Titania Content Research Articles

Pd Catalysts Supported on Mixed Iron and Titanium Oxides in Phenylacetylene Hydrogenation: Effect of TiO2 Content in Magnetic Support Material.

Recently, Pd catalysts supported on magnetic nanoparticles (MNPs) have attracted a great attention due to their ability of easy separation with an external magnet. Modification of MNPs is successfully used to obtain Pd magnetic catalysts with enhanced catalytic activity. In this work, we discussed the effect of titania content in TiO2/MNPs support materials on catalytic properties of Pd@TiO2/MNPs catalysts in phenylacetylene hydrogenation. TiO2/MNPs composites were prepared by simple ultrasound-assisted mixing of TiO2 and MNPs, synthesized by co-precipitation method. This was followed by deposition of palladium ions on the mixed metal oxides using NaOH as precipitant. The supports and catalysts were characterized using XRD, BET, STEM, EDX, XPS, and a SQUID magnetometer. Pd nanoparticles (5-6 nm) formed were found to be homogeneously distributed on support materials representing the well-mixed metal oxides with TiO2 content of 10, 30, 50, or 70%wt. Testing of the catalysts in phenylacetylene hydrogenation showed that their activity increased with increasing TiO2 content, and the process was faster in alkali medium (pH = 10). The hydrogenation rates of triple and double C-C bonds on Pd@70TiO2/MNPs achieved 9.3 × 10-6 mol/s and 23.1 × 10-6 mol/s, respectively, and selectivity to styrene was 96%. The catalyst can be easily recovered with an external magnet and reused for 12 runs without significant degradation in the catalytic activity. The improved catalytic properties of Pd@70TiO2/MNPs can be explained by the fact that the surface of the support is mainly composed of TiO2 particles, affecting the state and size of Pd species.

Porous alumina‐based ceramics with very low thermal conductivity prepared by the starch consolidation route

AbstractAlumina‐based porous ceramics were fabricated via the starch consolidation casting route, using titanium oxide as a sintering additive. Alumina‐titania‐starch slurries with starch contents of 2.5, 5, 7.5, and 10 wt% relative to the alumina‐titania system were prepared. Titania was added to the slurries in proportions of 0, 1, 3, and 5 wt%, relative to alumina. The effects of starch and titania contents in the green bodies on the linear and volumetric shrinkage, as well as the total and open porosities of the sintered alumina product, were investigated. The effect of titania addition on mechanical, electrical, and thermal properties of the obtained porous alumina ceramics was studied. Microstructure and pores morphology were characterized by SEM. The alumina‐based ceramics obtained had external porosities that varied between 54 and 76 vol%. Thermal conductivities as low as 0.06–0.1 W/m.K were achieved and the volume electrical resistivity ranged from 3.6 to 600 GΩ·m, while compressive strengths up to 2.8 MPa for a titania ratio of 1 wt% were attained.

The role of Ti in mitigating thermal expansion of silica from molecular dynamics simulations

AbstractMolecular dynamics simulations are performed to investigate the structural response of titania silicate glass to temperature. The coefficient of thermal expansion is computed for two titania silicate glasses with 0 and 10 mol% titania content, the structures of which are presented in terms of radial and angular distributions. Revealed by the different changing rates of intertetrahedra bond angles and bond lengths with respect to the Ti and Si atoms, the glass structures tend to exhibit a nonvectorized expansion process at elevated temperatures, leading to inconsistent expansion rates of the structures in different scales. While the average length of TiO and Si‐O bonds both increases with temperature, the decrease in the coefficient of thermal expansion by the addition of Ti atoms is associated with the different expansion rate of tetrahedra. Arising from the gradual decrease in atomic overlapping, decrease in free volume inside the glass with temperature is also identified.

