Papers by Keyword: Cerium Dioxide

Abstract: Fly ash/CeO₂ composite (FA/CeO₂) was prepared by acid modification and precipitation method using a low-cost waste fly ash (FA) as a raw material and characterized by X-ray diffraction (XRD) and the BET surface analysis. The adsorption of FA and FA/CeO₂ for Congo Red (CR) from simulated dye wastewater was studied. The different regeneration methods for the CR-saturated FA/CeO₂ were investigated. The results show that the adsorption capacity and removal rate of CR on FA/CeO₂ can respectively reach 175.35mg/g and 97.42%, 4.5 times higher than those on FA. The adsorption process of FA/CeO₂ for CR at different temperatures (25°C~55°C) can well be described by the pseudo-second-order adsorption model and is mainly controlled by intraparticle diffusion. The adsorption rate decreased slightly with increasing temperature, and the obtained adsorption apparent activation energy is 15.08kJ/mol. This indicates that CR is easily adsorbed on FA/CeO_2, and the adsorption of the process is mainly physical adsorption with exothermic nature. The room temperature is favorable to the adsorption and actual operation. NaOH solution of 0.01 mol/L can make CR-saturated FA/CeO₂ regenerated three times, and corresponding removal rate for CR can reach 97.82%, 80.21% and 66.04%, respectively. As a new kind of low-cost and high-efficient adsorbent, FA/CeO₂ composite has the potential value in the application of wastewater treatment.

Abstract: Fly ash/CeO₂ composite adsorbent (FA/CeO₂) was prepared by HCl treatment and precipitation method using a low-cost waste fly ash (FA) as the raw material and used for the removal of Congo Red (CR) from aqueous solution. Effects of important parameters such as contact time, initial dye concentration, pH value and temperature were explored. Adsorption equilibrium and isotherms were investigated. The adsorption of CR onto FA/CeO₂ is a fast process and to achieve a basic balance in 30 minutes. The removal of CR is strongly pH-dependent. FA/CeO₂ is an effective adsorbent for the CR removal with removal rate of 98.8% when initial CR concentration is 1000 mg/L. The experimental isotherm data were analyzed using Langmuir and Freundlich isotherm models. The results revealed that the adsorption behavior of CR on FA/CeO₂ fitted well with the Langmuir model at different temperatures. The maximum adsorption capacity obtained by Langmuir model is 232.56 mg/g which is nearly consistent with the actual adsorption value of 230.01 mg/g at 298K. The Adsorption amount decreases with increasing temperature, but the variation of the amplitude is very small.

Abstract: During electrodepositing pure lead dioxide, the electrocatalytic activity of PbO₂ electrodes, as well as their stability, can often be considerably enhanced by the incorporation of some fine particles added to the electrodeposition. The morphology, crystal phase, surface composition, microstructure, of the electrode were characterized by means of SEM, XRD and EDS. SEM-EDS analysis showed the addition of solid particles could inhibit the growth of α-PbO₂ unit cells, improving the specific surface areas of coating surface.Under all condition, the matrix was highly oriented α-PbO₂. The electrocatalytic activity of the prepared materials has been tested in Zn2+ 50g L-1, H2SO4 150g L-1 solution. It showed that the electrocatalytic activity of the A1/conductive coating/α-PbO₂-3.71 wt.% TiO₂-2.12 wt.% CeO₂ anode is the best.

Abstract: Conductive polyaniline/cerium dioxide (PANI/CeO2) composites have been synthesized by in-situ polymerization of aniline in the presence of CeO2 nanoparticles. The structure and thermal stability of obtained composites were characterized by Fourier-transform infrared spectra (FTIR), Fourier-transform Raman spectra (FT-Raman), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results showed that PANI and CeO2 nanoparticles were not simply blended, and a strong interaction existed at the interface of CeO2 and PANI. In the PANI/CeO2 composite, the degree crystallinity of PANI increased and diffraction pattern of CeO2 was amorphous. And that the composites were more thermally stable than that of the pure PANI. Electrical conductivity measurements indicated that the conductivity of PANI/CeO2 composites was much higher than that of the pure PANI and the maximum conductivity obtained was 11.68 S/cm at 17.5 wt% of CeO2.

