Search

[Display omitted] • Wall-flow channeled monoliths with trimodal pore-size distribution. • SiC monoliths with core-skin hierarchical macroporosity allow membrane coating. • Homogeneous loading of SiO 2 or Al 2 O 3 nanoparticles into the SiC macropores. • Texture defined by SiC porosity, nanoparticle composition, size and load, and calcination temperature. • Efficient Rh-catalyst immobilization, hydroformylation integrated membrane reactor feasible. Monolithic support materials with the mechanical resistance and thermal conductivity of SiC as well as tunable surface chemistry and textural properties were developed for their use in catalytic membrane reactors. After heat treatment, the extruded SiC monoliths have a monomodal distribution of macropores of a few μm in diameter depending on the particle size of the starting material. A macroporous, defect-free, smoother skin was applied onto the external wall using a solution of sub-micrometer SiC particles. These monoliths with skin could be coated successfully with molecularly selective membranes, and thus have application in membrane reactor processes. Finally, metal oxide nanoparticles were infiltrated into the macropores to modify the surface texture and chemistry, allowing the immobilization of liquid phase catalysts. The resulting multimodal distribution of pore sizes could be tuned by the choice of SiC and oxide particle sizes, number of wash-coats and calcination temperature. Mesopores created between nanoparticles had diameters of roughly 40 % of those of the nanoparticles. Small macropores, between 10−1000 nm, were also created, with bigger size and volume at higher calcination temperatures due to the metal oxide particles contraction. The developed materials were validated as support for PDMS membranes and for continuous gas-phase hydroformylation of 1-butene using Rh-diphosphite catalysts. [ABSTRACT FROM AUTHOR]

Summary: Although several therapeutic approaches are available for wound and burn treatment and much progress has been made in this area, room for improvement still exists, driven by the urgent need of better strategies to accelerate wound healing and recovery, mostly for cases of severe burned patients. Bacterial cellulose (BC) is a biopolymer produced by bacteria with several advantages over vegetal cellulose, such as purity, high porosity, permeability to liquid and gases, elevated water uptake capacity and mechanical robustness. Besides its biocompatibility, BC can be modified in order to acquire antibacterial response and possible local drug delivery features. Due to its intrinsic versatility, BC is the perfect example of a biotechnological response to a clinical problem. In this review, we assess the BC main features and emphasis is given to a specific biomedical application: wound dressings. The production process and the physical–chemical properties that entitle this material to be used as wound dressing namely for burn healing are highlighted. An overview of the most common BC composites and their enhanced properties, in particular physical and biological, is provided, including the different production processes. A particular focus is given to the biochemistry and genetic manipulation of BC. A summary of the current marketed BC‐based wound dressing products is presented, and finally, future perspectives for the usage of BC as wound dressing are foreseen. [ABSTRACT FROM AUTHOR]

The assessment of an integral catalytic reactor facilitating operando spectroscopic measurements on a monolith has been carried out using NH 3 -SCR on a vanadia-based catalyst as a probe reaction. The NH 3 -SCR mechanism is revisited by studying the adsorbed ammonia and ionically bound ammonium ions and their relations to Lewis and Brønsted acid sites during reaction. The simultaneous presence of molecular water and ammonia adsorbed on the surface is intrinsic to low temperature NH 3 -SCR, and their IR absorption bands overlap in the bending region around 1600 cm −1 . This has to be tackled in order to genuinely reproduce real reaction conditions and simultaneously extract relevant spectroscopic data of a working industrial monolithic catalyst. This operando study on a V 2 O 5 -WO 3 /TiO 2 –sepiolite monolith is performed without added water in the gas phase, but water formed upstream is adsorbed further down, and thus detected by FTIR spectroscopy. We observed that Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) analysis of the 1620 cm −1 envelope of peaks can successfully resolve the bands of adsorbed H 2 O and NH 3 in the monolith during transients between NH 3 and NO + O 2 flow. Their evolution along with that of surface ammonium ions indicates that generated water hydrolyzes molecularly dispersed vanadia species of the catalyst creating new Brønsted acid sites, and that adsorbed ammonia is either used for the SCR reaction, or converted into the ammonium ion, which then participates in the SCR reaction. [ABSTRACT FROM AUTHOR]

