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Two commercially available ▫$TiO_2$▫ (hexagonal-like and spherical-like particles) were used to investigate the effect of ▫$g-C_3N_4$▫ “melting” on the photocatalytic properties of ▫$g-C_3N_4/TiO_2$▫ composites. Improvement in the contact between the components was observed when they were thermally treated at 350 °C for an extended period of time (between 2 and 72 h) due to the partial melting and phase fusion of ▫$g-C_3N_4$▫. Consequently, the enhanced contact between the phases allows easier injection of photogenerated electrons from the conduction band of ▫$g-C_3N_4$▫ into ▫$TiO_2$▫, improving charge carrier separation. The prepared composites were tested for bisphenol A degradation under visible-light illumination, which showed that the components that had been calcined for 24 h performed better due to the improved charge carrier separation. Superoxide anionic radicals and photogenerated holes were identified as active species in the photooxidation experiments conducted under visible-light illumination. Nasl. z nasl. zaslona. Soavtorji: Gregor Žerjav, Matjaž Finšgar, Janez Zavašnik, Albin Pintar. Opis vira z dne 13. 3. 2023. Bibliografija: str. 14-16. Abstract.

Nasl. z nasl. zaslona. Soavtorji: Matjaž Finšgar, Janez Zavašnik, Nataša Novak Tušar, Albin Pintar. Opis vira z dne 17. 2. 2023. Bibliografija: str. 10-12. Abstract.

A new alternative synthetic route to the transition-metal free π-conjugated polyHIPEs is reported, which combines the Schiff-base condensation reaction and an emulsion-templating technology.

TiO2+Pt plasmonic solids with 1 wt% Pt and different TiO2 supports (anatase nanoparticles (TNP), polycrystalline nanorods (a-TNR) and single-crystal anatase nanorods (TNR)) were synthesized using the wet impregnation technique and tested as photo, thermal and photothermal catalysts in gas-solid and gas-liquid-solid reactions. Due to the different charges of the TiO2 support surfaces, Pt particles with different sizes, crystallinities and degrees of interaction with the TiO2 supports were formed during the synthesis. The heights of the Schottky barrier (SBH) were 0.38 eV for the a-TNR+Pt, 0.41 eV for the TNP+Pt, and 0.50 eV for the TNR+Pt samples, respectively. The low visible-light-triggered photocatalytic activity of the TNR+Pt catalyst toward the oxidation of water-dissolved bisphenol A (BPA) is attributed to its high SBH and active site deactivation due to the adsorption of BPA and/or BPA oxidation products. The highest photothermal catalytic H2-assisted NO2 reduction rate was expressed by the TNR+Pt catalyst. This can be ascribed to the presence of a narrow particle size distribution of small Pt particles, the absence of the Pt catalysed reduction of the TNR support at higher temperatures, and the lower rate of re-injection of “hot electrons” from the TNR support to the Pt particles. Nasl. z nasl. zaslona. Soavtorji iz Slovenije: Janez Zavašnik, Matjaž Finšgar, Albin Pintar. Opis vira z dne 30. 5. 2023. Bibliografija: str. 11-12. Abstract.

ChemCatChem 13(7), 1814 - 1823 (2021). doi:10.1002/cctc.202001829, We performed in‐situ XAS study of N$_{2}$O decomposition over CuO/CeO$_{2}$ catalysts. The Cu K‐edge and Ce L$_{3}$ ‐edge XANES and EXAFS analyses revealed the dynamic and crucial role of Cu$^{2+}$/Cu + and Ce$^{4+}$ /Ce$^{3+}$ ionic pairs during the catalytic reaction. We observed the initial formation of reduced Cu + and Ce$^{3+}$ species during activation in helium atmosphere at 400 °C, while concentration of these species decreased significantly during steady‐state nitrous oxide degradation reaction (2500 ppm N$_{2}$O in He at 400 °C). In‐situ EXAFS analysis further revealed a crucial role of copper‐ceria interface in this catalytic reaction. We observed dynamic changes in average number of Cu‐Ce scatters under reaction conditions, indicating an enlarging the interface between both copper and ceria phases, where electron and oxygen transfer occurs., Published by WILEY-VCH Verlag, Weinheim

