Role Of Surface Hydroxyl Groups Research Articles

Unveiling the Critical Role of Surface Hydroxyl Groups for Electro-Assisted Uranium Extraction from Wastewater.

The electro-driven extraction of uranium from fluorine-containing uranium wastewater is anticipated to address the challenge of separating fluoro-uranium complexes in conventional technologies. Herein, we developed hydroxy-rich cobalt-based oxides (CoOx) for electro-assisted uranium extraction from fluorine-containing wastewater. Relying on theoretical calculations and other spectral measurements, the hydroxy-rich CoOx nanosheets can enhance the affinity for uranium due to the existence of a substantial quantity of hydroxyl groups. Accordingly, the CoOx nanosheets exhibit outstanding U(VI) removal efficiency in the presence of fluorine ions. Through the utilization of X-ray absorption fine structure (XAFS), we confirm that hydroxy-rich CoOx nanosheets capture free uranyl ions to form a sturdy 2Oax-1U-3Oeq configuration, which can be achieved through electro-driven fluorine-uranium separation. Notably, for the first time, the whole reaction process of uranium species on the CoOx surface from the initial uranium single atom growth to uranium oxide nanosheets is monitored by aberration-corrected transmission electron microscopes (AC-TEM). This work provides a paradigm for the advancement of novel functional materials as electrocatalysts for uranium extraction, as well as a new approach for studying the evolution mechanism of uranium species.

Synergistic enhancement of the catalytic performance of BiOBr: The role of surface hydroxyl groups and amorphous FeOOH

The performance of photocatalysts need to be further improved in sewage treatment. In this study, polyethylene glycol (PEG) and zinc nitrate hexahydrate (Zn(NO3)2•6 H2O) co-modified BiOBr with deposition of amorphous FeOOH (AF/ZPBB) is synthesized via precipitation-immersion method. Amazingly, the adsorption capacity of catalysts for organic pollutants is enhanced through surface hydroxyl (-OH) induced by PEG and Zn2+. Meanwhile, the photocatalytic performance of AF/ZPBB is improved by reducing its energy gap (Eg) and suppressing the recombination of photogenerated carriers owing to the presence of amorphous FeOOH. Specifically, the degradation rates for rhodamine B (RhB) and tetracycline hydrochloride (TCH) are 5.5 times and 4.2 times higher than those of pure BiOBr catalyst, respectively. In addition, AF/ZPBB displays pH stability in the pH range of 2–10. After 5 cycles of reaction, only a slight catalytic performance is reduced. The reason is mainly attributed to the reduction of the -OH content, thus inhibiting the synergistic effect of adsorption and photocatalysis. Finally, •O2- is confirmed to be the main active species using ESR and active species capture tests. This work provides a new design approach for effectively enhancing catalytic performances of inorganic semiconductor photocatalysts.

Reduction of Cr(VI) to Cr(III) by Activated Carbon Cloth through Adsorption and Electrochemical Processes

Effective electrode materials are required to eliminate high concentrations of toxic Cr(VI) contaminants from industrial effluents. Kynol activated carbon cloth (CC) is a commercial, high-surface-area, and mechanically stable carbon material that can be used for adsorption and/or electrochemical reduction processes. Here, the mechanisms of Cr(VI) adsorption and reduction by CC in the absence or presence of an applied potential were investigated using X-ray photoelectron spectroscopy, scanning electron microscopy/energy-dispersive spectroscopy, Raman, cyclic voltammetry, and chronocoulometry experiments. The pH change close to the CC electrode during the electrochemical process was monitored using a solution containing Bromo-cresol green as an indicator of the solution pH. The role of surface hydroxyl groups (−OH) on CC in (1) the adsorption of Cr(VI) and (2) the reduction of Cr(VI) to Cr(III) was elucidated. As found, redox reactions between Cr(VI) and surface −OH groups on CC led to the chemical reduction of Cr(VI) to Cr(III). Without an applied potential, the chemical reduction of Cr(VI) to Cr(III) was limited by the number of surface −OH groups on CC. With an applied potential of −0.6 V on CC, the Cr(VI) adsorption/reduction was 2.1 times faster and 1.5 times higher than that without an applied potential after 7 h. With an applied potential, the CC adsorbed Cr(VI) and chemically and electrochemically reduced Cr(VI) to Cr(III). This work indicates that for Kynol CC, the electrochemical reduction process is superior to adsorption when optimizing an electrochemical system to achieve a faster and higher reduction of Cr(VI) to Cr(III).

