Atomic Absorption Flame Emission Spectroscopy Research Articles

Photocatalytic activity of Cu doped TiO 2 nanoparticles and comparison of two main doping procedures

In this reported work, TiO 2 nanoparticles containing anatase-rutile and pure rutile phases were prepared by sol-gel and hydrolysis in acidic solution methods, respectively. Two general procedures, doping during synthesis (DDS) via a hydrolysis method and doping on the provided TiO 2 nanoparticles (DOP) that is performed by the impregnation method have been studied by doping copper to these nanoparticles. The photocatalytic activity was evaluated by photodegradation of C.I. Acid Red 27 as a model contaminant. The prepared samples were characterised by X-ray diffraction, atomic absorption flame emission spectroscopy and scanning electron microscopy. It is found that the photosensitised degradation activity can be enhanced by doping an appropriate amount of Cu. Photocatalytic activity results indicated that samples that have been doped by the DDS procedure show higher photocatalytic efficiency than samples doped by the DOP procedure.

Enhanced Photocatalytic Activity of Nitrogen-Doped Titania by Deposited with Gold

N-doped TiO2 deposited with Au (Au/N−TiO2) was successfully prepared via hydrolysis of titanium sulfate and ammonia followed with a Au deposition−precipitation method. The resulting samples were characterized by X-ray diffraction (XRD), atomic absorption flame emission spectroscopy (AAS), UV−vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), N2 physical adsorption, high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra. The photocatalytic activities of the samples were evaluated for degradation of methyl orange (MO) under visible light and UV light irradiation. It was found that the Au/N−TiO2 samples presented much higher photocatalytic activity than N-doped TiO2 under both UV and visible light irradiation. Diffuse reflectance UV−vis spectra showed an extension of light absorption into the visible region for Au/N−TiO2, and PL analysis of the sample indicated that the electron−hole recombination has been effectively inhibited after Au particles deposition. XPS analysis displayed Au existing as Au0 on the surface of the N−TiO2 photocatalyst and nitrogen species in the form of N−Ti−O and Ti−O−N. The excellent photoactivities of Au/N−TiO2 compared with N-doped TiO2 could be explained by its appropriate Au particle sizes and cooperation effect between N species and metallic Au particles.

Preparation and characterization of TiO2 photocatalysts by Fe3+ doping together with Au deposition for the degradation of organic pollutants

Fe3+ doped TiO2 deposited with Au (Au/Fe–TiO2) was successfully prepared with an attempt to extend light absorption of TiO2 into the visible region and reduce the rapid recombination of electrons and holes. The samples were characterized by X-ray diffraction (XRD), N2 physical adsorption, Raman spectroscopy, atomic absorption flame emission spectroscopy (AAS), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The photocatalytic activities of the samples were evaluated for the degradation of 2,4-chlorophenol in aqueous solutions under visible light (λ>420nm) and UV light irradiation. The results of XRD, XPS and high-resolution transmission electron microscopy (HRTEM) analysis indicated that Fe3+ substituted for Ti4+ in the lattice of TiO2, Au existed as Au0 on the surface of the photocatalyst and the mean particle size of Au was 8nm. Diffuse reflectance measurements showed an extension of light absorption into the visible region for Au/Fe–TiO2, and PL analysis indicated that the electron–hole recombination rate has been effectively inhibited when Au deposited on the surface of Fe-doped TiO2. Compared with Fe doped TiO2 sample and Au deposited TiO2 sample, the Au/Fe–TiO2 photocatalyst exhibited excellent visible light and UV light activity and the synergistic effects of Fe3+ and Au was responsible for improving the photocatalytic activity.

Preparation of Fe 3+-doped TiO 2 catalysts by controlled hydrolysis of titanium alkoxide and study on their photocatalytic activity for methyl orange degradation

Fe 3+-doped TiO 2 (Fe–TiO 2) porous microspheres were prepared by controlled hydrolysis of Ti(OC 4H 9) 4 with water generated “in situ” via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption–desorption methods. All of the undoped TiO 2 and Fe–TiO 2 samples exclusively consist of primary anatase crystallites, which further form porous microspheres with diameters ranging from 150 to 500 nm. The photocatalytic activity of Fe–TiO 2 catalysts was evaluated from the photodegradation of methyl orange (MO) aqueous solution both under UV and visible light irradiation. Fe 3+ doping effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.1 and 0.2%, respectively. The photocatalytic mechanisms of Fe–TiO 2 catalysts were tentatively discussed.

Preparation of Au/TiO2 catalysts from Au(I)–thiosulfate complex and study of their photocatalytic activity for the degradation of methyl orange

Gold loaded on TiO2 (Au/TiO2) catalysts were prepared using Au(I)–thiosulfate complex (Au(S2O3)23−) as the gold precursor for the first time. The samples were characterized by UV–vis diffuse reflectance spectra, X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), and X-ray photoelectron spectroscopy (XPS) methods. Using Au(S2O3)23− as gold precursor, ultra-fine gold nanoparticles with a highly disperse state can be successfully formed on the surface of TiO2. The diameter of Au nanoparticles increases from 1.8 to 3.0nm with increasing the nominal Au loading from 1% to 8%. The photocatalytic activity of Au/TiO2 catalysts was evaluated from the analysis of the photodegradation of methyl orange (MO). With the similar Au loading, the catalysts prepared with Au(S2O3)23− precursor exhibit higher photocatalytic activity for methyl orange degradation when compared with the Au/TiO2 catalysts prepared with the methods of deposition–precipitation (DP) and impregnation (IMP). The preparation method has decisive influences on the morphology, size and number of Au nanoparticles loaded on the surface of TiO2 and further affects the photocatalytic activity of the obtained catalysts.

