168 research outputs found

    Synthesis, optical and magnetic behavior of (BiFeO3)1−x(α-Fe2O3)x nanocomposites

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    (BiFeO3)1−x(α-Fe2O3)x nanocomposites were synthesized from dried gels of BiFeO3 and α-Fe2O3. Samples with x = (0.00 (BiFeO3), 0.25, 0.50 and 1.00 (α-Fe2O3)) were studied using X-rays diffractions (XRD), UV–vis spectroscopy, photoluminescence spectroscopy (PL), electron spin resonance (ESR) and vibrating sample magnetometer (VSM). Amounts of α-Fe2O3 phase were 23 and 35% for samples x = 0.25 and 0.50, respectively. Microstrain of BiFeO3 phase tended to decrease with increasing α-Fe2O3. Optical band gap reduced from 2.42 eV for BiFeO3 to 2.35 eV for sample x = 0.25 and then increased to 2.56 eV for sample x = 0.50. From PL, intensity of near band emission peak of BiFeO3 increased with increasing α-Fe2O3 content. From ESR and VSM, the g-value and magnetization saturation were enhanced with embedding of α-Fe2O3 into BiFeO3

    Improving the energy values of rice straw and oil palm empty fruit bunch in ruminant feeding

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    Rice straw and oil palm empty fruit bunch were treated with urea and commercial effective microorganisms to study their ability to breakdown fibres, improved in protein and energy values. In rice straw, the crude protein and crude fibre treated with urea and urea + effective microorganisms showed significant differences from the untreated control. The neutral detergent fibre and nitrogen free extract values in the rice straw treatment did not show significant differences. Metabolizable energy values decreased with the treatment groups compared to the control. The results of keeping the treated rice straw in anaerobic plastic bags up to 30 days showed no significant breakdown of fibre components in the control and urea treated groups. But there is a significant dropped in the neutral detergent fibre in urea+effective microorganisms treatment. In oil palm empty fruit bunch, there were no significant differences seen in the crude protein, crude fibre, acid detergent fibre, neutral detergent fibre, nitrogen free extract and metabolisable energy values. Storage showed decreased in energy values in all treated groups. The addition of urea and microbes showed improved protein level and in the reduction of the fibre components in rice straw only

    Copper oxide nanoparticles-loaded zeolite and its characteristics and antibacterial activities

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    In the present work, a simple and green co-precipitation method was used to prepare copper oxide-zeolite nanocomposites (CuO-zeolite NCs). The weight ratio (1, 3, 5, 8 and 10 wt%) of CuO nanoparticles (NPs) loaded into zeolite was investigated to obtain the optimum CuO distribution for antibacterial activities. The prepared CuO-zeolite NCs were characterized by ultraviolet-visible (UV–vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), and energy dispersive X-ray fluorescence spectrometry (EDXRF). The transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) revealed a uniform surface morphology of the CuO-zeolite NCs. The UV–vis spectrum of NCs showed absorption peaks between 230 and 280 nm for nano-CuO in the XRD patterns, and new peaks appeared between (36.56°–38.83°) related to the CuO. At weight ratio less than 10 wt%, the CuO nanoparticles loaded to the zeolite exhibited spherical shapes with average particle diameter of 6.5 nm measured by TEM and XRD. Antibacterial activities were tested against Gram-negative and Gram-positive bacteria. The obtained results showed that, CuO-zeolite NCs with 8 wt% CuO nanoparticles had the highest antibacterial activities against Bacillus Subtilis B29 and Salmonella Choleraesuis ATCC 10708, which can be attributed to the good dispersion of CuO NPs on the zeolite surface

    Photocatalytic removal of 2,4,6-trichlorophenol from water exploiting commercial ZnO powder.

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    2,4,6-trichlorophenol is an important water pollutant owing to the severity of its toxicity. The aqueous phase photocatalytic oxidation of 2,4,6-trichlorophenol over ZnO was investigated as a potential method for the abatement of this pollutant. The effects of operating parameters such as initial ZnO doses and substrate concentration on the removal of 2,4,6-trichlorophenol were studied and optimised at 0.75 g L− 1 and 50 mg L− 1, respectively. The photocatalytic system afforded the highest degradation efficiency at neutral pH. The decomposition of 2,4,6-trichlorophenol by the photoprocess agreed satisfactorily with pseudo zero-order kinetic model. The effect of the presence of SO42−, S2O82−, HPO42− and Cl− on the 2,4,6-trichlorophenol removal rate was for the first time revealed. Some hitherto unreported pathway intermediates of ZnO-assisted 2,4,6-trichlorophenol degradation were recorded using gas chromatography–mass spectrometry (GC–MS) and high performance liquid chromatography (HPLC). A tentative reaction mechanism for the formation of these intermediates was proposed

    Photocatalytic degradation of 2,4-dichlorophenol in irradiated aqueous ZnO suspension.

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    This paper focuses on the destruction of aqueous 2,4-dichorophenol in ZnO suspension irradiated by low wattage UV light at 299 K. The operating variables studied include initial 2,4-dichlorophenol concentration, photocatalyst doses and pH. At 1.5 g l-1 feed concentration of ZnO and 50 mg l-1 initial 2,4-dichlorophenol level, a complete degradation was achieved in 180 min. The decomposition kinetics with respect to 2,4-dichlorophenol approximates pseudo zero-order with rate constant peaking at 0.38 mg l-1 min-1. High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) detected benzoquinone, 2-chlorohydroquinone, 4-chlorophenol, 3,5-dichlorocatechol, hydroquinone, 4-hydroxybenzaldehyde and phenol during the ZnO-assisted photodegradation of 2,4-dichlorophenol among which some pathway products are disclosed for the first time. The reaction mechanism accounting for the degradation pathway intermediates is proposed. Inorganic anion additives such as S2O8 2-, SO4 2-, Cland HPO4 2- manifested inhibition against 2,4-dichlorophenol removal

    Photocatalytic treatment of 4-chlorophenol in aqueous ZnO suspensions : intermediates, influence of dosage and inorganic anions.

