Search

In this study, platinized mixed oxides (TiO2–Nb2O5) were tested on photocatalytic hydrogen production from a glycerol solution under UV light. Different samples with different Ti:Nb ratios were prepared by using a simple method that simultaneously combined a physical mixture and a platinum photochemical reduction. This method led to improved physicochemical properties such as low band gap, better Pt nanoparticle distribution on the surface, and the formation of different Pt species. Niobia content was also found to be an important factor in determining the overall efficiency of the Pt–TiO2–Nb2O5 photocatalyst in the glycerol reforming reaction. The photocatalytic results showed that Pt on TiO2–Nb2O5 enhanced hydrogen production from the aqueous glycerol solution at a 5 wt% initial glycerol concentration. The influence of different operating conditions such as the catalyst dosage and initial glycerol concentration was also evaluated. The results indicated that the best hydrogen and methane production was equal to 6657 μmol/L and 194 μmol/L, respectively after 4 h of UV radiation using Pt/Ti:Nb (1:2) sample and with 3 g/L of catalyst dosage. Moreover, the role of water in photocatalytic hydrogen production was studied through photocatalytic activity tests in the presence of D2O. The obtained results confirmed the role of water molecules on the photocatalytic production of hydrogen in an aqueous glycerol solution.

This work aimed to synthesise a magnetic photocatalyst based on Ag-TiO2 nanoparticles supported on Algerian Halloysite clay (HKDD3) loaded with magnetite Fe3O4 through a solvothermal method. The pr...

Aims: The aim of this work was to investigate the impact of light modulation parameters on the degradation of terephthalic acid, an organic model pollutant, within a heterogeneous photocatalytic system under visible light. For this purpose, a fixed bed photocatalytic reactor, irradiated by white-light LEDs matrix controlled by a system for light dimming, was used. The bed consisted of a nitrogen-doped titania photocatalyst deposited on polystyrene pellets. Background: Wastewater containing TPA can be treated into conventional aerobic biological units. However, the mineralization of TPA is slow and inefficient and its presence negatively influences the biodegradation efficiency because this pollutant inhibits microbial growth. Nowadays, innovative technologies named advanced oxidation processes (AOPs), such as heterogeneous photocatalysis with UV and visible light, ozonation, and Fenton oxidation, have gained popularity for effective organic destruction of TPA from wastewater. The heterogeneous photocatalytic oxidation process of the TPA under visible light is the most advantageous process in terms of both fixed and operating costs. Objective: In this work, the successful application of light modulation techniques for degradation of TPA using a photocatalytic system with supported visible active photocatalysts (N-doped TiO2) immobilized on polystyrene pellets is reported. In particular, sinusoidal lighting has been used analyzing the influence of the period of oscillation and the amplitude of light modulation on the reaction kinetics, in such a way as to minimize the times and energy costs for the process. Methods: To evaluate the influence of light modulation on the efficiency of the TPA removal, a discontinuous system composed of a Recirculating Photocatalytic Fixed Bed Reactor (RPFBR) irradiated by a matrix of white light LEDs was used. The flat geometry of the photoreactor guarantees the efficient excitation of the photocatalyst. An amount of 250 mL of aqueous solution with the initial TPA concentration of 12.5 ppm was applied in the photocatalytic tests lasting 180 min of irradiation fixed or sinusoidal modulated. Results: The results show that the variation of the oscillation period of the sinusoidal modulation has a pertinent influence on the photodegradation of TPA and a maximum value of the apparent kinetic constant, 0.0045 min-1 is found when the period of oscillation is 0.24 s. The sinusoidal modulation with optimal amplitude occurs with current between 50-200 mA, that shows the highest value of the apparent kinetic constant equal to 0.0046 min-1. The optimal sinusoidal modulation, as a consequence is with current between 50-200 mA and period of 0.24 s. From the data collected from the tests, it is possible to evaluate the energy cost necessary to obtain the reduction of 90% of the terephthalic acid in 1 m3 of polluted water for each modulation (E E/O), and compare these values with other tests for TPA degradation reported in the literature. The internal comparison with the three systems of literature shows that the optima sinusoidal modulation of LEDs matrix permits a strong reduction in the electrical energy consumption. Conclusion: Photocatalytic tests have demonstrated the improvement of the process energy efficiency using the light modulation technique. A further confirmation of the advantage of light modulation was obtained by comparing the energy costs required for the abatement of 90% of the terephthalic acid in 1m 3 of the photocatalytic system. Finally, a mathematical model for photocatalytic degradation of terephthalic acid within the recirculating fixed bed photocatalytic reactor, irradiated by white-light LEDs was developed.

The performances of a visible light active structured photocatalyst in the oxidation of arsenite to arsenate in aqueous solution were investigated. In particular, the photocatalytic active phase was Cu-doped ZnO, while polystyrene (PS) pellets were used as support. The Cu-doped ZnO photocatalyst was immobilized on polystyrene pellets surface by “solvent casting method” and characterized by different techniques. The photocatalytic tests were performed in a floating bed reactor using a visible LEDs strip as light source. The complete As(III) oxidation was achieved after 120 min of visible irradiation at a Cu-doped ZnO loading on polystyrene pellets equal to 5 wt%. Furthermore, the optimized photocatalyst was reused for several cycles without any substantial decrease of photocatalytic performances. In order to determine which reactive species plays a more significant role in the oxidation of As(III), the effects of different radical scavengers were tested. The results evidenced that OH and O2 − seem not to be the main oxidant for the direct As(III) oxidation, whereas the oxidation mechanism of As(III) using Cu-doped ZnO structure photocatalyst seems to be related to the h+ holes generated under visible light irradiation.

Ceria-supported vanadium catalysts were studied for H2S removal via partial and selective oxidation reactions at low temperature. The catalysts were characterized by N2 adsorption at 77 K, Raman spectroscopy, X-ray diffraction techniques, and X-ray fluorescence analysis. X-ray diffraction and Raman analysis showed a good dispersion of the V-species on the support. A preliminary screening of these samples was performed at fixed temperature (T = 327 °C) and H2S inlet concentration (10 vol%) in order to study the catalytic performance in terms of H2S conversion and SO2 selectivity. For the catalyst that exhibited the higher removal efficiency of H2S (92%) together with a lower SO2 selectivity (4%), the influence of temperature (307–370 °C), contact time (0.6–1 s), and H2S inlet concentration (6–15 vol%) was investigated.

