consisting of a variety of different ceria – CNT combinations as ozonation catalysts. Two different synthesis routes were used for the preparation of the ceria: precipitation and sol-gel. The composite materials were prepared using different approaches: introduction of ball-milled CNT during the synthesis procedure; ball-milling the pure ceria together with as-received CNT; and decoration of ball-milled CNT with well-dispersed ceria through incipient wetness impregnation. The powder composite catalysts were then transferred onto macro-structured supports by using the aforementioned novel methodology for the preparation of slurries suitable to be used in the dip-coating of the macro-structures. A further structured composite catalyst was also prepared using a two-step approach by dipping a previously prepared CNT structured catalyst in a ceria solution. The powder and structured composite catalysts were then tested as ozonation catalysts in semi-batch and continuous experiments. It was found that the different ceria synthesis routes and the composite preparation methods affected both the catalytic performance of the powder composites and also the characteristics of the slurry used for dip-coating of the macro-structured supports. The ball-milling of sol-gel ceria together with CNT resulted in the most active powder catalyst, but the impregnated CNT with well-dispersed ceria was found to be the most active structured catalyst prepared from coating with the powder composites. The two-step structured catalyst prepared by dipping in a ceria-sol was able to achieve the highest removal of oxalic acid (85 % at steady-state continuous operation); however, due to the more energy intensive preparation procedure, its use in practical applications might not be the most recommendable.

Nanostructured Layers of Mechanically Processed Multiwalled Carbon Nanotubes for Catalytic Ozonation of Organic Pollutants

Multi-walled carbon nanotubes (MWCNT) are known to have great potential to be used as catalysts in the ozonation of organic pollutants in water. However, solutions are required towards their practi...

Carbon nanofibers doped with nitrogen for the continuous catalytic ozonation of organic pollutants

Catalytic ozonation using carbon materials, in particular nanocarbons, has been appointed as an interesting alternative for the abatement of recalcitrant emerging organic pollutants. Efforts to achieve more efficient catalysts have been carried out, including carbon doping with heteroatoms. In this study, the effect of nitrogen doping of carbon nanofibers in their catalytic activity for the ozonation of organic pollutants was assessed. For this end, pristine and N-doped carbon nanofibers were prepared, both in powder and in structured forms. The former were tested in semi-batch ozonation experiments, while the latter were used in continuous ozonation experiments. It was observed that the presence of N-containing functionalities on the surface of the carbon nanofibers enhances their capability as catalysts for the studied reaction.

Catalytic ozonation of organic pollutants from bio-treated dyeing and finishing wastewater using recycled waste iron shavings as a catalyst: Removal and pathways

Catalytic ozonation of organic pollutants from actual bio-treated dyeing and finishing wastewater (BDFW) with iron shavings was investigated. Catalytic ozonation effectively removed organic pollutants at initial pH values of 7.18–7.52, and the chemical oxygen demand (COD) level decreased from 142 to 70 mg·L−1 with a discharge limitation of 80 mg·L−1. A total of 100% and 42% of the proteins and polysaccharides, respectively, were removed with a decrease in their contribution to the soluble COD from 76% to 41%. Among the 218 organic species detected by liquid chromatography-mass spectrometry, 58, 77, 79 and 4 species were completely removed, partially removed, increased and newly generated, respectively. Species including textile auxiliaries and dye intermediates were detected by gas chromatography-mass spectrometry. The inhibitory effect decreased from 51% to 33%, suggesting a reduction in the acute toxicity. The enhanced effect was due to hydroxyl radical (OH) oxidation, co-precipitation and oxidation by other oxidants. The proteins were removed by OH oxidation (6%), by direct ozonation, co-precipitation and oxidation by other oxidants (94%). The corresponding values for polysaccharides were 21% and 21%, respectively. In addition, the iron shavings behaved well in successive runs. These results indicated that the process was favorable for engineering applications for removal of organic pollutants from BDFW.

