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Query: KEGG:D01931 (TiO2)
 11,320 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present paper reports photocatalytic degradation of bovine serum albumin (BSA) by TiO2 under near UV (365 nm) irradiation. Ultraviolet-Visible spectrometry, FTIR spectrometry and HPLC were used to study the degradation and characterize the final degradation products. It was found that under near UV irradiation, BSA (0.1 g x L(-1)) can be totally degraded to small fragments by TiQ2 in 5 h. Total mineralization of BSA (93.5%) is reached after reacting for 40 h. C, N and S in BSA are mineralized to give CO2, NO3- and SO4(2-). It is suggested that the degradation of BSA happens in two steps: first to small fragments, then further mineralized to small inorganic molecule. The absence of UV irradiation or TiQ2 can only lead to partial degradation of BSA (30%) in 5 h and no CO2 is observed even in longer reaction time.
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PMID:[Investigation of TiO2 photocatalytic degradation of bovine serum albumin]. 1632 8

Tricalcium phosphate (TCP) powders synthesised using the Ca(NO3)2 and Ca(OH)2 routes were doped with TiO2, ZrO2 and Al2O3 in order to increase their compressive strength. An ultimate compressive strength (UCS) of 255 +/- 6 MPa was achieved for approximately 10 vol% TiO2 doping compared to 30 +/- 3 MPa for an un-doped control processed and tested in the same manner. Higher levels of TiO2 doping resulted in smaller increases in UCS with 30 and 50 vol% achieving 213 +/- 9 and 178 +/- 15 MPa, respectively. Very small amounts of Al2O3 doping (< 0.5 vol%) also resulted in a stronger materials. However, under the processing conditions employed, higher levels of Al2O3 and ZrO2 doping resulted in no beneficial effect on the UCS. Polyvinyl alcohol (PVA) was used as binding agent to facilitate processing. As expected, higher levels of PVA were associated with smaller increases in UCS. Powders synthesised using the Ca(OH)2 route had smaller particle size and resulted in larger increases in UCS compared to the Ca(NO3)2-synthesised powders. Although some powders contained alpha and beta-TCP phases, no other calcium phosphate, CaO, CaTiO3 or CaZrO3 phases were detected. In conclusion, a significant increase in the UCS of TCP was achieved by doping with approximately 10 vol% TiO2 which is expected to have little or no effect on the bioactivity or bioresorbability of the material.
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PMID:Effects of TiO2, ZrO2 and Al2O3 dopants on the compressive strength of tricalcium phosphate. 1636 19

We report on the chemical activity of trapped electrons in wet titanium oxide gels. These electrons are generated under the band gap irradiation of gels in the spectral range between 3.25 and 4.4 eV and stored as Ti3+ centers that absorb in the visible. Chemical processes in photoirradiated gels are generally similar to those earlier reported in TiO2 colloids; however, peculiarities exist. In particular, a high internal surface of gels strongly enhances interface reactions. Measurements of UV-visible absorption kinetics allow conclusions to be made about extremely high available traps concentration and the activity of all trapped electrons toward nitrate and nitrite anion reduction according to a heterogeneous photocatalytic mechanism.
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PMID:Chemical activity of photoinduced Ti3+ centers in titanium oxide gels. 1647 53

Eu3+-doped TiO2 luminescent nanocrystals have been synthesized in this work via Ar/O2 thermal plasma oxidizing mists of liquid precursors containing titanium tetra-n-butoxide and europium(III) nitrate, with varied O2 input in the plasma sheath (10-90 L/min) and Eu3+ addition in the precursor solution (Eu/(Ti + Eu) = 0-5 atom%). The resultant nanopowders are mixtures of the anatase (30-36 nm) and rutile (64-83 nm) polymorphs in the studied range, but the rutile fraction increases steadily at a higher Eu3+ addition, as revealed by X-ray diffraction (XRD) and Raman spectroscopy, because of the creation of oxygen vacancies in the TiO2 gas clusters by substitutional Eu3+ doping. The amount of Eu3+ that can be doped into a TiO2 lattice was limited up to 0.5 atom%, above which Eu2Ti2O7 pyrochlore was formed in the final products. High resolution transmission electron microscopy (HRTEM) observation indicates that the particles are dense and have sizes ranging from several nanometers up to 180 nm. Efficient nonradiative energy transfer from the TiO2 host to Eu3+ ions, which was seldom reported in the wet-chemically derived nanoparticles or thin films of the current system, was confirmed by combined studies of excitation, UV-vis (ultraviolet-visible), and PL (photoluminescence) spectroscopy. As a consequence of this, bright red emissions were observed from the plasma-generated nanopowders either by exciting the TiO2 host with UV light shorter than 405 nm or by directly exciting Eu3+ at a wavelength beyond the absorption edge (405 nm) of TiO2.
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PMID:Phase structure and luminescence properties of Eu3+-doped TiO2 nanocrystals synthesized by Ar/O2 radio frequency thermal plasma oxidation of liquid precursor mists. 1647 53

