Strong Oxidant Species Research Articles

Boosting photocatalytic multi-VOCs decontamination over COF-based heterojunction via targeted construction of Ov–M–N charge channel (M = Ti, Zn, W, Ce) and –NH2 functionalization

Covalent organic frameworks (COF) based materials have exhibited excellent gas and visible light absorption capability, yet are very difficult to generate strong oxidative species for photocatalytic mineralization of volatile organic compounds (VOCs). Here, a facile in situ modulation protocol developed could enable the growth of MOx (M = Ti, Zn, W, Ce) with oxygen vacancy (Ov) on –NH2-functionalized COF surfaces to construct NH2–COF/Ov–MOx Z–scheme heterojunctions of excellent stability and efficiency (98.3 %) in photo-oxidation of formaldehyde, acetaldehyde, and acetone. The –NH2 functionalization enhanced VOC chemisorption via H-bond interaction. Moreover, the constructed fast charge transfer channel (Ov–M–N) at the interface not only promoted directional migration of photo-excited carrier, activated adsorbed O2 and H2O to quickly generate strong •OH, but also effectively inhibited injurant formation to realize the precise control of the conversion path. These findings offer new insights into customizing the interfacial structure of COF for indoor air purification.

Efficient catalytic activity of NiO and CeO2 films in benzoic acid removal using ozone.

This research focuses on the synthesis of NiO and CeO2 thin films using spray pyrolysis for the removal of benzoic acid using ozone as an oxidant. The results indicate that the addition of CeO2 films significantly enhances the mineralization of benzoic acid, achieving a rate of over 80% as the CeO2 films react with ozone to produce strong oxidant species, such as hydroxyl radicals, superoxide radicals, and singlet oxygen as demonstrated by the presence of quenchers in the reaction system. The difference in catalytic activity between NiO and CeO2 films was analyzed via XPS technique; specifically, hydroxyl oxygen groups in the CeO2 film were greater in number than those in the NiO film, thus benefitting catalytic oxidation as these species are considered active oxidation sites. The effects of nozzle-substrate distances and deposition time during the synthesis of the films on benzoic acid removal efficiency were also explored. Based on XRD characterization, it was established that the NiO and CeO2 films were polycrystalline with a cubic structure. NiO spherical nanoparticles were well-distributed on the substrate surface, while some pin holes and overgrown clusters were observed in the CeO2 films according to the SEM results. The stability of the CeO2 films after five consecutive cycles confirms their reusability. The retrieval of films is easy because it does not require additional separation methods, unlike the catalyst in powder form. The obtained results indicate that the CeO2 films have potential application in pollutant removal from water through catalytic ozonation.

Catalytic Ozonation of Polluter Benzene from -20 to >50 °C with High Conversion Efficiency and Selectivity on Mullite YMn2O5.

Catalytic decomposition of aromatic polluters at room temperature represents a green route for air purification but is currently challenged by the difficulty of generating reactive oxygen species (ROS) on catalysts. Herein, we develop a mullite catalyst YMn2O5 (YMO) with dual active sites of Mn3+ and Mn4+ and use ozone to produce a highly reactive O* upon YMO. Such a strong oxidant species on YMO shows complete removal of benzene from -20 to >50 °C with a high COx selectivity (>90%) through the generated reactive species O* on the catalyst surface (60 000 mL g-1 h-1). Although the accumulation of water and intermediates gradually lowers the reaction rate after 8 h at 25 °C, a simple treatment by ozone purging or drying in the ambient environment regenerates the catalyst. Importantly, when the temperature increases to 50 °C, the catalytic performance remains 100% conversion without any degradation for 30 h. Experiments and theoretical calculations show that such a superior performance stems from the unique coordination environment, which ensures high generation of ROS and adsorption of aromatics. Mullite's catalytic ozonation degradation of total volatile organic compounds (TVOC) is applied in a home-developed air cleaner, resulting in high efficiency of benzene removal. This work provides insights into the design of catalysts to decompose highly stable organic polluters.

