Decolorization of methylene blue by heterogeneous Fenton reaction using Fe3−xTixO4 (0 ≤ x ≤ 0.78) at neutral pH values

In this work, a series of Fe_3−xTi_xO₄ (0 ≤ x ≤ 0.78) was synthesized using a new soft chemical method. The synthetic Fe_3−xTi_xO₄ were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, thermogravimetric and differential scanning calorimetry (TG–DSC) analyses. The results showed that they were spinel structures and Ti was introduced into their structures.Then, decolorization of methylene blue (MB) by Fe_3−xTi_xO₄ in the presence of H₂O₂ at neutral pH values was studied using UV–vis spectra, dissolved organic carbon (DOC) and element C analyses. Furthermore, the degradation products remained in reaction solution after the decolorization were identified using ionic chromatography (IC), ¹³C nuclear magnetic resonance spectra (NMR), liquid chromatography and mass spectrometry (LC–MS). Although small amounts of MB were mineralized, the aromatic rings in MB were destroyed completely after the decolorization. Decolorization of MB by Fe_3−xTi_xO₄ in the presence of H₂O₂ was promoted remarkably with the increase of Ti content in Fe_3−xTi_xO₄ due to the enhancement of both adsorption and degradation of MB on Fe_3−xTi_xO₄.     

Electrochemical biosensors utilizing the electron transfer of hemoglobin immobilized on cobalt-substituted ferrite nanoparticles–chitosan film

Cobalt ferrite nanoparticles (Co_xFe_3−xO₄) and chitosan (CS) film were used to immobilize/adsorb hemoglobin (Hb) to create a protein electrode to study the direct electron transfer between the redox centers of the proteins and the electrode. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the Co_xFe_3−xO₄ particles were nanoscale in size and formed an ordered layered structure. The native structure of the immobilized Hb was preserved as indicated by Fourier-transform infrared (FTIR) and UV–visible (UV–vis) spectroscopy. The Hb-Co_xFe_3−xO₄–CS modified electrode showed a pair of well-defined and quasi-reversible cyclic voltammetric peaks at −0.373 V (vs. SCE) and exhibited appreciable electrocatalytic activity for the reduction of H₂O₂. The catalysis currents increased linearly with H₂O₂ concentration in a wide range of 5.0 × 10⁻⁸ to 1.0 × 10⁻³ mol L⁻¹ with a detection limit of 1.0 × 10⁻⁸ mol L⁻¹ (S/N = 3) and had long-term stability. Finally, the proposed method was applied to investigate the coexistence of hydrogen peroxide with the interfering substances. Experimental results showed that the ascorbic acid, glucose, l-cysteine, uric acid, and dopamine at corresponding concentrations did not influence the detection of H₂O₂.     

The role of particle size on the electrochemical properties at 25 and at 55 °C of the LiCr0.2Ni0.4Mn1.4O4 spinel as 5 V-cathode materials for lithium-ion batteries

The role of the particle size on the electrochemical properties at 25 and at 55 °C of the LiCr_0.2Ni_0.4Mn_1.4O₄ spinel synthesized by combustion method has been determined. Samples with different particle size were obtained by heating the raw spinel from 700 to 1100 °C, for 1 h in air. X-ray diffraction patterns revealed that all the prepared materials are single-phase spinels. The main effect of the thermal treatment is the remarkable increase of the particles size from 60 to 3000 nm as determined by transmission electron microscopy. The electrochemical properties were determined at high discharge currents (1C rate) in two-electrode Li-cells. At 25 and at 55 °C, in spite of the great differences in particle size, the discharge capacity drained by all samples is similar (Q_dch ≈ 135 mAh g⁻¹). Instead, the cycling performances strongly change with the particle size. The spinels with Φ > 500 nm show better cycling stability at 25 and at 55 °C than those with Φ < 500 nm. The samples heated at 1000 and 1100 °C, with high potential (E ≈ 4.7 V), elevate capacity (Q ≈ 135 mAh g⁻¹), and remarkable cycling performances (capacity retention after 250 cycles >96%) are very attractive materials as 5V-cathodes for high-energy Li-ion batteries.     