The important role of surface hydroxyl groups in aluminum activation during phyllosilicate mineral acidification

Phyllosilicate minerals are the important components in soils and an important source of activated aluminum (Al) during soil acidification. However, the mechanisms for Al activation in phyllosilicate minerals were not understood well. In this paper, the effect of phyllosilicate surface hydroxyl groups on Al activation during acidification was studied after the minerals were modified with inorganic and organic materials. After modification of kaolinite, montmorillonite, and illite with fulvic acid (FA-), iron oxide (Fe-), Fe combined with FA (Fe-FA-), and siloxane (Si–O-), the interlayer spaces were altered. For instance, when modified with Fe, Fe entered the interlayer spaces of kaolinite and montmorillonite and changed the interlayer spaces of both minerals but did not affect that of illite. Also, the other modification methods had significant effects on the interlayer space of montmorillonite but not on kaolinite and illite. It was observed that all the modification strategies inhibited Al activation during acidification by reducing the number of hydroxyl groups on the mineral surfaces and inhibiting protonation reactions between H+ and hydroxyl groups. Nevertheless, the inhibition effect varies with the type of phyllosilicate mineral. For kaolinite (Kao), the inhibition effect of the different modification methods on Al activation during acidification followed: Fe-FA-Kao > Fe-Kao > Si–O-Kao > FA-Kao. Additionally, for montmorillonite (Mon), the inhibition effect was in the order: Si–O-Mon > Fe-Mon > Fe-FA-Mon > FA-Mon, while for illite, it was: Fe-illite > Si–O-illite ≈ Fe-FA-illite > FA-illite. Thus, the hydroxyl groups on the surfaces and edges of phyllosilicate minerals play an important role in the activation of Al from the mineral structure. Also, the protonation of hydroxyl groups may be the first step during Al activation in these minerals. The results of this study can serve as a reference for the development of new technologies to inhibit soil acidification and Al activation.

Surface hydroxyl-riched calcium carbonate and copper oxide composites for Fenton-like removal of bisphenol A

Surface functional groups have a key role in the removal of contaminants by advanced oxidation technology. Here, we explored the role of surface hydroxyl groups on pollutant removal by constructing novel surface hydroxyl-riched CaCO3@CuO. The hydroxyl groups on the surface of the composite accelerated the adsorption between the peroxymonosulfate and the catalyst, accelerating the catalytic reaction, and the kinetic removal rate of bisphenol A increased by 2.76 times. 1O2 is the dominant reactive oxygen species in the CaCO3@CuO/PMS/BPA system. The system has wide pH adaptability (pH = 3–11), good tolerance to complex water environments. This study provides novel insights into the mechanism of polymerization by surface hydroxyl groups in Fenton-like reactions for contaminant removal.

A sensitive humidity sensor at low pressure with SnO2 QDs

The humidity sensor working at low pressure has importance in fruit processing industries, space applications, and vacuum coatings. So, it is imperative to develop a sensor to measure very low levels of humidity in a vacuum domain. In the present work, a resistive humidity sensor made of SnO 2 Quantum Dots(QDs) is demonstrated. The huge surface area (160 m 2 /g) of QDs provides plenty of oxygen vacancies at the surfaces which help to absorb moisture even at a low pressure of ~5 mbar starting from the atmospheric pressure. These QDs characterized by XRD, TEM, and optical spectroscopic techniques reveal structural details including the presence of vacancies. The performance of the QDs sensor due to the humidity effect is further proved by flow dry N 2 flow. The role of surface hydroxyl groups and their tie-in with RH sensing with high reproducibility performance under vacuum are exclusively highlighted for the first time with SnO 2 QDs at room temperature. • Surfactant free synthesis of SnO2 quantum dots. • Huge specific area and surface defects creation for adsorption of moisture. • Room temperature humidity sensor performing even at low pressure of ~ 5 mbar. • Spectroscopic evidences of surface hydroxyl and H+ mediated resistive mechanism for humidity sensor.

