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This article presents a study on the electrification of reforming processes, in which the heat required for the reaction is directly supplied by the surface of the structured catalyst, realized by using commercial silicon carbide (SiC) heating elements as catalyst carriers, so eliminating all resistances to heat transfer. Three commercial ceramic supports were loaded with a 5 wt% nickel and tested in the steam reforming reaction. The best performance was obtained by the silica-mullite composite based support with the highest specific surface area. The structured catalyst was prepared by washcoating a SiC heating element, using a slurry based on the silica-mullite composite, subsequently impregnated in a solution of the nickel precursor, and tested in the steam and dry reforming reactions. The experimental tests were properly designed in order to reach the goals of (i) obtaining the kinetic parameters for the MSR reaction, and (ii) evaluating the energy consumption for both processes. The catalysts were characterized by means of X-ray diffraction, specific surface area, ED-XRF, SEM-EDS and Hg porosimetry. The results of the tests demonstrated that is possible to heat the system up to 800 °C, and sustain the reaction obtaining a methane conversion higher than 85 % both in the case of steam and dry reforming. The analysis of the energy consumption in terms of kWh Nm−3H2 has shown that it is comparable with the one of the modern electrolysers. The results of these experiments unequivocally demonstrate that it is possible to realize a process by reversing the flow of heat, from the inside of the catalytic bed to the outside.

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.

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.

Climatic changes and the growing population call for innovative solutions that are able to produce biochemicals by adopting environmentally sustainable procedures. The biorefinery concept meets this requirement. However, one of the main drawbacks of biorefineries is represented by the feedstocks’ pretreatment. Lately, scientific research has focused on non-thermal plasma, which is an innovative and sustainable pretreatment that is able to obtain a high sugar concentration. In the present review, literature related to the use of non-thermal plasma for the production of fermentable sugar have been collected. In particular, its sugar extraction, time, and energy consumption have been compared with those of traditional biomass pretreatments. As reported, on one hand, this emerging technology is characterized by low costs and no waste production; on the other hand, the reactor’s configuration must be optimized to reduce time and energy demand.

In this work, photocatalytic oxidation of As(III) to As(V) by ZnO photocatalyts doped with Cu was investigated under visible light. Photocatalysts were successfully prepared by precipitation method. The obtained samples were characterized by N2 adsorption at −196 C, X-Ray fluorescence analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV–vis reflectance analysis. In particular, according to XRD analysis, all samples showed an hexagonal wurtzite structure with average crystallite sizes approximately in the range 32–33 nm. The doping with Cu allowed to obtain a decrease of band gap energy from 3.2 eV, typical of pure ZnO, to 2.92 eV. Photocatalytic oxidation tests under visible light showed that undoped ZnO is not able to oxidize the As(III) present in solution, while the complete conversion of As(III) to As(V) was achieved in the presence of Cu doped ZnO photocatalyst. The best photocatalytic activity was observed with ZnO doped with 1.08 mol% of Cu (1.08Cu_ZnO), within 120 min of exposure to visible light irradiation. The same result was observed under solar simulated radiation. Photocatalytic tests were carried out also in real drinking water and complete oxidation of As(III) to As(V) by 1.08Cu_ZnO photocatalyst was achieved in 120 min under both visible light (emitted by LEDs) and solar simulated radiation.

“Non-thermal plasma technology” (NTP) has notably increased [...]

Diclofenac (DCF), a non-steroidal anti-inflammatory drug, is considered one of the most widespread emerging contaminants. Its incidence in water can favor the growth of drug-resistant bacteria and harm aquatic organisms endangering both the human health and the ecosystem. Advanced oxidation processes (AOPs) based on the action of reactive oxygen species are very effective technologies for the removal of this contaminant from water. In this context, ZnO is one of the most studied semiconductors for photocatalytic water treatment. In this work, the photocatalytic activity of fluorine-doped ZnO nano- and meso-crystals synthesized by a hydrothermal approach is reported, exploring the role of a low F atomic concentration (0.25, 0.5 and 1 at. %) on the degradation of DCF in comparison with bare ZnO. All doped samples show high rates of DCF degradation and mineralization, which were realized primarily thanks to their high efficiency in the generation of hydroxyl radicals ( OH). The property-structure-function relationships of the materials are investigated by complementary techniques, such as SEM, XRD, EPR, UV–vis DRS and PL, with the aim to evaluate the role of fluorine in determining their morphological, electronic and optical properties.

