Single-Step Synthesis of SiO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> Hydrophobic Core–Shell Nanocomposite by Hydrothermal Method

The objective of this work is the synthesis and characterization of an appropriate hydrophobic nanoparticle as a collector for flotation of hematit in Gol-E-Gohar Iron Mine Iran. In this investigation, SiO₂–TiO₂ nanocomposites have been successfully synthesized by hydrothermal process. The morphology, structure, and composition of the as-synthesized nanostructures have been investigated by scanning electron microscopy and transmission electron microscopy. The ability of SiO₂–TiO₂ nanocomposite to facilitate the froth flotation of pyrite was correlated to the hydrophobicity of the nanoparticles. Furthermore, the efficiency of the mineral flotation process was evaluated in terms of final recovery and grade of S in Gol-e Gohar Iron Ore Complex, Sirjan, Iran.     

Hydrogen Production by Steam Reforming of Ethanol Over Mesoporous Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZrO<Subscript>2</Subscript> Catalysts

This review paper reports the recent progress concerning the application of nickel–alumina–zirconia based catalysts to the ethanol steam reforming for hydrogen production. Several series of mesoporous nickel–alumina–zirconia based catalysts were prepared by an epoxide-initiated sol–gel method. The first series comprised Ni–Al₂O₃–ZrO₂ xerogel catalysts with diverse Zr/Al molar ratios. Chemical species maintained a well-dispersed state, while catalyst acidity decreased with increasing Zr/Al molar ratio. An optimal amount of Zr (Zr/Al molar ratio of 0.2) was required to achieve the highest hydrogen yield. In the second series, Ni–Al₂O₃–ZrO₂ xerogel catalysts with different Ni content were examined. Reducibility and nickel surface area of the catalysts could be modulated by changing nickel content. Ni–Al₂O₃–ZrO₂ catalyst with 15 wt% of nickel content showed the highest nickel surface area and the best catalytic performance. In the catalysts where copper was introduced as an additive (Cu–Ni–Al₂O₃–ZrO₂), it was found that nickel dispersion, nickel surface area, and ethanol adsorption capacity were enhanced at an appropriate amount of copper introduction, leading to a promising catalytic activity. Ni–Sr–Al₂O₃–ZrO₂ catalysts prepared by changing drying method were tested as well. Textural properties of Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst produced from supercritical drying were enhanced when compared to those of xerogel catalyst produced from conventional drying. Nickel dispersion and nickel surface area were higher on Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst, which led to higher hydrogen yield and catalyst stability over Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst.     

Preparation and Photocatalytic Activity of SnO<Subscript>2</Subscript>@TiO<Subscript>2</Subscript> Core–Shell Composites Modified by Ag

Photocatalytic degradation is an important method to mediate organic pollution in the environment. This article reports Ag-modified SnO₂@TiO₂ core–shell composite photocatalysts prepared via a hydrothermal method. The Ag modification and core structure in the composite enhanced the photocatalytic activity and stability of TiO₂ in Rhodamine B degradation under visible light irradiation. The composite modified in 0.15 M AgNO₃ showed an optimal level of photocatalytic activity, as it degraded 99.14 % Rhodamine B in 60 min while pure TiO₂ only degraded 45.7 % during the same time.     

Effect of ZrO<Subscript>2</Subscript> on Catalyst Structure and Catalytic Sulfur-Resistant Methanation Performance of MoO<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