Phenol Removal Performance and Mechanism Using Catalytic Ozonation with the Catalyst of Cobalt-doped α-MnO2

In this paper, Cobalt-doped α-MnO2 (i.e., Co-α-MnO2) were synthesized through hydrothermal method. Phenol was employed as targeted pollutants to investigate the catalytic ozonation performance of Co-α-MnO2. Results showed that Co-α-MnO2 significantly improved the phenol removal increased to 97.47 % after 40 min, which was 16.46 %, 38.92 % higher than that of α-MnO2 catalytic ozonation and single ozonation without catalyst. Additionally, the physicochemical properties of α-MnO2 and Co-α-MnO2 were analyzed using technologies such as XRD, TEM, BET and XPS. Compared to α-MnO2, Co-α-MnO2 has larger specific surface area (79.496 m2/g) and pore volume (0.0396 cm3/g), higher Mn3+ relative content (41.16 %) and adsorbed oxygen content (18.99 %). Also, the oxygen vacancy content, lattice defect content and surface hydroxyl content of Co-α-MnO2 are higher than that of α-MnO2, which could result in higher catalytic oxidation performance of Co-α-MnO2. The influence of masking agent showed that surface hydroxyl group, •OH and •O2- were involved in the catalytic ozonation of phenol. This study could help recognize the role of surface hydroxyl groups and active free radicals and demonstrate the contribution of reactive oxygen species on phenol removal in Co-α-MnO2 systems.

Dual Role of Surface Hydroxyl Groups in the Photodynamics and Performance of NiO-Based Photocathodes.

Photoelectrochemical (PEC) cells containing photocathodes based on functionalized NiO show a promising solar-to-hydrogen conversion efficiency. Here, we present mechanistic understanding of the photoinduced charge transfer processes occurring at the photocathode/electrolyte interface. We demonstrate via advanced photophysical characterization that surface hydroxyl groups formed at the NiO/water interface not only promote photoinduced hole transfer from the dye into NiO, but also enhance the rate of charge recombination. Both processes are significantly slower when the photocathode is exposed to dry acetonitrile, while in air an intermediate behavior is observed. These data suggest that highly efficient devices can be developed by balancing the quantity of surface hydroxyl groups of NiO, and presumably of other p-type metal oxide semiconductors.

High-efficiency degradation of bisphenol A by heterogeneous Mn–Fe layered double oxides through peroxymonosulfate activation: Performance and synergetic mechanism

Mn–Fe bimetal catalyst possesses excellent activation properties, and the enhancement of Mn/Fe redox cycle for electron transfer is related to the crystalline structure and surface functional groups. Therefore, material structure optimization is an effective strategy to improve its activation performance in advanced oxidation. In this study, Mn–Fe LDO catalyst with strong Mn/Fe synergistic effect was synthesized, and used for bisphenol A degradation. Under the condition of 0.4 g/L Mn-Fe LDO, 1.5 mM PMS and pH 7.0, Mn-Fe LDO/PMS system exhibited excellent degradation performance that 100% of BPA (20 mg/L) and 72.0% of COD could effective be degraded within 50 min. Five-run recycle and metal ions leaching experiments proved the excellent reusability and stability of Mn-Fe LDO. To deepen the understanding of catalytic mechanism, the synergistic effect and electron transfer between Mn and Fe were confirmed via XPS and CVs results. Moreover, the indispensable role of surface hydroxyl groups were clarified via phosphate masking experiment, ATR-FTIR and LSV analysis. The presence of Mn and Fe active sites and hydroxyl groups on Mn-Fe LDO surface could efficiently promote electron transfer, thus accelerating the redox cycles of Mn3+/Mn2+ and Fe3+/Fe2+. The generation of SO4·− and HO· as the main radicals was occurred on the surface of Mn-Fe LDO, and SO4·− played a major role during the reaction. On the basis of these experimental conclusions, the mechanisms of Mn–Fe LDO/PMS system for high-efficiency BPA degradation were proposed. GC-MS analysis was performed to detect the BPA degradation intermediates and propose the possible degradation pathways.

