Synthesis and characterization of nanosized Ce1−xbixo2−δ solid solutions for catalytic applications

AbstractThis study consists of elaborating and characterizing some nanometric materials in basic of rare-earth oxides by the soft chemistry technique. the first step of this work consists of synthesizing nanometric pure ceria by sol-gel process. In the second one, the Bismuth doped ceria by co-precipitation method was realized in order to obtain ceria-based solid solution, to improve its catalytic property by creation of oxygen vacancies. The solubility limit of Bi2O3 in CeO2 was determined to be around 20 atom %. The effect of thermal treatment temperatures on the average crystallite sizes and lattice parameters was done for pure ceria and Ce1−xBixO2−x/2 (x = 0.15 and 0.2). The different elaborated samples are subject of structural characterization (XRD). Catalytic reactivity of these materials in presence of “air- toxic gas” mixtures is studied by Fourier Transform Infra-Red Spectroscopy (FTIR)

Structural and Raman Vibrational Studies of CeO

A series of ceramics samples belonging to the CeO2-Bi2O3 phase system have been prepared via a coprecipitation route. The crystallized phases were obtained by heating the solid precursors at 600∘C for 6 hours, then quenching the samples. X-ray diffraction analyses show that for x<0.20 a solid solution Ce1−xBixO2−x/2 with fluorine structure is formed. For x ranging between 0.25 and 0.7, a tetragonal β′ phase coexisting with the FCC solid solution is observed. For x ranging between 0.8 and 0.9, a new tetragonal β phase appears. The β′ phase is postulated to be a superstructure of the β phase. Finally, close to x=1, the classical monoclinic α Bi2O3 structure is observed. Raman spectroscopy confirms the existence of the phase changes as x varies between 0 and 1

Photocatalytic oxidation of pollutants in gas-phase via Ag3PO4-based semiconductor photocatalysts: Recent progress, new trends, and future perspectives

Air pollution has become a significant challenge for both developing and developed nations. due to its close association with numerous fatal diseases such as cancer, respiratory, heart attack, and brain stroke. Over recent years, heterogeneous semiconductor photocatalysis has emerged as an effective approach to air remediation due to the ease of scale-up, ready application in the field, use of solar light and ready availability of a number of different effective photocatalysts. To date, most work in this area has been conducted using UV-absorbing photocatalysts, such as TiO2 and ZnO; However, recent studies have revealed Ag3PO4 as an attractive, visible-light-absorbing alternative, with a bandgap of 2.43 eV. In particular, this material has been shown to be an excellent photocatalyst for the removal of many types of pollutants in the gas phase. However, the widespread application of Ag3PO4 is restricted due to its tendency to undergo photoanodic corrosion and the poor reducing power of its photogenerated conductance band electrons, which are unable to reduce O2 to superoxide •O2−. These limitations are critically evaluated in this review. In addition, recent studies on the modification of Ag3PO4 via combination with the conventional heterojunctions or Z-scheme junctions, as well as the photocatalytic mechanistic pathways for enhanced gas-pollutants removal, are summarized and discussed. Finally, an overview is given on the future developments that are required in order to overcome these challenges and so stimulate further research into this promising field

High photocatalytic activity for the degradation of rhodamine B in water

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VALORIZATION AND CHARACTERIZATION OF WOOD OF THE JUJUBE SHELL: APPLICATION TO THE REMOVAL OF CATIONIC DYE FROM AQUEOUS SOLUTION

In the present study, the powder of jujube shell (raw and modified) was tested for removing crystal violet (CV)from aqueous solution. The biosorbents were characterized by FTIR, SEM and pHZPC analysis.The biosorption behavior was studied in batch experiments such as biosorbent mass, contact time, temperature, initial dye pH, biosorbent particles size and initial dye concentration. The removal efficiency of crystal violet attained 95.84% and 98.16 %, using 0.2g of raw jujube shell (JS) of and 0.1g of modified jujube shell with sodium hydroxide (NMJS), respectively. The obtained results indicate the endothermic nature of biosorption and that the biosorption system studied belongs to the second-order kinetic model. Equilibrium data of the biosorption process fitted very well to Langmuir model. The maximum biosorption monolayer capacities of crystal violet on raw and modified jujube shell were found to be 59.84 mg/g and 288.18 mg/g at 50°C, respectively. Thus, the raw jujube shell treatment with base is very effective and greatly improves the dye adsorption capacity

Electrical impedance spectroscopy analyses and optical properties of the bismuth lutetium tungstate BiLuWO 6

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Multifunctional rare earth or bismuth oxide materials for catalytic or electrical applications

We present a review on catalytic or electrical properties of materials based on rare earth (RE) oxides (CeO2, La2O3, Lu2O3) or bismuth based composite systems CeO2-Bi2O3, susceptible to be integrated into catalytic microsystems or gas sensors. The polycrystalline solids can be used as catalysts allowing conversion of CO or CH4 traces in air-gas flows. Fourier Transform infrared spectroscopy is used to determine the conversion rate of CO or CH4 into CO2 through the variations versus time and temperature of vibrational band intensities. The time dependent reactivities are interpreted in terms of an adapted Avrami model. In these catalytic analyses the nature of surfaces of polycrystalline solids seems to play a prominent role in catalytic efficiency. Electrical impedance spectroscopy allows analyzing the variation of conductivity of the system CeO2-Bi2O3. In this system, the specific high ionic conduction of a Bi2O3 tetragonal phase might be linked to the high catalytic activity

Novel Lu-doped Bi2WO6 nanosheets: Synthesis, growth mechanisms and enhanced photocatalytic activity under UV-light irradiation (vol 42, pg 8552, 2016)

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