TiO2 Nanocatalysts Research Articles

Synthesis and characterization of carbon-covered alumina (CCA) supported TiO2 nanocatalysts with enhanced visible light photodegradation of Rhodamine B

The anatase phase of titania (TiO2) nano-photocatalysts was prepared using a modified sol gel process and thereafter embedded on carbon-covered alumina supports. The carbon-covered alumina (CCA) supports were prepared via the adsorption of toluene 2,4-diisocyanate (TDI) on the surface of the alumina. TDI was used as the carbon source for the first time for the carbon-covered alumina support system. The adsorption of TDI on alumina is irreversible; hence, the resulting organic moiety can undergo pyrolysis at high temperatures resulting in the formation of a carbon coating on the surface of the alumina. The TiO2 catalysts were impregnated on the CCA supports. X-ray diffraction analysis indicated that the carbon deposited on the alumina was not crystalline and also showed the successful impregnation of TiO2 on the CCA supports. In the Raman spectra, it could be deduced that the carbon was rather a conjugated olefinic or polycyclic hydrocarbons which can be considered as molecular units of a graphitic plane. The Raman analysis of the catalysed CCAs showed the presence of both the anatase titania and D and G band associated with the carbon of the CCAs. The scanning electron microscope micrographs indicated that the alumina was coated by a carbon layer and the energy dispersive X-ray spectra showed the presence of Al, O and C in the CCA samples, with the addition of Ti for the catalyst impregnated supports. The Brunauer Emmet and Teller surface area analysis showed that the incorporating of carbon on the alumina surface resulted in an increase in surface area, while the impregnation with TiO2 resulted in a further increase in surface area. However, a decrease in the pore volume and diameter was observed. The photocatalytic activity of the nanocatalysts was studied for the degradation of Rhodamine B dye. The CCA-TiO2 nanocatalysts were found to be more photocatalytically active under both visible and UV light irradiation compared to the free TIO2 nanocatalysts.

Study on the Photocatalytic Degradation of Ammonia Nitrogen in Aquaculture Wastewater by Fe<sup>3+</sup>-Doped Nano-TiO<sub>2</sub> under UV Irradiation

The Fe3+-doped nano-TiO2 catalyst with various amounts of dopant Fe3+ irons was prepared by a sol-gel method. The products were characterized by XRD and SEM. The photocatalytic degradation of ammonia nitrogen in aquaculture wastewater was investigated by using Fe3+-doped nano-TiO2 under UV irradiation. In the experiment, the effect of Fe3+/TiO2 dosage, the ratio of dopant Fe3+, ammonia-N initial concentration, pH value, H2O2 volume concentration, and reaction time, respectively, on the removal of ammonia-N was investigated. The experimental results can be stated as follows: when the ratio of dopant Fe3+ was 0.25% wt, the dosage of Fe3+/TiO2 was 0.7 g/L, the initial concentration of ammonia-N was 10 mg/L, H2O2 volume fraction was 4 %, respectively, if the reaction time may last 4 h, the removal rate of ammonia-N was expected to reach 97.17 %.

Photo Catalytic Degradation of Effluent of Iron and Power Plant Industries in Aqueous Solution by Tio2 Nano Catalyst Using Uv Irradiation

Photo Catalytic Degradation of Effluent of Iron and Power Plant Industries in Aqueous Solution by Tio2 Nano Catalyst Using Uv Irradiation

Synthesis and visible light photoactivity of anatase Ag and garlic loaded TiO2 nanocrystalline catalyst

An excellent visible light activated Ag and garlic loaded TiO2 nanocatalyst was prepared by using AgNO3 and garlic (Allium sativum) as the Ag+ and sulfur sources, respectively. The catalyst resisted the change from anatase to rutile phase even at high (700 °C) calcination temperature. The photocatalytic efficiency of as-prepared nanocatalysts was evaluated by degrading (100 ppm) azodye, methyl orange (MO), and dichloro phenol (DCP) under visible light irradiation for 3 to 4 h from an incandescent light bulb (300 W). The process followed first order reaction kinetics with reaction rates ranging from 9.5 × 10−4 to 19.4 × 10−3 min−1. The dye was decomposed in 3 h and more than 70% DCP degraded in 4 h in the presence of Ag and garlic loaded–TiO2 calcined at 700 °C. Demineralization of the solution was in the range 40 to 90%. A complete elimination of Vibrio fischeri was accomplished with 1 mg L−1 of nanocatalyst regardless the calcination temperature. The catalyst was used for up to 5 consecutive runs without the significant loss in the photocatalytic activity and could be regenerated by adopting a simple procedure of washing with water and acetone as well as drying at 200 °C for 2 h.