A novel γ-alumina-supported Ni-Ce-Zr catalyst with cellular structure was developed for oxidative dehydrogenation of ethane (ODHE). First, powdered samples were synthesized to study the effect of both the total metal content and the Ce/Zr ratio on the physicochemical properties and performance of these catalysts. All synthesized powdered samples were highly active and selective for ODHE with a maximum ethylene productivity of 6.94 µmolethylene gact cat −1 s −1 . According to the results, cerium addition increased the most reducible nickel species population, which would benefit ethane conversion, whereas zirconium incorporation would enhance ethylene selectivity through the generation of higher amounts of the least reducible nickel species. Therefore, the modification of active site properties by addition of both promoters synergistically increases the productivity of the Ni-based catalysts. The most efficient formulation, in terms of ethylene productivity per active phase amount, contained 15 wt% of the mixed oxide with Ni0.85Ce0.075Zr0.075 composition. This formulation was selected to synthesize a Ni-Ce-Zr/Al2O3 structured body by deposition of the active phase onto a homemade γ-alumina monolith. The structured support was manufactured by extrusion of boehmite-containing dough. The main properties of the Ni0.85Ce0.075Zr0.075 powder were successfully preserved after the shaping procedure. In addition, the catalytic performance of the monolithic sample was comparable in terms of ethylene productivity to that of the powdered counterpart. [ABSTRACT FROM AUTHOR]

Abstract: Photocatalytic oxidation (PCO) technology has a great potential for indoor air purification. However, the presence of humidity and different concentrations of a variety of pollutants are critical parameters that must be addressed for indoor air cleaning applications. In this work, the photodegradation over a commercial air cleaning TiO2 filter of a mixture of two common volatile organic compounds (VOCs), 2-propanol and toluene, at indoor air concentration levels was tested and the role played by water vapour on the PCO performance was discussed. Transient and steady state experiments were performed using different inlet VOCs concentrations (80–400ppbv) and relative humidity values (RH, 0% and 60% at 25°C) in a gas flow rate of 300mLmin−1. The adsorption, conversion and mineralization efficiencies were studied. The reaction products at ppbv levels were analysed by automated thermal desorption coupled to gas chromatography–mass spectrometry (ATD–GC–MS) and gas chromatography equipped with a pulsed discharge helium photoionization detector (GC–PDHID). Almost total conversion and mineralization of the less concentrated mixtures was achieved at 0% RH. A significant negative effect of water vapour was observed. This effect can be attributed to the weak adsorption and low solubility of toluene and to the fast desorption of 2-propanol reaction intermediates. The presence of different surface species, in the photocatalytic degradation tests performed in dry and humid conditions, suggests the occurrence of different reaction pathways depending on RH. [Copyright &y& Elsevier]

Abstract: M-MCM-41 molecular sieves (M=Ce or Cr) were prepared by a hydrothermal method and impregnated with TiO2. The materials were characterized by XRD, N2 adsorption–desorption, DRS and XPS. Their potential application to photooxidize H2S in a wet gas stream was tested in a continuous flow reactor operating at a flow rate of 110mLmin−1 at 50% relative humidity and using 30ppmv of the pollutant. The photocatalytic efficiency using UV-A and visible light was compared to the activity of TiO2/MCM-41 without heteroatoms incorporated into the MCM-41 structure. It was found that the incorporation of Ce did not improve the performance of TiO2/MCM-41, but Cr-containing samples presented higher initial efficiency and were able to photooxidize H2S without formation of SO2 as a by-product, in contrast to the other prepared samples and to Degussa P-25 TiO2. Moreover, no other gaseous by-product was detected. The isomorphic incorporation of Cr into the structure of MCM-41 followed by TiO2 incorporation produced photocatalysts that presented good adsorption capacity and were much more active under visible light than under UV-light. This performance represents an important advantage for solar applications. Their photoactivity depended on the concentration of chromium; the highest efficiency was attained with samples with a Si/Cr ratio of 50. Finally, deactivation was observed as a consequence of sulfate accumulation on the surface of the catalyst and reduction of Cr6+. [Copyright &y& Elsevier]