This study presents detailed experimental and theoretical investigation of manganese-based metal oxides, MnMOx (M: Fe, Ni, Cu) as potential catalysts for the low-temperature toluene oxidation. The first part of the paper deals with the detailed characterization of the prepared catalysts and testing of their catalytic activity and stability in the fixed-bed reactor. The MnFeOx exhibited superior and stable catalytic activity for toluene oxidation (T90 = 419–446 K), comparable with the activity of the commercial Pt–Al2O3 catalyst (T90 = 393–423 K). Among the studied catalysts the following order of catalytic activity was determined: MnFeOx > MnNiOx ≈ MnCuOx > MnOx. The one-dimensional (1D) pseudo-homogeneous model was applied to describe behavior of the fixed bed reactor for the low temperature toluene oxidation over prepared MnFeOx catalysts. The second part of the paper is focused on theoretical investigation of toluene interaction on the surface of the single metal oxides (Mn2O3, MnO2, Fe2O3, NiO and CuO) in the oxygen atmosphere using the ReaxFF method, since they were individual dominant phases in the prepared catalysts. A good correlation between the predicted binding energy of toluene adsorption on the surface of studied metal oxide phases and experimentally determined catalytic activities was observed.

Solution combustion synthesis was used to produce a junction between TiO2 and β-Bi2O3, which increases the photocatalytic activity of TiO2-β-Bi2O3 composites under visible and UV-light for the photocatalytic oxidation of aqueous Bisphenol A (BPA) solution. Surface (XPS, UV–vis DR analysis), electronic (EIS, EPR) and structural (SEM, TEM, XRD, N2 physisorption analysis) properties of the composites and BPA degradation performance were analyzed and correlated to the amount of β-Bi2O3 present in the composites (weight ratio Ti:Bi was varied between 1:0.2 and 1:0.8). The results show that (i) the narrow band gap semiconductor β-Bi2O3 acts as a visible-light photosensitizer for TiO2, (ii) a heterojunction between TiO2 and β-Bi2O3 enables the transfer of visible-light generated h+ from the valence band (VB) of β-Bi2O3 to the upper lying VB of TiO2, (iii) a p-n junction enables the transfer of visible-light photo-generated e− in the conduction band (CB) of β-Bi2O3 to the CB of TiO2, and (iv) under UV-light illumination both semiconductors act as scavengers for charge carriers generated by the other component. EPR measurements show that the amount of generated charge carriers and reactive oxygen species (ROS) was higher under UV-light illumination; besides, the amount of generated ROS increased with the increasing amount of β-Bi2O3 phase. On the other hand, BPA degradation runs and EIS measurements revealed that if the weight ratio Ti:Bi is over 1:0.4, the catalytic activity and the amount of generated charge carriers dropped due to excessive formation of a segregated β-Bi2O3 phase. The discrepancy between EPR measurements and catalytic BPA degradation tests can be contributed to the fact that BPA degradation proceeds either directly with photo-generated charge carriers (oxidizing organic species directly by photo-generated holes), or indirectly with ROS that include also EPR silent species (hydrogen peroxide and singlet oxygen).

A simple structural design principle of poly(arylene ethynylene) π-conjugated microcellular polymers as the pure organic, heterogeneous photocatalytic systems is presented. They are synthesized by the Sonogashira cross-coupling polymerization of 1,3,5-triethynylbenzene and 1,4-diiodobenzene, 2,5-dimethoxy-1,4-diiodobenzene or 2,6-diiodo-4-nitrophenol within the high internal phase emulsion (HIPE). Such poly(arylene ethynylene)-based polyHIPEs allow for fine alignment of the valence and conduction band levels to enhance their photocatalytic activity. The resulting polyHIPEs exhibit substantial semiconducting properties, such as strong light-harvesting capability in the visible-light region, most likely due to their π-extended poly(arylene ethynylene) main backbone with donor–acceptor characters having optical fine-tuned bandgaps over a range of 1.70–2.35 eV. The intriguing properties allow these polyHIPE photocatalysts to efficiently catalyze the degradation of water-dissolved endocrine disrupting compound bisphenol A (BPA) under visible light.