Modulating Hydroxyl-Rich Interfaces on Nickel-Copper Double Hydroxide Nanotyres to Pre-activate Alkaline Ammonia Oxidation Reactivity.

The surface hydroxyl groups of Nix Cu1-x (OH)2 play a crucial role in governing their conversion efficiency into Nix Cu1-x Ox (OH)2-x during the electro-chemical pre-activation process, thus affecting the integral ammonia oxidation reaction (AOR) reactivity. Herein, the rational design of hierarchical porous NiCu double hydroxide nanotyres (NiCu DHTs) was reported for the first time by considering hydroxyl-rich interfaces to promote pre-activation efficiency and intrinsic structural superiority (i.e., annulus, porosity) to accelerate AOR kinetics. A systematic investigation of the structure-function relationship was conducted by manipulating a series of NiCu DHs with tunable intercalations and morphologies. Remarkably, the NiCu DHTs exhibit superior AOR activity (onset potential of 1.31 V with 7.52 mA cm-2 at 1.5 V) and high ammonia sensitivity (detection limit of 9 μm), manifesting one of the best non-noble metal AOR electrocatalysts and electro-analytical electrodetectors. This work deepens the understanding of the crucial role of surface hydroxyl groups on determining the catalytic performance in alkaline medium.

The role of surface hydroxyl groups on a single-atomic Rh1/ZrO2 catalyst for direct methane oxidation.

A single atomic Rh catalyst immobilized on zirconia (Rh1/ZrO2) was modified by hydrothermal treatment to have surface hydroxyl groups and used for direct methane oxidation. Both O2 and H2O2 were used as oxidants. The amount of H2O2 could be reduced with enhanced methanol productivity in the presence of the surface hydroxyl groups. The formation of the surface hydroxyl groups upon hydrothermal treatment and their disappearance upon reaction were confirmed with diffuse reflectance infrared Fourier transform spectroscopy, indicating that the surface hydroxyl groups participate in the surface reaction.

Facet-dependent phosphate adsorptive reactivity by lanthanum hydroxides of different crystal structure: Role of surface hydroxyl groups

Lanthanum hydroxides (La(OH)3) materials play an important role in managing eutrophication. The crystal structure-reactivity relationship of La(OH)3 nanoparticles deserves in-depth investigation. Herein, three La(OH)3 nanomaterials of different crystal structures denoted as LH-1, LH-2 and LH-3 were freshly synthesized. LH-1 and LH-3 were in the form of rod-like crystallite with a dominant exposure of {100} facets which was occupied by singly La atom coordinated (-LaOH), doubly La atom coordinated (-La2OH) and triply La atom coordinated (-La3OH) hydroxyl groups. LH-2 presented as nano-plates and was majorly enclosed by {101} facets which was dominated by-La2OHhydroxyl groups. The quantity of -LaOH groups on three materials was positively correlated with the Langmuir constants derived from the adsorption isotherm, which suggested they were the predominant species for enhanced phosphate affinity. In comparison, the contribution of -La2OH to phosphate affinity was weaker, and function of -La3OH was negligible. The high affinity and fast kinetic of LH-3 towards phosphate could be attributed to the abundance of -LaOH groups on its main exposed crystal planes and relatively small grain size. These results provided new insights into the understanding of functions of facets onLa(OH)3 crystals which could generate new strategies for engineering novel materials for water treatment.

Defective magnesium ferrite nano-platelets for the adsorption of As(V): The role of surface hydroxyl groups.