Abstract: Supported-TiO2 is commonly used for the photocatalytic treatment of gas streams. Nevertheless, selection of the best support is not a trivial task. Cheap, lightweight and easily shaped polymeric materials which are transparent in the TiO2 activation range (poly(ethylene terephthalate) and cellulose acetate) were used as supports, as an alternative to borosilicate glass or opaque monoliths. The supports were coated with TiO2 sols containing anatase particles. Different treatments were applied to the sols in order to improve particle crystallinity and wettability on plastic surfaces. The resistance of the coated and uncoated supports against weathering and the photocatalytic activity for elimination of H2S from polluted air were tested. Both supports were successfully coated with TiO2. PET supports displayed the higher photocatalytic activity, while TiO2 caused the degradation of CA supports under UV illumination. The highest activity for H2S destruction was reached with 20% RH and increasing the temperature of operation in the range of 33–50°C resulted in higher conversion. Sulfate and SO2 were detected as byproducts, being the photocatalytic activity reduced when sulfate accumulates on the surface. Different washing procedures for removing the sulfate from the supported photocatalysts were tested. A simple wash with distilled water was found to successfully recover most of the initial activity of the photocatalyst, although basic pH or higher temperatures accelerate sulfate removal. [Copyright &y& Elsevier]

Promotion of Ni-based catalysts supported on cordierite monoliths was investigated for methane steam reforming. First, cordierite was coated by ɣ-Al 2 O 3, and then the catalyst components were deposited by successive wet impregnation, obtaining: NiAl/cordierite; NiCeAl/cordierite; NiCeLaAl/cordierite and NiCeZrAl/cordierite. The monolithic catalysts were characterized by adherence test, Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDX), N 2 physisorption, Temperature-Programmed Reduction (TPR), CO chemisorption, as well as by in situ and operando Raman spectroscopy. The catalyst layer showed very good adherence and distribution of the components over the cordierite surface. The catalysts presented high activity between 600 and 800 °C at a H 2 O/CH 4 molar ratio=1.5, except for NiCeAl/cordierite, which obtained lower methane conversion, associated with its lower nickel dispersion. The catalysts showed high stability under extreme conditions for carbon deposition (600 °C and H 2 O/CH 4 =1), over 90 h on stream. Raman spectroscopy revealed the presence of oxygen vacancies, which may be increased during ceria reduction, highlighting the potential of these catalysts to enhance the resistance to deactivation by carbon deposition in long-term tests. [Display omitted] • Ni-based catalysts showed strong adherence and uniform distribution over cordierite. • Raman spectroscopy identified NiO phase and CeO 2 solid solutions. • Oxygen vacancies in Ce-containing catalysts may help minimizing carbon deposits. • Monolithic catalysts exhibit high activity and stability in MSR. • Monolithic catalysts exhibit higher carbon deposition resistance than powder ones. [ABSTRACT FROM AUTHOR]

Low-energy wet milling was employed to activate commercial CoAl2O4 spinel and disperse mono- and multimetallic nanoparticles on its surface. This method yielded efficient Pt,Ni catalysts for soot oxidation in simulated diesel exhaust conditions. The characterization and activity results indicated that although Ni/CoAl2O4 was highly active, the presence of Pt was required to obtain a stable Ni(0.25 wt. %),Pt(0.75 wt. %)/CoAl2O4 catalyst under the operating conditions of diesel particulate filters, and that hot spots formation must be controlled to avoid the deactivation of the cobalt aluminate. Our work provides important insight for new design strategies to develop high-efficiency low-cost catalysts. Platinum-containing multimetallic nanostructures could efficiently reduce the amount of the costly, but to date non-replaceable, Pt noble metal for a large number of industrially important catalytic processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • W sites structure changes during the Na 2 WO4 and WO 3 phases transitions. • The oxidation state of the W sites remains mainly 6+ at heating pretreatment. • T d -W6+ sites are less distorted and more active in the presence of O h -Mn3+ sites. The performance of the Mn-Na 2 WO 4 /SiO 2 catalyst for oxidative coupling of methane (OCM) has been ascribed to crystalline phases that are not present at reaction temperatures (>700 °C). The evolution of W and Mn sites structure was monitored via in situ TPO-XRD, -Raman, and -XANES spectroscopies. TPO-XRD shows that the crystalline phases identified on the Mn-Na 2 WO 4 /SiO 2 , Na 2 WO 4 /SiO 2 , and WO 3 /SiO 2 catalysts at room temperature do not exist at relevant OCM temperatures. The γ → β → α-WO 3 , α → β-cristobalite, and cubic → orthorhombic → molten-Na 2 WO 4 phase transitions occur upon heating. TPO-Raman spectra show that the bond order of W sites with octahedral (O h) and tetrahedral (T d) symmetry changes during the δ → γ → β → α-WO 3 and cubic → orthorhombic → molten-Na 2 WO 4 transitions, respectively. TPO-XANES spectra show that bond order changes are due to distortion degree variations because all samples preserve essentially W6+ valence and O h -Mn3+ sites are always present on Mn-Na 2 WO 4 /SiO 2 catalyst. Steady-state OCM tests show that O h -W6+ sites are inactive and T d -W6+ sites are less distorted and more active towards methane activation in the presence of O h -Mn3+ sites. [ABSTRACT FROM AUTHOR]