The aim of this work is to minimize the consumption of electricity associated with the light source in a photocatalytic process for the removal of pollutants from wastewater. For this purpose, an optimized visible light active nitrogen-doped TiO2 was used. To reduce electric energy consumption, nitrogen-doped TiO2 was coupled with long-afterglow blue phosphors (chemical formula: Sr2.90Eu0.03Dy0.07Al4SiO11) able to emit visible light when excited with UV light. Specifically, the experimental tests were performed using crystal violet dye as a model pollutant at 10 mg L−1 initial concentration. The experimental campaign has been carried out with the aim of assessing whether the photocatalytic activity of the nitrogen-doped TiO2 catalyst is still present in dark conditions, thanks to the light emitted by phosphors and consequently to determine the energy saving in terms of electrical consumption and related costs. After having established the optimal content of nitrogen-doped TiO2 in the physical mixture with phosphors, tests were carried out by alternating lighting periods with dark periods in order to identify the optimal irradiation time to obtain not only the total crystal violet degradation, but also the highest energy savings. In particular, the simultaneous presence of long-afterglow photoluminescent materials, nitrogen-doped TiO2 photocatalyst and UV light emitting diodes resulted in an economic and energy saving of about 40% thanks to the possibility of alternating “light” and “dark” periods.

In recent years, the formulation of innovative photocatalysts activated by visible or solar light has been attracting increasing attention because of their notable potential for environmental remediation and use in organic synthesis reactions [...]

In this paper a UV-LEDs floating photocatalytic reactor was developed in order to remove caffeine and paracetamol from water using ZnO immobilized on low density macroscopic polystyrene pellets as floating photocatalyst. Different amounts of ZnO were immobilized on polystyrene pellets surface by solvent casting method and characterized from chemical-physical point of view using N2 adsorption at -196 °C, SEM analysis and XRD technique. Photocatalytic activity results evidenced that, during the irradiation time, the photocatalytic performances with the floating-bed reactor were strongly enhanced with respect to the fixed-bed reactor. The influence of process parameters, such as ZnO amount immobilized on polystyrene pellets, air flow rate and UV light intensity, has been investigated. The results showed that the complete caffeine degradation with a mineralization degree of about 86% was achieved after 240 min of UV irradiation at ZnO loading on polystyrene pellets of 1.1 wt%, air flow rate of 144 Ncc·min−1 and UV light intensity of 13 W·m−2. Furthermore, the optimized photocatalyst can be reused for several cycles without any substantial decrease of photocatalytic performances. Finally, the floating photocatalyst was able to remove simultaneously paracetamol and caffeine from drinking water with a very good efficiency.

The aim of this work is to preliminary investigate the photocatalytic performances toward the removal of eriochrome black-T dye under UV and visible irradiation using Eu-doped ZnO obtained through a supercritical antisolvent (SAS) process in comparison with Eu-doped ZnO prepared by drying-precipitation method and Eu-doped TiO2 prepared by sol–gel route. XRD patterns show that the presence of Eu+3 does not change the crystalline structure of both TiO2 and ZnO, evidencing that Eu+3 is successfully incorporated into the semiconductors lattice. The morphology of samples obtained after SAS micronization consists of nanoparticles with a regular shape and characterized by average size in the range 65.0–84.7 nm. UV–Vis DRS spectra evidence that the doping of TiO2 and ZnO with Eu+3 leads to an increase of band gap value with respect to undoped samples because of the presence of dopant ions into the host structure. Eu-doped ZnO sample synthetized by the SAS process shows better photocatalytic efficiency in terms of both discoloration and mineralization, reaching the almost total dye removal after 240 min of UV light irradiation. The enhancement of the photocatalytic activity of Eu-doped ZnO sample synthetized by SAS process is ascribed to the presence of Eu+3 in the lattice, but also to the higher specific surface area, smaller crystallite size and its morphology features, if compared with Eu-doped ZnO prepared by drying-precipitation method and Eu-doped TiO2 prepared by sol–gel route.

Heterogeneous photocatalysis in the gas phase has been applied as a promising technique for organic syntheses in mild conditions. Modified zeolites have been used under UV irradiation as novel photocatalysts. In this study, we preliminarily investigated the photoxidation of cyclohexane on ferrierite and MoOx-functionalized ferrierite in a gas&ndash, solid continuous flow reactor. In the presence of UV light, MoOx-functionalized ferrierite showed the formation of benzene and cyclohexene as reaction products, indicating the occurrence of photocatalysed cyclohexane oxydehydrogenation. By contrast, unmodified ammonium ferrierite exhibited relevant activity for total oxidation of cyclohexane to carbon dioxide and water. The influence of Mo loading on cyclohexane conversion and products selectivity was evaluated.

The aim of this work is to demonstrate the effectiveness of the photocatalytic process in the Methyl Orange azo dye degradation and simultaneous H2 production by using ZnO doped with ruthenium. Ru-modified ZnO photocatalysts were prepared by precipitation method and were characterized by different techniques (XRF, Raman, XRD, N2 adsorption at &minus, 196 &deg, C, and UV&ndash, vis DRS). The experiments were carried out in a pyrex cylindrical reactor equipped with a nitrogen distributor device and irradiated by four UV lamps with the main wavelength emission at 365 nm. Different Ru amounts (from 0.10 to 0.50 mol%) were tested in order to establish the optimal amount of the metal to be used for the ZnO doping. The photocatalytic activity was evaluated both in terms of Methyl Orange removal and hydrogen production. The experimental results showed that the best activity, both in terms of H2 production and Methyl Orange degradation, was obtained with the Ru-modified ZnO photocatalyst at 0.25 mol% Ru loading. In particular, after four hours of UV irradiation time, the discoloration and mineralization degree were equal to 83% and 78%, with a simultaneous hydrogen production of 1216 &micro, mol L&minus, 1. This result demonstrates the ability of the photocatalytic process to valorize a dye present in wastewater, managing to obtain a hydrogen production comparable with the data present in the literature today in the presence of other sacrificial substances.

In this work, composite monolithic aerogels based on syndiotactic polystyrene (s-PS) and N-doped TiO2 (NdT) photocatalyst characterized by high surface areas (up to 280 m2/g) and low density (0.1 g cm−3) are presented. These aerogels are obtained by supercritical carbon dioxide extraction of NdT/s-PS gels prepared by s-PS dissolution with NdT in suitable organic solvent. X-ray diffraction measurements and SEM analysis showed that a highly efficient dispersion of NdT nanoparticles can be achieved in the composite aerogels avoiding thus the aggregation phenomena that typically occur when the photocatalyst is used in slurry reactors. The optimization of NdT amount dispersed in s-PS was evaluated using phenol as model pollutant both under UV and visible light irradiation. The photoactivity of NdT/s-PS samples increased with increase of the amount of NdT dispersed in aerogel matrix up to NdT/s-PS weight ratio equal to 10/90 (10NdT/s-PS), for which the highest phenol degradation and TOC removal were achieved both under UV and visible light irradiation. Moreover, the photocatalytic activity of the optimized photocatalyst 10NdT/s-PS did not change significantly after several reuses underlining that any NdT particles are removed from the polymeric matrix.