Intrinsic mechanisms underlying the highly efficient removal of bacterial endotoxin and related risks in tailwater by dielectric barrier discharge plasma

Endotoxin is widely present in aquatic environments and can induce adverse health effects. In this study, dielectric barrier discharge (DBD) plasma was used to remove bacterial endotoxin from the tailwater of a wastewater treatment plant. The removal efficiency of total endotoxin activity was up to 92% with low electrical energy consumption (0.43 J mL−1%−1) after 180 s of the DBD plasma treatment, which was better than other previously reported methods. In the early stage of DBD plasma oxidation, the expression of genes related to cell morphology and bacterial antioxidant enzyme synthesis was distinctly down-regulated, suggesting that cell integrity was destroyed, leading to endotoxin release into the solution. Additionally, endotoxin synthesis in the cells was suppressed. The endotoxin in the solution was effectively removed by ·OH, 1O2, and O2·−generated by the DBD plasma, with second-order reaction rates of 2.69 × 1010, 2.20 × 107, and 8.60 × 108 mol−1 L s−1, respectively. The core toxic component of endotoxin (lipid A) was attacked by these strong oxidative species, generating smaller molecular fragments with low toxicity. Consequently, the inflammatory factors IL-6, IL-β, and TNF-α of endotoxin decreased by 3.4–4.8 folds after the DBD plasma treatment, implying that the health risks posed by endotoxin were greatly reduced. This study revealed the intrinsic mechanisms of the highly efficient removal of bacterial endotoxin by DBD plasma oxidation.

Diamondized carbon nanoarchitectures as electrocatalytic material for sulfate-based oxidizing species electrogeneration

The introduction of nanotechnology seems to be an imperative factor to intensify the synergic effects of electrocatalytic materials to produce strong oxidant species or to increase the active sites on their surfaces as well as to enhance the conversion yield in a fuel cell, high-added value products, electrolytic treatment for environmental protection or the detection limit in electroanalysis. Recently, a new type of 3D-diamond electrodes was developed with boron-doped carbon nanowalls (B:CNW), which was manufactured using the microwave plasma-assisted chemical vapor deposition (CVD) process, improving the charge transfer and enhancing the electrochemical performance. The applicability of a BDD/boron-doped carbon nanowalls (BDD/B:CNW) anodes to degrade organic pollutants has been already investigated; however, no attempts at the electrosynthesis of oxidizing species using these diamond-carbon nanostructures have been reported yet. Therefore, the electrosynthesis of sulfate-based oxidizing species was studied here to answer relevant questions from both fundamental and practical point-of-view. The results demonstrated that persulfate was efficiently produced at the BBD electrode, while that the ion-radical sulfate could be the most important oxidant at BDD/B:CNW anode when compared to other electrocatalytic materials, including BDD surfaces. Persulfate concentrations ranged from 3 to 6 µM, depending on the applied current density (2.5, 5.0, and 15 mA cm−2), at diamond electrodes. A dye-model pollutant - methyl orange (MO) was degraded below the limit of detection within 45 min using BDD/B:CNW when in-situ sulfate-based oxidizing species were electrogenerated. These kinds of 3D-diamond-carbon nanostructures are thus promising as novel electrocatalyst for various catalytic applications in the environmental and energy fields.

Removal of antibiotic rifampicin from aqueous media by advanced electrochemical oxidation: Role of electrode materials, electrolytes and real water matrices

One of the most commonly detected classes of pharmaceutical products in aquatic environments are antibiotics and their effective removal in sewage treatment plants is limited due to their refractory features. In this context, electrochemical technologies could be an alternative to decrease the pollution level and promote the complete elimination of antibiotics in water. For this reason, the electrochemical treatment of a synthetic effluent as well as different real water matrices polluted with antibiotic rifampicin was investigated, using different electrode materials (anodes: boron doped diamond, (BDD), Pt and PbO2; and cathodes: carbon felt (CF), graphite (Gr), stainless steel (SS) and titanium (Ti)). Effects on the variation of applied current density (j) and supporting electrolyte were examined during the degradation of the antibiotic. Comparative studies have clearly showed that the degradation of rifampicin had better results by using BDD and CF as anode and cathode, respectively, where the process efficiency increased when an increase on the j was attained. Complete color removal was achieved at all j applied (chromophore rifampicin group gives a red-orange color for solutions), whereas only at higher j leads to complete organic matter (in terms of chemical oxygen demand (COD)) removal. For a selected cathode, the efficiency of the anode materials follows the trends BDD>PbO2>Pt, whereas that of cathode follows CF>Ti>SS≈Gr for a selected anode material. Using Na2SO4, Na2CO3 or NaCl, the production of strong secondary oxidant species was favored, promoting the oxidation of dissolved organic matter in synthetic effluents. Meanwhile, when the BDD/CF electrochemical cell was employed with different real water matrices, the degradation and mineralization of the drug was independent of this parameter. Oxalic, acetic, fumaric and maleic acids were the final organic byproducts of rifampicin degradation with the release of heteroatom N under NO3‒ and NH4+ forms.