Catalytic ozonation of Orange II (100 mg/L) was studied using aluminosilicate Montanit300® (M) modified with H2SO4 (MS) and HCl (MH). Characterization of these samples was performed through several techniques: SEM/EDX, FTIR, XRD, FRX, TPD pyridine, surface area, pHPZC. Acid treatment increased surface area, Si:Al ratio and quantity of acid sites, but reduced pHPZC and Fe and Mn content. Ozonation experiments achieved complete decoloration and remarkable TOC conversions of 66, 65, 88 and 91 % by single ozonation and catalytic ozonation with MH, MS and M, respectively. Higher M and MS activity under acidic pH was attributed to Mn leaching. Decreased mineralization efficiency in the presence of tert-butanol suggested a radical mechanism. At neutral pH, M showed no activity, while MS presented mild activity owing to its enlarged hydrophobicity. The M sample sustained mineralization levels over 20 h. Lower O3 dose caused quick MS deactivation. However, it was reversed through calcination and prevented with a higher oxidant dose. Mn is naturally found in Montanit300®, thus making it an inexpensive catalyst. The development of a dynamic cycle combining reduced and oxidized forms of Mn was key to the outstanding activity observed. Fil: Inchaurrondo, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Di Luca, Carla. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Zerjav, G.. Department For Environmental Sciences And Engineering; Eslovenia Fil: Grau, Javier Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Pintar, A.. Department For Environmental Sciences And Engineering; Eslovenia Fil: Haure, Patricia Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina

Fenton and Fenton-like Advanced Oxidation Processes (AOP) have obtained large applicative use for the removal of organic pollutants from wastewater. Herein, we discuss a novel bimetal Cu-Mn porous silica-supported Fenton-like AOP catalyst with interparticle mesoporosity working under neutral pH and UV-VIS irradiation (CuMnKIL with Mn/Si = 0.01, Mn/Cu = 0.06). The photocatalyst was prepared via solvothermal synthesis (Mn incorporation into porous silica support) followed by incipient wetness impregnation (Cu loading into Mn containing porous silica support) and was tested for the decomposition of methylene blue as a model dye. Copper addition significantly reduced Mn leaching from the porous silica support (from 60 to 30 %) and functioned also as additional surface adsorption site. CuMnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) showed 20 % higher adsorption and 20 % lower efficiency if compared with MnKIL (Mn/Si = 0.01) in Fenton-like AOP system, however, addition of irradiation (photo-Fenton-like system) improved efficiency of Cu/MnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) for 10 % if compared to MnKIL (Mn/Si=0.01) due to the additional •OH radicals produced by the decomposition of H2O2 by the light. No synergistic effects between Cu and Mn were recorded, meaning that Cu and Mn sites were acting as separate sites, which was confirmed with AR-TEM imaging as well as UV spectroscopy studies.

Conjugated porous polymers through the emulsion-templating polymerization process are typically prepared as monoliths, and the emulsions are cured via metal-catalyzed cross-coupling reactions. Herein, we report the design and synthesis of well-defined, millimeter-sized conjugated porous polymer beads by combining an oil-in-oil-in-oil (O/O/O) double emulsion as a de novo template and an amino-catalyzed Knoevenagel condensation reaction as a polymerization chemistry to cure such emulsions. The 1,4-phenylenediacetonitrile is reacted with aromatic multialdehydes in the presence of piperidine, and a series of metal-free poly(arylene cyano-vinylene) beads are prepared. All beads exhibit 3D-interconnected microcellular morphology and substantial semiconducting properties, such as strong light harvesting ability in the visible light region with electrochemical band gaps in the range of 2.05-2.33 eV. Finally, the promising photocatalytic activity of these conjugated beads is demonstrated for a model sulfoxidation reaction under visible light irradiation, and near quantitative conversions with excellent chemoselectivities (99%) are obtained.

In this work, TiO2 thin films were deposited onto soda lime glass substrate by two different techniques: sol-gel (SG) and sputtering (SP). The photocatalytic film performance was assessed in a batch recycle reactor testing the photocatalytic degradation of aqueous solutions of bisphenol A (BPA). The use of supported catalysts in batch recycle reactor systems for the photocatalytic degradation of organic pollutants in waste water can be an alternative to nowadays more used slurry batch reactor systems and powdered catalysts, since it is more economically sustainable and not requiring the removal of catalyst particles after waste water treatment. The best photocatalytic activities were achieved with SG films due to their porosity, which allows BPA molecule to better access the catalytic site than in case of SP films. Raman spectroscopy also showed that SP films have more oxygen vacancies, which may end up acting as charge recombination centers. Doping of TiO2 thin films, either with N or Cu, enabled us to trigger the catalytic activity of films also under UV-free visible light radiation. Regardless the order of stacking in the double-layered films, the latter did not result in an increased catalytic activity towards the photodegradation of BPA.