Several supported liquid-phase (SLP) catalysts with immobilized Rh-biphephos complexes on monolithic supports were prepared and applied for continuous gas-phase hydroformylation (HyFo) of 1-butene. The support comprised macroporous monolithic silicon carbide (SiC) with deposited silica nanoparticles (NPs) in order to provide mesopores with enhanced capillary forces to retain the liquid-phase. Variable parameters were examined for the monolithic SiC supports, including size and loading of deposited silica NPs and intermediate calcination between silica deposition steps to obtain the most efficient support configuration for the SLP system. The SLP catalysts with larger deposited silica NPs gave higher catalytic activity (i.e. 1-butene conversion and turnover frequency) compared to the supports with smaller sized silica NPs. However, the selectivity towards the preferred linear aldehyde was higher in the SLP catalysts with supports containing less silica with small silica NPs. Importantly, the prepared SLP catalyst systems showed long-term stability in HyFo with negligible formation of high boiling aldol condensation products. [ABSTRACT FROM AUTHOR]

Raman spectroscopy is used in a wide variety of fields, and in a plethora of different configurations. Raman spectra of simple analytes can often be analyzed using univariate approaches and interpreted in a straightforward manner. For more complex spetral data such as time series or line profiles (1D), Raman maps (2D), or even volumes (3D), multivariate data analysis (MVDA) becomes a requirement. Even though there are some existing standards for creation, implementation, and validation of methods and models employed in industry and academics, further research and development in the field must contribute to their improvement. This review will cover, in broad terms, existing techniques as well as new developments for MVDA for Raman spectroscopic data, and in particular the use associated with instrumentation and data calibration. Chemometric models are often generated via fusion of analytical data from different sources, which enhances model discrimination and prediction abilities as compared to models derived from a single data source. For Raman spectroscopy, raw or unprocessed data is rarely ever used. Instead, spectra are usually corrected and manipulated, 1 often by case-specific rather than universal methods. Calibration models can be used to characterize qualitatively and/or quantitatively samples measured with the same instrumentation that was used to create the model. However, regular validation is required to ensure that aging or incorrect maintenance of the instrument does not alter the model's predictions, particularly when applied in regulated fields such as pharmaceuticals. Furthermore, a model transfer may be required for different reasons, such as replacement or significant repair of the instrumentation. Modeling can also be used to consistently harmonize Raman spectroscopic data across several instrumental designs, accounting for variations in the resulting spectrum induced by different components. Data for Raman harmonization models should be processed in a protocolled manner, and the original data accessible to allow for model reconstruction or transfer when new data is added. Important processing steps will be the calibration of the spectral axes and instrument dependent effects, such as spectral resolution. In addition, data fusion and model transfer are essential for allowing new instrumentation to build on existing models to harmonize their own data. Ideally, an open access database would be created and maintained, for the purpose of allowing for continued harmonization of new Raman instruments using an outlined and accepted protocol. Graphical Abstract [ABSTRACT FROM AUTHOR]

Over the past decades Raman spectroscopy has been extensively used both on an industrial and academic level. This has resulted in the development of numerous specialized Raman techniques and Raman active products, which in turn has led to the adoption and development of standards and norms pertaining to Raman unit's calibration, performance validation, and interoperability. Purpose of the present review is to list, classify, and engage in a comprehensive analysis of the different standards, guides, and practices relating to Raman spectroscopy. Primary aim of the review is to consider the commonalities and conflicts between these standards and norms and to identify any missing aspects. Standardization in the field of Raman spectroscopy is dominated by the work of American institutions, namely, the American Society of Testing Materials (ASTM or ASTM International), with several active standards in place pertaining to terminology, calibration, multivariate analysis, and specific applications, and the National Institute of Standards and Technology (NIST), providing numerous certified reference materials, referred to as standard reference materials. The industrial application of Raman spectroscopy is dominated by the pharmaceutical industry. As such, pharmacopoeias provide not only important information in relation to pharmaceutical-related applications of Raman spectroscopy, but also invaluable insight, into the basic principles of Raman spectroscopy and important aspects that include calibration, validation, measurement, and chemometric analysis processes, usually by referring to ASTM and NIST standards. Given the fact that Raman spectroscopy is a modern and innovative field, the standardization processes are complex and constantly evolving. Despite the seemingly high number of existing standards, the standardization landscape is incomplete and has not been modernized according to the developments in Raman spectroscopy techniques in recent years. This is evident by the lack of protocols for numerous areas as well as by the fact that some of the existing standards have not been updated to reflect the advances in the technique. Therefore, it is important for the Raman community to actively engage in and contribute to a modernization process that will result in updating existing and introducing new terms, protocols, and guides. Indeed, the development of optimized common standards would be extremely beneficial and would further foster the development and application of Raman spectroscopy techniques, most notably those of surface enhanced Raman spectroscopy and low-resolution portable analyzers. Graphical Abstract [ABSTRACT FROM AUTHOR]