An optimized Ru-doped LaFeO3 photocatalyst was coupled with magnetic Fe2O3 particles and was tested in the photocatalytic hydrogen production from glucose degradation under visible light irradiation. The catalysts were successfully synthesized by solution combustion synthesis using citric acid as organic fuel. Complete glucose degradation and hydrogen production of 5460 μmol/L was obtained after 4 h of irradiation using composite containing 67 wt% of Ru-doped LaFeO3. After seven cycles of reuse, the photocatalytic activity did not change, evidencing the high stability of the magnetic photocatalyst, which can be recovered from the photoreactor using an external magnetic force. The recyclable sample was finally tested in the treatment of real wastewater from cherries washing process, and a very high hydrogen production (12344 μmol/L) was achieved. Finally, the possibility to couple the photocatalytic process (used for the production of hydrogen) with a heterogeneous photo-Fenton process was investigated in order to mineralize the unconverted organics in the wastewater coming from the photoreactor.

Fe0 (ZVI) is one of the most effective reactants for treatment of water contaminated with chlorinated hydrocarbons, pollutants recalcitrant to degradation. Unfortunately, ZVI use is limited by corrosion and loss of reactivity over time. In order to suppress oxidation and passivation phenomena of iron, in this study ZVI was coupled to a suitable semiconductor (ZnS). Under UV light, electrons in the valence band of ZnS are promoted in the conducting band (ECB = − 1.04 eV vs NHE) and are able to reduce Fe2+ to Fe0 (E0 = − 0.44 eV vs NHE). The ZnS_ZVI composite was simply prepared by coating commercial ZnS with Fe0 obtained by reducing Fe (II) salt with sodium borohydride. The achieved ZnS_ZVI catalytic system was characterized by FESEM, WAXD, Raman and N2 adsorption at −196 °C, with the aim to analyze morphology and crystalline structure of both components of the ZnS_ZVI system. Catalytic activity tests showed that ZnS_ZVI is effective in degrading probe molecules, eriochrome black T dye (EBT) and chlorobenzene (PhCl), from aqueous solutions under UV light irradiation. The experimental results show that in both cases the reductive action of Fe0 on the N = N bond of EBT and C-Cl of PhCl is synergistically coupled to the oxidative action of ZnS towards by-products. OH radicals, generated by the reaction between the electron holes in the valence band of ZnS and H2O (OH−), were indeed confirmed by photoluminescence analysis. Recyclability tests indicate that ZnS_ZVI is highly stable since its catalytic activity, on both probe molecules, remains unchanged even after several cycles of reuse under UV irradiation. ZnS_ZVI catalytic behavior towards EBT has been carefully analyzed and a possible mechanism of EBT degradation has been proposed, which involves the formation of a Fe2+-EBT complex whose structure has also been suggested.

In this work the photocatalytic activity of Pr-doped ZnO (Pr-ZnO) photocatalysts has been addressed for the first time in the treatment of aqueous solutions at high concentration of organic dyes under UV or visible light irradiation. Pr-ZnO photocatalysts were prepared by a precipitation method. The catalysts have been characterized by different techniques such as X-ray diffraction (XRD), UV–Vis diffuse reflectance (UV–Vis DRS) and Raman spectroscopy. XRD results showed that Pr 3+ ions were successfully incorporated into the ZnO lattice. UV–Vis DRS spectra evidenced that Pr-ZnO samples present band-gap values of about 3.0 eV, lower than undoped ZnO (3.3 eV). The efficiency of photocatalysts has been tested in the photocatalytic removal of the azo dye Eriochrome Black T (EBT) under UV or visible light irradiation. The experimental results showed that the values of discoloration and mineralization rate are correlated to the Pr doping level, evidencing that the optimal loading of Pr in the ZnO structure is 0.46 mol%. The influence of process parameters (catalyst dosage, initial dye concentration and presence of carbonate ions) on the extent of photocatalytic performances has been investigated. The efficiency of the optimized photocatalyst was also evaluated in the photocatalytic treatment of aqueous solutions containing the triphenylmethane Patent Blue V (PB) dye and in the treatment of a solution containing simultaneously the two selected dyes (EBT and PB). Photocatalytic activity tests in presence of ion scavengers (carbonate ions) showed that the formulated Pr-ZnO photocatalyst is not subjected to deactivation phenomena. At last, a very interesting result was observed for the treatment of a real wastewater containing Basic Red 51 dye, showing that the complete discoloration and mineralization was achieved.

Photocatalytic degradation of terephthalic acid (TPA) has been studied on commercial ZnO immobilized on polystyrene (PS) beads (mean size: 1.5 × 1.5 × 0.1 cm) and located in a stainless steel flat plate reactor with an irradiation window realized in a UV transparent polymethylmethacrylate (PMMA UVT) in order to make the system able to work also at high pressure. In this way, it is possible to overcome, both the problems related to the photocatalysts separation after the wastewater treatment and those ones caused by the inlet pressure (which may be higher than atmospheric one) of incoming wastewater. The solvent casting-method used for photocatalyst preparation is able to induce the formation of ZnO particles in form of isles dispersed on PS macro surface. Moreover XRD analysis evidenced that the PS support didn’t influence the crystalline arrangement of ZnO in wurtzite phase. The structured composite photocatalyst ZnO-PS showed high ability in the degradation of TPA giving its total mineralization under UV irradiation at atmospheric pressure. Increasing the pressure, similar levels of TPA removal were observed. This finding demonstrated the possibility, for the developed photocatalytic system, to operate under moderate pressure without worsening the photocatalytic performances.

In the present study, we investigated the effect of cerium and erbium doping of the zirconium dioxide matrix. We synthesized doped samples using hydrothermal process. The amounts of dopant used were 0.5%, 1% and 5% molar (rare earth oxide over zirconium dioxide) respectively. The samples have been studied via X-ray Diffraction measurements for the structural characterization. UV visible diffuse reflectance was used for the optical analysis, Brunauer-Emmett-Teller (BET) model for the measurement of the surface area. Finally the samples have been analysed via electron paramagnetic resonance (EPR) for the electronic characterization. Then we tested the new synthetized materials to determine their photocatalytic activity in the reaction of degradation of methylene blue performed under irradiation by diodes (LEDs) emitting exclusively visible light.

This work is focused on the study of the correlation between the photocatalytic activity of N-doped TiO2 particles, achieved by a designed synthesis, and their degree of aggregation in aqueous suspension. N-doped TiO2 photocatalyst particles, suspended in bidistilled water, presented a trimodal (in the nano-micro metric range) aggregate size distribution. This distribution resulted monomodal, in the nanometric range, when in the aqueous solution was added an organic dispersing agent (azulene). This behavior was associated to the presence, on the N-doped TiO2 particle surfaces, of an organic phase which was detected by thermal and infrared analysis. This organic phase was assumed to have a stabilizing function for nanoparticles. The influence of aggregate size of N-doped TiO2 photocatalyst on the photocatalytic degradation of methylene blue has been studied. The aggregate size distribution of photocatalyst influenced the amount of methylene blue adsorbed on catalyst surface and increased the photocatalytic activity. The influence of operating parameters such as the amount of dispersing agent and the amount of photocatalyst in aqueous suspensions has also been examined.