Promote reactants activation and key intermediates formation for facilitated toluene photodecomposition via Ba active sites construction

The establishment of active sites can obviously promote photocatalytic efficiency, but its role in activation mechanism and generation of key reaction intermediates during toluene mineralization remains unsolved. We reveal that the benzene ring opening is the rate-limiting step of mineralization reaction, and the inert CC bond in the ring is the crucial reason for the shortage mineralization of previous catalysts. In this work, the Sr1-xBaxTiO3 solid solution was prepared as a model photocatalysts to reveal the mechanism of photocatalytic toluene degradation. The electronic local center was constructed at the substituted Ba sites, which intensified the charge transfer between catalyst surface and adsorbed molecules. The strong oxidative species generated by enhanced activation further facilitated the conversion of toluene to generate benzoic acid as the key reaction intermediate before ring-opening. Through the combined theoretical calculation and in situ characterization methods, it was revealed that efficient degradation and stable mineralization of toluene in photocatalysis can be achieved by activating toluene and promoting the formation of key reaction intermediates. This study could advance a new viewpoint for safe and efficient photocatalytic air purification.

Recent progress in transition metal oxide/sulfide quantum dots-based nanocomposites for the removal of toxic organic pollutants

Water is an essential solvent that is extremely necessary for the survival of life. Water pollution due to the increased utilization of water for various processes, including domestic and industrial activities, poses a special threat that contaminates both surface and ground water. In recent years, advanced oxidation processes (AOPs) have been applied to deal with wastewater problems, which is a green method used to oxidize organic contaminants with strong oxidative radical species. Among the AOPs, photocatalytic technology is one of the most promising strategies for wastewater cleaning, which fulfills the aims of environmentally friendly and sustainable development. Owing to their unique electronic, optical, and structural properties, nanoscale semiconductors have received substantial interest as materials for AOPs, particularly inspired by their superb quantum confinement effects and large surface-area-to-volume ratio, which are essential for catalytic reaction kinetics. Recent advancements have revealed that semiconductor nanocrystals, known as quantum dots (QDs), are newly emerging zero-dimensional (0-D) nanomaterials, which have garnered much attention owing to their special physiochemical characteristics such as high conductivity, thermo-chemical and opto-mechanical stability, high adsorption coefficients, and, most importantly, their admirable recyclability. In this review, we provide a clear understanding of the importance of semiconductor QD-based nanocomposites in the degradation of organic pollutants, in addition to the mechanism involved in the reaction process. Following this, the enhancement of different materials, such as metal oxides and metal sulfide QD-based nanocomposites, is discussed in the context of combating environmental pollution.

Photo-electrochemical degradation of wastewaters containing organics catalysed by phosphate-based materials: a review

Over the last few years, new advanced oxidation processes (AOPs) have been developed to the removal of organic pollutants from waters and wastewaters. The effectiveness of these AOPs as powerful way for the removal of POPs is related to the in situ production of strong oxidative species such as the hydroxyl radicals (·OH). Among the techniques involving AOPs, photo-electrocatalysis (PEC) has come out as a powerful AOP consisting of the combination of both photocatalytic and electrocatalytic processes for the objective to retard and/or avoid the fast recombination of the formed electron/hole pairs during the PEC. This can be achieved by the extraction of the photogenerated electrons directed to the cathode when an external bias potential is applied to the photoanode. This general and critical review deals with the application of PEC to the remediation of organic pollutants from wastewaters (i.e. dyeing effluents) using phosphate-based photoanodes namely BiPO4, Ag3PO4, Cu2(OH)PO4 and others. A detailed description of the PEC power of different photoanode has been discussed. The fundamentals and main applications of photo-electrochemical oxidation are reported. Finally, some critiques are proposed in order to improve and develop new effective photoanodes with perspectives to industrial applications.

Anodic Oxidation of Methylene Blue Dye from Aqueous Solution Using SnO2 Electrode

This study was performed to investigate the electrochemical oxidation of a solution containing methylene blue dye by using a tin oxide (SnO2) electrode. The effect of several operating factors such as electrolyte types, current density, initial dye concentration, and pH were investigated by following the discolorationand COD removal. The results show that the maximum color was removed by using chloride supporting electrolyte (i.e. KCl and NaCl) indicating that the indirect oxidation was promoted by the strong oxidant species (i.e. Cl2 and ClO–) generated at the anode surface. The best experimental conditions were attained for i = 60mA/cm2, 1% KCl and pH = 3, in which 100% of color was removed after 30 minutes and the COD removal reached 80.9% after 120 min. These results reveal that the anodic oxidation technique using SnO2 electrode could be used to remove the methylene blue dye from textile wastewater.

