Recent Advances in HPLC Packing Materials (original) (raw)
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Journal of Colloid Science and Biotechnology
This study deals with the immobilization of mixtures of two semiconductor oxides Cuo and TiO 2 on fi brous palygorskite clay minerai in order to evaluate their photocatalytic activity for removing Orange G dye as model pollutant from aqueous solutions. The elaboration of CuO-TiO:!Palygorskite nanocomposites was carried out by impregnation with Cu 2+ of before hand synthesized TiO 2 sup ported palygorskite (Pal) followed by air annealing for 5 h at 550 •c. ln the composite materials, different Cuo to Cuo+ TiO 2 molar ratios were used in order to obtain a Cuo content in the range 13-30 mol.%. XRD, SEM and TEM equipped with elemental EDS analysis are concordant for show ing the crystallization of anatase TiO 2 along with Cuo whose average size of nanoparticles (NPs) are in the range 6 to 20 nm as determined by TEM. By increasing the Cuo content the average size of this oxide remains constant at about 1 O nm while that of TiO 2 NPs is slightly decreasing from 8.4 to 5.1 nm. Both oxide NPs were successfully attached on palygorskite fibers where they form Cu0-TiO 2 heterojunctions (grain boundaries like). The Cu0-TiO 2 /Pal supported photocatalyst con taining 23% of Cuo was found to be the most photoactive material but itremained less active than TiO 2 /Palygorskite supported photocatalyst. The photocatalytic activity of the mixed nanocomposites is not readily correlated with only one of their main features as Cuo content or the average crystal lite size of functional oxides indicating that if there are synergistic effects there are also antagonistic effects in particular for high Cuo contents.
Colloid and Interface Science Communications, 2021
Single and mixed phases of Co 3 O 4 , NiO, and CuO nanocomposites were synthesized and investigated as photocatalysts under visible light for degradation of Congo Red dye. Selected parameters were monitored regarding their impacts on photocatalysis, including band gap, crystallite size, specific surface area, zeta potential, composition, and adsorption parameters such as adsorption capacity, equilibrium constant, rate, and thermodynamic quantities. The dominant adsorption mode was chemisorption. Adsorption capacity varied inversely with zeta potential due to repulsion between dye molecule and nanocomposites surface. As the metal content was varied, photocatalytic activity (PCA) depended strongly on type/number of oxides, on charge carrier separation, and adsorption capacity. Specific surface area was less influential to PCA. PCA had little or no dependence on crystallite size, surface charge, adsorption kinetics, equilibrium constant, and thermodynamic parameters. Variation of the band gap did not affect visible-light PCA since all nanocomposites (except NiO) exhibited band gaps in the near infrared.
The Journal of Physical Chemistry C, 2008
Coupled CuO-TiO 2 nanocomposite photocatalysts were prepared by a deposition precipitation method and were characterized with a variety of techniques. Electron paramagnetic resonance (EPR) spectroscopy was employed to study the local structures of surface/interfacial Cu 2+ sites using Cu 2+ as a sensitive paramagnetic probe. The addition of bulk CuO to TiO 2 led to decreased photocatalytic efficiency in the degradation of methylene blue. However, doping with a very small amount of CuO (0.1 wt % copper loading) significantly enhanced the photocatalytic activity of TiO 2 . EPR study of the TiO 2 surface revealed the presence of both highly dispersed CuO clusters and substitutional Cu 2+ sites (Ti-O-Cu linkages) at 0.1 wt % copper loading. The data suggest that the Ti-O-Cu linkages contributed to the improved photooxidative activity of the 0.1% CuO-TiO 2 nanocomposite. In contrast, at higher loadings the bulk form of CuO created charge recombination centers lowering the photoactivity of the composites.