The aim of this work was to analyze the effect of visible LED dimming duty-cycle modulation techniques in a photocatalytic system for urea degradation using a visible light photocatalyst immobilized on macroscopic supports. For this reason, the effect of different LED dimming techniques was investigated and compared in terms of urea degradation together with ammonia and nitrate production during the irradiation time. The experimental results evidenced that using a visible LED dimming modulation with variable-peak variable-duty pulse-width modulation (PWM) allows to improve the photocatalytic degradation process, with respect to classical LED dimming with fixed-peak fixed-duty PWM, and influences the product&rsquo, s distribution of ammonia and nitrate in water. Therefore, the proof of concept herein proposed could be considered as preliminary potential results to be used in water recycling applications with a particular emphasis in recovery of urea photodegradation byproducts, such as ammonia, from wastewater that could be used as potential resources and an energy resource.

Cu-doped ZnO photocatalysts at different Cu loadings were prepared by a precipitation method. The presence of Cu in the ZnO crystal lattice led to significant enhancement in photocatalytic activity for H2 production from an aqueous glycerol solution under visible light irradiation. The best Cu loading was found to be 1.08 mol %, which allowed achieving hydrogen production equal to 2600 &mu, mol/L with an aqueous glycerol solution at 5 wt % initial concentration, the photocatalyst dosage equal to 1.5 g/L, and at the spontaneous pH of the solution (pH = 6). The hydrogen production rate was increased to about 4770 &mu, mol/L by increasing the initial glycerol concentration up to 10 wt %. The obtained results evidenced that the optimized Cu-doped ZnO could be considered a suitable visible-light-active photocatalyst to be used in photocatalytic hydrogen production without the presence of noble metals in sample formulation.

Phosphors based photocatalyst (Nitrogen-doped TiO2 coupled with ZnS blue phosphors) immobilized on macroscopic polystyrene pellets was studied in the removal of ceftriaxone (third-generation β-lactam antibiotic) from water. The phosphors based structured photocatalyst was prepared using the solvent assisted procedure. According to spectroscopic and morphological characterization, the photocatalyst particles resulted effectively dispersed on polystyrene macroscopic pellets. The photocatalytic activity tests were carried out in a laboratory scale reactor configuration irradiated by UV or visible lamps and under natural sunlight in outdoor experiments. The structured photocatalyst was effective in the removal of ceftriaxone from water and demonstrated no deactivation phenomena also after several reuse cycles in both distilled and real water. Finally, in the outdoor experiment under natural solar light, total ceftriaxone degradation and higher than 95% mineralization (measured as TOC removal) was achieved after 150 min treatment time (less than 2 KJ/L of cumulative energy).

This chapter is related to the advances and innovations of photocatalytic processes in recent years. In particular, both the innovative aspects of the applicability of photocatalysis and technological advances were considered, with particular attention to the photocatalytic energy recovery, organic synthesis and new reactor configurations.

In this work it was studied the removal efficiency of several water pollutants (methylene blue, phenol, paracetamol, caffeine and ceftriaxone) by dielectric barrier discharge (DBD) non-thermal plasma (NTP) reactor. The results evidenced that using oxygen as process gas in the DBD reactor and 20 kV of applied voltage, the complete degradation and mineralization of methylene blue and ceftriaxone was achieved after only 5 min of treatment time, while 15 min were required for the complete degradation and mineralization, of phenol and paracetamol, and 25 min for the caffeine. In addition, kinetic evaluations evidenced that, for each pollutant, the degradation and mineralization occurred at the same rates, underling that the pollutants are selectively converted to carbon dioxide. For this reason, the results obtained in the present work were significantly better than those reported in the current literature about the use of non-thermal technology in the removal of organic pollutants from aqueous solutions.

Highly porous monolithic aerogels based on ZnO photocatalyst and syndiotactic polystyrene (s-PS) were obtained by supercritical CO2 treatment of ZnO/s-PS gels. The prepared aerogels were characterized and their photocatalytic activity was evaluated using phenol and toluene as water pollutant models. The s-PS nanoporous crystalline phase, able to absorb pollutant molecules, was proven to be necessary to ensure high photocatalytic efficiency as the aerogel acts not only as a support, but also as pollutant pre-concentrator. The reusability of ZnO/s-PS aerogels is also strong showing no decrease in photocatalytic activity after six consecutive degradation trials. Finally, the aerogel matrix prevents ZnO dissolution occurring under acidic conditions and promotes a selective removal of the pollutants. The synergy between the photocatalyst and the innovative polymeric support provides the composite system with robustness, chemical stability, easy recovery after treatment, high efficiency of pollutant removal with a marked selectivity which make these materials promising for large scale applications.

A packed bed photoreactor was developed using a structured photocatalyst active under visible light. The packed bed reactor was irradiated by visible light-emitting diodes (LEDs) for the evaluation of photocatalytic activity in the removal of different types of water pollutants. By using a flexible LEDs strip as the external light source, it was possible to use a simple cylindrical geometry for the photoreactor, thereby enhancing the contact between the photocatalyst and the water to be treated. The visible light active structured photocatalyst was composed by N-doped TiO2 particles supported on polystyrene spheres. Photocatalytic results showed that the almost total methylene blue decolorization was achieved after 120 min of irradiation. Moreover, the developed packed bed photoreactor was effective in the removal of ceftriaxone, paracetamol, and caffeine, allowing it to reach the almost total degradation of the pollutants and a total organic carbon removal above 80% after 180 min of visible light irradiation.

The presence of azo dyes in textile effluents is an issue of major concern due to their potential impact on the environment and human health. In this study we investigate the photocatalytic degradation under visible light of Reactive Violet 5 (RV5), an azo dye widely used in the textile industry. A preliminary screening of different titania-based catalysts was carried out to identify the best candidate for RV5 removal. The selected catalyst was then tested in a stirred and aerated lab-scale reactor illuminated with a blue light-emitting diode (LED) source emitting in the wavelength range of 460&ndash, 470 nm. The effects of pH, catalyst load, and hydrogen peroxide additions on the efficiency of dye removal were evaluated. Under the best conditions (pH 10, 3 g/L of catalyst, and 60 mM hydrogen peroxide), the dye solution was completely decolorized in about 2 h. Overall, the results obtained suggest that the proposed process may represent a suitable method for the removal of RV5 from textile effluents.

The use of a doped Ceria buffer layer and Physical Vapour Deposition (PVD) techniques for Solid Oxide Fuel Cells (SOFC) fabrication can limit the former, the formation of electrical insulating lanthanum, and strontium zirconates at the cathode/electrolyte interface, whereas the latter allows a better control of the materials interfaces. These effects allow for operation at intermediate temperature ranges. In this work, we study the structural and electrical properties of Gadolinium Doped Ceria (GDC) barrier layer deposited via the room temperature RF Sputtering technique on anode supported electrolytes and then annealed at high temperature. The crystal structure and the surface morphology of the GDC barrier layers have been analyzed and optimized varying the temperature ramp of the post-growth annealing procedure. The electrical behavior of the obtained samples has been investigated by Electrochemical Impedance Spectroscopy and compared to that of standard SOFC with screen-printed GDC barrier layers, the former showing a maximum high frequency and low frequency resistances reduction of about 50% and 46%, respectively, with respect to the latter at an operating temperature of 650 &deg, C. The results clearly show an important improvement of SOFC performances when using sputter deposited GDC layers, linking the electrical properties to the structural and stoichiometric ones.