Thermal and chemical stability of Cu–Zn–Cr-LDHs prepared by accelerated carbonation

Layered double hydroxides Cu_xZn_6 − xCr₂(OH)₁₆(CO₃)·4H₂O with different molar ratios of Cu/Zn/Cr were synthesized by accelerated carbonation. The products were characterized by XRD, SEM, FT-IR and TG-DTG-DSC-MS. The chemical stability was tested by the modified Toxicity Characteristic Leaching Procedure (TCLP). The results showed that the products were the mixture of Cu_xZn_6 − xCr₂(OH)₁₆(CO₃)·4H₂O and (CuZn)₂(CO₃)(OH)₂, with similar thermal behavior. All products were chemically stable with reduced leaching at pH > 6 (Cu²⁺, Zn²⁺) or > 5 (Cr³⁺).     

Effect of strontium and cerium doping on the structural characteristics and catalytic activity for C3H6 combustion of perovskite LaCrO3prepared by sol–gel

Two series of Sr- or Ce-doped La_1−xM_xCrO₃ (x = 0.0, 0.1, 0.2 and 0.3) catalysts were prepared by thermal decomposition of amorphous citrate precursors followed by annealing at 800 °C in air atmosphere. The effect of Ce and Sr on the morphological/structural properties of LaCrO₃ was investigated by means of thermogravimetric/differential thermal analysis (TG/DTA) of the precursors decomposition under air, X-ray diffraction (XRD), electron paramagnetic resonance (EPR), transmission electron microscopy–X-ray energy dispersive spectroscopy (TEM–XEDS), S_BET determination, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The characterization results are employed to explain catalytic activity results for C₃H₆ combustion. It is shown that the lanthanum chromite perovskite structure is obtained upon thermal treatment of the sol–gel derived precursors at T > ca. 800 °C. The presence of the dopant generally induces the formation of segregated oxide phases in the samples calcined at 800 °C although some introduction of the Sr in the perovskite structure is inferred from EPR measurements. The oxidation activity becomes maximised upon formation of such doped perovskite structure.     

Effect of ethyleneglycol addition on the properties of P-doped NiMo/Al2O3 HDS catalysts: Part I. Materials preparation and characterization

Phosphorous-doped NiMo/Al₂O₃ hydrodesulfurization (HDS) catalysts (nominal Mo, Ni and P loadings of 12, 3, and 1.6 wt%, respectively) were prepared using ethyleneglycol (EG) as additive. The organic agent was diluted in aqueous impregnating solutions obtained by MoO₃ digestion in presence of H₃PO₄, followed by 2NiCO₃·3Ni(OH)₂·4H₂O addition. EG/Ni molar ratio was varied (1, 2.5 and 7) to determine the influence of this parameter on the surface and structural properties of synthesized materials. As determined by temperature-programmed reduction, ethyleneglycol addition during impregnation resulted in decreased interaction between deposited phases (Mo and Ni) and the alumina carrier. Dispersion and sulfidability (as observed by X-ray photoelectron microscopy) of molybdenum and nickel showed opposite trends when incremental amounts of the organic were added during catalysts preparation. Meanwhile Mo sulfidation was progressively decreased by augmenting EG concentration in the impregnating solution, more dispersed sulfidic nickel was evidenced in materials synthesized at higher EG/Ni ratios. Also, enhanced formation of the so-called “NiMoS phase” was registered by increasing the amount of added ethyleneglycol during simultaneous Ni–Mo–P–EG deposition over the alumina carrier. That fact was reflected in enhanced activity in liquid-phase dibenzothiophene HDS (batch reactor, T = 320 °C, P = 70 kg/cm²) and straight-run gas oil desulfurization (steady-state flow reactor), the latter test carried out at conditions similar to those used in industrial hydrotreaters for the production of ultra-low sulfur diesel (T = 350 °C, P = 70 kg/cm², LHSV = 1.5 h⁻¹ and H₂/oil = 2500 ft³/bbl).     