Hydraulic retention time governed the micro/nanostructures of titanium-incorporated diatoms and their photocatalytic activity

Titanium-incorporated diatoms are promising biomaterials to photodegrade micropollutants such as pharmaceuticals and personal care products (PPCPs). Hydraulic retention time (HRT) is a key parameter for diatom cultivation and the incorporation of titanium into diatom frustules. This study assessed how HRT governs the micro/nanostructures, titania (TiO2) content and distribution, and the photocatalytic activity of titanium-incorporated diatom frustules. We cultivated a diatom strain Stephanodiscus hantzschii using a feed solution containing titanium(IV) in membrane bioreactors (MBRs) at a solids retention time (SRT) of 10 d and staged HRTs from 24 to 12 and to 6 h. The decrease in HRT reduced the porosity of diatom frustules but increased their silicon and titania contents. When the HRT decreased from 24 to 12 and to 6 h, the specific surface areas of the diatom decreased from 37.65 ± 3.19 to 31.53 ± 3.71 and to 18.43 ± 2.69 m2·g−1 frustules, while the titanium (Ti) contents increased from 53 ± 14 to 71 ± 9 and to 85 ± 13 mg Ti·g−1 frustules. The increase in the influent flow rates of the MBRs with decreasing HRTs likely enhanced nutrient diffusion inside the diatom valve pores, facilitating the uptake and incorporation of silicon and titanium. The titanium-incorporated frustules were effective in removing two representative PPCPs, bisphenol A (BPA) and N,N-diethyl-meta-toluamide (DEET), from water. As photocatalytic activity depends on the amount of titanium, decreasing the HRT substantially increased the photocatalytic activity of the titanium-incorporated frustules. In batch tests under ultraviolet light, frustules from the diatom cultivated at HRTs of 24, 12, and 6 h had the pseudo-first-order removal (mainly through photodegradation) rate constants of BPA of 0.376, 0.456, and 0.683 h−1, respectively. Under the same experimental condition, the pseudo-first-order removal rate constants of DEET by the frustules cultivated at HRTs of 24, 12, and 6 h increased from 0.270 to 0.330 and to 0.480 h−1.

Sulfur-Rich Polyimide/TiO2 Hybrid Materials with a Tunable Refractive Index.

High refractive index (RI) polyimide/titania nanoparticle hybrid materials were synthesized and characterized in this study. The polyimide synthesis took place via the conventional polycondensation process following the preparation of poly(amic acid), and the nanoparticles were incorporated using an in situ sol-gel process. Thin films of the polyimide/titania nanoparticle hybrids were prepared by optimizing the coating conditions using a spin coater. Thermal imidization of the nanoparticle containing poly(amic acid) films on Si wafers was completed in a temperature-controlled drying oven under a N2 atmosphere. Fourier transform infrared spectroscopy revealed the successful formation of inorganic bonds as well as imide linkages, and transmission electron microscopy results show well-dispersed nanocrystalline TiO2 nanoparticles of around 5 nm in the polymer matrix. Thorough optimization of the reaction time and concentration of TiO2 precursors enabled to achieve a titania content as high as 30% (wt). The RI of the resultant hybrid materials was found to be tunable according to the titania content, while the RI increased linearly with increasing titania content. A homogeneous hybrid material with a very high RI of 1.84 at 589 nm was achieved in this work for 30% (wt) TiO2.

Effects of Aluminosilicate Gel Treatment and TiO2 Loading on Photocatalytic Properties of Au–TiO2/Zeolite Y

The present work reports the synthesis of efficient Ti–Au/zeolite Y photocatalysts by different processing of aluminosilicate gel and studies the effect of titania content on the structural, morphological, textural, and optical properties of the materials. The best characteristics of zeolite Y were obtained by aging the synthesis gel in static conditions and mixing the precursors under magnetic stirring. Titania (5, 10, 20%) and gold (1%) species were incorporated in zeolite Y support by the post-synthesis method. The samples were characterized by X-ray diffraction, N2-physisorption, SEM, Raman, UV–Vis and photoluminescence spectroscopy, XPS, H2-TPR, and CO2-TPD. The photocatalyst with the lowest TiO2 loading shows only metallic Au on the outermost surface layer, while a higher content favors the formation of additional species such as: cluster type Au, Au1+, and Au3+. A high TiO2 content contributes to increasing the lifetime of photogenerated charge careers, and the adsorption capacity of the pollutant. Therefore, an increase in the photocatalytic performances (evaluated in degradation of amoxicillin in water under UV and visible light) was evidenced with the titania content. The effect is more significant in visible light due to the surface plasmon resonance (SPR) effect of gold interacting with the supported titania.