The aim of this work was the optimization of the performance of the cold plasma technology coupled with a structured catalyst for the discoloration and mineralization of &ldquo, acid orange 7&rdquo, (AO7) azo dye. The structured catalyst consists of Fe2O3 immobilized on glass spheres, and it was prepared by the &ldquo, dip coating&rdquo, method and characterized by different chemico-physical techniques. The experiments were carried out in a dielectric barrier discharge (DBD) reactor. Thanks to the presence of the catalytic packed material, the complete discoloration and mineralization of the dye was achieved with voltage equal to 12 kV, lower than those generally used with this technology (approximately 20&ndash, 40 kV). The best result in terms of discoloration and mineralization (80% after only 5 min both for discoloration and mineralization) was obtained with 0.25 wt% of Fe2O3 immobilized on the glass spheres, without formation of reaction by-products, as shown by the HPLC analysis. The optimized catalyst was reused for several reuse cycles without any substantial decrease of performances. Moreover, tests with radical scavengers evidenced that the most responsible oxidizing species for the degradation of AO7 dye was O2&bull, &minus

Hydrogen production by photocatalytic water splitting is one of the most promising sustainable routes to store solar energy in the form of chemical bonds. To obtain significant H

Hydrogen production by photocatalytic water splitting is one of the most promising sustainable routes to store solar energy in the form of chemical bonds. To obtain significant H2 evolution rates (HERs) a variety of defective TiO2 catalysts were synthesized by means of procedures generally requiring highly energy-consuming treatments, e.g. hydrogenation. Even if a complete understanding of the relationship between defects, electronic structure and catalytic active sites is far from being achieved, the band gap narrowing and Ti3+-self-doping have been considered essential to date. In most reports a metal co-catalyst (commonly Pt) and a sacrificial electron donor (such as methanol) are used to improve HERs. Here we report the synthesis of TiO2/C bulk heterostructures, obtained from a hybrid TiO2-based gel by simple heat treatments at 400 °C under different atmospheres. The electronic structure and properties of the grey or black gel-derived powders are deeply inspected by a combination of classical and less conventional techniques, in order to identify the origin of their photoresponsivity. The defective sites of these heterostructures, namely oxygen vacancies, graphitic carbon and unpaired electrons localized on the C matrix, result in a remarkable visible light activity in spite of the lack of band gap narrowing or Ti3+-self doping. The materials provide HER values ranging from about 0.15 to 0.40 mmol h−1 gcat−1, under both UV- and visible-light irradiation, employing glycerol as sacrificial agent and without any co-catalyst.

This chapter describes the characteristics of photoelectrochemical cells and their applications with particular attention to the function of the membrane to be used in these devices. The typical configuration of a photoelectrochemical reactor has been described and the typical applications of photoelectrochemical cells have been reported distinguishing the function of the photoanode and the cathode and highlighting in each case the specific requests that the cell must satisfy in terms of mass transport, structural characteristics of the photoanode as well as applied current. Furthermore, the membrane function and the critical parameters that influence its activity have been exposed and a discussion about the different solutions proposed in the literature to improve the membrane performances is presented.

The water pollution by atrophic and natural sources is one of the major problems of our planet. Unfortunately, there are many types of pollutants that can be found in wastewater and drinking water, and these concern both organic and inorganic pollutants. The common problem to these contaminants is their difficult removal through conventional water treatment methods. In particular, the scientific community is showing a strong interest in the removal of heavy metals present in water because of their toxic effects on the environment and on human health. The conventional techniques used to remove these elements from the waters, with their advantages and disadvantages have been described. In particular, an efficient alternative method for the removal of heavy metals has been described in detail: the heterogeneous photocatalysis. In this chapter the characteristics of this process has been reported, highlighting the recent applications in the removal of heavy metals using photocatalysts active under visible light.

Heterogeneous photocatalysis (HPC) has been widely investigated in recent decades for the removal of a number of contaminants from aqueous matrices, but its application in real wastewater treatment at full scale is still scarce. Indeed, process and technological limitations have made HPC uncompetitive with respect to consolidated processes/technologies so far. In this manuscript, these issues are critically discussed and reviewed with the aim of providing the reader with a realistic picture of the prospective application of HPC in wastewater treatment. Accordingly, consolidated and new photocatalysts (among which the visible active ones are attracting increasing interest among the scientific community), along with preparation methods, are reviewed to understand whether, with increased process efficiency, these methods can be realistically and competitively developed at industrial scale. Precipitation is considered as an attractive method for photocatalyst preparation at the industrial scale; sol-gel and ultrasound may be feasible only if no expensive metal precursor is used, while hydrothermal and solution combustion synthesis are expected to be difficult (expensive) to scale up. The application of HPC in urban and industrial wastewater treatment and possible energy recovery by hydrogen production are discussed in terms of current limitations and future prospects. Despite the fact that HPC has been studied for the removal of pollutants in aqueous matrices for two decades, its use in wastewater treatment is still at a "technological research" stage. In order to accelerate the adoption of HPC at full scale, it is advisable to focus on investigations under real conditions and on developing/improving pilot-scale reactors to better investigate scale-up conditions and the potential to successfully address specific challenges in wastewater treatment through HPC. In realistic terms, the prospective use of HPC is more likely as a tertiary treatment of wastewater, particularly if more stringent regulations come into force, than as pretreatment for industrial wastewater to improve biodegradability.

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.

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.

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.

