Bi12TiO20 synthesized directly from bismuth (III) nitrate pentahydrate and titanium glycolate and its activity

Pure phase of sillenite structure, Bi₁₂TiO₂₀, was directly synthesized using stoichiometric bismuth (III) nitrate pentahydrate and titanium glycolate by co-precipitation. The influence of pH on the structure of Bi₁₂TiO₂₀ was studied in the pH range of 3–10. The sillenite structure was characterized using XRD and FTIR. The photo-degradation reaction of 4-nitrophenol (4-NP) was used to study photocatalytic activity of Bi₁₂TiO₂₀ as a function of the preparation pH. The rate of decomposition was followed by UV-vis and TOC. The beginning concentration of 4-NP, 44 ppm, decreased to less than 1 ppm within 30 min for all prepared catalysts. It was found that the decomposition rate constant of Bi₁₂TiO₂₀ is six times higher than those of either TiO₂ or Bi₂O₃ under the same conditions.     

软铋矿铁酸铋活化过一硫酸盐降解环丙沙星机理及产物研究

运用共沉淀-低温水热技术制备软铋矿铁酸铋（S-BFO）,构建S-BFO非均相活化过一硫酸盐（PMS）降解环丙沙星（CIP）体系。考察了氧化剂浓度、初始pH、催化剂投加量等关键因素对体系的影响,并模拟天然水体,探究了S-BFO/PMS体系稳定性。实验结果表明：在初始pH、25℃条件下,加入0.675 mmol/L PMS,1000 mg/L的催化剂,初始浓度为5.0 mg/L的CIP经反应60 min后去除率为84.8%。通过活性物质淬灭实验结果,发现体系中对目标有机污染物起主要降解作用的活性物质是单线态氧（1O2）,而不是硫酸根自由基（·SO4-）和羟基自由基（·OH）。通过LC/MS/MS技术检测到了9种CIP降解过程中的主要中间产物,并确定了CIP通过羟基加成反应（路径I）及脱羧反应（路径II）被氧化去除的降解路径。     

Synthesis and properties of novel inorganic red chromophore based on Cr4+ in tetrahedral coordination in Bi24Al2-xCrxO39

The novel orange to red color Bi₂₄Al_2-xCr_xO₃₉ (0≤ x ≤ 0.5) compounds were successfully synthesized by the solid state method. With the increase of Cr content, the colors of compounds are tuned from orange red to dark red. The X-ray diffraction patterns of all samples are indexed with cubic Bi₂₄Al₂O₃₉ structure with the space group of I23. The oxidation state of Cr in the oxide is confirmed to be +4 valence by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Based on the analysis of Cr oxidation state and UV–Visible spectrum, the red hue is due to the d-d transition of Cr⁴⁺ in tetrahedral sites. The as-synthesized red color compounds also show excellent stability in acid and base environments.     

Electrical properties of bismuth ferrites: Bi2Fe4O9 and Bi25FeO39

Bi₂Fe₄O₉ was prepared by solid-state reaction and the electrical properties measured by impedance spectroscopy. After annealing in O₂ at 900 °C, Bi₂Fe₄O₉ is an electrically-homogeneous insulator. Its high frequency permittivity is constant (∼14.1) over the temperature range 300–400 °C and shows no evidence of incipient ferroelectricity at lower temperatures. On annealing in N₂ at 900 °C, the pellets gradually decompose.Bi₂₅FeO₃₉ was prepared by both solid-state reaction and mechanosynthesis. It showed a modest amount of mixed conduction of both oxide ions and holes. Impedance analysis showed a complex response that best fitted an equivalent circuit consisting of a parallel combination of long-range conduction and short range dielectric relaxation elements.The electrical conductivity of both Bi₂Fe₄O₉ and Bi₂₅FeO₃₉ is less than that of BiFeO₃ prepared by solid-state reaction, which indicates that any leakage conductivity of BiFeO₃ is not due to the possible presence of small amounts of these secondary phases.     

Phase diagram of the pseudobinary system Bi–Co–O

Samples with different ratios of Bi₂O₃ and Co₂O₃ were prepared by ceramic route. Based on the results of differential thermal analysis, X-ray powder diffraction, SEM–EDXA and FactSage database the phase diagram of the Bi–Co–O diagram in air atmosphere was assessed and calculated using the FactSage software. The sillenite structure of Bi₂₄Co₂O₃₉ was identified and the single phase homogeneity range of Bi₂₄Bi_2?xCo_xO₃₉, x = 0.9–2.0 was determined by Rietveld analysis and SEM–EDXA. To verify the composition in the various parts of the phase diagram at elevated temperatures, a number of high-temperature annealing experiments was performed followed by rapid quenching to room temperature.     

Preparation and photocatalytic properties of sillenite Bi12TiO20 films

Sillenite Bi₁₂TiO₂₀ thin films with high photocatalytic activity have been successfully fabricated by means of chemical solution decomposition, and characterized by X-ray diffraction, energy-dispersive spectroscopy, atomic force microscopy, scanning electron microscopy and UV-Vis spectrophotometry. The photocatalytic activity of Bi₁₂TiO₂₀ thin films has been evaluated by photodegrading methyl orange solution and the effect of processing conditions on the photocatalytic activity has been studied in detail.