Electrochemical performance of the carbon coated Li3V2(PO4)3 cathode material synthesized by a sol-gel method

A carbon coated Li₃V₂(PO₄)₃ cathode material for lithium ion batteries was synthesized by a sol-gel method using V₂O₅, H₂O₂, NH₄H₂PO₄, LiOH and citric acid as starting materials, and its physicochemical properties were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscope (TEM), and electrochemical methods. The sample prepared displays a monoclinic structure with a space group of P2₁/n, and its surface is covered with a rough and porous carbon layer. In the voltage range of 3.0-4.3 V, the Li₃V₂(PO₄)₃ electrode displays a large reversible capacity, good rate capability and excellent cyclic stability at both 25 and 55 °C. The largest reversible capacity of 130 mAh g⁻¹ was obtained at 0.1C and 55 °C, nearly equivalent to the reversible cycling of two lithium ions per Li₃V₂(PO₄)₃ formula unit (133 mAh g⁻¹). It was found that the increase in total carbon content can improve the discharge performance of the Li₃V₂(PO₄)₃ electrode. In the voltage range of 3.0-4.8 V, the extraction and reinsertion of the third lithium ion in the carbon coated Li₃V₂(PO₄)₃ host are almost reversible, exhibiting a reversible capacity of 177 mAh g⁻¹ and good cyclic performance. The reasons for the excellent electrochemical performance of the carbon coated Li₃V₂(PO₄)₃ cathode material were also discussed.     

Hydrothermal synthesis of crystalline α-/β-MnO2 nanorods via γ-MnOOH nanorod precursors

The crystalline α-MnO₂ and β-MnO₂ nanorods have been successfully prepared via a facile hydrothermal method from γ-MnOOH nanorods precursor, respectively. The samples were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscope (FESEM) and Fourier transformed infrared spectra (FTIR). The morphology and structure of γ-MnOOH nanorods precursors have a great influence on the crystal structure of the obtained products. The α-MnO₂ nanorods are prepared from the 100°C γ-MnOOH precursor, while the β-MnO₂ nanorods are obtained from the 150°C γ-MnOOH precursor, respectively. Besides, the catalytic activity of the prepared α-MnO₂ and β-MnO₂ nanorods for the H₂O₂ decomposition has been investigated comparatively, and the latter shows better catalytic activity.     

Synthesis of an industrially important zinc borate, 2ZnO·3B2O3·3H2O, by a rheological phase reaction method

2ZnO·3B₂O₃·3H₂O is an industrially important zinc borate. Herein, 2ZnO·3B₂O₃·3H₂O has been prepared via a rheological phase reaction method using zinc oxide and boric acid as starting materials. This route is facile and acceptable for green chemical synthesis, producing no pollution and giving a yield of near 100% of theoretical value. And in this method, the complete conversion of the starting materials can be achieved in the presence of only 0.04 mL water (one drop of water). The products have been characterized by X-ray powder diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), scanning electron microscopy (SEM) and particle size distribution. The effects of experimental conditions on the products were investigated. The main factors that affect the formation of zinc borate are water volume, sealing state, reaction time and temperature.     