Intrinsic Activity of SBA-like Silica in the Catalytic Ozonation of Organic Pollutants

ABSTRACTHydrothermal synthesis using two gel compositions: i. 1 SiO2: 0.059 P123: 56.130 HCl: 607.638 H2O; ii. 1 SiO2: 0.006 P123: 0.013 F127: 42.439 HCl: 442.876 H2O, resulted in highly crystalline SBA-15 and SBA-16 like silica with intrinsic activity in the catalytic ozonation of oxalic acid (OA), phenol (φ-OH) and Orange G (OG) in water at room temperature. X-ray diffraction, nitrogen adsorption–desorption, transmission and scanning electron microscopies revealed highly ordered mesoporous structure, with large surface area, regular channels and uniform particle size. UV-Vis analysis provided faster, more precise and reliable assessments of the decomposition yield and process selectivity than the conventional and laborious method of Chemical Oxygen Demand (COD). The ozone reactivity was found to be favored by increasing size of the organic substrate. OG and phenol decomposition required shorter ozonation time (20, 15 min, respectively) than OA, involving mainly phenyl ring hydroxylation and cleavage. Measurements through thermal programmed desorption of carbon dioxide and water revealed that the catalytic activity of the SBA samples involves adsorption via both acid-base and hydrophobic interactions. Suitable SBA modifications allow tailoring these interactions for even faster ozonation without persistent traces of short chain derivatives.

Enhanced inhibition of bromate formation in catalytic ozonation of organic pollutants over Fe–Al LDH/Al2O3

Fe–Al layered double hydroxides (Fe–Al LDH, the molar ratio of Fe(II) to Fe(III) was about 1:10) was successfully supported and highly dispersed on mesoporous Al2O3 based on the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Fe–Al LDH/Al2O3 was more efficient in inhibiting BrO3− formation and removing organic pollutant taking ozonation alone as control. Further investigation indicated that BrO3− reduction by surface Fe(II) was responsible to the complete inhibition of BrO3− formation. Fe(II) was reduced from the Fe(III)-intermediates complex via an electron transfer process and the reaction of Fe(III) and HO2−/O2− in catalytic ozonation. The amount of surface Fe(II) in catalytic ozonation of amitrole (AMT), phenazone (PZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) was 0.34, 2.47 and 3.30μmol/g, which proved that most of Fe(II) was generated from the reaction of ozone and Fe–Al LDH/Al2O3 since 0.33μmol/g of Fe(II) existed within the catalyst. The increase of ozone amount and the formation of Fe(III)-intermediates complex could enhance the Fe(II) generation, leading to more efficient inhibition of BrO3− formation. Finally, Fe–Al LDH/Al2O3 still showed effectiveness in the inhibition of BrO3− and TOC removal for a raw drinking water under the realistic conditions, which could be applied to the BrO3− mineralization in catalytic ozonation of Br−-containing drinking water.

ChemInform Abstract: Advances in Catalytic Oxidation of Organic Pollutants — Prospects for Thorough Mineralization by Natural Clay Catalysts.

Abstract This review is devoted to oxidative water treatments, with emphasis on catalytic ozonation. The approach tackled herein resides in exposing a wide variety of oxidative treatments attempts as a basis for summarizing the main findings that allow envisaging improvements aiming towards total mineralization of organic pollutants. Comparison between specific operating conditions for specific pollutant-catalyst-oxidizing systems is quite difficult, and is not targeted in the present work. However, when deeply and judiciously analyzed, such a comparison allows demonstrating that, except for some works, most of these attempts seldom took into accounts basic requirements such as the parameter interactions, the role of cation mobility around a solid surface, if any, the multiple pollutant-catalyst-oxidizing species interactions and the significant contribution of adsorption, etc. Otherwise, how to explain that many experiments are still conducted with unsuitable catalysts under totally inadequate operating conditions? A better understanding of the essential requirements for a catalyst to achieve total mineralization of any organic molecules is the main objective of this work. The data summarized herein allow devoting a special interest to ozone, which is a powerful oxidizing agent and probably the most easily handleable, in spite of its low solubility in water. The use of catalysts is an ultimate strategy to improve the ozonation performance, by reducing the chemical oxygen demand (COD), even until total disappearance. However, solid catalysts, more particularly those developing high specific surface areas, such as silicates, aluminosilicates, zeolites, pseudozeolites, and clay minerals and derivatives are expected to display appreciable performances in ozonation. The latest findings show strong dependency of their catalytic activity on the chemical and physical characteristics of their surface, their concentration in the liquid media, the pH level of the reaction mixture and other parameters. The effects of these factors will be systematically examined in this review paper. The state-of-the-art in the catalytic ozonation of organic pollutants may be useful to understand the contribution of both surface and bulk ozonation reaction in the vicinity of the surface of a solid catalyst, and more particularly the role of the catalytic agent and its mobility near the solid surface. A rigorous data synthesis, made available in the present paper, allows understanding the ozone scavenging by the very species present in water, and correlating the highest effectiveness of ozone in the presence of optimum catalyst concentration at optimum pH. This supposes strong interactions between the main factors, which remain to be elucidated for each type of catalyst. The structure of this review makes emphasis on montmorillonite, which exhibits most of the required properties for effective ozonation catalysts. These are common features of natural clay minerals and zeolites, which appear as interesting candidates for large-scale water treatments, targeting complete mineralization of organic pollutants without generating persistent toxins.