Phenol is an important chemical compound since it is a precursor of the industrial production of many materials and useful compounds. Nowadays, phenol is industrially produced from benzene by the multi-step “cumene process”, which is energy consuming due to high temperature and high pressure. Moreover, in the “cumene process”, the highly explosive cumene hydroperoxide is produced as an intermediate. To overcome these disadvantages, it would be useful to develop green alternatives for the synthesis of phenol that are more efficient and environmentally benign. In this regard, great interest is devoted to processes in which the one-step oxidation of benzene to phenol is achieved, thanks to the use of suitable catalysts and oxidant species. This review article discusses the direct oxidation of benzene to phenol in the liquid phase using different catalyst formulations, including homogeneous and heterogeneous catalysts and photocatalysts, and focuses on the reaction mechanisms involved in the selective conversion of benzene to phenol in the liquid phase.

The focus of the present study is to assess the performances of H 2 O 2 assisted non-thermal plasma (NTP) technology for the degradation of the Acid Orange 7 textile azo dye in aqueous solution. The reactor configuration used during the experiments was the “dielectric barrier discharge” (DBD). The comparison between DBD (only non-thermal plasma) and H 2 O 2 /DBD system (in the presence of H 2 O 2 in the solution) was also performed. The experimental tests were carried out using 100 mL of aqueous solution with an initial Acid Orange 7 concentration equal to 10 mg/L, in the presence of oxygen as process gas in the DBD reactor operating with 20 kV of applied voltage. The results demonstrated that in presence of only oxygen in the DBD reactor, a discoloration and simultaneous mineralization of about 60% was obtained after only 2.5 min, while the addition of H 2 O 2 enhanced the dye degradation rate, obtaining in the same a discoloration and simultaneous mineralization of about 80%. The higher degradation rate achieved by adding H 2 O 2 could be attributed to the presence of higher amounts of hydroxyl radicals in DBD reactor. A deeply study on the influence of the main macroscopic parameters such as O 2 flow rate, H 2 O 2 and Acid Orange 7 initial concentration has been assessed in order to find the optimal operating conditions for the H 2 O 2 /DBD system. The kinetic evaluation and the energy yield study were performed under specific experimental condition. If compared with traditional AOPs, the results obtained with the H 2 O 2 /DBD system, showed that this technology is faster and extremely efficient and consequently very promising for the removal of Acid Orange 7 azo dye in aqueous solutions.

Imogolite-like nanomaterials were tested as heterogeneous catalysts for the photo-catalytic degradation of tartrazine (a food dye recalcitrant to biodegradation and responsible of allergic and/or intolerance reactions) in the presence of H 2 O 2 . Methyl-imogolite, a hybrid organic/inorganic material with chemical composition (OH) 3 Al 2 O 3 SiCH 3 , occurs as single-walled nanotubes with an inner surface lined by Si-CH 3 groups and an aluminum oxo-hydroxide outer surface, where octahedral Al 3+ ions may be isomorphically substituted by Fe 3+ ions. Besides bare methyl-imogolite, novel Fe doped nanotubes (with nominal composition (OH) 3 Al 2-x Fe x O 3 SiCH 3 , where x = 0.025 or 0.050) were prepared by ion exchange of preformed methyl-imogolite with FeCl 3 × 6H 2 O in water. Physico-chemical characterization of the materials showed that Fe doping positively modifies nanotubes light absorption capacity by lowering the band gap of methyl-imogolite from 4.9 eV to 2.4 eV. At higher Fe content (sample with nominal composition (OH) 3 Al 1.950 Fe 0.050 O 3 SiCH 3 ), some Fe oxo-hydroxide clusters form, due to the natural tendency of Fe to form aggregates. Photo-degradation tests of tartrazine show that both bare and Fe-doped methyl-imogolite efficiently remove the dye from aqueous mixtures through different mechanisms. With bare methyl-imogolite, under UV light almost 65% Total Organic Carbon (TOC) is removed within 2 h, likely due to the formation of reactive AlOOH groups promptly generating HO radicals. With sample having nominal composition (OH) 3 Al 1.975 Fe 0.025 O 3 SiCH 3 , Fe 3+ species undergo efficient photo-Fenton reaction under UV light, leading to 90% TOC removal after 2 h. Conversely, the Fe oxo-hydroxide clusters at nanotubes outer surface likely worsen the photo-Fenton activity of the sample with (OH) 3 Al 1.950 Fe 0.050 O 3 SiCH 3 nominal composition as far as the TOC removal is concerned.

An optimized fluorinated TiO2 catalyst with high {001} facet exposure loaded with platinum (TiO2-PtFAC) was tested in the photocatalytic hydrogen production from glycerol solution under UV light irradiation. The samples were synthesized by direct hydrothermal treatment starting from two different types of precursors that are titanium tetraisopropoxide (I) or titanium butoxide (B), while platinisation was performed by photodeposition method. The obtained catalysts were characterised by different techniques (XRD, FESEM, TEM, BET, UV–vis DRS, XRF and XPS) and the results evidenced that anatase is the only crystalline phase present in all TiO2 samples. The morphology of the samples was seen as rectangular platelets particles where Pt particles were was observed all over the surface. The presence of Pt and F in the platinised samples was also confirmed by XRF and XPS analysis. The photocatalytic results have shown that the presence of Pt on TiO2{001}facet surface remarkably enhanced the hydrogen production from aqueous solution at 5 wt % of glycerol. Comparing the results obtained from the photocatalysts prepared by the two different precursors, it was found that the best performances in terms of H2 production was achieved with TiO2-PtFAC(I) (about 13 mmol L−1 after 4 h of irradiation time), while the H2 production was lower for TiO2-PtFAC(B) (about 9 mmol L−1 after 4 h of irradiation time). The effect of the operating conditions using TiO2-PtFAC(I) evidenced that the highest H2 production was obtained with a photocatalyst dosage equal to 1.5 g L−1, initial glycerol concentration at 5 wt% and a pH value equal to 7. Finally, a photocatalytic test was also performed on glycerol solution prepared with a real water matrix. Despite the presence of ions scavengers (chlorides and carbonates) in solution, TiO2-PtFAC(I) was able to reach a photocatalytic H2 production of about 6 mmol L−1 after 4 h of UV light irradiation.