A series of MoO₃/ZrO₂–Al₂O₃ catalysts was prepared and investigated in the sulfur-resistant methanation aimed at production of synthetic natural gas. Different methods including impregnation, deposition precipitation, and co-precipitation were used for preparing ZrO₂–Al₂O₃ composite supports. These composite supports and their corresponding Mo-based catalysts were investigated in the sulfur-resistant methanation, and characterized by N₂ adsorption–desorption, XRD and H₂-TPR. The results indicated that adding ZrO₂ promoted MoO3dispersion and decreased the interaction between Mo species and support in the MoO₃/ZrO₂–Al₂O₃ catalysts. The co-precipitation method was favorable for obtaining smaller ZrO₂ particle size and improving textural properties of support, such as better MoO₃ dispersion and increased concentration of Mo⁶⁺ species in octahedral coordination to oxygen. It was found that the MoO₃/ZrO₂–Al₂O₃ catalyst with ZrO₂Al₂O₃ composite support prepared by co-precipitation method exhibited the best catalytic activity. The ZrO₂ content in the ZrO₂Al₂O₃ composite support was further optimized. The MoO₃/ZrO₂–Al₂O₃ with 15 wt % ZrO₂ loading exhibited the highest sulfur-resistant CO methanation activity, and excess ZrO₂ reduced the specific surface area and enhanced the interaction between Mo species and support. The N₂ adsorption-desorption results indicated that the presence of ZrO₂ in excessive amounts decreased the specific surface area since some amounts of ZrO₂ form aggregates on the surface of the support. The XRD and H₂-TPR results showed that with the increasing ZrO₂ content, ZrO₂ particle size increased. These led to the formation of coordinated tetrahedrally Mo⁶⁺(T) species and crystalline MoO₃, and this development was unfavorable for improving the sulfur-resistant methanation performance of MoO₃/ZrO₂–Al₂O₃ catalyst.     

Possibility of using an UV–nano-TiO<Subscript>2</Subscript>–K<Subscript>2</Subscript>Cr<Subscript>2</Subscript>O<Subscript>7</Subscript> system for the determination of COD

The results of a study of the optimum oxidation conditions in the system UV?nano-Т?О₂–K₂Cr₂O₇ in a specially designed photoreactor are presented. The basic parameters of the photocatalytic oxidation of glucose and acetic acid were studied and optimized. The oxidation of organic compounds under the optimized conditions was studied. Nano-TiO₂ was shown to be a promising photocatalyst in the design of new oxidation systems for analytical purposes.     

Thermal studies of ZnO–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–TeO<Subscript>2</Subscript> glasses

The effect of TeO₂ additions on the thermal behaviour of zinc borophosphate glasses were studied in the compositional series (100 − x)[0.5ZnO–0.1B₂O₃–0.4P₂O₅]–xTeO₂ by differential scanning calorimetry, thermodilatometry and heating microscopy thermal analysis. The addition of TeO₂ to the starting borophosphate glass resulted in a linear increase of glass transition temperature and dilatometric softening temperature, whereas the thermal expansion coefficient decreased. Most of glasses crystallize under heating within the temperature range of 440–640 °C. The crystallization temperature steeply decreases with increasing TeO₂ content. The lowest tendency towards crystallization was observed for the glasses containing 50 and 60 mol% TeO₂. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were Zn₂P₂O₇, BPO₄ and α-TeO₂. Annealing of the powdered 50ZnO–10B₂O₃–40P₂O₅ glass leads at first to the formation of an unknown crystalline phase, which is gradually transformed to Zn₂P₂O₇ and BPO₄ during subsequent heating.     

Hydrodeoxygenation of Vegetable Oil on NiMoS/WO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

Tungstate-containing aluminum oxide is suitable as a catalyst support for hydrodeoxygenation of sunflower oil, ensuring 81–83 wt % yield of liquid products at 380°С, 4.0 MPa, and feed space velocity of 1 h^–1. The catalyst acidity increases with increasing tungsten oxide content, leading to an increase in the content of decarboxylation/decarbonylation products and isoparaffins in the product mixture.     

Polytherm of the CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>–KNO<Subscript>3</Subscript>–H<Subscript>2</Subscript>O phase diagram

The crystallization polytherm of the ternary CO(NH₂)₂–KNO₃–H₂O system is plotted for the first time via visual polythermal analysis and calculating ternary eutonics characteristics from data on the boundary elements of two-component systems. The ternary eutonics modeling error does not exceed 3.5%. In addition to the crystallization fields of individual components, the field of the redox reaction that occurs in the system between potassium nitrate and carbamide is shown in the CO(NH₂)₂–KNO₃–H₂O diagram by a dashed outline.     