Catalytic ozonation for the removal of organic contaminants in water on alumina

This study aims to understand the efficiency and role of adsorption of common water pollutants (volatile organic chemicals (VOCs), pharmaceuticals and carboxylic acids) in the catalytic ozonation process on γ-alumina. In order to understand the catalytic processes occurring, the effects of pH, hydroxyl radical scavengers, humic acids and phosphates on the efficiency of catalytic ozonation on alumina were studied. The results revealed that catalytic ozonation on alumina could substantially enhance the removal of ibuprofen and acetic acid when compared with ozonation alone. However, alumina did not catalyse the removal of VOCs. The adsorption of pollutants plays a key role in the effectiveness of this process. The presence of hydroxyl radical scavengers, phosphates and humic acids had a significant effect on the removal of pollutants on alumina. It is therefore suggested that catalytic ozonation of organic pollutants on alumina proceeds via a radical mechanism that involves reactions of hydroxyl radicals with pollutants adsorbed on the surface of alumina.

Catalytic ozonation for the removal of organic contaminants in water on ZSM-5 zeolites

The results presented in this study aim to show the potential of ozonation of common water pollutants (volatile organic chemicals, pharmaceuticals and carboxylic acids, ozonation by-products) on ZSM-5 zeolites and to investigate the effect of the nature of pollutants on the efficiency of catalytic ozonation. Both the H-ZSM-5 and Na-ZSM-5 forms 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) have been used. The effects of pH, adsorption, presence of hydroxyl radical scavengers, phosphates and humic acids on the efficiency of catalytic ozonation have been investigated. The results revealed that catalytic ozonation on zeolites could substantially enhance the removal of VOCs and ibuprofen when compared with ozonation alone and that adsorption plays a key role in the effectiveness of this process. Zeolites with high SiO2/Al2O3 ratios were found to have a high adsorption capacity towards VOCs and as a result high catalytic activity. On the other hand zeolites with low SiO2/Al2O3 ratios had a high adsorption capacity towards ibuprofen in its ionised form. Catalytic processes have been found to be pH dependent with the highest activity at acidic pH. The presence of hydroxyl radical scavengers (phosphates and humic acid) did not have a significant effect on the removal of contaminants on ZSM-5 zeolites. Despite high activity towards VOCs and ibuprofen, zeolites did not catalyse the removal of acetic acid in water at studied pH values. It is therefore suggested that catalytic ozonation of organic pollutants on ZSM-5 zeolites proceeds via direct reactions of molecular ozone with pollutants adsorbed on the surface of zeolites.

Inhibition of bromate formation by surface reduction in catalytic ozonation of organic pollutants over β-FeOOH/Al2O3

BrO3− formation was investigated over β-FeOOH/Al2O3 during the catalytic ozonation of Br−-containing water. The effect of several representative compounds in aqueous environment such as 2,4-dichlorophenoxyacetic acid (2,4-D), phenazone (PZ), diphenhydramine (DP), amitrole (AMT) and Br−-containing raw drinking water was examined on the formation of BrO3−. No significant BrO3− formation and higher removal of total organic carbon (TOC) were observed during the catalytic ozonation of the tested samples except AMT. Moreover, it was found that the adsorbed BrO3− was reduced to Br−, which was greatly enhanced by the degradation of organics according to the order AMT<DP<PZ<2,4-D. The surface Fe(II) of β-FeOOH/Al2O3 was responsible for the reduction of BrO3− on the basis of in situ diffuse reflection UV–vis spectra and the determination of surface Fe(II) under different conditions. It was generated from the reaction of surface Fe(III) with HO2−/O2− during the catalytic ozonation of different pollutants. Furthermore, FTIR and GC–MS analysis verified that the complexation of surface Fe(III) with the oxygen-containing functional groups (OH, COOH) of pollutants or their intermediates enhanced the reaction of Fe(III) with HO2−/O2−, resulting in more surface Fe(II) to cause higher BrO3− reduction rate. The catalyst still showed effectiveness for the inhibition of BrO3− formation and TOC removal for a Br−-containing raw drinking water under the realistic conditions. These findings could be applied to the minimization of BrO3− formation in catalytic ozonation of Br−-containing drinking water.