Different photocatalysts based on commercial ZnO modified by silver photodeposition were prepared in this work. The samples were characterized by X-ray fluorescence spectrometry (XRF), specific surface area (SSA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV–vis diffuse reflectance (UV–vis DRS). XRD and XPS showed that Ag/ZnO samples are composed of metallic Ag (Ag0) and ZnO structure was identified. Furthermore, TEM analysis evidenced that the number of silver particles increased with the Ag content. At last, UV–vis DRS results revealed a reflectance band for Ag/ZnO samples, ascribed to the surface plasmon resonance (SPR) absorption of metal silver particles. Commercial ZnO and Ag/ZnO samples were evaluated in the phenol removal under UV light irradiation. It was observed an enhancement of photocatalytic phenol removal from aqueous solutions by silver addition in comparison to commercial ZnO. In particular, the phenol removal increased with the silver content from 0.14 to 0.88 wt%, after this content (i.e 1.28 wt%) the phenol degradation significantly decreased indicating that the optimal Ag content was equal to 0.88 wt%. The influence of the best photocatalyst dosage and the change of the initial phenol concentration in solution were also investigated in this work and the best photocatalytic performance was obtained by using 50 mg L−1 of phenol initial concentration and 0.15 g L−1 of photocatalyst dosage. Finally, the optimized Ag/ZnO photocatalyst was employed for the treatment of a real drinking wastewater containing phenol in which the almost total phenol removal was achieved after 180 min of UV irradiation time., This work was financed by Fondo Nacional de Financiamiento para la Ciencia, la Tecnología y la Innovación “Fransisco José de Caldas – Colciencias”, Project 279-2016, Universidad Pedagógica y Tecnológica de Colombia and by research fund from Project Ref. CTQ2015-64664-C2-2-P (MINECO/FEDER, UE).

Heterogeneous photocatalysis (HPC) is a subset of Advanced Oxidation Processes (AOPs) with potential future applications in water disinfection. Herein, a zinc oxide photocatalyst was doped with cerium at various atomic ratios ranging from 0 to 0.1 Ce:Zn. Keeping in mind that the application of HPC is often limited by its cost of use, a simple and easy to upscale method, that is the hydroxide induced hydrolysis of zinc nitrate in the presence of Ce3+ followed by calcination at 300 °C, was used to synthesise the catalysts. The catalysts have been characterized by different techniques such as X-ray diffraction (XRD), UV-vis diffuse reflectance (UV-vis DRS) and Raman spectroscopy. XRD results showed that Ce3+ ions were successfully incorporated into the ZnO lattice. UV-vis DRS spectra evidenced that Ce–ZnO samples present band-gap values of about 2.97 eV, lower than those of undoped ZnO (3.21 eV). These various photocatalysts, at 0.1 g L−1 in saline 0.85%, were used to inactivate Escherichia coli previously isolated from an urban wastewater treatment plant. Higher atomic ratios of Ce in the ZnO lattice, as confirmed by XRD and Raman spectroscopy, showed significant improvements to the inactivation rate; the resulting recommended optimum cerium loading of 0.04:1 Ce:Zn gave multiple orders of magnitude higher rate of inactivation after 60 min of treatment when compared to un-doped ZnO. This optimum loading of cerium was faster than the de facto literature standard TiO2-P25 tested under identical conditions.

A continuous flow micro-reactor irradiated by UV-LEDs was employed to treat coloured wastewater by adsorption and simultaneous photocatalysis. Zinc oxide (ZnO) immobilized on commercial zeolites pellets in spherical shape (ZEO) was used as catalytic material in a micro-reactor maximizing the photocatalyst exposition to light sources, irradiating uniformly the entire solution volume and improving the mass transfer phenomena. Experimental tests were carried out on crystal violet dye (CV) as one of the main dying agent present in textile wastewater. The comparison between adsorption and adsorption/photocatalytic tests showed that UV irradiation can achieve a steady state CV concentration value corresponding to an equilibrium condition between adsorption and photocatalytic oxidation. The higher removal efficiency (i.e. 93%) was observed with a liquid flow rate of 1.1 mL/min (contact time = 4.7 min; CV = 10 mg/L) under UV light irradiation. In the steady state, CV removal remained constant for the overall testing time. Bioassays evidenced that toxicity was not completely removed (i.e. final effluent ranked as “slight acute toxic”) from wastewater suggesting its suitability for sewage collection discharge. A Dubinin Radushkevich (D-R) isotherm model was applied for studying the adsorption behaviour of ZnO/ZEO sample. CV adsorption constants were evaluated from experimental data carried out in dark conditions in a batch system. Kinetic expression of CV removal and the D-R adsorption were incorporated in the CV mass balance estimating the kinetic parameter. The model was validated comparing the calculated CV conversion with the experimental tests collected at different CV inlet concentration.

The aim of this preliminary investigation was to verify the possibility of increasing the photoactivity of semiconductors, such as TiO2 and ZnO, with the goal to minimize the volume of slurry-photoreactors to be used in wastewater treatment. The enhancement of photocatalytic activity has been reached through the doping of ZnO and TiO2 nanoparticles with nitrogen and supporting them on ZnS-based luminescent microparticles (phosphors). The coupling of ZnS-based phosphors with N-TiO2 and N-ZnO leads to an increase of the photocatalytic reaction rate in removal of organic dyes from wastewater allowing to reach the process intensification for the large scale design of a photocatalytic system.

The photocatalytic activity of N-doped TiO2 particles supported on polystyrene (PS) surface by using a solvent-cast method at ambient temperature was evaluated on methylene blue (MB) dye decolourization. Subsequently, the effect of the new photocatalyst was evaluated in the inactivation of an antibiotic resistant (AR) Escherichia coli (E. coli) strain selected from the effluent of the biological process of an urban wastewater treatment plant. N-doped TiO2 particles supported on PS were characterized by UV–vis DRS reflectance and Laser Raman spectra measurements. The results of photocatalytic tests with MB water solutions showed that MB can be successfully degraded (83–100%) under visible light after 180 min of irradiation. The system was also effective in the phenol photocatalytic degradation. Moreover, photocatalytic process effectively inactivated AR E. coli strain which was reduced by 97% after 30 min treatment. The developed preparation method could be a promising simple and low cost procedure for preparing immobilized photocatalysts for large scale commercial applications to wastewater treatment under direct solar light.

BACKGROUND Heterogeneous photocatalysis for the degradation of non-biodegradable organic contaminants in wastewater is an alternative to traditional treatment techniques. Since the applications developed employ photocatalysts in powder form, a main disadvantage remains related to the recovery of photocatalysts from the treated wastewater, resulting in damage and shorter lifetime for the recirculation pumps. Structured photocatalysts offer a valid solution to simplify the process; however, they have to guarantee light transmission, long-term stability under different operating conditions and under mechanical stress. RESULTS The photocatalytic performances of N-doped TiO2 nanocomposite syndiotactic polystyrene aerogels (Nt-sPS) were analyzed in the presence of visible light. A widely used model pollutant, methylene blue (MB), was chosen to verify the photocatalytic performance. After about 180 min of irradiation, on Nt-sPS, the conversion of MB reached 30%, higher than that obtained (16%) when the photocatalyst is suspended as powder in the liquid reaction medium. CONCLUSION N-doped TiO2, obtained by direct nitration during the hydrolysis of titanium tetraisopropoxide with ammonia solutions, was immobilized in s-PS aerogels, yielding high activity in the removal of methylene blue under visible light irradiation, in comparison with N-doped TiO2 dispersed as powder in solution. © 2014 Society of Chemical Industry