Preparation and microstructure analysis of Fe-doped PbTiO3 ceramic

Fe-doped PbTiO₃ (PT) powder and bulk materials were prepared successfully by sol-gel technique and a subsequent sintering process using Fe (C₅H₅)₂ as a dopant agent. The effects of pH and temperature on the Fe-doped PT system were investigated. Thermogravimetry/differential thermal analysis (TG/DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the composition and the microstructure of the PT ceramics. The results indicated that the thermal decomposition of xerogel included three stages: volatilization of adsorption water and organic composition, oxygenolysis of n-butyl and acetate, and transformation of the crystalline phase. Well-stabilized collosol and gel could be obtained at 60°C and pH = 4.5. It was found that PbTiO₃, PbFe₂O₄, and TiO₂ crystalline appeared in the Fe-doped PT system when the mass fraction of the dopant Fe was 0.03%. Furthermore, from STM analysis, it could be seen that the grain size of doped PT ceramics was homogeneous and about 1–2 μm, and the pore of the PT ceramic was small. As a result, the PT ceramic had high tightness. __________ Translated from Journal of Harbin Institute of Technology, 2007, 39 (1): 165–168 [译自: 哈尔滨工业大学学报]     

Electro-oxidation of methanol on co-deposited Pt-MoO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> prepared by cyclic voltammetry with different scanning potential ranges

Pt-MoO _x supported on glassy carbon was co-deposited by cyclic voltammetry (CV). The lower limit of potential was fixed at −0.25 V (vs. SCE), whereas the upper limit was adjusted to be 0.0, 0.10, 0.40, 0.60 and 1.0 V. The as-prepared catalysts were characterized by X-ray photoelectron microscopy, scanning electron microscopy and transmission electron microscopy. The results show that Pt-MoO _x particles are uniformly dispersed on the substrate and the agglomerated microparticles are composed of numerous nanoparticles with a size of several nanometers. The catalytic capabilities of Pt-MoO _x for methanol oxidation were examined by CV and chronoamperometry. Electrochemical measurements demonstrate that the catalytic activities and stabilities of Pt-MoO _x prepared in the potential ranges from −0.25 to both 0.60 and 1.0 V were higher than the others, which may due to the higher active surface area, more appropriate Pt/Mo ratio and more preferred Pt crystallographic orientation.     

A novel platform of hemoglobin on core–shell structurally Fe3O4@Au nanoparticles and its direct electrochemistry

A novel platform, which hemoglobin (Hb) was immobilized on core–shell structurally Fe₃O₄/Au nanoparticles (simplified as Fe₃O₄@Au NPs) modified glassy carbon electrode (GCE), has been developed for fabricating the third biosensors. Fe₃O₄@Au NPs, characterized using transmission electron microscope (TEM), scanning electron microscope (SEM) and energy dispersive spectra (EDS), were coated onto GCE mediated by chitosan so as to provide larger surface area for anchoring Hb. The thermodynamics, dynamics and catalysis properties of Hb immobilized on Fe₃O₄@Au NPs were discussed by UV–visible spectrum (UV–vis), electrochemical impedance spectroscopy (EIS), electrochemical quartz crystal microbalance technique (EQCM) and cyclic voltammetry (CV). The electrochemical parameters of Hb on Fe₃O₄@Au NPs modified GCE were further carefully calculated with the results of the effective working area as 3.61 cm², the surface coverage concentration (Γ) as 1.07 × 10⁻¹² mol cm⁻², the electron-transfer rate constant (K_s) as 1.03 s⁻¹, the number of electron transferred (n) as 1.20 and the standard entropy of the immobilized Hb (ΔS⁰′) as calculated to be −104.1 J mol⁻¹ K⁻¹. The electrocatalytic behaviors of the immobilized Hb on Fe₃O₄@Au NPs were applied for the determination of hydrogen peroxide (H₂O₂), oxygen (O₂) and trichloroacetic acid (TCA). The possible functions of Fe₃O₄ core and Au shell as a novel platform for achieving Hb direct electrochemistry were discussed, respectively.     