2D/2D Wg-C3N4/g-C3N4 composite as “Adsorb and Shuttle” model photocatalyst for pollution mitigation

Semiconductor mediated photodegradation of dyes is an important application of heterogeneous photocatalysis. Frequently, transitional metal oxides, sulfides and oxometallate photocatalyst are accentuated in pollutants degradation burdening the cost and secondary pollution of metal leaching. In this work, a metal-free 2D/2D photocatalyst is built by pristine g-C3N4; supported on the acid-treated protonic white g-C3N4 substrate for concurrent high adsorption and excellent visible light absorption as “Adsorb & Shuttle (A&S)” model photocatalyst. Herein, oxidized white g-C3N4 provides excess active sites for binding of dye molecules through adsorption and delivers it to photoactive g-C3N4 sites by surface diffusion, while g-C3N4 degrades the organic pollutants by releasing strong reactive oxidative species (ROS). The formation of face-to-face matching 2D/2D Van der Waal’s (vdW) type homojunction reduced exciton recombination and improved photoactivity. The current A&S strategy may provide new insights into the rational design of g-C3N4 based adsorption induced photocatalysts for effective and rapid decomposition of organic pollutants.

Electrochemical oxidation of paracetamol in water by graphite anode: Effect of pH, electrolyte concentration and current density

Paracetamol is one of the micropollutant in water and most frequently used drugs as moderate pain reliever. These micropollutants are serious threat to human and environment. In the present investigation, we made attempt to degrade the electrochemical oxidation of paracetamol in water by graphite as anode. Electrooxidation behavior of paracetamol at graphite anode was tested by cyclic voltammetry technique performed in the potential range of -1.0 to +1.0 V versus Ag/AgCl. The optimized conditions were obtained by varying different factors, such as electrolyte concentration (0.02-0.1 M), current density (3.1–7.1 mA/cm2), initial pH (4–8) and paracetamol concentration (20 mg L−1). The results showed that the maximum removal of paracetamol concentration, chemical oxygen demand (COD) and total organic carbon (TOC) reached >90%, >82% and >65% after 240 min electrolysis at an initial pH 4, having paracetamol concentration of 20 mg L−1 at a constant current density of 5.1 mA/cm2 with 0.1 M Na2SO4 supporting electrolyte. Different SO42- concentrations in water promoted the electro generation of strong mediator oxidant species, such as OH, SO4- and S2O82- increasing the removal efficiency of paracetamol. The degradation of paracetamol and its mineralization trend were monitored by UV–vis spectrophotometric method and total organic carbon (TOC) analyzer, respectively. FT-IR spectra confirmed that the functional group changes after electrolysis of paracetamol. HPLC studies revealed the byproduct (hydroquinone, benzoquinone and carboxylic acid) formation during the electrolysis process. On the other hand, researchers are actively involved in ozonation, photocatalysis, activated charcoal and biological treatments etc., to remove/degrade micropollutant, which are major drawbacks for the implications.

Electrochemical Decontamination Process an Effective Alternative to Treat Textile Effluents

Keeping in view the growing concern regarding aquatic pollution by effluent water from textile industries containing complex compounds, the present study was under taken with the view to study the efficiency of the removal by electrochemical oxidation. In recent year the use of electrochemistry for the investigation of environmental pollution is being thoroughly investigated. Reactive dye mainly composed of complex organic molecules are highly stable to decomposition in normal condition. Textile industry wastewater containing dyes poses a chronic and synergistic effects to environment. This study examines the electrochemical oxidation of the organic dyes. All the experiments were performed using a Filter Press Flow Cell Reactor containing Ti/Ti0.7Ru0.3O2 anode and stainless steel as cathode in which impact of the current density (5 – 20 mA cm-2), electrolytes (NaCl, Na2SO4, H2SO4), Sodium chloride concentration (0.02 – 0.10 mol L-1) were studied. The electrode used were characterized by the cyclic voltammetry experiments. The Reaction Kinetics and energy consumption parameters were studied of the electrochemical process. Results obtained in this research clearly demonstrated that the effect of the electro generated strong oxidant species active chlorine, depends on electro catalytic mechanism followed on surface of Ti/Ti0.7Ru0.3O2 resulting in the improvement of the color. Results also confirmed a high removal efficiency according to environment and electrolyte used in the process. However, there is a limit of NaCl for treating real effluents avoiding the formation of organochloride compounds; and it is a subject of critical importance, from the environmental point of view, to apply this alternative treatment. Keyword: textile effluents, contaminants, electrochemical process, Kinetics