Hybrid structured photocatalysts based on sepiolite, an adsorbent, and hO2 were prepared by extrusion of ceramic dough and conformed as plates. The influence of the photocatalyst configuration was studied either by including TiO2 in the extrusion process (incorporated materials) or by coating the sepiolite plates with a hO2 film (coated materials). The influence of the OH- surface concentration in the photocatalytic performance was studied by treating the ceramic plates at different temperatures. The samples were characterized by N2 adsorption-desorption, MIP, SEM, XRD, and UV-vis-NR spectroscopy and tested in the photocatalytic degradation of trichloroethylene (TCE) as a target VOC molecule. Most of the catalysts presented high photoactivity, but considerable differences were observed when the CO2 selectivity was analyzed. The results demonstrate that there is a significant effect of the catalyst configuration on the selectivity of the process. An intimate contact between the sepiolite fibers and hO2 particles for incorporated materials with a corncob-like structure favored the migration of nondesirable reaction products such as COCl2 and dichloroacetyl chloride (DCAC) to the adsorbent, reacting with OH- groups of the adsorbent and favoring the TCE mimeralization. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a widely recognized global problem due to their prevalence in natural environments and the food chain. However, the impact of microplastics on human microbiota and their possible biotransformation in the gastrointestinal tract have not been well reported. To evaluate the potential risks of microplastics at the digestive level, completely passing a single dose of polyethylene terephthalate (PET) through the gastrointestinal tract was simulated by combining a harmonized static model and the dynamic gastrointestinal simgi model, which recreates the different regions of the digestive tract in physiological conditions. PET MPs started several biotransformations in the gastrointestinal tract and, at the colon, appeared to be structurally different from the original particles. We report that the feeding with microplastics alters human microbial colonic community composition and hypothesize that some members of the colonic microbiota could adhere to MPs surface promoting the formation of biofilms. The work presented here indicates that microplastics are indeed capable of digestive-level health effects. Considering this evidence and the increasing exposure to microplastics in consumer foods and beverages, the impact of plastics on the functionality of the gut microbiome and their potential biodegradation through digestion and intestinal bacteria merits critical investigation. [ABSTRACT FROM AUTHOR]