Process design for wastewater treatment: catalytic ozonation of organic pollutants

Emerging micropollutants have been recently the target of interest for their potential harmful effects in the environment and their resistance to conventional water treatments. Catalytic ozonation is an advanced oxidation process consisting of the formation of highly reactive radicals from the decomposition of ozone promoted by a catalyst. Nanocarbon materials have been shown to be effective catalysts for this process, either in powder form or grown on the surface of a monolithic structure. In this work, carbon nanofibers grown on the surface of a cordierite honeycomb monolith are tested as catalyst for the ozonation of five selected micropollutants: atrazine (ATZ), bezafibrate, erythromycin, metolachlor, and nonylphenol. The process is tested both in laboratorial and real conditions. Later on, ATZ was selected as a target pollutant to further investigate the role of the catalytic material. It is shown that the inclusion of a catalyst improves the mineralization degree compared to single ozonation.

Novel magnetically separable nanomaterials for heterogeneous catalytic ozonation of phenol pollutant: NiFe2O4 and their performances

Magnetic NiFe2O4 nanomaterials were proposed as novel ozonation catalysts for the first time. The samples which were synthesized by the hydrothermal method and the calcined method were dominated as NiFe2O4–H and NiFe2O4–C, respectively. Compared with ozonation alone, the presence of NiFe2O4–H significantly enhanced the degradation of phenol, while NiFe2O4–C was noneffective. The interaction between NiFe2O4–H and ozone was obviously stronger than that in ozonation/NiFe2O4–C. This interaction between catalyst and ozone was proved to be a surface process and played a vital role in the heterogeneous catalytic ozonation. Phosphate revealed significantly inhibitive influence on the decomposition of ozone and the degradation of phenol in ozonation/NiFe2O4. Lewis acid sites were proved as reactive centers for catalytic ozonation in aqueous solution. The results indicated that not only the more surface Lewis acid sites, causing the strong interaction between catalyst and ozone, but also the enhanced interfacial electron transfer lead to the higher catalytic activity of NiFe2O4–H than NiFe2O4–C. Furthermore, the NiFe2O4–H nanocatalyst could be easily and efficiently separated from the reaction mixture with an external magnet, which made it an attractive nanomaterial with prospective application in catalytic ozonation of organic pollutants in water treatment.

Role of surface hydroxyl groups of acid-treated natural zeolite on the heterogeneous catalytic ozonation of methylene blue contaminated waters

The effect of surface properties of zeolites on the kinetics of heterogeneous catalytic ozonation of organic pollutants is still under discussion. In this work, the influence of hydroxyl groups (Z-OH2+, Z-OH, Z-O−) of acid-treated natural zeolite on the catalytic ozonation of methylene blue (MB) contaminated waters is analysed. A Chilean natural zeolite was acid-treated using HCl (2.44M). Acid-treated zeolite was chemically and physically characterised by N2 adsorption at 77K, X-ray fluorescence, acidimetric–alkalimetric titration, and by NH3 and CO2 temperature-programmed desorption methods. Fourier transform infrared spectroscopy of pyridine adsorption was used to elucidate the nature and strength of acidic sites resulting from the acid treatment of natural zeolite. Experimental results obtained here are kinetically modelled using a set of two homogeneous and three heterogeneous surface reactions. Moreover, the quantitative effects of single ozonation, adsorption and coupled treatment on MB removal rate, together with the effect of pH and the presence of radical scavengers are analysed. Brønsted acid sites in the form of proton-donating OH groups (Z-OH) of acid-treated zeolite are claimed here to play an important role on the catalytic ozonation of MB in water, acting as active sites for the adsorption of reacting species. The higher catalytic activity is observed at pH above the pH of point of zero charge (pHPZC) and could be related to the presence of surface hydroxyl groups in the deprotonated form.