Electrochemical decolorization of Rhodamine B dye: Influence of anode material, chloride concentration and current density

Surface water contamination by dyes released from a variety of industries is an environmental problem of great concern. However, electrochemical oxidation is a promising alternative for water treatment. In this paper, we studied the electrochemical oxidation of Rhodamine B (RhB) dye on the Ti/RuO2–IrO2 (DSA®) and SnO2 anodes comparing their efficiencies. The effect of some parameters, such as current density, initial pH (pH0), nature, concentration of electrolyte and temperature at the electrochemical oxidation was investigated evaluating the decolorization and the chemical oxygen demand (COD) removal at optimal conditions. Complete decolorization of RhB was achieved in the presence of chloride ions at different times using both electrodes. An optimum efficiency was obtained at pH 6.5, T = 25 °C. Also, the current density of 40 mA cm−2 using the DSA electrode in NaCl 0.05 mol L−1+ Na2SO4 0.1 mol L−1 mixture solution as a supporting electrolyte, 100% color removal and 61.7% chemical oxygen demand removal after 90 min of electrolysis were achieved. DSA showed better performance than SnO2 in wide operating conditions and was proved to be more cost-effective and more efficient. The effectiveness of the degradation is explained by indirect electrochemical oxidation, where in the presence of chlorides electrolyte leads to the electro-generation of strong oxidant species, such as Cl2 and ClO− ions, improving the efficiency of treatment at both electrodes.

Performance of (in)active anodic materials for the electrooxidation of phenolic wastewaters from cashew-nut processing industry

This study investigated the anodic oxidation of phenolic wastewater generated by cashew-nut processing industry (CNPI) using active (Ti/RuO2-TiO2) and inactive (boron doped diamond, BDD) anodes. During electrochemical treatment, various operating parameters were investigated, such as current density, chemical oxygen demand (COD), total phenols, O2 production, temperature, pH, as well as current efficiency and energy consumption. After electrolysis under optimized working conditions, samples were evaluated by chromatography and toxicological tests against L. sativa. When both electrode materials were compared under the same operating conditions, higher COD removal efficiency was achieved for BDD anode; achieving lower energy requirements when compared with the values estimated for Ti/RuO2-TiO2. The presence of Cl− in the wastewater promoted the electrogeneration of strong oxidant species as chlorine, hypochlorite and mainly hypochlorous acid, increasing the efficiency of degradation process. Regarding the temperature effect, BDD showed slower performances than those achieved for Ti/RuO2-TiO2. Chromatographic and phytotoxicity studies indicated formation of some by-products after electrolytic process, regardless of the anode evaluated, and phytotoxic action of the effluent. Results encourage the applicability of the electrochemical method as wastewater treatment process for the CNPI, reducing depuration time.

Anisotropic Electronic Characteristics, Adsorption, and Stability of Low-Index BiVO4 Surfaces for Photoelectrochemical Applications.

Many experimental results reveal different activities among different low-index surfaces of photocatalysts. The current investigation focuses on the theoretical understanding of the electronic characteristics, surface activity, and stability of different low-index surfaces of BiVO4 toward water splitting using first-principle calculations. The results indicate that BiVO4 has four types of low-index surfaces, namely, (010)T1, (010)T2, (110)T1, and (1̅11)T1. The different band edge potentials of the surfaces, resulting from the variation of the electrostatic potential, lead to a higher oxidation ability for (010)T1 and (010)T2 than for (110)T1 and (1̅11)T1 surfaces. The electrons prefer to accumulate on (010)T1 and (010)T2 surfaces, whereas holes like to accumulate on (110)T1 and (1̅11)T1 surfaces during a photocatalytic process. Moreover, investigation on the adsorbed intermediates during the water-splitting process indicates that the oxygen evolution reaction on BiVO4 surfaces is mainly dominated by the reaction OH* ↔ O* + H+ + e-, and (110)T1 and (1̅11)T1 surfaces are energetically more favorable as photoanodes for water splitting than (010)T1 and (010)T2. Furthermore, the BiVO4 surface as photoanodes tend to be unstable and can easily be corroded with or without the presence of an oxidative environment, however, there is an exception for the BiVO4 (010)T1 and (010)T2 surfaces, which are thermodynamically stable in the solution when there are no strong oxidative species. These results provide important insights into the anisotropy behaviors among low-index surfaces of BiVO4 for photocatalytic reactions.