Synthesis and characterization of nano-CuO and CuO/TiO 2 photocatalysts
Advances in Natural Sciences: Nanoscience and Nanotechnology, 2013
CuO nanocrystals were prepared by thermal decomposition of Cu-oxalate at 400 • C; then CuO/TiO 2 core/shell nanocrystals were formed via the hydrolysis of titanium isopropoxide (TIP) on the surface of CuO nanocrystals. The characteristics of the synthesized nanocrystals were systematically studied using appropriate techniques, namely the morphology by using scanning electron microscopy (SEM), and the crystalline structure by x-ray powder diffraction (XRD) and Raman spectroscopy. The structure, shape and size of the CuO and CuO/TiO 2 nanocrystals could be tuned by changing various technological parameters: (i) the reaction/growth time (from several minutes to several hours), (ii) reaction temperature (from room temperature to 90 • C) and (iii) the molar ratios of the precursors. The results showed that the reaction temperature and the molar ratio of the precursors play important roles in controlling the morphology and size of both CuO and CuO/TiO 2 nanocrystals. With increasing reaction temperature, nano-CuO evolved from spherical shaped nanoparticles to microspheres. By shelling the large-bandgap TiO 2 layers on CuO nanocrystals, the core/shell structure is formed and the narrow-bandgap nano-CuO core is expected to be resistant to photocorrosion.
2020
A series of CuO-Cu2O/TiO2 nanocomposite samples were prepared by the sol-gel method. Before applying the sol-gel method, the Cu(OH)2 nanostructure on Cu powders were formed by in-situ solution treatment. The samples were characterized through some techniques and the photocatalytic performance of CuO-Cu2O/TiO2 nanocomposites for gas-phase 2-propanol photo-oxidation under UV and sunlight type illumination was evaluated. The effect of calcination process on the synthesis and photocatalytic activity of the samples was studied. The calcination process plays an important role in improving the properties of nanocomposite powders. The results showed that the nanocomposite formed successfully in desirable structure and morphology. The nanocomposite is composed by the mixture of TiO2 particle with an average particle size of about 300 nm and the copper oxide nanorods with a diameter of 50-100 nm. In this nanocomposite, the copper oxides nanostructures and TiO2 particles are the main component...
Desalination and Water Treatment, 2015
In this paper, various morphologies of copper oxide (CuO) were synthesized from acetate, sulfate, and nitrate precursors using hydrothermal bath method. The photoluminescence spectra revealed that CuO-Ni sample contains the strongest surface defect peak which can be related to its highest active surface area. The Fourier transform infrared (FT-IR) results showed that the concentration of the surface OH − group on the samples varies considerably according to CuO-Ac > CuO-Ni > CuO-Su. From structural results, it could be observed that all the samples crystallized into a monoclinic crystal structure. The photocatalytic activity of CuO samples was evaluated by the catalytic oxidation of methylene blue in the presence of hydrogen peroxide. Concerning the nearly same optical band gap for the samples, the best photocatalytic performance of CuO-Ni nanorods was assigned to its highest active surface area and surface hydroxyl groups.
Journal of Photochemistry and Photobiology A-chemistry, 2017
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University of Kashan, 2022
In this work, CuO/CeO 2 nancomposite was prepared via hydrothermal route. The product was prepared under 12 h and 150 o C. The shape, size, and crystalline structure have been investigated through using various techniques such as the scanning electron microscopy (SEM), with energy dispersive X-ray (EDX), the X-ray diffraction analysis (XRD), the Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The magnetic properties of prepared nanocomposites were studied via vibrating-sample magnetometer (VSM). Consequently, acid violet and rhodamine B dyes were applied for investigation the photocatalytic activity of prepared CuO/CeO 2 nanocomposite. Results showed that Acid violet and rhodamine B were photo-decolorization under UV irradiation after 120 minutes with 95.8 % and 88.2% respectively. This excellent performance was due to the suitable band structure of synthesized CuO/ CeO 2 nanocomposites which led to depress the recombination of photogenerated electrons and holes with increased the acidity of CeO 2 after incorporation it with CuO in the crystal lattice. This work introduces new nanocomposites for decolorization of organic pollutants from wastewater.