The results of investigating the morphological, optical and electronic properties of three synthesized TiO2 polymorphs (anatase (A and A2), brookite (B and B2) and rutile (R)) show that the origin of their different catalytic efficiency in the heterogeneous photocatalytic process lies in the depths of the charge carrier traps. The presence of shallow electron traps in brookite extends the number and “lifetime” of generated holes, so brookite is a good choice as a photocatalyst in such heterogeneous photocatalytic systems where these two variables are the reaction limiting factors. Low generation and high recombination rate of charge carriers in rutile are the consequence of too deep electron traps, therefore the generated electrons are not able to participate in reactive oxygen species generation reactions on the catalyst surface. The longer “lifetime” of charge carriers generated in anatase is due to the fact that anatase belongs to the indirect band gap semiconductors. It was further revealed that the increase of the anatase crystallite size (from 10 to 20 nm) can compensate the negative effect of decreasing specific surface area (from 129.5 to 65.0 m2/g) on the photocatalytic activity of anatase. The negative effect of decreasing specific surface area was very well expressed in the case of brookite, where the photocatalytic activity dropped with decreasing specific surface area (from 17.2 to 3.0 m2/g) while keeping constant brookite crystallite size (≈ 80 nm). Heterogeneous photocatalytic experiments with the model pollutant bisphenol A show that the deposition of bisphenol A degradation products on the catalyst surface can have a detrimental effect on photocatalytic activity of low specific surface area TiO2 polymorphs. The specifics (electronic properties, geometry of particles and photocatalytic activity of each TiO2 polymorph) of the investigated heterogeneous photocatalytic system for reactive oxygen species generation are the reason that the “synergistic effect” between the anatase and rutile phase when used as a physical mixture, regardless of the ratio between them, was not expressed. The anatase phase was shadowed by small and abundant rutile nanoparticles with low photocatalytic activity, which acted also as a harvester of UV-light due to a wider UV-light absorption range. We can conclude that the less studied TiO2 polymorph brookite is worthy of investigation, as the results of the present study show that the photocatalytic activity of brookite with the adequate specific surface area is comparable to the photocatalytic activity of the widely investigated anatase TiO2. In addition, it can be concluded that in the physical mixtures of different TiO2 polymorphs, the use of TiO2 particles of close diameters is of crucial importance to achieve a “synergistic” photocatalytic effect triggered by particle collisions.

The structure–property relationship of catalytic supports for the deposition of redox-active transition metals is of great importance for improving the catalytic efficiency and reusability of the catalysts. In this work, the role of alumina support precursors of Cu-Fe/Al2O3 catalysts used for the total oxidation of toluene as a model volatile organic air pollutant is elucidated. Surface characterization of the catalysts revealed that the surface area, pore volume and acid site concentration of the alumina supports are important but not the determining factors for the catalytic activity of the studied catalysts for this type of reaction. The determining factors are the structural order of the support precursor, the homogeneous distribution of the catalytic sites and reducibility, which were elucidated by XRD, NMR, TEM and temperature programed reduction (TPR). Cu–Fe/Al2O3 prepared from bayerite and pseudoboehmite as highly ordered precursors showed better catalytic performance compared to Cu-Fe/Al2O3 derived from the amorphous alumina precursor and dawsonite. Homogeneous distribution of FexOy and CuOx with defined Cu/Fe molar ratio on the Al2O3 support is required for the efficient catalytic performance of the material. The study showed a beneficial effect of low iron concentration introduced into the alumina precursor during the alumina support synthesis procedure, which resulted in a homogeneous metal oxide distribution on the support.