Levels of essential and non-essential metals in leaves of the tea plant ( Camellia sinensis L.) and soil of Wushwush farms, Ethiopia

Five tea clones of the Camellia assamica variety grown in Wushwush tea plantation farms, Ethiopia, were analyzed for their contents of essential, non-essential and toxic metals (K, Ca, Mg, Fe, Mn, Cu, Zn, Na, Cd and Pb) by atomic absorption flame emission spectroscopy. Both the tea leaves and the soils of the study farms showed similar accumulation patterns in their contents of the studied macronutrients. Among the macronutrient metals, K was the most abundant element in the tea leaves (17.7–24.8 mg/g) and the soils (7.14–9.73 mg/g). Mn was the predominant micronutrient heavy metal in the tea leaf tissues ranging between 501 and 1281 mg/kg. Level of Fe (29.6–100 mg/kg) in the leaf tissue was found to be the second most abundant micronutrient next to Mn whereas concentrations of Cu and Co were relatively lower both in the soil and tea samples. The toxic heavy metals Pb and Cd in the leaf tissues were present at levels too low to be detected by the analytical technique used in this study. The soils were found to be acidic (pH 5.04–5.49) with high organic matter (5.48–6.02%). Fe was the most abundant metal followed by Mn, Na and Zn in the soils. Unlike the tea leaves, the soils were found to contain traces of the toxic metal, Cd (0.02–1.10 mg/kg). The levels of most of the metals determined in this study compared well with those reported for tea leaves from some other parts of the world.

Effect of Water Washing Treatment on the Photocatalytic Activity of Au/TiO 2 Catalysts

By using Au(S 2O 3) 2 3– as the gold precursor, Au/TiO 2 photocatalysts were prepared by water washing (W) and rotary evaporation (E) processes, respectively. The samples were characterized by UV-Vis diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic absorption flame emission spectroscopy (AAS). The photocatalytic activity of the samples was evaluated from the analysis of the photodegradation of methyl orange (MO). By using the water washing treatment, well-dispersed gold nanoparticles with the diameter of 2–5 nm were formed on the surface of TiO 2, whereas only the gold coating was formed for rotary evaporation processes. The photocatalytic activity of Au/TiO 2 photocatalysts is related to the preparation process. With a similar gold loading, the photocatalysts prepared by water washing showed higher photocatalytic activity compared to the catalysts prepared by rotary evaporation.

Preparation of Ce–TiO 2 catalysts by controlled hydrolysis of titanium alkoxide based on esterification reaction and study on its photocatalytic activity

The Ce–TiO 2 catalysts were prepared by controlled hydrolysis of Ti(OC 4H 9) 4 with water generated “in situ” via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), atomic absorption flame emission spectroscopy (AAS), and nitrogen adsorption–desorption methods. Both of undoped TiO 2 and Ce–TiO 2 samples exclusively consist of primary anatase crystallites, which further form spherical aggregates with diameters ranging from 100 to 500 nm. The photocatalytic activity of Ce–TiO 2 was investigated for the photocatalytic degradation of Rhodamine B (RB) aqueous solution both under UV and visible light irradiation. Doping of Ce 4+ effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.2 and 0.4%, respectively. The photocatalytic mechanisms of Ce–TiO 2 catalysts were tentatively discussed.

Fe 3+-TiO 2 photocatalysts prepared by combining sol–gel method with hydrothermal treatment and their characterization

Fe 3+-doped anatase nanosized TiO 2 photocatalysts have been prepared by combining sol–gel method with hydrothermal treatment. The samples were characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET)-specific surface area ( S BET), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS). From results of UV–vis diffuse reflectance spectroscopy, Fe 3+-doped TiO 2 extends its absorption to longer than 500 nm, which leads to an obvious photocatalatic activity under visible irradiation. From XRD, EPR, AAS and XPS, it was found that Fe exist in trivalent ionic state substituting Ti 4+ in TiO 2 lattice and its concentration decreases from the surface to the center of doped TiO 2. The photocatalytic activity of prepared samples was investigated for the photocatalytic degradation of active yellow XRG dye. The photocatalytic activity of TiO 2 doped with appropriate content of Fe 3+ exceeded those of non-doped TiO 2 and P25 both under UV and visible light irradiation.

Hydrothermal doping method for preparation of Cr3+-TiO2 photocatalysts with concentration gradient distribution of Cr3+

Cr3+-doped anatase titanium dioxide photocatalysts were prepared by the combination of sol–gel process with hydrothermal treatment. The samples were characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area (SBET), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was confirmed that Cr substitutes Ti4+ in TiO2 lattice in trivalent ionic state, and the concentrations of dopants Cr3+ decrease from the exterior to the interior of doped TiO2. The photocatalytic activity of Cr-TiO2 was investigated for the photocatalytic degradation of XRG aqueous solution both under UV and visible light irradiation. Due to the excitation of 3d electron of Cr3+ to the conduction band of TiO2, Cr-TiO2 shows a good ability for absorbing the visible light to degrade XRG. Doping of chromium ions effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.15% and 0.2%, respectively. The special distribution of dopants Cr3+ seems having a good effect on enhancing the photocatalytic activity of Cr-TiO2.