In this work, the synthesis of zinc oxide (ZnO) photocatalyst from thermal decomposition of zinc acetate (ZnAc) nanoparticles obtained by supercritical antisolvent (SAS) precipitation was investigated. The optimization of calcination conditions of the SAS ZnAc was carried out, studying the effect of temperature (in the range 300&ndash, 600 &deg, C) on the production of ZnO nanoparticles. In particular, it was demonstrated that the organic residues in ZnO and its particle size, thus the specific surface area, strongly affect the photocatalytic performances. SAS micronization of ZnAc produces regular nanoparticles with a mean diameter of about 54.5 &plusmn, 11.5 nm, whereas unprocessed ZnAc is characterized by very large crystals. The experimental results evidenced that ZnAc prepared by SAS process calcined at 500 &deg, C showed a regular nanometric structure (mean diameter: 65.0 &plusmn, 14.5 nm) and was revealed to be the best choice for the photocatalytic removal of crystal violet dye (CV). In fact, the photocatalytic activity performances of ZnO nanoparticles prepared by this route were higher with respect to that of ZnO from unprocessed ZnAc calcined at 500 &deg, C (which is characterized by irregular tetrapods with mean size 181.1 &plusmn, 65.5 nm). The optimized photocatalyst was able to assure the complete CV decolorization in 60 min of UV irradiation time and a mineralization degree higher than 90% after 120 min of treatment time.

In this work, the results of gas phase cyclohexane photocatalytic oxidative dehydrogenation on MoOx/SO4/TiO2 catalysts with DRIFTS analysis are presented. Analysis of products in the gas-phase discharge of a fixed bed photoreactor was coupled with in situ monitoring of the photocatalyst surface during irradiation with an IR probe. An interaction between cyclohexane and surface sulfates was found by DRIFTS analysis in the absence of UV irradiation, showing evidence of the formation of an organo-sulfur compound. In particular, in the absence of irradiation, sulfate species initiate a redox reaction through hydrogen abstraction of cyclohexane and formation of sulfate (IV) species. In previous studies, it was concluded that reduction of the sulfate (IV) species via hydrogen abstraction during UV irradiation may produce gas phase SO2 and thereby loss of surface sulfur species. Gas phase analysis showed that the presence of MoOx species, at same sulfate loading, changes the selectivity of the photoreaction, promoting the formation of benzene. The amount of surface sulfate influenced benzene yield, which decreases when the sulfate coverage is lower. During irradiation, a strong deactivation was observed due to the poisoning of the surface by carbon deposits strongly adsorbed on catalyst surface.

In this work gas phase photocatalytic selective oxidation of ethanol to acetaldehyde was studied with directly fluidizable photocatalysts made of grafted VOx on titania/silica in presence of phosphors as light carriers to test their performances in the photocatalytic system. The presence of VOx species anchored on TiO2/SiO2 enhanced ethanol conversion up to 66%, with acetaldehyde selectivity higher than 99%. The performances of V-based sample at 11 wt% of TiO2 supported on fluidizable support were higher than those evaluated when nano-TiO2 powder is used as support. Moreover, the photocatalytic conversion of ethanol was further increased in presence of phosphors as light carriers. From the obtained results, it is concluded that by preparing VOx based catalyst through grafting method allows a dramatic enhance in the productivity of acetaldehyde, even when the concentration level of alcohol at photoreactor inlet is increased.

The aim of this work was the developing and the verification of a mathematical model for the photocatalytic degradation of methylene blue (MB) with N-doped TiO2 under visible light in a batch photoreactor. To define the reaction system and its advancement, an innovative approach, conducted both performing the mass balance on carbon in liquid and gaseous phase, and determining the reaction products in gaseous evolved phase, was proposed. Total oxidation of MB was achieved, yielding CO2, SO2, N2 and Cl2 as gaseous products. The mathematical modeling of the system has been developed by using the Langmuir–Hinshelwood type kinetics for MB consumption. To consider the effect of photocatalyst screening, a Lambert–Beer type relation for the effective light energy received by the N-doped TiO2 particles was used. Moreover the dependence of reaction rate on photonic flux was modeled considering that photons can be treated as immaterial reactants. Model parameters estimation was realized by individuating the best agreement between the calculated values and experimental data as a function of irradiation time. On the basis of these results, the accuracy of the model was tested in different experimental conditions, evidencing the ability of the mathematical model to be predictive.

This work focused on the development and the validation of a mathematical model for the UV-C photo-Fenton degradation of acetic acid using a LaFeO3 heterogeneous structured catalyst with a monolithic structure. A combined study of the evolved gases and the liquid phase was conducted. The experimental results led to the identification of the main reactions that occur in the system: the complete mineralisation of acetic acid by H2O2 due to the presence of the catalyst and the decomposition of H2O2 to water and O2 in the homogeneous phase. A mathematical model was then developed using Eley–Rideal-type kinetics for the acetic acid consumption and first-order kinetics for the photolysis of hydrogen peroxide. The apparent kinetic constants were estimated, and the accuracy of the model was tested under different experimental conditions to evidence the predictive capability of the model. A very good agreement between the mathematical model calculations and the experimental data obtained in the presence of various H2O2 dosages was achieved. The results demonstrate that the continuous addition of H2O2 during the photo-Fenton reaction ensures the fruitful utilisation of the produced hydroxyl radicals in the acetic acid oxidation reaction to minimise the oxidant consumption and maximise the TOC removal in a shorter irradiation time.

In this work, an innovative and effective formulation of photocatalysts is presented. The highly selective photocatalysts at 5 wt% of nominal V2O5 on TiO2 for the photoconversion of ethanol to acetaldehyde was supported on the surface of commercial ZnS based phosphors (ZSP), on the base of the evidence that the addition of these phosphors, physical mixed with the photocatalysts, as light carriers inside a gas-solid fluidized bed photoreactor resulted in a significantly improved photoefficiency. Structured vanadia-titania catalysts in the form of micropellets were successfully synthesised by sol–gel method on the UV activated luminescent phosphors microparticles. The catalysts were investigated by TG-MS analyses, Raman and UV–vis spectroscopy, X-ray diffraction, as well as adsorption of N2 at −196 °C. A progressive increase of the amount on titania on the phosphors was realized to get the well dispersed nanoparticles of TiO2 on ZSP surface, able to absorb the UV light needed by the photoreaction in the proximity of light source. The residual UV light can penetrate up to the phosphors core, leading to their excitation and emission of further radiation at 440 nm useful to proceed the photoreaction in darker zones. The performances of structured VOx/TiO2/ZSP have been compared to physical mixtures of VOx/TiO2 catalyst with phosphors in the partial photooxidation of ethanol to acetaldehyde with the gas-solid fluidized bed photoreactor at high illumination efficiency. The ethanol consumption rate increased linearly with the ethanol initial concentration and at given alcohol concentration, its value was significantly higher on VOx/TiO2/ZSP with respect to the case in which the photocatalyst was only mixed with them. The results underlined as the higher capture of the structured photocatalyst, due to the additional light harvesting of support, gives enhanced activity in the selective oxidation of ethanol to acetaldehyde already dramatically improved by the innovative use of light emitting phosphorescent particles.