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    The photocatalytically driven removal of eco-persistent 4-chlorophenol from water using ZnO is reported here. Kinetic dependence of transformation rate on operating variables such as initial 4-chlorophenol concentration and photocatalyst doses was investigated. A complete degradation of 4-chlorophenol at 50 mg L−1 levels was realised in 3 h. Analytical profiles on 4-chlorophenol transformation were consistent with the best-line fit of the pseudo zero-order kinetics. The addition of small amounts of inorganic anions as SO42−, HPO4−, S2O82− and Cl− revealed two anion types: active site blockers and rate enhancers. Fortunately, Cl− and SO42− commonly encountered in contaminated waters enhanced the rate of 4-chlorophenol degradation. The reaction intermediates and route to 4-chlorophenol mineralisation were elucidated by combined RP-HPLC and GC–MS methods. In addition to previously reported pathway products of 4-chlorophenol photo-oxidation catechol was detected. A radical mechanism involving o-hydroxylation is proposed to account for the formation of catechol

    Effects of aging time on microstructure, hydrophobic and optical properties of BiFeO3 thin films synthesized via sol-gel method

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    BiFeO3 (BFO) films were synthesized with the sol-gel method followed by the spin coating technique using 2-methoxyethanol as solvent and acetylacetone as chelating agent. The effects of aging time (t = 0, 1, 3, 6 days) of the BFO sol on the microstructure, wettability and optical properties of BFO films were investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle (CA) measurement, Uv-vis and photoluminescence. The crystallinity of films was affected by t. Crystallite size of the films changed slightly in the range of 14.2 – 15.2 nm while the lattice parameters clearly varied with t. The average particle size of BFO films ranged between 45.9 and 52.7 nm while the mean square roughness (Rq) varied between 1.0 and 4.2 nm. The films showed maximum optical transmittance (81 – 90 %) in the range 600 – 800 nm. The band gap of the films was also affected with t, and it has a value of 2.85 to 2.76 eV. The films showed a hydrophobic property with CA ranging between 95.3 to 104.7 °. The best crystallinity, lowest Rq and highest Eg = 2.85 eV were obtained for the film with t = 1 day. The results demonstrate possible development of a superhydrophobic coating using BiFeO3 coating

    Brown macroalgae as bio-indicators for heavy metals pollution of Al-Jubail coastal area of Saudi Arabia

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    Wastes from both industrial and domestic sources, as well as habitat destruction have a substantial impact on the coastal environments. It causes serious problems in many countries and for several seas and oceans which leads to the extinction of several plant and animal species. Many water resources are no longer suitable for drinking or for agriculture as a result of pollution. The main aim of this study was to investigate the efficiency of four brown macroalage as bioindicators for toxic heavy metals (manganese (Mn), copper (Cu), zinc (Zn), arsenite (As), cadmium (Cd), and lead (Pb)) along Al-jubail industrial city coast at Persian Gulf (Saudi Arabia). Brown macroalage samples were collected from three different sites in three time points, January, March and May, 2010. The four collected brown macroalgae were identified as Sargassum angustifolium, Sargassum boveanum, Sargassum latifolium, and Padina gymnospora. The algal samples were cleaned using sea water and distilled water, dried, and the concentrations of various toxic metals were determined. The average concentrations of Mn, Co, Ni and Cd were within the expected limits of un-contaminated areas. However, the results indicate the high level of Zn ion accumulation in all tested brown algae, showing highest concentration in S. angustifolium > P. gymnospora > S. latifolium > S. boveanum with highest Zn concentration of 991 ± 49.1, 988 ± 47.5, 980 ± 44.2, and 911 ± 39.7 µg g-1 dry weights, respectively. In addition, Cu was detected at high concentration of 92.1 ± 3.7 ìg g-1 dry weight in S. boveanum. These results clearly indicate the high pollution levels of Al-jubail industrial city coast with Zn and Cu toxic heavy metals, which is mostly due to uncontrolled disposal of industrial waste into coastal area. Furthermore, the consistency of Zn concentrations in all tested brown algae indicated the efficiency of the tested algae, including P. gymnospora, S. angustifolium, S. latifolium, and S. boveanum, for bioaccumulation and bio-monitoring studies of Zn.Key words: Brown algae, heavy metals, bio-indicators, Sargassum sp., Padina sp

    Physical properties of Fe doped In2O3 magnetic semiconductor annealed in hydrogen at different temperature

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    The effects of hydrogen-annealing at different temperatures (300, 400, 500 and 600°C) on physical properties of In2−xFexO3 (x=0.025) thin film were investigated. The structural measurement using XRD shows that the film has a single In2O3 phase structure when annealed in hydrogen at 300–500°C, however when annealed in hydrogen at 600°C the film has a mixed phase structure of In2O3 and In phases. The electrical measurements show that the carrier concentrations of the films decrease with the increase of hydrogen-annealing temperature in the range 300–500°C. The optical band gap of the films decreases with increasing hydrogen-annealing temperatures. The saturation magnetisation, Ms, and coercivity of films increase with the increment of hydrogen annealing temperature. The film annealed at 300°C has the lowest resistivity, ρ=0.03 Ω cm, and the highest carrier concentrations, n=6.8×1019 cm−3, while film annealed at 500°C has both good electrical (ρ=0.05 Ω.cm and n=2.2×1019 cm−3) and magnetic properties, Ms=21 emu/cm-3
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