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1.
Gaseous NO was photocatalytically reduced at room temperature by photo-assisted selective catalytic reduction (photo-SCR) with ammonia over TiO 2 in this study. NO reduction efficiency and N 2 selectivity were determined from gases composition at the outlet stream of photoreactor. Effect of operating conditions, e.g. light intensity and inlet concentrations of ammonia and oxygen, on the NO reduction efficiency and N 2 selectivity were discussed to determine the feasible operating condition for photocatalytic reduction of NO. Experimental results showed that selective catalytic reduction of NO with ammonia over TiO 2 in the presence of oxygen was a spontaneous reaction in dark. The photoirradiation on the TiO 2 surface caused remarkable photocatalytic reduction of NO to form N 2, NO 2, and N 2O under 254 nm UV illuminations, while almost 90% of N 2 selectivity was achieved in this study. The ammonia and oxygen molecules played the roles of reductant and oxidant for NO reduction and active sites regeneration, respectively. The reduction of NO was found to be increased with the increase of inlet ammonia and oxygen concentrations until specific concentrations because of the limited active sites on the surface of TiO 2. The kinetic model proposed in this study can be used to reasonably describe the reaction mechanism of photo-SCR. 相似文献
2.
ZnS-loaded TiO 2 (ZnS–TiO 2) was synthesized by a sol–gel method. The catalyst was characterized by using different techniques (XRD, HR-SEM, EDS, DRS, PL, XPS, and BET methods). The photocatalytic activity of ZnS–TiO 2 was investigated for the degradation of Sunset Yellow FCF (SY) dye in an aqueous solution using ultraviolet light. ZnS–TiO 2 is found to be more efficient than prepared TiO 2, TiO 2–P25, TiO 2 (Merck), and ZnS at pH 7 for the mineralization of SY. The effects of operational parameters such as the amount of photocatalyst, dye concentration, and initial pH on photo mineralization of SY have been analyzed. The mineralization of SY has been confirmed by chemical oxygen demand measurements. The catalyst is found to be reusable. 相似文献
3.
Great attention should be paid to the possible impacts of various nanoparticles on aquatic organism. Freshwater diatoms are essential components of phytoplankton and play a critical role in bioassessment of nanoparticle exposure in the environment. In this study, cell growth was inhibited by TiO 2-NPs and MWCNTs, the 24?h EC 50 values of TiO 2-NPs and MWCNTs to Nitzschia frustulum were 20.75 and 24.64?mg?L ?1, respectively. Significant decreases of Chl a content after TiO 2-NPs exposures were detected and the Chl a content of N. frustulum was obviously increased by MWCNTs treatment at lower concentration. The ROS was detected in N. frustulum after TiO 2-NPs and MWCNTs exposures. The MDA content was significantly induced by TiO 2-NPs at lower concentrations of 24 and 48?h exposure; meanwhile, it increased at all tested concentrations at 24?h MWCNTs exposure. The SOD enzyme was induced by 72 and 96?h TiO 2-NPs exposure, and increased by MWCNTs treatment at 96?h in N. frustulum. Scanning electron microscopy results revealed that N. frustulum had obvious cell deformation after TiO 2-NPs treatment. The result showed that the physiological and biochemical response mechanisms after NPs exposure of diatom were species-specific, and in relation to the exposure concentration and time. 相似文献
4.
The TiO 2/SiO 2 composite was prepared by means of the SiO 2-particle-entrapment method. The FTIR data showed the presence of Si–O–Ti stretching vibration band at 970 cm −1 in the TiO 2/SiO 2 composite, suggesting a reaction between TiO 2 and silica on the TiO 2 particle surface during the silicagel formation around the TiO 2 particles. The photocatalytic efficiency of TiO 2 immobilized in silicagel was compared with that of the conventional TiO 2 Degussa P25 catalyst. For this purpose, the degradation of indigo carmin (IC) dye was used as model molecule in the tests.
The effect of operational parameters such as catalyst loading and dye concentration on the photocatalytic degradation of the
model dye was investigated. The rate of degradation increased with increasing catalyst loading, and when the concentration
of the dye decreases. 相似文献
5.
Little information is available on the potential ecotoxicity of nanomaterials in the marine environment. In particular, the aquatic ecotoxicity impact of titanium dioxide (TiO 2) has been rarely reported. To carefully address this issue, we report on the synthesis of TiO 2 NPs using solvothermal process. The structure and morphology of the prepared TiO 2 nanoparticles were characterised using different techniques. To study the potential ecotoxicity effect of TiO 2, antioxidant system of mediterranean bivalves ( Mytilus galloprovincialis) was used, measuring three oxidative biomarkers (ROS production, SOD activity and GSH/GSSG level). No considerable effect was found in the digestive glands of any of the groups treated with TiO 2 with concentration gradients ranging from 1 to 100?mg/L. Thus, the level of the superoxide anion, the activity of an antioxidant enzyme superoxide dismutase (SOD) and the GSH/GSSG ratio showed no significantly differences in digestive glands of all treated groups compared to the control. However, slight modifications were observed in the gills at high concentrations. These results demonstrated that TiO 2 appears to exert little toxicity on marine mussels after a short-term exposure at high concentration. However, before considering the use of this nanomaterial in various applications, further complementary studies are required in order to ensure the environmental safety of these NPs. 相似文献
6.