The accumulation of alkali metals generated during biomass combustion onto the catalysts employed for off-gas treatment can have a detrimental effect on their performance. This work investigates the effect of potassium as a model alkali on an efficient copper-based catalyst supported on SmCeO 2 @TiO 2. The addition of potassium modifies the redox properties of the Cu species or, more specifically, the metal-ceria interface, providing better catalytic activity for NO reduction in oxidizing conditions. SmCeO 2 @TiO 2 stabilizes highly dispersed copper species, and the presence of potassium introduces surface distortions that modify the lability of oxygen atoms. The results demonstrate the key role of surface defects and labile oxygen species associated with the CeO 2 support. It was found that both Cu/SmCeO 2 @TiO 2 and K/Cu/SmCeO 2 @TiO 2 catalysts fully oxidized CO below 350 °C and actively reduced NO with CO in the presence of excess oxygen, reaching a maximum NO conversion of 65% at 316 °C and 83% at 330 °C, respectively, while undesired NO 2 release was minimized in the alkaline-loaded sample. [Display omitted] • Potassium was used as a model alkali on a Cu/SmCeO 2 @TiO 2 catalyst. • The addition of potassium modifies the redox properties of the Cu species. • SmCeO 2 @TiO 2 stabilizes highly dispersed copper species. • The presence of potassium introduces surface distortions that modify the lability of oxygen atoms. • Both Cu/SmCeO 2 @TiO 2 and K/Cu/SmCeO 2 @TiO 2 reach a maximum NO conversion of 65% at 316 °C and 83% at 330 °C, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient microwave-assisted flow synthesis of TiNS and their transformation to TiNT. • Visible-light photocatalyst from nano-confinement of platinum clusters in TiNT. • Deep photocatalytic oxidation of diclofenac by Pt-TiNT mitigate toxicity. • Enhanced quantum efficiency of Pt-TiNT compared to parent TiNT. Pt-TiNT with PtO nanoparticles dispersed within the lumen and interlayer spaces of titania nanotubes (TiNT) were prepared by a new process involving titanate nanosheets (TiNS) synthesis in an optimized microwave-assisted flow reactor, followed by ion-exchange with a Pt precursor, before triggering the titanate layer rolling to trap the Pt precursor clusters inside the titania nanotubes, followed by a thermal treatment. TEM, XRD, and Raman analyses confirm the total conversion of TiO 2 into TiNS in 15 min at 120 °C and 4 bar, and the TiNS transformation into 181 nm-long TiNT with 10 and 6 nm outer and inner diameter, respectively. The 2% Pt-TiNT comprises 0.7 nm PtO clusters (according to XPS), causing slight distortions of the interlayer spaces, while a few larger 2–3 nm Pt clusters reside within the lumen. As a result, Pt-TiNT is 14-fold more active than TiNT for visible light (400–780 nm) photocatalytic oxidation of diclofenac under 2136 μW·cm−2 irradiation, and>1000-fold better than the uncatalyzed photoconversion reaction under 100 mW·cm−2 artificial solar lighting. In addition, nano-confinement of PtO clusters narrowed the bandgap of the TiNT, which, combined with its excellent absorptivity to harvest light, allowed a broader spectral range of photon energies to activate the photocatalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent advances of microwave-synthesized catalysts for air treatment are reviewed. • Fast and homogeneous microwave heating allows delicate control of catalyst properties. • Microwave-synthesized catalysts generally perform better than conventional catalysts. • Microwave irradiation is also used to activate catalytic air remediation processes. Microwave-assisted synthesis has attracted wide attention as an efficient and energy-saving synthesis strategy due to its unique heating mechanism. Environmental catalysts prepared via microwave heating process typically exhibit uniform crystal size with desired morphology, porous structure and interfacial properties, which are important for the catalytic remediation of air pollution. This review first summarizes the principles of microwave heating, followed by the characteristics of the obtained catalysts. The research progress of representative materials (e.g., supported metal catalysts, metal oxides, and porous carbon materials) in the treatment of gaseous pollutants are then categorized in detail. Meanwhile, this review compiles the recent research outputs of air pollutants remediation by environmental catalysts from the perspective of features and reaction pathways facilitated by microwave-assisted synthesis. It demonstrates that microwave-assisted heating can not only improve the synthesis efficiency and the catalytic activity but also modify the selectivity by tuning the catalyst properties. Finally, the use of microwave irradiation to activate environmental catalytic reactions is reviewed, as the application of microwaves can lead to significant improvements due to the possibility of delivering energy directly to the catalytic materials. Nevertheless, challenges remain in the development of highly active and efficient catalyst to realize its practical application. These, together with prospects on the development of environmental catalysts using microwave techniques are provided for enlightening the future of this field of research. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bacterial cellulose's water retention capacity is hindered after the first dehydration. • Bacterial cellulose crosslinking is able to reduce the water retention capacity loss after the first dehydration. • The bacterial cellulose crosslinking with Citric Acid and Epichlorohydrin is efficient. • The crosslinked bacterial cellulose membranes are suitable for applications such as wound and diapers dressing or sanitary pads. Recently, increasing attention has been given to bacterial cellulose-based membranes to be applied as dressings for healing purposes. Bacterial cellulose (BC) is an attractive biomaterial due to its unique structural characteristics such as high porosity, high water retention capacity, high mechanical strength, low density, and biodegradability. One drawback of bacterial cellulose hydrogels is that, after the first dehydration, the water retention capacity is hindered. In this work we produced, modified, and characterized hydrated and de-hydrated BC membranes for biomedical applications. Two crosslinking methods were adopted (using citric acid and epichlorohydrin as crosslinking agents), and the results obtained from the characterization, such as water retention capacity, mechanical properties or contact angle, were compared to those of unmodified bacterial cellulose. We demonstrate that the cross-linked bacterial cellulose membranes present physical properties suitable to be used as wound dressings when hydrated, or as exuding wound dressings, when dehydrated. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present research was to gain further insight into the differences of the trichloroethylene photodegradation routes when using TiO2 (Degussa P25) and protonated titanate nanotubes (H2Ti3O7). These last materials have structural hydroxyls that, along with the surface OH groups present in both photocatalysts, could mediate in the mineralization of the pollutant. In order to obtain a realistic view, an operando Diffuse Infrared Fourier Transform Spectroscopy (DRIFTS) approach has been adopted for surface analysis during the photocatalytic oxidation. The study revealed that the mineralization yield of trichloroethylene on the titanate nanotubes calcined at 300°C was better than the one obtained with the benchmark photocatalyst Degussa P25. In particular, the synthesized nanotubes showed the selective removal of some specific hydroxyl groups, suggesting that their high density and, probably, the specific characteristics of their hydroxyl species can be responsible for the enhanced dechlorination photoactivity exhibited by these nanotubular structures. [Copyright &y& Elsevier]

