Studies on influence of hydrogen and carbon monoxide concentration on reduction progression behavior of molybdenum oxide catalyst

Temperature programmed reduction (TPR) analysis was applied to investigate the chemical reduction progression behavior of molybdenum oxide (MoO₃) catalyst. The composition and morphology of the reduced phases were characterized by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM). The reduction progression of MoO₃ catalyst was attained with different reductant types and concentration (10% H₂/N₂, 10% and 20% CO/N₂ (%, v/v)). Two different modes of reduction process were applied. The first approach of reduction involved non-isothermal mode reduction up to 700 °C, while the second approach of reduction involved the isothermal mode reduction for 60 min at 700 °C. Hydrogen temperature programmed reduction (H₂-TPR) results showed the reduction progression of three-stage reduction of MoO₃ (Mo⁶⁺ → Mo⁵⁺ → Mo⁴⁺ → Mo⁰) with Mo⁵⁺ and Mo⁴⁺. XRD analysis confirmed the formation of Mo₄O₁₁ phase as an intermediate phase followed by MoO₂ phase. After 60 min of isothermal reduction, peaks of metallic molybdenum (Mo) appeared. Whereas, FESEM analysis showed porous crater-like structure on the surface cracks of MoO₂ layer which led to the growth of Mo phase. Meanwhile, the reduction of MoO₃ catalyst in 10% carbon monoxide (CO) showed the formation of unstable intermediate phase of Mo₉O₂₆ at the early stage of reduction. Furthermore, by increasing 20% CO led to the carburization of MoO₂ phase, resulted in the formation of Mo₂C rather than the formation of metallic Mo, as confirmed by XPS analysis. Therefore, the presented study shows that hydrogen gave better reducibility due to smaller molecular size, which contributed to high diffusion rate and achieved deeper penetration into the MoO₃ catalyst compared to carbon monoxide reductant. Hence, the reduction of MoO₃ in carbon monoxide atmosphere promoted the formation of Mo₂C which was in agreement with the thermodynamic assessment.     

Highly efficient photocatalytic degradation of methylene blue using carbonaceous WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> composites

Recent improvements in the performance of photocatalysts made it possible to tackle pollution through environment friendly methods. This study investigates the modification of the photocatalytic activity of TiO₂ by employing WO₃ and conductive polymers, namely, polyaniline (Pani) and polypyrrole (Ppy). Basing on our previous improvement of TiO₂ using a conductive polymer and activated carbon (AC), this study determines the activated carbon forms of TiO₂. The prepared composites are characterized using X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared, thermogravimetric analysis, Brunauer–Emmet–Teller, and UV–Vis spectroscopy. The specific surface area of the mesoporous composites is as follows: WO₃/TiO₂·AC (Pani) > WO₃/TiO₂·AC (Ppy) > WO₃/TiO₂·Pani > WO₃/TiO₂·Ppy (127 > 98 > 68 > 44 m² g^?1), which exhibited a similar trend to the photocatalytic performances (100 > 95 > 91 > 72 % conversion rate). This result could be attributed to higher porosity, surge of charge separation, and photo-responding range extension induced by the synergistic effect of WO₃, conducting polymers, and TiO₂ in the samples.     

Distribution of ytterbium (Yb) in cells of Streptomyces sp. YB-1 which can accumulate Yb, and reusability of cells and cell membrane as bioadsorbent for Yb

The cells of Streptomyces sp. YB-1 adsorbed 4-6 mg ytterbium (Yb) per g dry weight. The Yb contents of the cell wall fraction, cell-free extract, and cell membrane fraction were 11%, 2%, and 87%, respectively. The Yb content in the cell membrane fraction was 20-25 mg per g dry weight. The adsorbed Yb could be quantitatively desorbed by treating the cell membrane fraction with 1 mM EDTA and 1 M HCl at 37 degrees C for 4 h. Treatment with 1 M NaOH caused Yb desorption to some extent. Treatments with proteinase K, lysozyme, 0.5% Triton X-100, 0.4% sodium dodecyl sulfate, and 1 M NaCl did not cause Yb desorption. Elemental analysis of Yb-adsorbed materials after removal of proteins and then extraction of lipids from the membrane fraction revealed that the molar ratio of Yb and P in the materials was about 1:1. The cells and the membrane fraction could be used repeatedly as a bioadsorbent for Yb.     

Study on Alloying Behaviour of Uranium Zirconium Alloy

Uranium–zirconium alloy is the potential candidate material as metallic fuels for nuclear reactor applications. Fabrication of uranium zirconium alloy can be made either by powder metallurgy or by melting method. Both the method has its own advantages and selection of the fabrication route depends on its application as fuel. In this work investigations were carried out on fabrication of uranium–zirconium alloys (i.e. U–40 wt% Zr, U–50 wt% Zr, U–60 wt% Zr and U–70 wt% Zr) using both powder metallurgy and melting method. It is heat treated at different conditions. Apart from other characterization, X-ray diffraction analysis was carried out to evaluate phase content of the alloy and reported here.     