In this work, magnesium ferrite (MgFe2O4) nano-platelets with rich defects and abundant surface hydroxyl groups were synthesized, and used for the removal of low concentration As(V) in aqueous solution. Results from scanning electron microscopy (SEM) showed that the as-synthesized MgFe2O4 nano-platelets were consisted of many individual nanospheres. Rietveld refinement of X-ray diffraction (XRD) data indicated that the Mg2+ ions substituted the Fe3+ ions at both the octahedral and the tetrahedral sites of the crystal structure. Batch adsorption experiment showed that the equilibrium concentration of As(V) could be reduced down to 4.9 μg·L-1 when the initial concentration of As(V) is 1 mg·L-1, which complied with the drinking water standard of WHO (10 μg·L-1). The adsorption capacity of synthesized MgFe2O4 towards As(V) was higher than commonly used iron oxide adsorbents (Fe3O4, γ-Fe2O3 and α-Fe2O3). Mechanistic studies proved that the superior adsorption capacity was attributed to: (1) increased amount of surface hydroxyl groups that resulted from the surface defects. (2) formation of tridentate hexanuclear surface complexes instead of bidentate binuclear complexes, and (3) formation of excess Mg-OH surface hydroxyl groups and As-Mg monodentate mononuclear surface complexes. This work disclosed the correlation of the superior As(V) adsorption ability with the surface hydroxyl groups in defective MgFe2O4, and propose MgFe2O4 as a potential candidate for the remediation of As-contaminated water.

Key Role of Surface Hydroxyl Groups in C–O Activation during Fischer–Tropsch Synthesis

C–O activation is a crucial step in Fischer–Tropsch synthesis (FTS). Several pathways have been proposed to activate CO, namely, direct C–O dissociation, activation via hydrogenation, and activation by insertion into growing chains. Invariably, very high barriers are calculated for both direct C–O dissociation and for hydrogenation at the O atom in CO* and RCO*, while hydrogenation at the C atom leads to oxygenates. We demonstrate that surface hydroxyl groups open a new pathway for CO* and RCO* activation via proton transfer to the O atom. In combination with the CO insertion mechanism, the calculated rate for this new pathway is consistent with the selectivity in FTS, and is in agreement with the kinetic effect of water. Hydroxyl group formation from O* is sufficiently fast to be quasi-equilibrated, and is much faster than CO2 formation. The role of surface hydroxyl groups as hydrogenating species is likely general, and involved in several oxygenate transformation reactions.

Evaluation of a Novel Water Treatment Residual Nanoparticles as a Sorbent for Arsenic Removal

A novel sorbent, water treatment residual nanoparticles (nWTR), was synthesized and used to remove As(V) from water solutions. The kinetics and equilibrium of As(V) adsorption by nWTR were evaluated. The kinetic data for nWTR at 3 different pH values indicate that As(V) sorption is biphasic, is favored at low pH values, and followed the power function and first‐order kinetics models fit. The results of the batch adsorption study showed that nWTR was effective in As(V) removal and its removal capability was 16 times higher than that of bulk WTR. Fourier transmission infrared (FTIR), SEM‐EDX spectra, and As fractionation results indicate the crucial role of surface hydroxyl groups in As retention onto nWTR and the high capability of nWTR to immobilize As(V). The stability of As‐nWTR surface complexes is suggested as less than 2% of adsorbed As(V) was released from nWTR after 4 consecutive desorption cycles.

Titanium Dioxide Nanoparticle Surface Reactivity with Atmospheric Gases, CO2, SO2, and NO2: Roles of Surface Hydroxyl Groups and Adsorbed Water in the Formation and Stability of Adsorbed Products

The reactivity of O–H groups on titanium dioxide nanoparticle surfaces with gas-phase carbon dioxide, sulfur dioxide, and nitrogen dioxide is compared. Carbon dioxide, sulfur dioxide, and nitrogen dioxide react with ca. 5, 50, and nearly 100%, respectively, of all hydroxyl groups on the surface at 298 K. As shown here, the surface reactivity of O–H groups with these three triatomic gases differs considerably due to different reaction mechanisms for adsorption and surface chemistry. In addition to investigating O–H group reactivity, the role of adsorbed water in the stability of different surface species that form from adsorption of carbon dioxide, nitrogen dioxide, and sulfur dioxide on hydroxylated TiO2 nanoparticles is probed as a function of relative humidity as is quantitative measurements of water uptake on TiO2 nanoparticles before and after surface reaction. These water uptake studies provide insights into the stability of adsorbed species on oxide surfaces under atmospherically relevant conditions as well as changes in particle hygroscopicity and adsorbed water dynamics following reaction with these three atmospheric gases.