The effects of firing temperature and Ti/Si ratio on the H2 permeation characteristics of microporous TiO2-SiO2-organic chelating-ligand composite membranes

Titania-silica composite materials were synthesized and successfully employed in the preparation of microporous gas separation membranes via sol–gel processing. Acetylacetone (ACA), an organic-chelating ligand (OCL), was introduced as a reaction modulator to control the hydrolysis/condensation reactions of titan alkoxide, which resulted in formation of well combined titania and silica structures. The membrane material had a molar ratio of Ti/ACA = 1/1 and was coated onto an intermediate layer with an average pore diameter of about 1 nm. The effect of firing temperature on gas permeability was examined at 300 and 500 °C under a nitrogen atmosphere. As a result, for the case of Ti/Si/ACA = 1/1/1, the membrane fired at 300 °C under nitrogen (300 N) showed a molecular sieving permeation mechanism and a permeance that depended on molecular diameter. This membrane achieved H2 permeance of 0.63 × 10-6 mol/(m2 s Pa), H2/CH4 selectivity of 72.8, and H2/SF6 selectivity of 534.7. The membrane fired at 500 °C under nitrogen (500 N) showed a similar molecular sieving performance, albeit with smaller values for H2 permeance and H2/SF6 selectivity. For this study, the Ti/Si ratios were also altered and studied. Membranes with ratios of Ti/Si/ACA = 1/2/1 and 2/1/2 were prepared by firing under nitrogen at the optimal temperature of 300 °C, and the Ti/Si molar ratio effect on the gas permeance was examined. H2/SF6 selectivity was increased with an increase in the silica content (Ti/Si/ACA = 1/2/1 membrane: H2 permeance 1.26 × 10-6 mol/(m2 s Pa), H2/SF6 = 1350.7). On the other hand, H2/SF6 selectivity became smaller as the titania composite content was increased (Ti/Si/ACA = 2/1/2 membrane: H2 permeance 1.16 × 10-6 mol/(m2 s Pa, H2/SF6 = 53.0). Therefore, by optimizing the titania content, it is expected to achieve the H2 gas separation performance of the TiO2-SiO2-ACA membrane according to the application of the membrane.

Resistive coupled microwave sintering of hydroxyapatite/titania nano-biocomposite and tailoring its mechanical properties

Tailoring the mechanical properties of bioceramics plays a crucial role in the fabrication of hard tissue substitutes. In this work, phase pure nanostructured hydroxyapatite and titania were synthesized using a single-step combustion technique. To study the influence of titania in the mechanical properties of hydroxyapatite, hydroxyapatite/titania (TiO2-0%, 10%, 20%, and 30%) nanocomposites were prepared. The sample containing 20% titania showed maximum sinterability and was analysed in detail. The samples were sintered by a novel resistive coupled microwave sintering to 98.9% of the theoretical density at 1020 °C for a soaking duration of 20 min. A substantial reduction in sintering temperature of ∼165 °C and a significantly low soaking duration were observed in the samples sintered using the new technique and it yielded pellets with reduced grain size compared to the samples sintered via conventional resistive heating. They have shown better microhardness of 7.7 GPa, enhanced compressive strength of 194.9 MPa, and improved elastic modulus of 136.2 GPa without compromising the cell viability, cell adhesion, differentiation, proliferation, and biomineralization. The results indicate that by varying the titania content in hydroxyapatite and by adopting a suitable low-temperature sintering strategy like resistive coupled microwave sintering, one can tailor the mechanical properties of bone implants.