Poly(vinylidene fluoride) (PVDF)/titanium dioxide (TiO 2) hybrid membranes were prepared using nano-TiO 2 as the modifier, and characterized by Transmission Electron Microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The characterization results demonstrated that nano-sized TiO 2 particles dispersed homogeneously within the PVDF matrix, contributing to more hydroxyls and smoother surfaces. Moreover, permeate flux, retention factor, porosity, contact angle and anti-fouling tests were carried out to evaluate the effect of TiO 2 concentration on the performance of PVDF membranes. Among all the prepared membranes, PVDF/TiO 2 membrane containing 10 vol.% TiO 2 exhibited the best hydrophilicity with an average pure water flux up to 237 L·m ?2·h ?1, higher than that of unmodified PVDF membranes (155 L·m ?2·h ?1). Besides, the bovine serum albumin rejection of the hybrid membrane was improved evidently from 52.3% to 70.6%, and the contact angle was significantly lowered from 83° to 60°, while the average pore size and its distribution became smaller and narrower. 相似文献
7.
The photocatalytic degradation of the herbicide isoproturon under solar light was investigated in aqueous solution containing a Bi–TiO 2/zeolite photocatalyst. The catalysts were characterized using X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, Fourier transform-infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The effect of Bi–TiO 2 loading onto the zeolite support and influence of the parameters such as catalyst amount, pH, and initial concentration of isoproturon on the degradation rate were evaluated. The recycling ability of the catalyst was found to be sustainable for elongated periods. The high activity of the Bi–TiO 2/zeolite was attributed to its absorptivity of visible light and its high adsorption capacity for the pollutant molecules. 相似文献
8.
Tetracycline (TC), one of the most common antibiotics, is often poorly bio-degraded in conventional wastewater treatment plants. In this study, the sonocatalytic degradation of TC was investigated using TiO 2 nano-particles as catalyst. The effect of pH, initial TC concentrations, reaction times, and H 2O 2 concentrations were evaluated. The efficacy of ultrasonic irradiation alone in the removal of this pollutant was negligible but removal efficiency increased upon addition of TiO 2 up to 250 mg L ?1; increase of pH and initial TC concentration attenuated TC degradation. Addition of H 2O 2 raised the removal efficiency so that complete removal of TC was achieved within 75 min. 相似文献
9.
In this work, Er 3+:YAlO 3/TiO 2 composite was synthesized by a ultrasonic dispersion and liquid boil method. The Er 3+:YAlO 3/TiO 2 composite and pure TiO 2 powder were characterized by XRD. The degradation of different organic dyes was used to evaluate the photocatalytic activity of the Er 3+:YAlO 3/TiO 2 composite. It is found that the photocatalytic activity of Er 3+:YAlO 3/TiO 2 composite is much higher than that for the similar system with only TiO 2. Moreover, this Er 3+:YAlO 3/TiO 2 composite provides a new way to take advantage of TiO 2 in sewage treatment aspects using solar light. 相似文献
10.
The use of aquatic organisms to monitor for contamination is well-established. Therefore, this study was designed to assess the adverse effects of titanium dioxide nanoparticles (TiO 2NP) in freshwater snail Lymnea luteola L. ( L. luteola). For TiO 2NPs ecotoxicity tests, snails were exposed for seven days. A dose and time-response relationship was observed for TiO 2NP-induced genotoxicity. Induction of oxidative stress in digestive gland was observed by a decrease in glutathione and gluthathions-S-transferase levels accompanied by elevated malondialdehyde levels at TiO 2NP (9 and 28 µg/mL). Superoxide dismutase activities were markedly reduced at TiO 2NP (9 and 28 µg/mL) at days 1 and 3, but not at day 7. Catalase activities were decreased at days 1 and 3 but increased at higher concentration of TiO 2NP at day 7. DNA fragmentation occurring in L. luteola due to ecotoxic impact TiO 2NP was further substantiated by alkaline single-cell gel electrophoresis assay and expressed in terms of percent tail DNA and olive tail moment. The results indicate that the interaction of these TiO 2NP with snail influences the toxicity, which is mediated by oxidative stress in a dose- and time-dependent manner. The measurement of DNA integrity in L. luteola thus provides an early warning signal of contamination of the aquatic ecosystem by TiO 2NP. Data suggest the freshwater snail L. luteola is a potential biomonitor organism. 相似文献
11.