Thermal characterisation of raw aluminosilicate glazes in SiO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–CaO–K<Subscript>2</Subscript>O–Na<Subscript>2</Subscript>O–ZnO system with variable content of ZnO

Thermal properties of raw aluminosilicate ceramic glazes in the multicomponent system of SiO₂–Al₂O₃–CaO–K₂O–Na₂O–ZnO modified by ZnO addition were studied by differential thermal analysis (DTA), dilatometry (DIL), hot-stage microscopy (HSM), X-ray diffraction and fourier transform infrared spectroscopy (FTIR). Using the method of differential thermal analysis, the ways in which zinc oxides affect the temperature of transition (T _g), crystallisation (T _c) were determined. An analysis of the DTA data obtained during thermal tests showed that an increase in ZnO content results in decreasing the T _g value. Also, the influence of ZnO on characteristic temperatures and viscosity of glazes was checked. The introduction of zinc oxide (ZnO) into the glaze composition contributes to the decrease in viscosity of such glazes. An increasing ZnO content in the glazes also causes the reduction in softening (T _s), half-sphere (T _half-sphere) and fusion (T _fusion) temperatures. The mid-infrared spectroscopy showed that the thermal properties of glazes in SiO₂–Al₂O₃–CaO–K₂O–Na₂O–ZnO system modified by addition of ZnO can be associated with the depolymerising influence of zinc ions on the structure of the tested glazes.     

Multicomponent systems LiCl–LiBr–Li<Subscript>2</Subscript>SO<Subscript>4</Subscript> and LiCl–LiBr–Li<Subscript>2</Subscript>SO<Subscript>4</Subscript>–Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>

Phase equilibria in the LiCl–LiBr–Li₂SO₄ ternary system and the LiCl–LiBr–Li₂SO₄–Li₂MoO₄ quaternary system were studied by differential thermal analysis. The compositions and temperatures of minima in the ternary and quaternary systems were determined to be (31.2 mol % LiCl, 46.8 mol % LiBr, 22.0 mol % Li₂SO₄, 460°C) and (25.2 mol % LiCl, 30.2 mol % LiBr, 14.6 mol % Li₂SO₄, 30.0 mol % Li₂MoO₄, 411°C), respectively.     

Ternary Systems LiBr–LiVO<Subscript>3</Subscript>–Li<Subscript>2</Subscript>CrO<Subscript>4</Subscript> and KBr–KVO<Subscript>3</Subscript>–K<Subscript>2</Subscript>CrO<Subscript>4</Subscript>

The binary system KVO₃–K₂CrO₄ and two ternary systems, LiBr–LiVO₃–Li₂CrO₄ and KBr–KVO₃–K₂CrO₄, were studied. In the ternary systems, the compositions and melting points of eutectic alloys were determined by differential thermal analysis: (49.0 mol % LiBr, 5.0 mol % LiVO₃, 46.0 mol % Li₂CrO₄, 400°C) and (17.0 mol % KBr, 78.0 mol % KVO₃, 5.0 mol % K₂CrO₄, 458°C), respectively.     

Photoelectrochemical performance of bilayered Fe–TiO<Subscript>2</Subscript>/Zn–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films for solar generation of hydrogen

A visible-light sensitive bilayered photoanode of Fe–TiO₂/Zn–Fe₂O₃ has been developed by spray pyrolytically depositing Zn–Fe₂O₃ layers onto predeposited Fe–TiO₂ thin film on ITO substrate. Fe–TiO₂/Zn–Fe₂O₃ photoelectrodes were characterized by XRD, Raman, AFM, UV-vis absorption spectroscopy. Photoelectrochemical properties of bilayered Fe–TiO₂/Zn–Fe₂O₃ photoelectrode were studied by Mott–Schottky curves and I–V characteristics. Bilayered Fe–TiO₂/Zn–Fe₂O₃ photoelectrode was observed to possess much higher separation efficiency of photogenerated charge carriers and could generate nine times better photocurrent density than pure Fe–TiO₂. Solar to hydrogen conversion efficiency exhibited by this electrode was 0.77%.     

Ionic mobility and electrophysical properties of solid solutions in PbF<Subscript>2</Subscript>–SbF<Subscript>3</Subscript> and PbF<Subscript>2</Subscript>–SnF<Subscript>2</Subscript>–SbF<Subscript>3</Subscript> systems

Ionic mobility and electrical conductivity of solid solutions with fluorite structure, obtained with solid-state approach in PbF₂–SbF₃ and PbF₂–SnF₂–SbF₃ systems, are studied by 19F NMR and electrochemical impedance spectroscopy methods. The 19F NMR spectra parameters, types of ion motions in the fluoride sublattice, and the ionic conductivity magnitude are shown to be determined by the temperature and fluoride concentration in the solid solutions. The solid solution specific conductivity in the PbF₂–SbF₃ and PbF₂–SnF₂–SbF₃ systems at 420–450 K is as high as ~10^–2 S/cm, which allows accounting the solid solutions as a base for preparation of functional materials.     

Formation of solid solutions of multiferroics in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The sequence of phases appearance during the formation of Bi_1–xNd_xFeO₃ solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO₃ or NdFeO₃) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi_1–xNd_xFeO₃ as the final product, due to the prevalence of various interphase contacts in the starting reaction zone.     

Physicochemical Analysis of the System Zr(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>–Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O at 25°С

The solubility in the quaternary water–salt system Zr(SO₄)₂ · 4Н₂О–Na₂SO₄–H₂SO₄–H₂O at 25°C was studied. It was found that, in the system, there is crystallization of not only Na₂SO₄ and Zr(SO₄)₄ · 4H₂O, but also sodium sulfate zirconates Na₂Zr(SO₄)₂(OH)₂ · 0.3H₂O, Na₄Zr(SO₄)₄ · 3H₂O, and Na₂Zr(SO₄)₂ · 3H₂O and two new compounds, S₁ and S₂, which are presumably Na₂ZrO(SO₄)₂ · 2H₂O and Na₂Zr₂O₂(SO₄)₃ · 6H₂O.     

Effects of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> on the crystallization and structure of CaO–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass ceramics

Radiation-induced degradation of the weakly and strongly 4-vinylpyridine basic ion exchange resins by gamma radiolysis was investigated in the presence of air and liquid water. This study is focused on evaluating the radiolytic gases (H₂, CO, CO₂ and CH₄) and liquid products (water-solute TOC and NH₄ ⁺). The weakly basic resin yielded lower amounts of H₂ and CO and higher amounts of CO₂ than those of the strongly basic resin. Moreover, the strong basic resin tended to yield greater amounts of NH₄ ⁺. Resins were characterized by the FTIR spectroscopy technique and the results showed that the resins structures are relatively stable.     

Effect of Calcination Temperature on the Catalytic Oxidation of Formaldehyde Over Co<Subscript>3</Subscript>O<Subscript>4</Subscript>–CeO<Subscript>2</Subscript> Catalysts

The effect of calcination temperature (350–650?°C) on the structure and catalytic activity of Co₃O₄–CeO₂ mixed oxides prepared by sol–gel method was investigated by XRD, H₂-TPR, O₂-TPD and formaldehyde (HCHO) oxidation. The Co₃O₄–CeO₂ calcined at 450?°C (Co₃O₄–CeO₂-450) exhibited the best performance, showing that the complete oxidation of HCHO was achieved at temperature as low as 80?°C. The results of characterizations revealed that the Co₃O₄–CeO₂-450 had excellent catalytic activity due to the larger specific surface area, the best reducibility and more abundant surface active oxygen species.     

Diagram of the PbF<Subscript>2</Subscript>–SnF<Subscript>2</Subscript> system

A phase diagram of the PbF₂–SnF₂ system has been studied by differential thermal analysis and X-ray powder diffraction. The system forms Pb_1–хSn_хF₂ (х ≤ 0.33) solid solution and three compounds. Pb₂SnF₆ decomposes in solid state by a peritectoid reaction at 350°С; Pb₃Sn₂F₁₀ and PbSnF₄ melt by peritectic reactions at 565 and 380°С, respectively. The eutectic coordinates are 180°С, 90 mol % SnF₂.