Abstract: Cerium dioxide (CeO2) is a well-studied oxide because of its technological applications, such as a major component in the catalysts, stable capacitors and so on. CeO2 with a cubic fluorite structure is also expected as the material for simulating behaviors of uranium dioxide under energetic particle irradiation, which leads high burn-up structure attributable to pressure increase in fuel cladding tubes. In this work, the stability of crystal structure and surface morphology change in CeO2 will be clarified. Polycrystalline samples were irradiated with 300 keV Xe+, 18 MeV I5+, 350 keV O+ and 12 MeV O3+ ions at temperatures from 370 to 1000 K. Microstructural evolutions was investigated with Scanning electron microscopy, Raman Spectroscopy and X-ray diffractometry. Irradiation effects at high temperature were observed as surface etching and resulting bubble formation, however blistering was not detected. Raman spectra and diffraction data indicates diffusion of oxygen vacancies is sufficient at 900 K and above.

Abstract: Cerium hydrate fiber (CHF), which showed an aspect ratio greater than 100, was synthesized by a novel method, which used the mixing of cerium nitrate (Ce(NO3)3), sodium hydrate (NaOH) and citric acid (C6H8O7) synthesized at a relative low temperature and ambient pressure. The precipitates were characterized by XRD, SEM and TEM. The results showed that in addition to fibers, two morphologies could be obtained depending on the synthesizing conditions. Aging time and formulation were two key factors for the control of the aspect ratio of the precipitates. By a heating treatment at 600oC for 2 h, the homogenous and well-crystallized cerium dioxide (CeO2) fiber can be fabricated. The effects of synthesis parameters, such as the concentration of the starting solution, aging period, and pH value were reported and discussed.

Abstract: The traditional precipitation method and a novel inorganic-organic hybrid method were used to control the morphology of nanocrystalline CeO2. By adjusting the methods and the preparation conditions, spherical and rode-shaped cerium dioxides with the nanoparticle sizes were prepared. Their structures and properties were characterized by XRD, BET and TEM.

Abstract: Cerium dioxide (CeO2) nanoparticles were synthesized by a novel mechanochemical process. The precursors of Ce2(CO3)3.xH2O and NaOH were mixed at a weight ratio of 4 to 1. The mixtures were milled using a planetary ball mill with ball to powder ratio of 10:1. The products were then characterized using a battery of characterization methods, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and gas adsorption-desorption measurement. The as-prepared particles were largely amorphous with an average specific surface area of about 119.94 m2/g. Nanocrystalline CeO2 with crystallite size of 4.5 nm was obtained when the sample was annealed in air at 350 oC. The heat treatment results showed that the crystallinity of nanocrystalline CeO2 increased with increasing annealing temperature.

Abstract: Carbon monoxide (CO) is a significant air pollutant produced in incomplete oxidation of carbon in combustion. From the viewpoint of environmental protection, it is important that the concentration of CO gas is lowered in air. Catalysis is proving to be an effective route for removing this pollutant. Therefore, a design of nano-structured catalysts with high efficiency is required. In the present work, we focus on a development of nano-size CuOx-CeO2 catalysts for CO oxidation reaction. To prepare nano-structured Cu loaded CeO2 catalysts, a combined method of the conventional impregnation and ammonium carbonate co-precipitation was examined. Morphology, crystal phase and surface structure of prepared catalysts were characterized using High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM) and Powder X-ray Diffraction (XRD). Catalytic properties of CuOx-CeO2 for CO oxidation were investigated in gas flow reactor system under atmospheric pressure and compared with copper oxide loaded zinc oxide. We expected that nano-structured CuOx-CeO2 catalysts could be used for removing CO produced in a wet reforming reaction of fuel cell applications.

Abstract: The structural analysis of thin cerium dioxide films doped with Cu, produced by laser ablation for applications in catalytic and gas sensors, was the general aim of the study. The thin films deposited on a (100) silicon substrate were nanocrystalline structure with a well-developed texture. The morphology, as well as the preferred films orientation, is changed with the volume fraction of Cu. The observed changes affect the catalytic properties of the materials obtained which was confirmed by the catalytic tests undertaken with CH4.