Synthesis of <I>N</I>-Doped Nano TiO<SUB>2</SUB> Using Guanidine Nitrate: An Excellent Visible Light Photocatalyst

An excellent visible light active nitrogen-rich TiO2 nanocatalyst has been synthesized by using guanidine nitrate as the nitrogen source. The catalytic efficiency of the catalyst has been demonstrated by the decomposition of the dye, methyl orange (MO), and the pollutant, 2,4 dichlorophenol (DCP), under common household lightbulbs as well as sunlight. The reactions proceed faster on exposure to solar light (less than 1 h for MO and 4 h for DCP) compared with the commercial light bulbs (3 h for MO and 6 h for DCP). The catalyst could be used up to five times without loss of activity and regenerated for further use just by washing and drying at 200 degrees C.

Studies on Characterization and Photocatalytic Activities of Visible Light Sensitive TiO2 Nano Catalysts Co-doped with Magnesium and Copper

Studies on Characterization and Photocatalytic Activities of Visible Light Sensitive TiO2 Nano Catalysts Co-doped with Magnesium and Copper

Studies on Characterization and Photocatalytic Activities of Visible Light Sensitive TiO2 Nano Catalysts Co-doped with Magnesium and Copper

Studies on Characterization and Photocatalytic Activities of Visible Light Sensitive TiO2 Nano Catalysts Co-doped with Magnesium and Copper

Photodegradation of rhodamine B and methyl orange over one-dimensional TiO2 catalysts under simulated solar irradiation

In this paper, two one-dimensional (1D) TiO2 nanostructures, nanotube and nanowire were synthesized by a hydrothermal method using Degussa P25 TiO2 as a precursor. The synthesized anatase TiO2 nanotubes with the diameters of 10–20nm and length of several hundred nanometers were formed from P25 and NaOH with the hydrothermal treatment temperature at 150°C, and anatase TiO2 nanowires with the diameters of 10–40nm and length up to several micrometers were prepared at 180°C. The photocatalytic activity of the two nanostructures was evaluated by degrading rhodamine B (RhB) and methyl orange (MO) in aqueous solutions under simulated solar light irradiation. The results suggested that the TiO2 nanocatalysts displayed higher degradation activity compared to P25. For RhB, 98.9% and 91.9% of RhB were removed by nanotubes and nanowires, respectively after 60min irradiation in comparison to the 81.8% removal by P25. Similar trend was observed for MO, with the removal percentage of 95.6%, 88.3% and 74.9%, respectively by TiO2 nanotubes, nanowires and P25. Meanwhile, RhB and MO showed different photodegradation rates in nanotubes and nanowires suspensions, probably due to the morphology and crystal structure of the TiO2 nanocatalysts which play important roles in the degradation activity of the catalysts.

Iron (Fe3+) loaded TiO2 nanocatalysts: characterization and photoreactivity

Iron (Fe3+) loaded TiO2 nanocatalysts were prepared by the photochemical reduction process. These supported nanocatalysts were characterized by X-ray diffraction (XRD), surface area (BET) measurements, scanning electron microscopy SEM with energy dispersive X-ray (EDX-elemental mapping) analysis and atomic force microscopy (AFM) with adhesion force measurements. XRD and BET results showed adsorption of iron species on the surface of the TiO2 support. AFM and SEM images revealed obvious variations in the surface morphology of the support after loaded with Fe3+ ions. Photocatalytic activities of the supported nanocatalysts were examined for decolorization and degradation processes of Congo red (CR) under UV irradiation. Fe3+ ions improved the performances of the supported nanocatalysts by suppressing the electron–hole recombination reactions. Effects of Fe3+ ion content and initial CR concentration were investigated. A tentative model was proposed for the photocatalytic degradation of CR.

Visible light induced photobleaching of methylene blue over melamine-doped TiO2 nanocatalyst

TiO(2) doping with N-rich melamine produced a stable, active and visible light sensitized nanocatalyst that showed a remarkable efficiency towards the photobleaching of a model compound - methylene blue (MB) in aqueous solution. The photobleaching followed a mixed reaction order kinetics with the distinctive induction and acceleration periods.

Synthesis of 2-Indolyl-1-nitroalkane Derivatives Using Nanocrystalline Titanium(IV) Oxide

The catalytic Friedel–Crafts alkylation of indoles with nitroalkenes to furnish 2-indolyl-1-nitroalkane derivatives at room temperature with moderate to excellent yields is reported using nanocrystalline titanium(IV) oxide (nano-TiO2) catalyst. In all cases, a single regioisomer was obtained. After completion of the reaction, the catalyst was recovered by centrifugation and activated under a nitrogen flow for 1 h at 250°C for further reuse. The nano-TiO2 can be reused for four cycles with a slight decrease of activity under the same reaction conditions.