In the present work, we have studied the photocatalytic degradation of trichloroethylene (TCE) under sunlight illumination with the aim of determining the feasibility of using this technology for gas purification. For these experiments, a continuous flow reactor was employed. This system is basically constituted by a Pyrex glass tube located in the focus of a compound parabolic collector made of anodized aluminum. Raschig rings of borosilicate glass coated with TiO2 and randomly packed within the reactor tube were used as photocatalyts. Results obtained using sunlight illumination indicate that this continuous flow solar reactor can achieve complete TCE degradation. Experimentally, it is found that for moderate conversions, the TCE degradation rate increases linearly with solar irradiance, but a dependence of lower order is observed when removal of the pollutant is almost complete. On the other hand, photonic efficiency decreases linearly with solar irradiance, and it is higher when the molar flow fed to the photoreactor increases. In contrast, the selectivity toward the different partial degradation products (dichloroacetyl chloride, COCl2, etc.) is basically insensitive to solar irradiance. [ABSTRACT FROM AUTHOR]

Abstract: The photocatalytic elimination of microorganisms from indoor air in realistic conditions and the feasibility of simultaneous elimination of chemical contaminants have been studied at laboratory scale. Transparent polymeric monoliths have been coated with sol–gel TiO2 films and used as photocatalyst to treat real indoor air in a laboratory-scale single-step annular photocatalytic reactor. The analytical techniques used to characterize the air quality and analyze the results of the photocatalytic tests were: colony counting, microscopy and PCR with subsequent sequencing for microbial quantification and identification; automated thermal desorption coupled to gas chromatography with mass spectrometry detection for chemical analysis. The first experiments performed proved that photocatalysis based on UVA-irradiated TiO2 for the reduction of the concentration of bacteria in the air could compete with the conventional photolytic treatment with UVC radiation, more expensive and hazardous. Simultaneously to the disinfection, the concentration of volatile organic compounds was greatly reduced, which adds value to this technology for real applications. The fungal colony number was not apparently modified. [Copyright &y& Elsevier]

Abstract: The aim of the present research is to determine the optimum hydrothermal synthesis procedure for using TiO2-based one-dimensional materials as photocatalysts for air treatment applications, in order to enhance their mineralization capacity. The prepared samples were thoroughly characterized by means of TEM, N2 adsorption–desorption isotherms, XRD and Raman spectroscopy. Trichloroethylene (TCE) was selected as a convenient model volatile organic compound (VOC) due to its elevated reactivity. In this study, it is described how the selection of the synthesis parameters (TiO2 precursor, hydrothermal treatment conditions, washing procedure or calcination temperature) allows modulating the nanotubes physicochemical characteristics and, thus, photoactivity. The optimization process led to nanotubes with remarkable photocatalytic performance, with high TCE conversion and selectivity to CO2, which can be favourably compared to that of the benchmark photocatalyst Degussa P25. [Copyright &y& Elsevier]

Abstract: This paper presents the first data on the performance of polyethylene terephthalate (PET) monoliths as photocatalytic support. For this purpose, first a protective layer of SiO2 was applied to the polymer to prevent oxidation of the substrate, and subsequently the photoactive layer of TiO2 was deposited on PET monoliths using the dip-coating technique. In order to increase the adherence of inorganic coatings, two different synthesis procedures were evaluated. One approach was based on reducing the surface tension of the SiO2 sol using a fluorinated surfactant to increment the PET wettability. The second approach consisted in modifying the PET surface with a layer of the polymer poly(diallyldimethylammonium) chloride (PDDA), which provides a positively charged surface for the fixation of the alkaline SiO2 sol. Both TiO2/SiO2 coated PET monoliths were assayed in a single-pass annular reactor for the destruction of trichloroethylene (TCE). The two coating procedures were compared in terms of homogeneity, durability and photocatalytic activity. [Copyright &y& Elsevier]