When whitewater circuits in the paper industry are closed, organic compounds accumulate and cause adverse production problems, such as the formation of slime and pitch. Since wood-free whitewater is usually a mixture of additives for paper production and an efficient cost-effective purification technology for their removal is lacking, the aim of our study was to find an effective bio-based strategy for whitewater treatment using a selection of indigenous bacterial isolates. We first obtained a large collection of bacterial isolates and then tested them individually for their ability to degrade the organic additives used in papermaking, i.e. carbohydrates, resin acids, alkyl ketene dimers, polyvinyl alcohol, latex, and azo and fluorescent dyes. Out of the 355 bacterial isolates, we selected a combination of four strains (Xanthomonadales bacterium sp. CST37-CF, Sphingomonas sp. BLA14-CF, Cellulosimicrobium sp. AKD4-BF and Aeromonas sp. RES19-BTP), which cover the entire spectrum of the tested organic additives. A proof-of-concept study in pilot scale was then performed by immobilizing the cells of our artificial bacterial consortium in a 33-liter tubular flow-through reactor with a retention time of Graphical abstractHighlightsA strategy for selecting a consortium of indigenous bacteria with a high potential for bioaugmentation of wood-free whitewater is presented.Study of bacterial degradation of eight chemically diverse substances used in paper production is presented. Methods for the selection of bacteria suitable for industrial application were developed.The constructed artificial bacterial consortium consisted of strains belonging to genera Xanthomonadales bacterium, Sphingomonas, Aeromonas and Cellulosimicrobium.The proof of concept of the industrial application, consisting of a 33-L-column filled with the immobilized artificial consortium, was an 88% decrease in COD of the whitewater effluent.

This work reports the effectiveness of TiO2 photocatalysts modified by defect engineering methods. The prepared photocatalysts were characterized by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) measurements and electron spin resonance (ESR) technique. The immobilized photocatalyst layer was prepared using an abrasive material as a support and a mineral binder. To the best of our knowledge, this is the first time that such type of the immobilized photocatalytic layer has been prepared and tested. A home-made flat-plate photoreactor (FPP) with artificial light sources was used for the degradation of an aqueous solution of imidacloprid using an immobilized TiO2. The effects of different operating variables such as irradiation source, recirculation flow rate, irradiated surface area and photoreactor volume on the photocatalytic performances were investigated. The hydrodynamic behavior of the flat-plate photoreactor (FPP) was studied utilizing a residence time distribution (RTD) technique using the axial dispersion model. Based on kinetic measurements it was found that the photocatalytic degradation of imidacloprid under the conditions used in this study can be described by a complex kinetic model that follows pseudo-zero order kinetics at the beginning of the degradation, and with the progress of the reaction at higher irradiation times changes to the pseudo-first order. Liquid chromatography - quadrupole time‐of‐flight mass spectrometry (LC‐QTOF‐MS) was used to identify imidacloprid degradation by-products as a function of irradiation time. Theoretical modeling of the geometry and electronic structure of imidacloprid in aqueous solution was performed using density functional theory (DFT) calculation. Based on the results of theoretical simulations and experimental measurements, the possible pathway for photodegradation of imidacloprid in aqueous phase after irradiation with UVA was proposed and discussed.

Experimental and theoretical modeling on low-temperature dry methane reforming over Ni-containing CeO2 rods was studied. The catalyst was characterized by means of N2 physisorption, in-situ XRD, TPR and H2 chemisorption techniques. The characterization studies revealed the distortion of CeO2 flourite structure due to the Ni incorporation. Lattice expansion (due to reduction) and contraction (due to oxidation) suggest the reversible redox nature of CeO2. Ni–O–Ce solid solution formation was evidenced by both XRD and TPR studies. H2 chemisorption study revealed that the catalyst reduction temperature plays a significant role in Ni dispersion. The catalyst showed similar activity trends in two model geometries: a between-two-plates microchannel fixed-bed reactor and a conventional fixed-bed reactor. The activity tests were conducted in the kinetic regime, where conversions of CH4 were not influenced with the gas flow rate. A lattice Boltzmann model for mixed gas flow was developed along with a boundary condition for catalytic sites. The lattice Boltzmann model was used in a multiscale simulation of the studied reaction systems and produced data that qualitatively matched the experiments.

The effects of cobalt in the CeZrO2-supported NiCo (3 wt%, Co/ :Ni=3/2) on the DRM at 750oC were investigated by the transient method and use of 18O2 and 13CO2. Transient kinetic rates of carbon deposition and gasification by the support’s oxygen, TOF (s-1) and concentration of active carbon were determined. Higher TOF and reduced carbon accumulation rates were measured on NiCo than Ni at the initial stage of reaction. However, oxidation of Co with time-on-stream led to lower and higher concentration of active metal sites and deposited carbon, respectively. These results appear important for catalyst design improvements (e.g. metal alloy composition).