Heterogeneous Uptake and Adsorption of Gas-Phase Formic Acid on Oxide and Clay Particle Surfaces: The Roles of Surface Hydroxyl Groups and Adsorbed Water in Formic Acid Adsorption and the Impact of Formic Acid Adsorption on Water Uptake

Organic acids in the atmosphere are ubiquitous and are often correlated with mineral dust aerosol. Heterogeneous chemistry and the uptake of organic acids on mineral dust particles can potentially alter the properties of the particle. In this study, heterogeneous uptake and reaction of formic acid, HCOOH, the most abundant carboxylic acid present in the atmosphere, on oxide and clays of the most abundant elements, Si and Al, present in the Earth's crust are investigated under dry and humid conditions. In particular, quantitative adsorption measurements using a Quartz Crystal Microbalance (QCM) coupled with spectroscopic studies using Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy are combined to allow for both quantification of the amount of uptake and identification of distinct adsorbed species formed on silica, alumina, and kaolinite particle surfaces at 298 K. These oxides and clay particles show significant differences in the extent and speciation of adsorbed HCOOH due to inherent differences in surface -OH group reactivity. Adsorbed water, controlled by relative humidity, can increase the irreversible uptake of formic acid. Interestingly, the resulting layer of adsorbed formate on the particle surface decreases the particle hydrophilicity thereby decreasing the amount of water taken up by the surface as measured by QCM. Atmospheric implications of this study are discussed.

Radical Chain-Reaction of Terminal-Unsaturated Organic Molecules on Water-Saturated Si(100)-(2 × 1): The Role of Surface Hydroxyl Groups

The radical initiated hydrosilylation of terminated unsaturated organic molecules on water saturated Si(100)-(2 × 1) is systematically studied using density functional theory (DFT) calculations in the framework of periodic surface model. Two possible radical chain-reaction mechanisms including the H-abstraction from surface Si–OH or Si–H group and the direct abstraction of a −OH group are studied. It is found that the surface −OH group acts as a medium for the radical chain-reaction. The chain-reaction can proceed through abstracting a H-atom from surface −OH group, while the direct abstraction of −OH group is prevented by high energy barriers. The O-adatom caused by the H-abstraction from surface −OH group promotes the reactivity of the newly generated surface dangling bond toward sequentially attached molecules. Nonetheless, it shows double-side effects on the following H-abstraction along the dimer row direction. It can either facilitate or hinder the following H-abstraction process depending on its insertion mode into the surface Si–Si skeleton. Based on the computed reaction rates of H-abstractions in different pathways, the possible growth behaviors of organic molecules on water-saturated Si(100)-(2 × 1) are predicted. The reaction of propylene and aldehyde without a conjugate βC substituent is predicted to lead to formation of disordered monolayer structures. In contrast, the styrene and benzaldehyde tend to grow quasi-one-dimensional molecular wires within the single Si–Si dimer row.

Time-Resolved DRIFTS, MS, and Resistance Study of SnO2 Materials: The Role of Surface Hydroxyl Groups in Formation of Donor States

Time-resolved DRIFTS, MS, and resistance measurements were used to study the interaction of undoped and Pd-doped SnO2 with H2 in air and argon at 300 °C. Using first-order kinetics, we compare the time constants for the resistance drop and its partial recovery with those of the surface hydroxyl evolution and water formation in the gas phase upon exposure to hydrogen. In the case of the undoped oxide, resistance and bridging hydroxyls (BOHs) evolve similarly, manifesting a fast main drop followed by recovery at a similar rate. The rate of water formation for this material was found to be much slower than that of the main drop in both the resistance and BOHs. In contrast, the resistance change for SnO2–Pd appeared to be similar to that of water formation, and no correlation was found between the evolution of resistance and surface OHs. Isotopic exchange on both materials revealed that water formation occurs via fast and slow hydrogen transfer to surface oxygen species. While the former originates from just-...

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.