Synthesis and electrochemical characterization of nano-CeO2-coated nanostructure LiMn2O4 cathode materials for rechargeable lithium batteries

LiMn₂O₄ spinel cathode materials were coated with 0.5, 1.0, and 1.5 wt.% CeO₂ by a polymeric process, followed by calcination at 850 °C for 6 h in air. The surface-coated LiMn₂O₄ cathode materials were physically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron microscopy (XPS). XRD patterns of CeO₂-coated LiMn₂O₄ revealed that the coating did not affect the crystal structure or the Fd3m space group of the cathode materials compared to uncoated LiMn₂O₄. The surface morphology and particle agglomeration were investigated using SEM, TEM image showed a compact coating layer on the surface of the core materials that had average thickness of about 20 nm. The XPS data illustrated that the CeO₂ completely coated the surface of the LiMn₂O₄ core cathode materials. The galvanostatic charge and discharge of the uncoated and CeO₂-coated LiMn₂O₄ cathode materials were measured in the potential range of 3.0-4.5 V (0.5 C rate) at 30 °C and 60 °C. Among them, the 1.0 wt.% of CeO₂-coated spinel LiMn₂O₄ cathode satisfies the structural stability, high reversible capacity and excellent electrochemical performances of rechargeable lithium batteries.     

The effects of regeneration-phase CO and/or H2 amount on the performance of a NOX storage/reduction catalyst

The effects of regeneration-phase CO and/or H₂, and their amounts as a function of temperature on the trapping and reduction of NO_X over a model and a commercial NO_X storage/reduction catalyst have been evaluated. Overall, for both catalysts, their NO_X removal performance improved with each incremental increase in H₂ concentration. For the commercial sample, using CO at 200 °C, beyond a small amount added, was found to decrease performance. The addition of H₂ to the CO-containing mixtures resulted in improved performance at 200 °C, but the presence of the CO still resulted in decreased performance in comparison to activity when just H₂ was used. With the model sample, the presence of CO resulted in very poor performance at 200 °C, even with H₂. The data suggest that CO poisons Pt sites, including Pt-catalyzed nitrate decomposition. At 300 °C, H₂, CO, and mixtures of the two were comparable for trapping and reduction of NO_X, although with the model sample H₂ did prove consistently better. With the commercial sample, H₂ and CO were again comparable at 500 °C, but mixtures of the two led to slightly improved performance, while yet again H₂ and H₂-containing mixtures proved better than CO when testing the model sample. NH₃ formation was observed under most test conditions used. At 200 °C, NH₃ formation increased with each increase in H₂, while at 500 °C, the amount of NH₃ formed when using the mixtures was higher than that when using either H₂ or CO. This coincides with the improved performance observed with the mixtures when testing the commercial.     

Photocatalysis of methylene blue on titanium dioxide nanoparticles synthesized by modified sol-hydrothermal process of TiCl4

Titanium dioxide nanoparticles were synthesized by the hydrolysis and condensation of TiCl₄, an economic titanium precursor, in a mixed solvent of iso-propyl alcohol and water. As-prepared powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy filtering transmission electron microscopy (EF-TEM). To examine the photocatalytic activity of the as-prepared TiO₂, the photodegradation of MB which is a typical dye resistant to biodegradation has been investigated on TiO₂ powders in aqueous heterogeneous suspensions. The photocatalytic activity of TiO₂ powders prepared by the hydrolysis of TiCl₄ in the mixed solutions of iso-PrOH/H₂O exceeded that of commercial TiO₂ powders. The apparent first order rate constants (k _app) for the photodegradation of methylene blue (MB) showed a good correlation with the absorbance area obtained by UV-VIS DRS on wavelength in the limits of used lamp emission 300∼420 nm.     

A novel 2D luminescent lead(II) framework with 3-carboxylic acid-4H-1,2,4-triazole based on binuclear Pb2Cl2(H2O)2 building blocks

Under hydrothermal conditions using a triazole derivative ligand 3-carboxylic acid-4H-1,2,4-triazole (HL) and corresponding lead(II) salts, a novel two-dimensional(2D) lead(II) complex {[Pb(L)(μ₂-Cl)(H₂O)}_n (1) has been isolated. In 1 Pb₂Cl₂(H₂O)₂ building blocks can be observed, which are extended by tetra-dentate coordinated L ligands to form a 2D corrugated layered structure. 1 also represents a novel example of luminescent lead(II) frameworks with triazole derivatives. Solid-state fluorescence spectrum of 1 exhibits the excited peak at 376 nm while the emission peak at 604 nm.     