Characterization of 3Y-TZP/TiO2 hybrid experimental dental ceramics

The addition of titania to zirconia dental implants has been considered a promising choice to improve its bioactivity. This study aimed to evaluate the effect of different sintering conditions on the microstructure, density, optical properties and flexural strength of a 3Y-TZP/TiO2 dental ceramic based on zirconia with two different titania contents (7.5 mol% and 12.5 mol%). 3Y-TZP/TiO2 ceramic powders were synthesized by coprecipitation, uniaxially pressed and sintered at six different sintering conditions. Microstructural analysis of the sintered samples was performed by scanning electron microscopy and X-ray diffraction. Optical properties were measured using a spectrophotometer. The density was determined by Archimedes principle. Flexural strength was estimated by the biaxial flexure device. The microstructure and flexural strength of the 3Y-TZP/TiO2 dental ceramic with 7.5% and 12.5 mol% were affected by the sintering conditions. Sintering the specimens at 1460 °C for 2 h increased the grain size and significantly decreased the flexural strength of 3Y-TZP/TiO2 dental ceramic. The interaction (titania content x sintering conditions) affected the relative density and optical properties. A relative density greater than 98% was achieved for the T7.5 groups (sintered at 1260 °C/1 h, 1300 °C/1 h and 1300 °C/2 h) and for the T12.5 groups (sintered at 1260 °C/1 h, 1260 °C/4 h, 1300 °C/1 h and 1300 °C/2 h). The highest values of L*, a* and b* were respectively 87.2 (T7.5 group sintered at 1460 °C/2hs), 4.3 (T12.5 group sintered at 1300 °C/2hs) and 15.8 (T12.5 group sintered at 1300 °C/1 h). The material developed with 12.5 mol% of titania and sintered at 1300 °C/2 h showed high densification, flexural strength of 670 MPa and has good potential to be used in dentistry.

Structural Characterization of Polycrystalline Titania Nanoparticles on C. striata Biosilica for Photocatalytic POME Degradation.

The biosilica shell of marine diatoms has emerged as a unique matrix for photocatalysis, owing to its sophisticated architecture with hierarchical nanopores and large surface area. Although the deposition of titania nanoparticles on diatom biosilica has been demonstrated previously, their photocatalytic activity has been tested only for degradation of pure compounds, such as dyes, nitrogen oxide, and aldehydes. The efficiency of such photocatalysts for degradation of mixtures, for instance, industrial wastewaters, is yet to be investigated. Furthermore, reports on the lattice structures and orientation of nanotitania crystals on biosilica are considerably limited, especially for the underexplored tropical marine diatoms. Here, we report an extensive characterization of titania-loaded biosilica from the tropical Cyclotella striata diatom, starting from freshly grown cell cultures to photodegradation of wastewaters, namely, the palm oil mill effluent (POME). As Indonesia is the largest palm oil producer in the world, photocatalytic technology could serve as a sustainable alternative for local treatment of POME. In this study, we achieved a 54% loading of titania on C. striata TBI strain biosilica, as corroborated by XRF analyses, which was considerably high compared to previous studies. Through visualization using HR-TEM, supported by SAED and XRD analyses, nanocrystal TiO2 appeared to be trapped in an anatase phase with polycrystalline characteristics and distinct crystallographic orientations. Importantly, the presence of C. striata biosilica lowered the band gap of titania from 3.41 eV to around 3.2 eV upon deposition, enabling photodegradation of POME using a broad-range xenon lamp as the light source, mimicking the sunlight. Kinetic analyses revealed that POME degradation using the photocatalysts followed quasi-first-order kinetics, in which the highest titania content resulted in the highest photocatalytic activity (i.e., up to 47% decrease in chemical oxygen demand) and exhibited good photostability throughout the reaction cycles. Unraveling the structure and photoactivity of titania-biosilica catalysts allows transforming marine diatoms into functional materials for wastewater photodegradation.

CeO2–TiO2 oxides with core-shell structure

A series of CeO2–TiO2 composites were synthesized using sol-gel method, and the structures were investigated by HR TEM, XRD, TG-DSC-MS, N2 adsorption-desorption isotherms. The titania coating layer consisting of fine crystallites contributes to properties of the CeO2@TiO2 nanocomposite. The development of the fast, simple, and facile route for the synthesis of novel CeO2@TiO2 core-shell nanocomposite particles was suggested. An approach to increase the shell thickness of titania is to increase the concentration of the precursor of titania, but it also observed the formation of a small amount of independent titania clusters. It is shown that an increase in the titania content leads to the formation of a larger proportion of the rutile phase and a decrease in the proportion of metastable anatase and brookite, while reducing the particle size of the initial ceria core and the specific surface area due to the contact of titania shells, caused by the closer connections between nanoparticles.