Surface Modification of a Magnetic SiO2 Support and Immobilization of a Nano-TiO2 Photocatalyst on It

This study presented an effective method to modify the surface chemical reactivity of a SiO2/Fe3O4 support. The unmodified SiO2/Fe3O4 support was prepared by the hydrolysis and condensation of tetraethoxysilane on the surface of hydrophilic Fe3O4 nanoparticles. These were then modified by a heat treatment in an ethanol/water solution under reflux. The resulting samples were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission/scanning electron microscopy. The immobilization of a TiO2 nanocatalyst on both unmodified and modified supports was performed to investigate the effects of the modification of the magnetic silica support on the loading of a TiO2 nanocatalyst and the photocatalytic activity. The loading of TiO2 and the photocatalytic activity were both improved.

Facile Synthesis of Anatase–Brookite Mixed‐Phase N‐Doped TiO2 Nanoparticles with High Visible‐Light Photocatalytic Activity

AbstractN‐Doped anatase–brookite bicrystal TiO2 nanocatalysts were successfully synthesized by a facile solvothermal route. The ratio of brookite to anatase can be easily tuned by changing the composition of the phase‐selective agents (acetylacetone). The samples were fully characterized. The band‐gap energy, chemical states of Ti, O, and N species, and photocatalytic activity of the as‐prepared catalysts were affected by the mixed‐phase effect of brookite and anatase. In the optimum ratio range of the phase effect from 24.6 to 75.4 % (brookite to anatase), the N‐doped TiO2 bicrystal catalyst exhibits maximum activity under both visible and UV light, which can be attributed to high quantum efficiency induced by the high concentration of OHsurface, the relatively low amount of Ti3+ sites, active N– species concentration, the relatively large surface areas, and a moderate band‐gap energy.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A study on the degradation of methamidophos in the presence of nano-TiO2 catalyst doped with Re

A new Re-doped nano-TiO2 photocatalyst was synthesized by immersion method. The novel doped nano-TiO2 photocatalyst utilizing visible light was firstly prepared. The doped nano-TiO2 powder was charactered by XRD, FTIR, UV-Vis, and its photocatalytic activity was tested through the photocatalytic degradation of methamidophos as a model compound under ultraviolet irradiating and in sunlight, respectively. In order to compare the photocatalytic activities, the same experiment was carried out for undoped nano-TiO2. The degradation ratio of methamidophos in the presence of doped nano-TiO2 reached 64.40% under sunlight for 12 h, which was 2.64% in the presence of undoped nano-TiO2. The degradation ratio of methamidophos in the presence of doped nanoTiO2 reached 90.39% under UV irradiationat 2.5 h, which was 51.29% in the presence of undoped nano-TiO2. All the results show that the doped TiO2 is a promising photocatalyst using sunlight for treating the organophosphorous pesticide wastewater.

New approaches to prepare nitrogen-doped TiO2 photocatalysts and study on their photocatalytic activities in visible light

Nitrogen-doped TiO2 nanocatalysts were successfully synthesized by adjusting a pH range using the ammonium nitrate and ammonia water as the nitrogen source. The samples were characterized by XRD, XPS and UV-DRS. When the total amount of ammonium nitrate and ammonia water was unchanged, different pH values were modified by changing the NH4NO3/NH3·H2O ratio to prepare nitrogen-doped TiO2. The prepared photocatalyst showed the highest photo-activity for the degradation of 2,4-dichlorophenol (2,4-DCP) under visible light when prepared at pH 5.87. XPS analysis showed the presence of nitrogen in two states doped in TiO2. The results indicated the photocatalytic activity of N-TiO2 is varied with the change of pH values, the amount of the nitrogen sources and water. The experimental results showed that the higher activity is due to the variation in the concentration and states of nitrogen-doped in TiO2. In the preparation methods, the photocatalyst was treated with the hydrogen peroxide before calcination, resulting in the decrease of nitrogen doped into the lattice and the photo-degradation rate of 2,4-DCP. The results suggested that the nitrogen source could be doped into the crystal lattice only in the form of reduction state as NH4+ ion during the calcination process.