Synthesis of LiVOPO4 for cathode materials by coordination and microwave sintering

Lithium vanadyl phosphate (LiVOPO₄) sample, as one potential cathode materials, was synthesized via a route of coordination and microwave sintering. The precursors were prepared by coordination reactions among LiOH·H₂O, NH₄VO₃, NH₄H₂PO₄, C₆H₈O₇·H₂O and a small amount of water, and then they were sintered in a microwave furnace at 600 °C for 50 min. X-ray diffraction (XRD) results confirmed the formation of crystallized LiVOPO₄ with orthorhombic structures belonging to the space group of Pnma. Scanning electron microscopy (SEM) measurements indicated that the average particle size was less than 500 nm. After undergone an “activation” process, the sample exhibited a high discharge capacity for about 154 mA h g⁻¹ by the 22nd cycle at a current of 18.5 mA g⁻¹, which was very close to the theoretical values. Though the discharge capacity decreased obviously with the increased current, 110 as well as 80 mA h g⁻¹ can still be sustained within 40 cycles at 38 and 75 mA g⁻¹ respectively. This paper showed that submicron-sized LiVOPO₄ materials prepared through above way should be prospective for the application to 4 V system of lithium ion batteries.     

Fabrication of novel BPO4 ceramic foams using the combination of the direct foaming method and freeze-drying techniques

In this study, ammonium phosphate monobasic and boric acid were used as the primary starting materials to produce BPO₄ powder by solid-state reaction. Using BPO₄ powders as the main raw material, BPO₄ ceramic foams were prepared for the first time using the direct foaming method and freeze-drying techniques. The effects of the additive content and solid loading on the slurry's rheological behavior were investigated, and the microstructures and properties of the as-prepared BPO₄ ceramic foams were examined. The results reveal that the porosity of the BPO₄ ceramic foams synthesized at 1223 K ranged from 84.2% to 90.4%, the compressive strength ranged from .12 MPa to .72 MPa, and the thermal conductivity ranged from .32 W/(m·K) to .74 W/(m·K) (298 K). The findings of this study have great significance for the development of new thermal insulation ceramic materials.     

Synthesis of spinel Li4Ti5O12 anode material by a modified rheological phase reaction

Using lithium acetate dihydrate and tetra-n-butyl titanate as the raw materials, spinel Li₄Ti₅O₁₂ was successfully synthesized by a modified rheological phase method. Thermogravimetric analysis and differential scanning calorimetry (TG–DSC) of the thermal decomposition process of the precursor and X-ray diffraction (XRD) data indicate the crystallization of lithium titanates has occurred at 580 °C, and main phase Li₄Ti₅O₁₂ has obtained at 600 °C. Laser granulometer and scanning electron microscope (SEM) have been employed to estimate the particle size distribution, morphology and microstructure of the products. It reveals the prepared Li₄Ti₅O₁₂ powder had a small particle size (about 140 nm) and narrow size distribution (d_0.1 = 0.07, d_0.5 = 0.139, d_0.9 = 2.813 μm). Galvanostatic charge and discharge tests were carried out to characterize the electrochemical performances of Li₄Ti₅O₁₂. The result indicates that the Li₄Ti₅O₁₂ electrode material obtained from the precursor that had been experienced heat treatment at 110 °C exhibited discharge capacities of 161.6, 156.5 and 112.3 mAh g⁻¹ after 50 cycles at current rates 1, 2.5 and 10 C, respectively, demonstrating excellent high rate performance, due to the pure and well crystallized Li₄Ti₅O₁₂ with ultrafine particles and narrow size distribution.