Elucidating the mechanisms of titanium–induced morphological and structural changes in catalysts on mesoporous Al2O3–TiOx mixed oxides: Effect of non–stoichiometric TiOx phase

In the present work, mesoporous Al 2 O 3 –TiO x composites with different titania loadings (4, 8 and 12 wt%) were synthesized to evaluate the effect of non-stoichiometric TiO x phases on the hydrodesulfurization (HDS) ability of the CoMo/Al 2 O 3 –TiO x catalysts. The activity of the catalysts was evaluated in the dibenzothiophene (DBT) HDS reaction carried out at 593 K, 5.5 MPa in a batch reactor. Regardless of the TiO x content, all sulfided CoMo Al 2 O 3 –TiO x catalysts were more active than the CoMo/Al 2 O 3 catalyst. For all catalysts, DBT HDS occurs mainly through the direct desulfurization (DDS) pathway (95–97% selectivity). The most active catalysts (CoMo-12 and CoMo-4) showed evidence of the presence of non-stoichiometric titanium oxides. The synthesized materials were characterized in depth to evaluate their crystallinity, textural and morphological properties, elemental composition and acidity. Their characterization showed that: (i), the Al 2 O 3 –TiO x interaction increased with decreasing TiO x content; (ii) the strong interaction between TiO x particles and alumina led to the formation of more defined TiO x structures; (iii), an increase in titania content led to the growth of TiO x crystals along the [101] direction (relative to the [001] direction), which in turn, led to the different TiO x morphologies: nanorods → nanotubes → U-shaped nanotubes. The TiCoMoS phase can be formed if the process is performed on Ti 3 O 5 instead of TiO 2 . • Titania loading influenced on the metal–support interaction and the type of titania phases. • Ti–promoted species are related to increase of the direct desulfurization route. • Non–stoichiometric titanium oxides are necessary to formation of TiCoMoS active phase.

Tuning Photophysical Properties of ZnO/TiO2 Nanocomposite Thin Films by Controlling Anatase Titania Content

The influence of the anatase titania nanoparticles (TiO2 NPs) content on the structural and optical properties of ZnO/TiO2 nanocomposites (ZTNCs) was demonstrated. The solution blending method was employed to prepare the ZTNCs with various ratios prior to their deposition onto glass substrates to form thin films. The X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscope (TEM) techniques revealed that the crystallite size, grain size, and particle size of each TiO2 and ZnO NPs are almost equal. In addition to these techniques, Fourier transform infrared spectroscopy (FTIR) evidenced the homogeneity distribution of the TiO2 within the ZnO NPs. The structural properties of the wurtzite ZnO NPs such as crystallite size, lattice strain, dislocation density, bond length (L) of Zn–O, energy density (u), lattice stress (L S), Young’s modulus, and unit cell volume (V), can be tuned by incorporation of anatase TiO2 NPs in various content. Moreover, the optical properties of the wurtzite ZnO NPs such as absorbance, optical energy band gap (E g), energy gap tail (E u), steepness parameter (σ), and emission intensity can be tuned by incorporation of anatase TiO2 NPs in various contents. The E g and σ of ZnO NPs were decreased to reach at 2.41 eV and 0.0051, respectively, whereas the E u was increased to 4.598 eV upon the increment content of TiO2 NPs.

Effect of Briquette Thickness on Iron Nugget Formation in Fluxless Processing of Iron Sand Concentrate under Isothermal – Temperature Gradient Profiles

Currently, electric furnaces and blast furnaces are used to process iron sand concentrate or titanomagnetite to produce pig iron and titanium slag. The titania content in the slag ranges from 10 to 25 mass% of blast furnaces and 30 to 35 mass% of electric furnaces. The low titania content in the slag is due to the addition of flux, some iron oxide must be retained in the slag to adjust the viscosity of the slag and the mixing of iron sand concentrate with ordinary iron ore. The low titania content in the slag makes titania extraction economically unattractive. One method to achieve high titania slag is the carbothermic reduction process without flux addition. A series of experiments have been carried out on the carbothermic reduction of cylindrical briquettes consisting of iron sand concentrate and coal under an isothermal – temperature gradient profile up to 1380°C to produce iron nuggets separated from slag. The briquettes have a diameter of 13 mm, and the thickness varied from 2 to 18 mm. The results showed that the thickness of the briquettes significantly affected the iron recovery in the nuggets. The briquettes with 2 mm thickness showed higher iron recovery in the nugget. The study also found that the sulfur content in coal may have contributed to the formation of iron nuggets.