In this paper, the photocatalytic degradation of glyphosate by zinc oxide (ZnO) photocatalysts doped with tungsten (W) was investigated under solar simulated light. The photocatalysts were successfully synthesized through a simple precipitation method and subsequently characterized by different techniques: Raman spectroscopy, UV–Vis, N2 adsorption at −196 °C, X-ray diffraction, and SEM analysis. In particular, all the prepared catalysts were characterized by a crystallite size of about 28 nm and a hexagonal wurtzite structure. After the W doping, the bandgap energy decreased from 3.22 of pure ZnO to 3.19 for doped ZnO. This allowed us to obtain good results in terms of glyphosate degradation and simultaneous mineralization under solar simulated lamps, making the process environmentally friendly and with almost zero energy costs. In particular, the best photocatalytic performance was obtained with 100 W-ZnO (prepared with 1.5 mol % of W). With this catalyst, after 180 min of exposure to solar simulated light, the glyphosate degradation and mineralization was equal to 74% and 30%, respectively. Furthermore, it has been shown that the best catalyst dosage was equal to 1.5 g/L. The study on the influence of pH evidenced that the best photocatalytic performances are obtained at spontaneous (neutral) pH conditions. Finally, to determine the main reactive species in the glyphosate oxidation, the effects of different radical scavengers were tested. The results evidenced that the glyphosate oxidation mechanism seems to be related mainly to the O2•− generated under simulated solar light irradiation, but also in minor part to h+.

In the present paper, a stable MoO x /TiO 2 photocatalyst, active in the photocatalytic oxidation of As(III) to As(V), was successfully immobilized on quartz flakes and tested under different UV irradiation intensities and initial As(III) concentration. The structured photocatalyst was prepared in two steps, realizing a coating of TiO 2 on quartz flakes by sol–gel method, and then transferring the molybdenum species through an equilibrium adsorption method. The obtained samples were characterized by SEM–EDAX analysis, N 2 adsorption at −196 °C and Laser Raman spectra. SEM–EDAX results showed the preferential interaction between Mo species and titania layer and a very good dispersion of MoO x on the TiO 2 film deposited on the transparent support. Raman spectra confirmed the presence of hydrated octahedrally polymolybdate species well anchored to the TiO 2 surface. Photocatalytic oxidation tests showed that the complete conversion of As(III) to As(V) was achieved in the presence of MoO x /TiO 2 catalyst supported on quartz flakes within 120 min of UV irradiation. The catalyst maintained an excellent photocatalytic activity and durability after four cycles in aerated water avoiding the photoreduction of the MoO x species. The developed structured photocatalyst can be easily separated from the reaction mixture, making it a very promising catalyst to be employed in continuous reactors for the photocatalytic treatment of arsenic polluted water.

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.

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 Ce

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.

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.

In order to apply the photocatalytic processes on a real scale for the treatment of industrial wastewaters, the use of slurry reactors employing suspended photocatalysts is not suitable due to the need for an uncomfortable and expensive separation phase of photocatalyst. To overcome this disadvantage, the photocatalyst particles must be immobilized on a transparent support: our work proposes, for this reason, a simple and cost effective method for the deposition of ZnO photocatalyst on glass spheres in order to formulate a structured photocatalyst effective in the treatment of aqueous solutions containing various organic dyes, commonly used in the tannery industries and in the treatment of a real wastewater at high COD content (11 g/L) coming from the refining unit of the tanning process. In particular, ZnO was immobilized on glass spheres (ZnO/GS) with a simple dip coating method, starting from zinc acetate aqueous solution, without using complexing agent and strong basic compounds. The optimization of ZnO amount on glass spheres was evaluated employing Acid Blue 7 dye, as model pollutant. In particular, it was found that best performances in terms of discoloration and mineralization of the target dye were obtained using the photocatalyst with a ZnO loading equal to 0.19 wt% (ZnO_ac1), prepared through only one dip-coating step. Moreover, the ZnO_ac1 photocatalyst can be easily separated from the reaction mixture, maintaining excellent photocatalytic activity and durability even after several reuse cycles. Finally, ZnO_ac1 showed a high photocatalytic activity in the treatment of the real wastewater, obtaining a COD removal equal to 70% after 180 min of UV light irradiation.

The development of photocatalytic processes is strongly related to an efficient irradiation of the catalyst surface. A chance to get a significant reactivity enhancement is the promotion of the photocatalyst with up-conversion phosphors able to convert low-energy into high-energy photons. In this work it was found that the photocatalytic activity of visible active N-doped TiO2 (NdT) can be strongly enhanced when it is promoted by the presence of organic up-conversion phosphors (OP) in the catalyst formulation. Such photocatalysts (NdT/OP) have been prepared and tested in the photocatalytic degradation of a wide range of organic dyes in the presence of visible light irradiation emitted by green or white LEDs. The photocatalytic activity of NdT/OP in the presence of green LEDs is attributed to the up-conversion property of OP phosphors that emit at 434 nm, wavelength suitable for photoexciting NdT. Moreover, NdT/OP showed a dramatic enhancement of photocatalytic activity when white LEDs were used as light source. In this case, the NdT supported on OP surface is excited both by the emission spectrum of the white LEDs and by the blue emission of the phosphors (OP), excited by the green component emitted by white LEDs. The obtained results make NdT/OP photocatalyst a very suitable system to achieve high photocatalytic activity with solar light.