Photoassisted catalysis is a novel and attractive means of obtaining value-added chemicals. Photocatalytic reactions occur on the surface of photocatalyst particles and, as a consequence, it is necessary to maximize exposure of the catalyst to the radiation. Irradiation efficiency can be improved by using a fluidized bed to enhance photon and mass transfer; compared with fixed-bed reactors this results in better use of irradiation and favours adsorption and desorption phenomena between reactants and photocatalysts. In this work formation of styrene from ethylbenzene was investigated on sulfated MoO x /γ-Al2O3 catalysts in a gas–solid bi-dimensional photocatalytic fluidized-bed reactor with high illumination efficiency. Photocatalytic tests showed that for all the catalysts the only product detected was styrene (100 % selectivity). The highest photoactivity was obtained by use of a catalyst with nominal loading 8 wt% MoO3 and 2.4 wt% SO4.

In this work it was studied the efficiency of a photocatalytic process for the removal of patent blue V. This dye is very difficult to remove by conventional treatments such as adsorption or coagulation therefore the photocatalytic process is a very interesting alternative for the removal this dye mainly because it does not require expensive oxidants and it can be carried out at mild temperatures and pressures. In this work it was tested the efficiency of Au-TiO2 and Pt-TiO2 photocatalysts in the Patent blue V removal. The Au-TiO2 catalysts were prepared by two different methods: chemical reduction and photochemical deposition; Pt-TiO2 catalysts were obtained only by photochemical deposition. In the synthesis of the catalysts prepared by photochemical deposition, it was evaluated the influence of some parameters, such as deposition time and the intensity of the light source over the physicochemical properties and photocatalytic activity of the materials obtained. An analysis of the effect of the catalyst dosage and initial patent blue V concentration over the dye degradation efficiency was also attempted. In general, it was observed that the presence of Au or Pt on TiO2 enhances the patent blue V photodegradation; it was found that noble metal particle size and distribution on TiO2 surface are important factors influencing the dye removal. The highest dye degradation was obtained over the Au-TiO2 catalyst prepared by photochemical deposition, using high light intensity and 15 min of deposition time during the synthesis. A discoloration and a total organic carbon (TOC) removal of 93 and 67% respectively, were obtained over this material after 180 min of UV irradiation. These values are higher than that the obtained on S-TiO2 (discoloration and TOC removal of about 25% and 3%, respectively).

The release of antibiotics into the environment can result in antibiotic resistance (AR) spread, which in turn can seriously affect human health. Antibiotic resistant bacteria have been detected in different aquatic environments used as drinking water source. Water disinfection may be a possible solution to minimize AR spread but conventional processes, such as chlorination, result in the formation of dangerous disinfection by-products. In this study advanced oxidation processes (AOPs), namely H2O2/UV, TiO2/UV and N-TiO2/UV, have been compared with chlorination in the inactivation of an AR Escherichia coli (E. coli) strain in surface water. TiO2 P25 and nitrogen doped TiO2 (N-TiO2), prepared by sol-gel method at two different synthesis temperatures (0 and -20°C), were investigated in heterogeneous photocatalysis experiments. Under the investigated conditions, chlorination (1.0 mg L(-1)) was the faster process (2.5 min) to achieve total inactivation (6 Log). Among AOPs, H2O2/UV resulted in the best inactivation rate: total inactivation (6 Log) was achieved in 45 min treatment. Total inactivation was not observed (4.5 Log), also after 120 min treatment, only for N-doped TiO2 synthesized at 0°C. Moreover, H2O2/UV and chlorination processes were evaluated in terms of cytotoxicity potential by means of 3-(4,5-dime-thylthiazol-2-yl)-2,5-diphenylte-trazolium colorimetric test on a human-derived cell line and they similarly affected HepG2 cells viability.

In this work the hydrogen production from photocatalytic degradation of glucose aqueous solution using LaFeO 3 catalysts was investigated under UV or visible light irradiation by light-emitting diodes (LEDs). Different LaFeO 3 catalysts were prepared by solution combustion synthesis, starting from lanthanum nitrate and iron nitrate aqueous solution, and different amounts of citric acid as organic fuel. The influence of light irradiation and amount of citric acid was evaluated. The photocatalysts were characterized by different techniques, such as XRD, BET, UV–Vis DRS and Raman spectroscopy. As the amount of citric acid was increased from 0.86 to 2.15 g, the specific surface area of perovskite was increased from 4 to 24 m 2 /g, with crystallite size of 38 and 6 nm, respectively. Moreover, the different amounts of citric acid induced changes in the crystallinity degree of LaFeO 3 perovskite. LaFeO 3 catalyst prepared with a double amount of citric acid (1.72 g) compared to the initial content (0.86 g), was the most active in the photocatalytic production of H 2 (up to 1.6 mmol/g cat after 4 h of UV irradiation, corresponding to 16% of hydrogen yield). With this photocatalyst the simultaneous degradation of glucose was 73% after 4 h of UV irradiation. These results are encouraging with respect to the possibility to produce hydrogen during photocatalytic treatment of sugar-containing water by using photocatalysts in the absence of noble metals.

This study was focused on the application of white and blue light emitting diodes (LEDs) as sources for the photocatalytic degradation of organic dyes in liquid phase with visible light. The photocatalytic activity of N-doped titanium dioxide, synthesized by direct hydrolysis of titanium tetraisopropoxide with ammonia, was evaluated by means of a batch photoreactor. The bandgap energy of titanium dioxide was moved in the visible range from 3.3 eV to 2.5 eV. The visible light responsive photocatalysts showed remarkably effective activity in decolorization process and in the removal of total organic carbon. Methylene blue was also used as a model dye to study the influence of several parameters such as catalyst weight and initial concentration. The effect of dye on the photocatalytic performance was verified with methyl orange (MO). The results demonstrated that the right selection of operating conditions allows to effectively degrade different dyes with the N-doped TiO2photocatalysts irradiated with visible light emitted by LEDs.

Ethanol oxidative dehydrogenation over Pt/TiO 2 photocatalyst, in the presence and absence of blue phosphors, was performed. The catalyst was prepared by photodeposition of Pt on sulphated TiO 2. This material was tested in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. The effect of the addition of blue phosphors into the fluidized bed has been evaluated. The synthesized catalysts were extensively characterized by different techniques. Pt/TiO 2 with a loading of 0.5wt of Pt appeared to be an active photocatalyst in the selective partial oxidation of ethanol to acetaldehyde improving its activity and selectivity compared to pure TiO 2. In the same way, a notable enhancement of ethanol conversion in the presence of the blue phosphors has been obtained. The blue phosphors produced an increase in the level of ethanol conversion over the Pt/TiO 2 catalyst, keeping at the same time the high selectivity to acetaldehyde. Copyright © 2012 J. J. Murcia et al.