• Ibuprofen monoacylglycerol (MAG) was selectively obtained at 1:4 profen:glycerol ratio. • 75 % enantiomeric excess towards R-ibuprofen MAG was achieved. • Mono and diacylglycerol of ketoprofen are obtained regardless of the profen:glycerol ratio. • Profens' structure has a key role in esterification with glycerol. • CALB secondary structure is modified due to the interaction with ibuprofen and ketoprofen. The esterification of rac -ibuprofen and rac -ketoprofen with glycerol catalyzed with the commercial biocatalyst Novozym® 435 was investigated at 45 °C with various profen: glycerol molar ratios using 2-propanol as co-solvent in a batch type reaction. The conversion of rac -ibuprofen reached 46%, with an enantiomeric excess towards the S -enantiomer of 42%. When 1:4 ibuprofen:glycerol molar ratio was assayed, 75% of the R -ibuprofen reacted with glycerol towards the monoglyceride with 99% selectivity, which is highly relevant in the field of prodrugs synthesis. The conversion of rac -ketoprofen was lower, 17 % vs. 46 % of rac -ibuprofen, and the esterification afforded both the monoglyceride (70%) and diglyceride (30%) regardless of the ketoprofen:glycerol molar ratio. Investigations of the esterification at molecular level through concentration-modulated infrared spectroscopy, static ATR-FTIR and in situ Raman spectroscopy showed the continuous decay of the species belonging to rac -ibuprofen and glycerol providing further evidences of the reaction. Moreover, the interaction of CALB with ibuprofen modifies the contribution of the ordered structures of the lipase, which might be related with the improved catalytic performance in the esterification of that profen. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sepiolite increased the activity of MnO x -based ceramic bodies. • Sepiolite modulates both the acidity of the catalyst and the Mn reducibility. • Better results obtained when catalysts are synthesized by equilibrium impregnation. • MnO 2 reducibility is associated to a higher catalytic activity. • A higher selectivity to N 2 is linked to the formation of nitrites. Catalytic bodies for selective reduction of NO x with NH 3 based on MnO x , TiO 2 and sepiolite as active phase, support, and binder, respectively, were prepared. The same amount of MnO x (5 w%) was added by impregnation of the precursor over a 70/30 titania/sepiolite. One catalyst was obtained by wet equilibrium impregnation of the pre-shaped support, while the other was prepared by incipient wetness impregnation of the TiO 2 and then mixed with the binder and the PGA, and finally extruded. In order to study the role of the binder in the catalytic system, four models were also synthesized. According to characterization data and to catalytic activity results, sepiolite not only confers the rheological properties needed for extrusion, but it also modifies the physicochemical properties of the catalysts: it modulates the acidity and the NO x adsorption capacity and lability, and, depending on the synthesis procedure, it enhances catalytic activity. [ABSTRACT FROM AUTHOR]

In this work, the influence of the reactor configuration and the characteristics of the catalysts on the photodegradation of trichloroethylene (TCE) vapors are studied under sunlight illumination. The photocatalytic activity tests were carried out using two types of continuous flow reactors: (i) a compound parabolic collector (CPC) and (ii) a simple flat reactor. Three different photocatalysts based on TiO2 were utilized: (i) commercial powders calcined at 500°C (ii) a TiO2-xNx sample synthesized by treating the commercial sample at 500°C in an NH° gas flow, and (iii) TiO2 thin film coatings on differently shaped borosilicate glass supports prepared by a sol-gel procedure. The obtained data reveal that the photonic efficiency for the removal of TCE is quite high but slightly decreases with increasing the light intensity. The commercial TiO2 sample presents the highest efficiency while nitrogen doping seems to be slightly detrimental for photoactivity, despite the fact that certain photoresponse in the visible can be envisaged. In contrast, transparent sol-gel TiO2 coatings present the highest TCE degradation rate per mass of catalyst. Regarding the type of reactor, it is found that the use of CPCs can be advantageous, especially when dealing with high volumes of effluent and elevated concentration of TCE, although flat reactor also shows a considerable efficiency. [ABSTRACT FROM AUTHOR]