Photocatalytic Degradation of Organic Dye on Sulfated Nanosize TiO<sub>2</sub> Sensitized by H<sub>2</sub>O<sub>2</sub> under Visible irradiation

Nano-TiO2 synthesized by hydrolysis of TiCl4 demonstrated high reactivity in presence of peroxide hydrogen under visible light (λ>420nm).The nano-TiO2 powders were characterized by XRD, Uv-Vis, FT-IR. The results showed that the TiO2 nanocatalyst sensitized with peroxide hydrogen could absorb visible light up to 550nm, and Vis absorption could be extended to 600 nm for the sulfated TiO2 .Photocatylytic degradations of methyl orange and methylene blue were above 90% for sulfated TiO2 in 180min. The inorganic sulfate species absorbing on the surface of titania were mainly responsible for the high activity of the TiO2 under visible light regions．

Preparation and application of nano-TiO<sub>2</sub> catalyst in dye electrochemical treatment

This paper reports results of an investigation into the removal of ARB (Acid Red B) dye in an electrochemical oxidation reactor with semi-conductor suspended in the electrolyte. TiO2 nano-powders spiked with various elements, including Si, Co, Zn, La, Ag, Ce, W and Bi, were prepared by sol-gel method to improve colour removal efficiency. Through the L16(44) orthogonal experiment, the optimised preparation conditions of nano-TiO2 catalyst were obtained, namely prepared at 400oC and spiked with 10% Co(in molar ratio). The XRD (X-ray diffraction) analysis indicated that TiO2 prepared at 400oC occurred predominantly in the anatase crystalline form and the particle size was below 20 nm. The BET (Brunauer, Emmet and Teller) surface area was 69.2m2/g. The decolourisation efficiency using Co (10%)/TiO2 as catalyst was 33.1% and increased by 5.7% (about 1.21 times) compared with the colour removal without catalyst. The DRS (diffuse reflectance spectroscopy) demonstrated that the improvement of colour removal of Co(10%)/TiO2 compared with pure TiO2 was probably due to its better light absorption and photocatalytic activity in the visible region. Water SA Vol. 32(2) 2006: pp.205-210

Photocatalytic and UV Characterization of TiO<sub>2</sub> Nanofluid Prepared by SANSS on HVAC

This study develops a measurement method for testing the efficiency of photocatalysts in the degradation of NH3 gaseous concentrations. The catalysts used in this study are the same as those used previously in our UV/VIS spectrophotometer. Reaction measurements were carried out at 27°C and 17°C under ambient pressure on Heat Ventilating and Air Conditioning (HVAC) system. Quartz plates were coated with TiO2 nanocatalyst. Then the plate was put in the stable reaction cell under different flow rates of circulation. The experiment gives a direct and simple measurement of ammonia flux and hence of overall ammonia emission rate. The results reveal that the Submerged Arc Nanoparticle Synthesis System (SANSS) TiO2 nanocatalyst has excellent degradation efficiency towards NH3, so that when it is exposed to UV irradiation for 60 minutes, the gaseous concentration can be reduced to 10% of the original concentration. In addition, the rate constant of the degradation reaction of the self-made TiO2 nanocatalyst towards NH3 is as high as 0.039min-1.

Synthesis of a CNT-grafted TiO2 nanocatalyst and its activity triggered by a DC voltage

Carbon nanotube (CNT)-graftedTiO2 (CNT/TiO2) was synthesized as an electrically conductive catalyst that exhibits redoxability under electrical excitation besides ultraviolet (UV) irradiation. TheCNT/TiO2 material was synthesized by a two-step process. Ni nanoparticles were photodeposited ontoTiO2 first.The Ni nanoparticles then served as seeds for the growth of CNTs using the chemical vapor deposition(CVD) of C2H2. The CNT/TiO2 nanocomposite exhibits strong oxidation activity toward NO gas molecules via bothphotocatalysis under UV irradiation and electrocatalysis under a DC voltage of 500 V indark conditions.

Synthesis and Characterization of Nitrogen-Doped TiO2 Nanophotocatalyst with High Visible Light Activity

Nitrogen-doped TiO2 nanocatalysts with a homogeneous anatase structure were successfully synthesized through a microemulsion−hydrothermal method by using some organic compounds such as triethylamine, urea, thiourea, and hydrazine hydrate. Analysis by Raman and X-ray photoemission spectroscopy indicated that nitrogen was doped effectively and most nitrogen dopants might be present in the chemical environment of Ti−O−N and O−Ti−N. A shift of the absorption edge to a lower energy and a stronger absorption in the visible light region were observed. The results of photodegradation or the organic pollutant rhodamine B in the visible light irradiation (λ > 420 nm) suggested that the TiO2 photocatalysts after nitrogen doping were greatly improved compared with the undoped TiO2 photocatalysts and Degussa P-25; especially the nitrogen-doped TiO2 using triathylamine as the nitrogen source showed the highest photocatalytic activity, which also showed a higher efficiency for photodecomposition of 2,4-dichlorophenol. T...