Fluorescent real-time quantitative measurements of intracellular peroxynitrite generation and inhibition

Peroxynitrite (ONOO-), a strong oxidant species, is produced by the reaction of nitric oxide (NO) and superoxide (O2.-) radicals. It plays an important role as a biological regulator in numbers of physiological and pathological processes. In this study, we developed fluorescence-based real-time quantitative measurements to detect intracellular ONOO-. The probe DAX-J2 PON Green showed high selectivity toward ONOO- over other competing species, and has been successfully applied in microplate reader and flow cytometer to quantitatively measure endogenous ONOO- production. Moreover, the results demonstrated the inhibitory effects of curcumin on intracellular ONOO- generation.

Enhanced Degradation of the Industrial Textile Dye Disperse Red BG by Electrochemical Process with Different Anodes

The in-situ generation of strong oxidants, such as hydroxyl radicals (•OH), persulfates and/or active chlorine species, which react with organics up to conversion into CO2, H2O and inorganic ions, depends on the nature of electrode surface; and their applicability have currently received great attention for the remediation of toxic and biorefractory organic pollutants. Therefore, the effect of four electrocatalytic materials (Boron doped diamond (BDD), PbO2, Ti/Ru0.3Ti0.7O2 and Ti/Pt) for the electro-oxidation of the industrial textile dye DRBG was studied in sulfate and chloride medium in order to understand the role of anodic material as well as the production of oxidants. Results showed that, a higher mineralization rate was obtained using BDD and PbO2 electrodes in sulfate media, due to the generation of •OH and persulfate. However, the mineralization rate of DRBG increased when NaCl was used as supporting electrolyte, reaching almost a total mineralization of the solutions using Ti/Ru0.3Ti0.7O2 and BDD electrodes at short electrolysis time, due to the action of active chlorine species. Aromatic intermediates are formed initially, during the electrochemical oxidation of DRBG, then, short-linear carboxylic acids and inorganic ions were formed until a complete mineralization of initial dye as a consequence of the homogeneous reactions of strong oxidant species.

Parabens abatement from surface waters by electrochemical advanced oxidation with boron doped diamond anodes.

The removal efficiency of four commonly-used parabens by electrochemical advanced oxidation with boron-doped diamond anodes in two different aqueous matrices, namely ultrapure water and surface water from the Guadiana River, has been analyzed. Response surface methodology and a factorial, composite, central, orthogonal, and rotatable (FCCOR) statistical design of experiments have been used to optimize the process. The experimental results clearly show that the initial concentration of pollutants is the factor that influences the removal efficiency in a more remarkable manner in both aqueous matrices. As a rule, as the initial concentration of parabens increases, the removal efficiency decreases. The current density also affects the removal efficiency in a statistically significant manner in both aqueous matrices. In the water river aqueous matrix, a noticeable synergistic effect on the removal efficiency has been observed, probably due to the presence of chloride ions that increase the conductivity of the solution and contribute to the generation of strong secondary oxidant species such as chlorine or HClO/ClO -. The use of a statistical design of experiments made it possible to determine the optimal conditions necessary to achieve total removal of the four parabens in ultrapure and river water aqueous matrices.

Keggin heteropolyacids supported on TiO2 used in gas-solid (photo)catalytic propene hydration and in liquid-solid photocatalytic glycerol dehydration

(Photo)catalytic propene hydration to 2-propanol and glycerol dehydration to acrolein were carried out by using Keggin heteropolyacids (HPAs) supported on TiO2. Binary materials have been prepared by impregnation of H3PW12O40, H3PMo12O40 and H4SiW12O40, on TiO2 Evonik P25. Moreover, a binary material consisting of H4SiW12O40 and TiO2 was prepared via a hydrothermal treatment and tested for the same reactions. All the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with energy dispersive X-ray (EDX) measurements, diffuse reflectance spectroscopy (DRS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The supported Keggin HPA species played a key role both for the catalytic and for the photo-assisted catalytic reactions due to their strong acidity and ability to form strong oxidant species under UV irradiation.