Recent studies reported the use of suspended TiO2 powder as photo catalyst in the degradation process of several organic and inorganic substances in water, like chlorinated hydrocarbons, alkyl- and alkanoloammines and ammonia. In order to evaluate the possibility of using this method for a further removal of ammonia from wastewater after a biological nitrification/denitrification treatment, a kinetic study of photo oxidation over TiO2 of NH3/NH4 in the high concentration range of 26 - 214 mg/I, has been carried out. Effects of pH, TiO2, ammonium and dissolved O2 concentration on the degradation efficiency and reaction products distribution (NO2-, NO3- e N2) were studied. The results have shown that, at a catalyst concentration of 0.012% (p/v), the photo catalytic oxidation of ammonia can be described with the Langumuir- Hinshelwood kinetic model, as reported by several authors.
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PMID:Photocatalytic degradation of high ammonia concentration water solutions by TiO2. 1647 41

This study was undertaken to examine the photocatalytic degradation of explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) with a circular photocatalytic reactor, using a UV lamp as a light source and TiO2 as a photocatalyst. The effects of various parameters, such as the RDX or HMX concentration, the amount of TiO, and the initial pH, on the photocatalytic degradation rates of explosives were examined. In the presence of both UV light and TiO2 RDX and HMX were more effectively degraded than with either UV or TiO2 alone. The degradation rates were found to obey pseudo-first-order kinetics represented by the Langmuir-Hinshelwood model. Increases in the RDX and HMX degradation rates were obtained with decreasing initial concentrations of the explosives. The RDX and HMX degradation rates were higher at pH 7 than at either pH 3 or pH 11. A dose of approximately 0.7 g l(-1) of TiO2 degraded HMX more rapidly than did higher or lower TiO2 doses. RDX (20 mg l(-1)) photocatalysis resulted in an approximately 20% decrease in TOC, and HMX (5 mg l(-1)) photocatalysis resulted in a 60%, decrease in TOC within 150 minutes. A trace amount of formate was produced as an intermediate that was further mineralized by RDX or HMX photocatalysis. The nitrogen byproducts from the photocatalysis of RDX and HMX were mainly NO3- with NO2-, and NH4+. The total nitrogen recovery was about 60% from RDX (20 mg l(-1)), and 70% from HMX (5 mg l(-1)), respectively. Finally, a mechanism for RDX/HMX photocatalysis was proposed, along with supporting qualitative and quantitative evidence.
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PMID:Degradation kinetics and mechanism of RDX and HMX in TiO2 photocatalysis. 1650 18

This study investigates photocatalytic degradation of nitrogen oxides overtitania-based photocatalysts illuminated by ultraviolet and visible light. The TiO2 photocatalyst was synthesized in a sol-gel process using titanium butoxide as the precursor. After calcination between 150 and 300 degrees C, the synthesized TiO2 responded strongly to visible light photocatalytically degrading NO(x), probably because of the existence of carbonaceous species that act as sensitizers. The optimum calcination temperature was found to be around 200 degrees C. Additionally, platinum ion-doped TiO2 was prepared by impregnation using Pt(NH3)4(NO3)2 as a dopant, which improved the photocatalytic activity that degraded NO(x) in the visible light region. The Pt ion was doped in oxide form at the surface of TiO2 and was expected to be responsible for sensitization. At an optimum calcination temperature of around 200 degrees C, the Pt ion-doped TiO2 exhibited higher activity in the further oxidation of NO2 to NO3- clearly reducing NO2 selectivity. The TiO2 catalysts chemically prepared by either the sol-gel process or impregnation exhibited stronger activity than conventional TiO2 when illuminated under a fluorescent lamp. Rinsing with water was responsible for the restored reactivity of prepared TiO2 catalysts for NO(x) degradation.
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PMID:Photocatalytic activity for degradation of nitrogen oxides over visible light responsive titania-based photocatalysts. 1656 78