The course of the thermogravimetric degradation of LDPE in the presence of different aluminosilicate catalysts was modelled by applying a differential isoconversional Friedman approach. An analysis of catalyst-free PE-TG profiles confirmed that the degradation profiles predicted by various reaction models overlap over the entire conversion range once the data are analysed using a differential isoconversional Friedman approach. The results demonstrate that the catalytic degradation of LDPE can be predicted by a correlation twin, i.e. the two specific functional relations between the activation energy, pre-exponential factor and conversion. The crucial step for ensuring good agreement between the predicted and the measured profiles is to extrapolate the discrete values of the activation energies and pre-exponential factors to the zero conversion. It turns out that linear extrapolation and interpolation from the discrete values outperforms regression functions based on various order polynomials, and that apparent deviations from the global trend at lower conversions are not a consequence of the misinterpretation of the experimental results but are an experimental fact. The assumption about the compensation effect between the pre-exponential factor and activation energy holds within the conversion range from 10 to 90%. However, it is generally unsuitable for modelling purposes due to the uncertain extrapolation of the kinetic parameters to the zero conversion.

TiO2 nanorods (T) were combined with a narrow band gap semiconductor β-Bi2O3 (B) to form a heterojunction, which makes it possible for TiO2 to become active as a photocatalyst also under visible light illumination. To further increase the photocatalytic activity of TiO2 + Bi2O3/(BiO)2CO3 (TB) composite, we used a hydrothermal procedure to link it with reduced graphene oxide (rGO). Structural, surface and electronic properties of the obtained catalysts were analyzed and correlated to their performance in photocatalytic oxidation of aqueous bisphenol A (BPA) solution conducted in a batch reactor under visible light illumination. XRD, FTIR, UV–vis DR spectroscopy and photocurrent measurements of visible light illuminated TB composite catalyst clearly showed that (i) β-Bi2O3 acts as a photosensitizer for TiO2 and (BiO)2CO3 present in the TB composite, (ii) holes (h+) are photo-generated in valence band (VB) of β-Bi2O3 and due to the β-Bi2O3/TiO2 heterojunction transferred into VB of TiO2, (iii) p-n junction between β-Bi2O3 and TiO2 allows the photo-generated electrons (e−) in the conduction band (CB) of β-Bi2O3 to transfer to TiO2, and (iv) p-n junction between β-Bi2O3 and (BiO)2CO3 allows the photo-generated electrons in the conduction band of β-Bi2O3 to transfer to (BiO)2CO3. This means that more charge carriers are available to participate in the catalytic visible-light triggered oxidation process for the degradation of organic pollutants dissolved in water. The highest photocurrent density was measured for multi-phase TBR (TB + rGO) composite, which indicates that visible-light generated charge carriers in TB composite are injected into the reduced graphene oxide. The latter acts as a web for charge carrier percolation and suppresses the recombination of electron-hole pairs, thus resulting in improved catalytic activity of TBR. The results of UV–vis DR spectroscopy and photocurrent density measurements were entirely in line with the results of photocatalytic oxidation of water dissolved bisphenol A (BPA) in batch reactor under visible light illumination.

For the photocatalytic wastewater treatment containing lower concentrations of dyes as pollutants, a suitable photocatalyst may be selected for anionic or cationic dye removal according to the photocatalyst surface charging and desired adsorption/degradation ratio. Herein, for the first time, we evaluate mesoporous silica supported TiO 2 versus mesoporous silica supported ZnO photocatalysts at neutral pH and at equal conditions. The evaluation shows that model anionic dye Reactive Blue 19 (RB19) was adsorbed onto silica supported ZnO nanoparticles at neutral pH in a much higher rate than on silica supported TiO 2 nanoparticles, even though the surfaces of ZnO and TiO 2 –silica composite catalysts were negatively charged in both cases (ca. −20 mV of zeta potential). This was ascribed to the strong positive zeta potential of pure ZnO nanoparticles at neutral pH value (ca. +37 mV) and consequently to more mixed oxide (spinel-like) ZnO/silica composite behaviour if compared to the physical mixture of oxide TiO 2 /silica composites. The highest dye adsorption (50%) and the fastest dye degradation (k app = 0.0544 min −1 at 25 °C) was observed on disordered ZnO/silica with Zn:Si molar ratio 1:1. Pure TiO 2 or silica supported TiO 2 nanoparticles were stable under UV irradiation. On the other hand, the interaction between SiO 2 and ZnO resulted in increased resistance of ZnO to photocorrosion, which was proven to be an issue in pure ZnO nanoparticles.