Vanadium pentoxide: Synthesis and characterization of nanorod and nanoparticle V2O5 using CTAB micelle solution

Using a surfactant-mediated method (surfactant based on cetyltrimethyl ammonium bromide, CTAB) V₂O₅ nanorod and nanoparticles have been successfully prepared. Morphologies of V₂O₅ nanostructures can be controlled by applying different precursors and by varying reaction conditions within the CTAB soft template. With ammonium metavanadate and sulfuric acid as precursors, nanoparticles are synthesized in the size range of 45–160 nm. Precursors of vanadyl sulfate hydrate and sodium hydroxide yield vanadium pentoxide nanorods with diameters of 30–90 nm and lengths of 260–600 nm. The resulting products are characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), variable pressure scanning electron microscopy (VPSEM) and X-ray photoelectron spectroscopy (XPS). Temperature programmed reduction (TPR) is included to test catalytic performance. The results show that V₂O₅ nanoparticles and nanorods achieve better catalytic performance compared to bulk V₂O₅, i.e. lower onset temperature, workability at lower temperatures, and higher H₂ consumption (μmol/g).     

Zirconium sulfate supported on activated carbon as catalyst for esterification of oleic acid by n-butanol under solvent-free conditions

It has been shown that the activated carbon-supported zirconium sulfate (ZS) is an efficient solid catalyst for the esterification of oleic acid by n-butanol under solvent-free condition. The effect of mole ratio of the reactant, time and catalyst loading on the conversion was examined. The correlation among XRD, nitrogen adsorption data and catalytic activity suggested that ZS has been finely dispersed on activated carbon, which are active in the esterification of oleic acid. The reaction shows that the supported ZS exhibits a higher activity than that of parent ZS and conventional resins.     

Palm-Based Nonionic Surfactants as Emulsifiers for High Internal Phase Emulsions

In the present study, a series of as-synthesized palm-based nonionic surfactants with various hydrophile–lipophile balance values were successfully synthesized. The critical micelle concentration and the Gibbs energy of the surfactants were determined and discussed. For the first time, the surfactants were used to stabilize three-component olein oil-in-water high internal phase emulsions, with an oil volume fraction of 0.85, and which were easily prepared by one-pot homogenization. Proof of high stability was confirmed by the satisfactory rheological profiles and further enhanced by a three-month storage exercise at an elevated temperature which showed no significant physical and rheological changes. These results suggest that low concentration of the surfactants efficiently stabilized the emulsions with high content of oil. Based on the optical micrograph observation, an average droplet size of less than 10 μm increased with increasing ethylene oxide chain length and temperature. The varying degree of viscosity resulted from the various ethylene oxide chain lengths of the surfactants. The hydration efficacy of the emulsions was examined in vivo using a corneometer. The impressive hydration efficacy of olein oil suggests that it could well be a potential moisturizing lipid which might interest dermatologists.     

Crystallization behavior of iron- and boron-containing nepheline (Na2O·Al2O3·2SiO2) based model high-level nuclear waste glasses

This study focuses on understanding the relationship between iron redox, composition, and heat-treatment atmosphere in nepheline-based model high-level nuclear waste glasses. Glasses in the Na₂O–Al₂O₃–B₂O₃–Fe₂O₃–SiO₂ system with varying Al₂O₃/Fe₂O₃ and Na₂O/Fe₂O₃ ratios have been synthesized by melt-quench technique and studied for their crystallization behavior in different heating atmospheres—air, inert (N₂), and reducing (96%N₂–4%H₂). The compositional dependence of iron redox chemistry in glasses and the impact of heating environment and crystallization on iron coordination in glass-ceramics have been investigated by Mössbauer spectroscopy and vibrating sample magnetometry. While iron coordination in glasses and glass-ceramics changed as a function of glass chemistry, the heating atmosphere during crystallization exhibited minimal effect on iron redox. The change in heating atmosphere did not affect the phase assemblage but did affect the microstructural evolution. While glass-ceramics produced as a result of heat treatment in air and N₂ atmospheres developed a golden/brown colored iron-rich layer on their surface, those produced in a reducing atmosphere did not exhibit any such phenomenon. Furthermore, while this iron-rich layer was observed in glass-ceramics with varying Al₂O₃/Fe₂O₃ ratio, it was absent from glass-ceramics with varying Na₂O/Fe₂O₃ ratio. An explanation of these results has been provided on the basis of kinetics of diffusion of oxygen and network modifiers in the glasses under different thermodynamic conditions. The plausible implications of the formation of iron-rich layer on the surface of glass-ceramics on the chemical durability of high-level nuclear waste glasses have been discussed.     

Removal of nitrophenols from water using cellulose derived nitrogen doped graphitic carbon material containing titanium dioxide

Nitrophenols (NPs) and their derivatives are highly toxic, mutagenic and bio-refractory pollutants commonly present in natural water resources and industrial wastewater. To remove NPs from water, N-doped graphitic carbon (NGC) and NGC adsorbent containing titanium dioxide (NGC–TiO₂) were synthesized by pyrolysis of microcrystalline cellulose and dopamine mixture, and the mixture along with TiO₂ at 500°C, respectively. NCG-TiO₂ was thoroughly characterized using various analytical techniques. NP adsorption on the NGC–TiO₂ adsorbent surface was studied by varying the pH, initial concentration of NP, and adsorbent dose. The results showed that the most efficient adsorption was achieved at pH 3. After 4?h sonication at pH 3, 80% 4-NP adsorption was achieved using NGC–TiO₂ compared to 74% with NGC adsorbent. The percentage removal of 4-NP was higher than 3-NP which was also higher than 2,4-DNP using NGC–TiO₂. 4-NP adsorption best fitted to the Langmuir isotherm plot with R² value of 0.9981 and adsorption capacity of 52.91?mg?g^?1. The adsorption process of NP was found to follow a pseudo-second-order kinetic model. The rate constant value for the adsorption of 10^?4?M 4-NP at pH 3 using 10?mg of NGC–TiO₂ adsorbent was found to be 3.76?×?10^?5?g.mg^?1.min^?1