Enhanced product quality through hydrodesulfurization of pyrolysis gasoline over a mixed metal oxide catalyst: An experimental and DFT study

Manipulating electronic properties of the hydrodesulfurization (HDS) catalysts can greatly impact the resulting product distribution. To address such effect decently in theoretical and experimental approaches, high-performance cobalt-molybdenum-supported alumina-titania (CoMo/Al2O3-TiO2) with different TiO2 loadings of 10–28 wt% were synthesized. The characterization of the catalysts was implemented by FE-SEM, TEM, XRD, BET/BJH (based on N2 adsorption–desorption), Fourier transform infrared spectroscopy (FTIR), H2-Temperature programmed reduction (H2-TPR), NH3-Temperature programmed desorption (NH3-TPD), and Thermal gravimetric analysis (TGA). The synthesized catalysts were evaluated through HDS of an industrial feedstock– pyrolysis gasoline (Pygas) in a pilot plant tubular fixed bed reactor. It was found that the modification of the electronic properties by titania could also increase the surface acidity while improving the reductive behavior of the tetrahedral and octahedral molybdenum species. In addition, the CoMo/Al2O3-TiO2 with 10 wt% titania content could excellently remove over 96% of sulfur-containing molecules in Pygas. Besides, the developed CoMo catalyst showed an increase in the aromatic compounds, resulting in improved product quality and value through the HDS process. Furthermore, the contribution of TiO2 to the synthesized catalyst was theoretically interpreted through the density functional theory (DFT) method. It was found that lower adsorption energy levels were estimated for the adsorption of the sulfur-bearing molecules on the CoMo/Al2O3-TiO2 than the CoMo/Al2O3 catalyst.

Crystallization of the glasses within the SiO2-Li2O-TiO2 system

Glasses from the ternary system SiO2-Li2O-TiO2 with increasing titania content replacing silica were prepared by melting-annealing technique. Structural FTIR, thermal and differential thermal analysis (DTA) properties of the glasses were measured and evaluated. X-ray diffraction and scanning electron microscope investigations were done to identify the crystalline phases formed together with revealing their morphological features. The coefficient of thermal expansion (CTE) data of glass-ceramic samples are identified to be between 80.83 × 10−7 °C−1 and 120.04 × 10−7 °C−1 (23–500 °C). The increase of the CTE is assumed to be concomitant with the increase of the crystallization of lithium metasilicate (Li2SiO3) phase or quartz (SiO2). Titania is assumed to behave primarily partly as a modifier oxide and at high titania content; it is assumed to act as former (TiO4) groups. X-ray diffraction patterns indicate that the pure lithium silicate glass produces lithium disilicate (LS2) and quartz (SiO2) as crystalline phases and with increasing TiO2, first it acts as a nucleating agent initiating the formation of different crystalline silica phases beside (LS2) then titania is separated at 15 %TiO2 and 30%TiO2 as lithium titanate. The microhardness and densities values are calculated. The studied samples show promising thermal and mechanical properties especially for both CTE and microhardness values, beside their chemical stability which could be applied for commercial uses.

Fabrication and Characteristics of Methyl-Modified TiO2-SiO2 Membrane by Sol-Gel Method: Effect of Titania Content

Titania-doped methyl-modified silica membrane was prepared via an acid-catalyzed sol-gel method using tetraethylorthosilicate and methyltriethoxysilane as the silicon source and tetraethylorthosilicate as the titanium source. The influence of titanium/silicon molar ratio (nTi ) on the properties of TiO2-SiO2 sol and microstructure of unsupported TiO2-SiO2 membrane was systematically studied. The gas permeance and vapor stability of TiO2-SiO2 membrane were also tested. The results showed that, as nTi increased, the density, viscosity, refractive index and viscous activation Gibbs free energy of TiO2-SiO2 sol gradually decreased, while the particle size increased. The existence of Si-CH3 and Ti-O-Si bonds in TiO2-SiO2 membrane proved that the hydrophobic modification was successful and that SiO2 was chemically bonded to TiO2, respectively. The titanium element exists in form of Ti-O-Si structure and anatase phase TiO2 in TiO2-SiO2 membrane. When operated at 150 °C and a pressure difference of 0.3 MPa, the H2 permeance and H2/CO2 permselectivity of TiO2-SiO2 membrane with nTi =0.1 is 6.84 × 10−6 mol·m −2·Pa−1·s −1 and 6.96, respectively. After aging in the moist circumstance for 9 d, the H2 permeance of TiO2-SiO2 membrane reduced by 6.86%, while the H2/CO2 permselectivity increased by 2.71%.

Advantages of the Incorporation of Luffa-Based Activated Carbon to Titania for Improving the Removal of Methylene Blue from Aqueous Solution

This research aims to study the possible improvement of methylene blue (MB) removal from aqueous solution by hybrid adsorbent-catalysts (AdsCats) prepared through the incorporation of activated carbon derived from Luffa cylindrica fibers (LAC) to TiO2 photocatalysts. LAC with a specific surface area of 1170 m2/g was prepared by chemical activation with phosphoric acid at 500 °C. TiO2/LAC composites with 70 and 90 wt.% Degussa P25 titania content were prepared. The materials were characterized by N2 physical adsorption, XRD, FTIR, and XPS. The AdsCats displayed a very good dispersion of TiO2 over LAC, a surface area of close to 200 or 400 m2/g, depending on the composition, and high crystallinity, showing the presence of anatase and rutile phases. MB removal was studied in two different scenarios: under UV-light after reaching adsorption equilibrium, and under UV-light once the liquid effluent and the AdsCats were in contact. The MB removal by LAC has proved to be very efficient, highlighting the predominant role of adsorption over photodegradation. The prepared AdsCats have also been compared with their components. The results showed that TiLAC hybrids have superior photocatalytic performance than P25, showing TiLAC-7/3 90% MB removal with respect to the initial concentration just after 30 min of UV light irradiation for both studied scenarios.

Changes in Optical Parameters of SiO2:TiO2 Films Obtained by Sol-Gel Method Observed as a Result of Thermal Treatment.

The research focused on materials having potential applications in technology of planar evanescent wave sensors. Four samples of binary SiO2:TiO2 thin films having different titania content were manufactured through the sol-gel method and dip-coating technique on polished silicon substrates. The samples were subjected to repeated heating/cooling protocols. Simultaneously, their optical parameters were monitored by spectroscopic ellipsometry as they evolved under varying temperature. Subsequent analysis confirmed linear dependence of refractive index on titania content, at least in vis-NIR wavelengths, as well as a low value of the thermal expansion coefficient. It was shown that the thickness of SiO2:TiO2 films decreased as a result of annealing processes, which may be a consequence of reduced porosity.

Heterostructural transformation of mesoporous silica\u2013titania hybrids

Mesoporous silica (SBA-15 with the BJH pore size of 8 nm) containing anatase nanoparticles in the pore with two different titania contents (28 and 65 mass%), which were prepared by the infiltration of the amorphous precursor derived from tetraisopropyl orthotitanate into the pore, were heat treated in air to investigate the structural changes (both mesostructure of the SBA-15 and the phase and size of the anatase in the pore). The mesostructure of the mesoporous silica and the particle size of anatase unchanged by the heat treatment up to 800 °C. The heat treatment at the temperature higher than 1000 °C resulted in the collapse of the mesostructure and the growth of anatase nanoparticles as well as the transformation to rutile, while the transformation of anatase to rutile was suppressed especially for the sample with the lower titania content (28 mass%). The resulting mesoporous silica-anatase hybrids exhibited higher benzene adsorption capacity (adsorption from water) over those heated at lower temperature, probably due to the dehydroxylation of the silanol group on the pore surface. The photocatalytic decomposition of benzene in water by the present hybrid heated at 1100 °C was efficient as that by P25, a benchmark photocatalyst.