Amorphous TiO2 based nanotubes (TN) obtained through alkaline hydrothermal restructuring of P25 were treated with various acids and functionalized with hydrogen peroxide in order to tailor formation of structurally distinctive titanium peroxo species. Obtained solids were used as catalysts in the catalytic wet peroxide oxidation (CWPO) of model methyl orange (MO) aqueous solution under mild conditions. With the usage of 2 g/L of peroxide modified TN/ClO4p 0.01 catalyst and double stoichiometric amount of hydrogen peroxide, 50 ppm MO solution was purified up to 93% during 1 h at 40°C. No decay of catalyst activity was observed in 5 consecutive runs using the same catalyst batch. 17O NMR and TPD/MS analyses have revealed that catalytic activity of TN/ClO4p 0.01 sample can mainly be assigned to bidentate η2 surface peroxo species whose amount during 5 consecutive catalytic runs is almost constant, namely 5.9×10−7 and 5.2×10−7 mol/m2 prior and after usage, respectively. In addition, it has been observed that considerable amount of thermally labile oxygen species is used during 5 consecutive runs. From 17O NMR analysis we have observed that these species can be attributed to two coordinated (OTi2) oxygen formed on the place of terminal intra/interlayered −OH groups. Former can serve as structural stabilizing agents which enable formation of new η2 surface peroxo species during CWPO runs. To the best of our knowledge, this study is the first attempt to explain the possibility for η2 peroxo species structural stabilization during CWPO under mild conditions.

In this study, two series of TiO2 polymorphs (anatase (A and A1), rutile (R and R1), brookite (B and B1)) and nanocomposite mixtures of TiO2 polymorphs (anatase A/rutile R (AR), anatase A/TiO2-B polymorph (ATB), anatase A1/rutile R1/brookite B1 (ARB)) were synthesized and tested in the process of catalytic wet air oxidation (CWAO). The goal was total removal of the endocrine-disrupting chemical bisphenol A and its intermediates from a model aqueous solution. TiO2 polymorphs A1, B1 and R1 were prepared with a similar synthesis procedure and from the same TiO2 precursor to investigate the influence of catalyst preparation on their performance. To discover which is the main driving property of the catalyst that enables enhanced BPA degradation and mineralization in the CWAO process, different surface, textural and morphological characterization techniques (XRD, SEM, UV–vis-DRS, FT-IR, TG and N2 sorption) were used. CHNS elemental analysis was applied to reveal which of catalysts is suitable for use in a long-term CWAO process. Characterization and catalytic tests of solids examined show that the key factor enabling enhanced activity in the CWAO process is high BET specific surface area of the catalysts. It was found that low specific surface area of a solid can be compensated either by the presence of an appropriate crystallinity, or improved charge separation. Catalysts A, A1 and ATB showed encouraging results of BPA degradation and mineralization in the CWAO process and would also be appropriate for long-term use, since negligibly small amounts of carbonaceous deposits were accumulated on the surface of these solids during tests performed in the period of 40 h.

Natural materials were evaluated in the Catalytic Wet Peroxide Oxidation of a commonly used azo-compound, Orange II. Volcanic ash, black sand, pumice and Montanit300® were selected for evaluation. The materials were thoroughly characterized by several techniques (XRD, SEM/EDX, BET surface area and pore size distribution, TPD, Mössbauer spectroscopy, etc.). Peroxidation experiments were performed varying reaction temperatures (50-80°C), catalyst loads and pH value (3-8). Complete decolouration was reached in most experiments; however, mineralization levels, peroxide consumptions and stabilities differed between materials. The activity of Fe leached during the reaction was evaluated and a combination of heterogeneous and homogeneous mechanism cannot be discarded. Thus, the materials may behave as Fe dispensers. Long-term stability experiments were also performed. While Montanit300® showed a decreased performance (20% activity reduction in 16h) due to a higher leaching (20% Fe loss), ash and pumice performances remained almost steady at pH3 (Fe loss: 3% ash and 1.3% pumice). Mineralization levels obtained were outstanding (40-70%) and comparable to performances showed by more sophisticated catalysts. The use of these natural materials will optimize the Fenton process economics, since they are unexpensive, abundant and require only minimal modifications. Fil: Inchaurrondo, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Maestre, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Zerjav, Gregor. National Institute Of Chemistry; Eslovenia Fil: Pintar, Albin. National Institute Of Chemistry; Eslovenia Fil: Ramos, Cinthia Paula. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Haure, Patricia Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina