Catalytic degradation of gaseous benzene by using TiO2/goethite immobilized on palygorskite: Preparation,characterization and mechanism

The nano-TiO₂/goethite/palygorskite catalysts were prepared by sol–gel method. The morphology and structure of the catalysts were analyzed by X-ray diffraction (XRD), UV–Vis reflection spectrometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N₂ adsorption-desorption measurement. The results indicated that the self-made catalysts had excellent catalytic performance on gaseous benzene degradation. In the case of benzene concentration at 30 mg/m³, the degradation efficiency, over TiO₂/goethite/palygorskite composite with mass ratio of 10:5:5, reached 70.4% after 180 min 254 nm UV irradiation. The reaction mechanism and kinetics study showed that palygorskite/goethite/TiO₂ composites photocatalytic degradation benzene was mainly caused by oxidizing property of electron–holes and oxygen synergy effect.     

Influence of MoSi2 content in suspension on the phase, microstructure and properties of hydrothermal electrophoretic deposited SiC n �CMoSi2 coating for SiC pre-coated C/C composites

To protect carbon/carbon (C/C) composites from oxidation at high temperature, a nano SiC?CMoSi₂ (SiC _n ?CMoSi₂) coating on SiC pre-coated C/C composites was prepared by hydrothermal electrophoretic deposition. The phase composition, surface and cross-section microstructures of the prepared SiC _n ?CMoSi₂ coating deposited with different MoSi₂/SiC _n mass ratio were characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The influence of MoSi₂ content in the hydrothermal electrophoretic deposition suspension on the phase composition, microstructure and high-temperature oxidation resistance of the multi-layer coatings were investigated. Results showed that the content of MoSi₂ phase in the prepared coating increases with the increase of MoSi₂ content in the suspension. The density and oxidation resistance of the SiC_n-MoSi₂ coating improve with the increase of MoSi₂ mass content from 20 to 60 wt% in the deposition suspension. However, micro-cracks and micro-holes in the coating are found when deposited with 80 wt% MoSi₂, and a decrease in oxidation resistance was also detected. The multi-layer coatings deposited with suspension of 60 wt% MoSi₂ exhibited the best anti-oxidation ability, which can effectively protect C/C composites from oxidation in air at 1,873 K for 90 h with weight loss of 2.08%.     

Synthesis,characterization of palygorskite supported zero-valent iron and its application for methylene blue adsorption

In this work, natural palygorskite impregnated with zero-valent iron (ZVI) was prepared and characterized. The combination of ZVI particles on surface of fibrous palygorskite can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. There is a significant increase of methylene blue (MB) decolourized efficiency on acid treated palygorskite with ZVI grafted, within 5 min, the concentration of MB in the solution was decreased from 94 mg/L to around 20 mg/L and the equilibration was reached at about 30–60 min with only around 10 mg/L MB remained in solution. Changes in the surface and structure of prepared materials were characterized using X-ray diffraction (XRD), infrared (IR) spectroscopy, surface analysing and scanning electron microscopy (SEM) with element analysis and mapping. Comparing with zero-valent iron and palygorskite, the presence of zero-valent iron reactive species on the palygorskite surface strongly increases the decolourization capacity for methylene blue, and it is significant for providing novel modified clay catalyst materials for the removal of organic contaminants from waste water.     

Sensitive phenol determination based on co-modifying tyrosinase and palygorskite on glassy carbon electrode

A sensitive tyrosinase biosensor, based on co-modifying tyrosinase and palygorskite on glassy carbon electrode, was developed for phenol analysis. Palygorskite, a kind of natural one-dimensional clay with good biocompatibility, high specific surface area and porous morphology, works as a perfect matrix of enzyme. Tyrosinase retains its inherent bioactivity when immobilized in palygorskite, which leads to a high sensitivity of 1.897 A mol^?1 L. The sensor response achieves 95% of steady-state-current in no more than 3 s, and the linear range of the bioelectrode spans the concentration of phenol from 5?×?10^?8 to 1?×?10^?4 mol L^?1 with a correlation coefficient of 0.9992. The results show no apparent decrease in the response over 2 weeks, and about 80% of the response was retained after 2 months when the electrode was stored at 4–5 °C.     

In-vitro hemolytic activity and free radical scavenging by sol-gel synthesized Fe3O4 stabilized ZrO2 nanoparticles

Zirconia ceramics have attained much consideration owing to the amazing mechanical strength and white color. These properties provide an opportunity for the use in biomedical applications. In the present study, an application oriented sol-gel route was adapted for synthesis of zirconia nanoparticles. ZrOCl₂·8H₂O was used as a precursor, iron oxide (Fe₃O₄) nanoparticles (pH 2 & pH 9) as a stabilizer and de-ionized water was used as a solvent. Sol-gel synthesized iron oxide stabilized zirconia nanoparticles were prepared by varying concentrations of iron oxide nanoparticles in the range of 2–10 wt%. X-ray diffraction results showed mixed phases at all wt% with acidic pH value, while pure tetragonal phase of zirconia was observed for stabilization with 6 wt% basic iron oxide. Maximum value of dielectric constant (~80 at log f = 4) and minimum value of tangent loss (~0.66 at log f = 4) were observed for zirconia stabilized with basic 6 wt% iron oxide. Maximum value of hardness (1410 ± 10 HV) along with high fracture toughness were observed with optimized stabilization. Very weak hemolytic activity and maximum scavenging (~76) antioxidant activity was observed under optimized conditions. Thus, it can be suggested that optimized nanoparticles, i.e. tetragonal zirconia stabilized with 6 wt% of basic Fe₃O₄, can be further useful for therapeutical and pharmaceutical applications.     

Adsorption of Corrosion Inhibitors onto Iron Carbonate (FeCO3) Studied by Zeta Potential Measurements

The adsorption of cetyl trimethyl ammonium bromide (CTAB) and two commercial inhibitor base chemicals, an oleic imidazoline salt (OI) and a phosphate ester (PE), onto iron carbonate (FeCO₃), was studied by zeta potential measurements in a 0.1 wt% sodium chloride (NaCl) solution under 1 bar CO₂ at 22°C, in the absence and presence of a refined low-aromatic oil. The zeta potential of oil-in-water emulsion droplets was also determined. Surface tension of 0.1 wt% and 3 wt% brines was measured as a function of inhibitor concentration. The isoelectric point was pH 6.0 in the 0.1 wt% NaCl solution under 1 bar CO₂. The results show that all three inhibitor compounds adsorbed onto the iron carbonate particles both at pH 4.0 and pH 6.0. Adsorption on both negatively charged surfaces and surfaces with no charge were thus found for all inhibitors. The addition of oil had no significant effect on the measured zeta potential on iron carbonate particles.     

Highly efficient mesoporous WO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/KIT-6 catalysts for oxidative desulfurization of dibenzothiophene with hydrogen peroxide

Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m²/g), and three-dimensional pore network (WO _x /KIT-6). The prepared WO _x /KIT-6 catalysts (5–20 wt% WO _x ) were characterized by X-ray diffraction analysis, N₂ sorption measurements, electron microscopy, H₂-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WO _x /KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WO _x /KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity.     

Novel Bi2O3 nanoporous film fabricated by anodic oxidation and its photoelectrochemical performance

Novel bismuth oxide (Bi₂O₃) nanoporous films were fabricated through anodization of bismuth foil in electrolytes containing glycol, ammonium sulfate ((NH₄)₂SO₄) and deionized (DI) water. Scanning electron microscopy analysis indicated that morphology of the anodized bismuth foil changed markedly along with the changing of oxidation time, water content, electrolyte concentration, temperature, and applied voltages. The optimized morphology was obtained when bismuth was anodized at 20 V, 40 °C for 40 min in glycol solution containing 0.3 wt% (NH₄)₂SO₄ and 5 wt% DI water. The composition and crystal structure of the samples formed in the optimized conditions were characterized by energy-dispersive spectroscopy and X-ray diffraction. Results showed that the as-prepared nanoporous structures were amorphous. β-Bi2O3 was obtained when the samples were annealed at 200 °C. The photocurrent response experiments demonstrated that the Bi₂O₃ nanoporous film can generate photocurrent as large as 2.893 and 6.980 μA/cm² under 0 and 0.5 V bias voltage versus saturated calomel electrode, respectively.     

Effects of calcination and support on supported manganese catalysts for the catalytic oxidation of toluene as a model of VOCs

The conventional impregnation method was used to prepare 15 wt% Mn-supported catalysts, which were applied to the catalytic oxidation of volatile organic compounds (VOCs; toluene, benzene, and o-xylene). The effects of calcination temperatures in the range of 500–900 °C and supports (γ-Al₂O₃, SiO₂, and TiO₂) on the property and performance of 15 wt% Mn-supported catalysts were investigated. Their physicochemical characteristics were analyzed by the BET, XRD, NH₃–TPD, H₂–TPR, and XPS. The calcination temperature greatly affected the crystalline structure and O1s _D (defect oxides)/O1s _L (lattice oxides) area ratio of the 15 wt% Mn/γ-Al₂O₃ (15 Mn/Al) catalyst. The order of the O1s _D/O1s _L area ratios of the 15 Mn/Al catalysts with respect to calcination temperature was 900 > 500 > 700 °C, which was in good agreement with that observed for the catalytic activity. In addition, the activity order of the 15 wt% Mn-supported catalysts with respect to the type of support was γ-Al₂O₃ > SiO₂ > TiO₂. The 15 wt% Mn/Al catalyst, which had a higher O1s _D/O1s _L area ratio, showed better activity than the 15 wt% Mn/SiO₂ (15 Mn/Si) and 15 wt% Mn/TiO₂ (15 Mn/Ti) catalysts. Defect oxides played a significant role in the catalytic oxidation of VOCs. The catalytic activity with respect to the type of VOC decreased in the order of benzene > toluene > o-xylene.     

Influence of barium titanate nanofiller on PEO/PVdF-HFP blend-based polymer electrolyte membrane for Li-battery applications

Organic-inorganic hybrid membranes based on poly(ethylene oxide) (PEO) 6.25 wt%/poly(vinylidene fluoride hexa fluoro propylene) [P(VdF-HFP)] 18.75 wt% were prepared by using various concentration of nanosized barium titanate (BaTiO₃) filler. Structural characterizations were made by X-ray diffraction and Fourier transform infrared spectroscopy, which indicate the inclusion of BaTiO₃ in to the polymer matrix. Addition of filler creates an effective route of polymer-filler interface and promotes the ionic conductivity of the membranes. From the ionic conductivity results, 6 wt% of BaTiO₃-incorporated composite polymer electrolyte (CPE) showed the highest ionic conductivity (6 × 10^?3 Scm^?1 at room temperature). It is found that the filler content above 6 wt% rendered the membranes less conducting. Morphological images reveal that the ceramic filler was embedded over the membrane. Thermogravimetric and differential thermal analysis (TG-DTA) of the CPE sample with 6 wt% of the BaTiO₃ shows high thermal stability. Electrochemical performance of the composite polymer electrolyte was studied in LiFePO₄/CPE/Li coin cell. Charge-discharge cycle has been performed for the film exhibiting higher conductivity. These properties of the nanocomposite electrolyte are suitable for Li-batteries.     

Preparation and characterization of activated carbon fibers from liquefied wood

Wooden activated carbon fibers (WACFs) were prepared from phenolated Chinese fir (Cunninghamia lanceolata) using CO₂ activation; microstructure characterization, the adsorption capacity, BET-specific surface area, and pore distribution of WACFs were investigated by SEM and X-ray analysis. Results showed that WACFs have a smooth surface and round or elliptical cross-section. The (002) crystal plane diffraction peak of the WACFs was obviously heightened, also showing an apparent (100) diffraction peak. With increased activation temperature, the value of d ₍₀₀₂₎ gradually decreased, whereas the values of the crystallite sizes L _a and L _c initially decreased and then increased. The L _c/d ₍₀₀₂₎ and g values corresponding to the degree of change in the graphitization structure increased. WACFs mainly have micropores as well as a few macro- and mesopores. The micropore diameter of WACFs has a narrow range (0.3–0.5 nm). With increased activation temperature, the single-point surface area, Brunauer-Emmett-Teller surface area, micropore area, single-point total pore volume, and micropore volume of WACFs increased, while the pore diameter decreased. At 900 °C, the iodine adsorption and yield rate of WACFs were 779.22 mg/g and 51.48 %, respectively.     

Some thermal characteristics of a mineral mixture of palygorskite,metahalloysite, magnesite and dolomite

An industrial raw material taken from Sivrihisar (Eskişehir, Turkey) region was heat-treated at different temperatures in the range of 100–1000°C for 2 h. The volumetric percentage of the particles having a diameter below 2 μm after staying in an aqueous suspension of the material was determined as 67% by the particle size distribution analysis. The mineralogical composition of the material was obtained as mass% of 32% palygorskite, 10% metahalloysite, 35% magnesite, 20% dolomite and 3% interparticle water by using the acid treatment, X-ray diffraction and thermal analysis (TG, DTA) data. The temperature ranges were determined for the endothermic dehydrations for the interparticle water as 25–140°C, for the zeolitic water as 140–320°C, and for the bound water as 320–480°C, in the palygorskite. The temperature range for the endothermic dehydroxylation and exothermic recrystalization of the palygorskite is 780–840°C. The temperature range for the endothermic dehydroxylation of the metahalloysite and calcinations of magnesite are coincided at 480–600°C. Dolomite calcined in the temperature range of 600–1000°C by two steps. The zig-zag changes in the specific surface area (S/m² g⁻¹) and specific micro and mesopore volume (V/cm³ g⁻¹) as the temperature increases were discussed according to the dehydrations in the palygorkskite, dehydroxylation of palygorskite and metahalloysite, and calcinations in magnesite and dolomite.     

The Influence of Copolymerization Condition on Rheology,Morphology and Thermal Behavior of Polypropylene Heterophasic Copolymers

In this work, the polypropylene impact copolymers were synthesized by a modified sequential polymerization process. The copolymerization of ethylene and propylene was carried out between two homopolymerization stages at two different pressures and temperatures and the rheology, morphology and thermal properties of reactor alloys were studied. It is found that the ethylene propylene rubber (EPR) content increased up to 32 wt% by increasing the copolymerization time to 20 min. At a fixed copolymerization time of 10 min, the addition of 50 ppm hydrogen (H₂), increased the EPR content from 9.7 to 12.8 wt%. By doubling H₂ concentration, no considerable change in EPR wt% was observed. It is found that the zero shear viscosity of the alloys is significantly under the influence of EPR wt%, not the molecular weight of matrix. The molecular weight of PP matrices determined by rheological data, mildly decreased from 463000 to 458000 g/mol by increasing the copolymerization time from 10 min to 15 min. At high copolymerization time/high H₂ concentration, a melting peak in the differential scanning calorimetry test around 165°C for isotactic PP and also an endothermic peak around 127°C for the block copolymer with long ethylene segments, is observed. The study of interfacial strength by theoretical emulsion models showed that 15 min copolymerization time is optimum considering EPR wt%.     

Crystallization behaviors and optical properties of isotactic polypropylene: comparative study of a trisamide and a rosin-type nucleating agent

The effects of concentrations of N, N’, N”-tris- tert. butyl- 1,3,5- benzene- tricarboxamide (NA) and a hemiacid of dehydroabietic acid (1:1 K) on the optical properties of iPP were compared with each other. It revealed that the NA was an effective transparent nucleating agent for iPP. The NA had advantage at very concentration (0.02 wt%), while the 1:1 K had some advantage at high concentrations (0.3 wt%～0.5 wt%), The optimal concentration range of the NA was 0.1 wt% to 0.4 wt%, while the value for 1:1 K was 0.3 wt% to 0.5 wt%. The absence of detectable spherulites in nucleated iPP was confirmed by SEM and POM. This was an important reason why the nucleated iPPP showed improved optical properties. The results of WAXD showed that preferential growth along the b-axis during crystallization and more disordered structures were formed in the nucleated samples. The results of DSC disclosed increased crystallization peak temperature and melting temperature in the nucleated samples.     

Synthesis and characterization of a new surface modified Amberlite-7HP resin by nano-iron oxide (Fe3O4) and its application for uranyl ions separation

A new sorbent Amberlite-7HP modified by the nanoFe₃O₄ (7HPNFeO) formed by surface modification of Amberlite-7 HP using iron oxide magnetic nano-particles which was prepared by precipitation of iron(II) and iron(III) ions in an aqueous solution. The prepared particles have been characterized with transmission electron microscopy, energy dispersive X-ray/scanning electron microscope, X-ray diffraction, and infrared techniques. The sorption kinetics of U(VI) obeyed pseudo second-order and fitted to the intra-particle diffusion model. The sorption isotherms can be correlated to Langmuir isotherm with monolayer capacity of 47.169 mg/g. The breakthrough data obtained by column studies then utilized to model it with Thomas model and to estimate the loading capacity of U(VI) under the specified column conditions. The interfering effect of various anion and cations on the sorption process was examined. Oxalic acid was found suitable for U(VI) separation from the interfering ions Co(II), Cd(II), and Zr(IV) in aqueous solution. Results obtained showed that 7HPNFeO is a promising and effective sorbent and could be used in real samples for safeguard verification purposes.     

Mechanism of Electrical Percolation of w/o Microemulsions Formed by Nonionic Surfactants

A study was carried out on the mechanism of electrical conductivity percolation of H₂O/C₁₆EO₂₀/n-butanol/heptane microemulsions. Electrical conductivity, UV-vis spectroscopy and FTIR spectra were used to study the diluted “dry” microemulsions with the mass ratio of C₁₆EO₂₀/n-butanol/heptane = 3:3:4. The results of electrical conductivity showed that the percolation occurred around φ_w = 20 wt% and the transition of w/o microemulsions to bicontinueous microemulsions happened when φ_w = 45 wt%. From the UV-vis absorption spectra, it was found that the absorption of methyl orange (MO) in microemulsions shifted red than that of in oil phase, but the maximal absorption peak (λ_max) remained unchanged when φ_w > 20 wt%. It implied that the position of MO solubilized in microemulsions was unvaried after free water appeared in the core. FTIR spectra revealed that the OH band of water in microemulsions moved to high frequency at low φ_w (< 20 wt%) and became broader at high φ_w. It indicated that the added water only caused the hydration of EO at low φ_w, the hydration completed when φ_w > 20 wt% and then the residual water entered into the core with properties similar to bulk water. The presence of free water as ions exchange medium will cause the electrical conductance increased. The percolation appeared after the hydration of EO completed.     

Prereforming of <Emphasis Type="Italic">n</Emphasis>-tetradecane over Ce-promoted 50 wt% Ni/MgO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst with high coke resistance

The effect of Ce-promotion on 50 wt% Ni-based catalysts during the prereforming of n-tetradecane and its optimum content were investigated. The Ni catalyst was synthesized by deposition–precipitation method. Next, various amounts of Ce (0–13 wt%) were loaded on the Ni catalyst by impregnation. The characteristics of the prepared catalysts were analyzed by XRD, H₂-TPR, BET, BJH, and H₂-chemisorption analyses. The prepared catalysts were tested under the prereforming conditions (temperature = 400 °C, GHSV = 3000 h^?1, and S/C = 3 and 4). The Ni catalyst was easily deactivated under the following conditions: temperature = 400 °C, GHSV = 3000 h^?1, and S/C = 4. The stability of all Ce-promoted Ni catalysts was improved as compared to that of the Ni catalyst. Among the Ce-promoted catalysts, 5 wt% Ce/50 wt% Ni/MgO–Al₂O₃ catalyst showed excellent stability even under the severe condition of S/C = 3. SEM, TEM, and TG analyses were performed in order to identify the main factor responsible for the rapid deactivation of the Ni catalyst. In the case of 0Ce/50Ni, Ni particles were encapsulated by many folds of coke and it was related to the rapid catalyst deactivation. However, after Ce promoted on the Ni catalyst, the thickness of the coke layers and the number of encapsulated Ni particles decreased and the deposited amount of coke on the catalyst also decreased.     

Thermal analysis of palygorskite

Slickensides and fissures in a fresh outcrop of silicified limestones at the Bürgenstock (Switzerland) contained palygorskite. According to TG, DTA and heating X-ray experiments, dehydration of the palygorskite took place in four steps. Each step clearly showed an alteration in the unit cell dimensions. Exothermic reactions which occur at higher temperatures resulted in the formation of a Mg-Al- silicate high phase together with some clinoenstatite and the formation of β- cristobalite with some cordierite, respectively.     

Magneli phase Ti n O2n − 1 as corrosion-resistant PEM fuel cell catalyst support

Magneli phase titanium suboxide, Ti _n O_{2n ? 1}, with Brunauer–Emmett–Teller surface area up to 25 m² g^?1 was prepared using the heat treatment of titanium oxide (rutile) mixed with polyvinyl alcohol in ratios from 1:3 to 3:1. XRD patterns showed Ti₄O₇ as the major phase formed during the heat treatment process. The Ti _n O_{2n ? 1} showed excellent electrochemical stability in the potential range of ?0.25 to 2.75 V vs. standard hydrogen electrode. The Ti _n O_{2n ? 1} was employed as a polymer electrolyte membrane fuel cell catalyst support to prepare 20 wt% platinum (Pt)/Ti _n O_{2n ? 1} catalyst. A fuel cell membrane electrode assembly was fabricated using the 20 wt% Pt/Ti _n O_{2n ? 1} catalyst, and its performance was evaluated using H₂/O₂ at 80 °C. A current density of 0.125 A?cm^?2 at 0.6 V was obtained at 80 °C.