There has been growing interest in new ways to produce composite nanofibers. Continuous TiO2 (anatase phase) nanofibers with silver nanoparticles were prepared successfully via sol-gel and electrospinning. A sol containing poly(vinyl pyrrolidone), titanium tetraisopropoxide, and silver nitrate was injected through a conductive capillary where high voltage was applied. As a result of electrospinning, continuous composite nanofibers were collected and they were calcined in air at 500 degrees C in order to complete the crystallization of anatase phase. The anatase-silver nanocomposite fibers were characterized with X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy.
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PMID:Synthesis of anatase-silver nanocomposite fibers via electrospinning. 1657 60

The solar photocatalytic degradation of methyl parathion was investigated using a circulating TiO2/solar light reactor. Under solar photocatalysis condition, parathion was more effectively degraded than solar photolysis and TiO2-only conditions. With solar photocatalysis, 20 mg/L of parathion was completely degraded within 60 min with a TOC decrease of 63% after 150 min. The main ionic byproducts during photocatalysis recovered from parathion degradation were mainly as NO3-, NO2- and NH4+, 80% of the sulphur as SO4(2-), and 5% of phosphorus as PO4(3-). The organic intermediates 4-nitrophenol and methyl paraoxon were also identified, and these were further degraded in solar photocatalytic condition. Two different bioassays (Vibrio fischeri and Daphnia magna) were used to test the acute toxicity of solutions treated by solar photocatalysis and photolysis. The Microtox test using V. fischeri showed that the toxicity expressed as EC50 (%) value increased from 5.5% to >82% in solar photocatalysis, indicating that the treated solution is non-toxic, but only increased from 4.9 to 20.5% after 150 min in solar photolysis. The acute toxicity test using D. magna showed that EC50 (%) increased from 0.05 to 1.08% under solar photocatalysis, but only increased to 0.12% after 150 min with solar photolysis, indicating the solution is still toxic. The pattern of toxicity reduction parallels the decrease in TOC and the parathion concentrations.
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PMID:Parathion degradation and toxicity reduction in solar photocatalysis and photolysis. 1660 11

The nanometer rutile titanium dioxide (TiO2) powder was adopted to act as the sonocatalyst after treatment of high-temperature activation and the ultrasound of low power was used as an irradiation source to induce heat-treated TiO2 powder performing sonocatalytic degradation of parathion. Although there are many factors influencing sonocatalytic degradation of parathion, the experimental results demonstrate that the optimal degradation condition of parathion can be obtained when the experimental conditions such as initial concentration of 50 mg/L parathion, addition amount of 1000 mg/L nanometer rutile TiO2, ultrasonic of 30-50 kHz frequency and 50 W output power, acidity of pH 10.0 and temperature of 20 degrees C are adopted. The degradation ratio of parathion surpassed 90% within 120 min ultrasonic irradiation in these optimal experiment conditions. The total degradation process of parathion has been monitored by UV-vis spectra and ion chromatography. At last, the parathions in aqueous solution are completely degraded and become some simple inorganic ions such as NO3(-), PO4(3-), SO4(2-), etc. In addition, the sonocatalytic activities of reused TiO2 catalysts were also studied and found to decline gradually along with the reused times. In this paper, the research on sonocatalytic degradation kinetics was also been performed and found to follow pseudo first-order reaction. All experiments indicated that the sonocatalytic method in the presence of nanometer rutile TiO2 powder was an advisable choice for the treatments of non- or low-transparent organic wastewaters in future.
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PMID:Investigation on the sonocatalytic degradation of parathion in the presence of nanometer rutile titanium dioxide (TiO2) catalyst. 1670 1


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