The synthesis of silver doped nano-particulate titanium dioxide (Ag/TiO 2) using a microemulsion method and an investigation of its photocatalytic activity for the degradation of Acid Red 27 in distilled water under UV-irradiation is reported. The prepared Ag/TiO 2 is characterized using transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The size of the Ag nanoparticles is around 5–15?nm, with almost uniform distribution on the TiO 2 particles. The efficiency of the photocatalytic process is evaluated to establish the optimum conditions, found to be at 2?wt% of Ag loading on TiO 2, catalyst dosage of 400?mg?L ?1, and calcination temperature of 300°C. Complete decolorization of the dye solution on Ag/TiO 2 was observed in 20?min of UV irradiation in the optimum conditions. 相似文献
12.
Photodegradation kinetics of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) in photoreactor with immobilized and suspended
TiO 2 photocatalyst were studied. The effect of addition of ferric or ferrous perchlorate was investigated. Whatever the concentration
of Fe(III/II) added there is no significant negative effect on the photodegradation rate of pollutants. On the contrary, depending
on speciation and concentration of iron salts, slight or marked acceleration of the photodegradation kinetics was observed.
This positive influence was more pronounced in the case of TiO 2 suspensions than for TiO 2 layers. Fe(III) was generally more effective than Fe(II). 相似文献
13.
In this study, we report the effects of pH and divalent cations on the adsorption of arsenate (As(V)) by titanium dioxide
(TiO 2) nanoparticles. The extent of As(V) adsorption on TiO 2 decreased with increasing pH due to the decrease of positively charged binding sites on the TiO 2 surface. The Langmuir maximum uptake capacity at pH 4 is about three times higher than that at pH 7. Here we show that the
relatively low As(V) uptake at circumneutral pH could be substantially enhanced by the addition of common divalent cations
such as magnesium and calcium. At a concentration of approximately 7 mM, magnesium and calcium increased the extent of As(V)
adsorption from 2.1 to 6.5 and 7.7 mg As(V)/g TiO 2, respectively. 相似文献
14.
Degradation and toxicity reduction of perfluorooctanoic acid (PFOA) were investigated using TiO 2 adsorption, vacuum ultraviolet (VUV) photolysis, and VUV/TiO 2 photocatalysis in acidic and basic aqueous solutions. Chemical analyses of PFOA and its selected by-products and an acute toxicity assessment using the luminescent bacteria Vibrio fischeri (Microtox®) were conducted during and after the various treatment methods. PFOA was found to be best treated by VUV/TiO 2 at pH 4 with HClO 4, as illustrated by the almost complete degradation of PFOA within 360?min and rapid removal of acute microbial toxicity within 60?min. This difference in the efficiency may be attributed to the strong oxidation effectiveness of the radical species generated in acidic media and the electron scavenger effect of the addition of HClO 4 in VUV/TiO 2 photocatalysis. In addition, the proposed method could effectively decompose other perfluorocarboxylic acid (PFCA) species (C 3–C 7 perfluoroalkyl groups) if the initial intermediates formed were longer-chain species that degraded stepwise into shorter-chain compounds by VUV photolysis and VUV/TiO 2 photocatalysis in acidic and basic aqueous solutions. 相似文献
15.
Titanium dioxide (TiO 2) nanoparticles possess the potential to coexist with Copper (Cu 2+) in soil. The individual and combined toxicity of these two chemicals was evaluated using the bacterium Bacillus subtilis, a known soil model bacterium. Cu 2+ (6.25–50?µg?mL ?1) alone produced toxicity to bacteria as evidenced by the decreased cell viability and deceased α-amylase production. The addition of TiO 2 (50?mg?mL ?1) enhanced the Cu 2+-induced decrease in cell viability but elevated amylase activity. TiO 2 did not markedly affect the growth rate and lag period. A primary cause of TiO 2 increasing Cu 2+ toxicity is presumed to be associated with hydroxyl radical formation, while increased amylase activity is considered to arise from Cu 2+ facilitating TiO 2 degradation ability. 相似文献
16.
BackgroundIn this study, the photodegradation of three pharmaceuticals, namely Ibuprofen (IBP), Naproxen (NPX), and Cetirizine (CIZ) in aqueous media was investigated under UV irradiation. The photocatalyst used in this work consists of surface functionalized titanium dioxide (TiO2–NH2) nanoparticles grafted into Polyacrylonitrile (PAN)/multi-walled carbon nanotube composite nanofibers. Surface modification of the fabricated composite nanofibers was illustrated using XRD, FTIR, and SEM analyses.ResultsSets of experiments were performed to study the effect of pharmaceuticals initial concentration (5–50 mg/L), solution pH (2–9), and irradiation time on the degradation efficiency. The results demonstrated that more than 99% degradation efficiency was obtained for IBP, CIZ, and NPX within 120, 40, and 25 min, respectively.ConclusionsComparatively, the photocatalytic degradation of pharmaceuticals using PAN-CNT/TiO2–NH2 composite nanofibers was much more efficient than with PAN/TiO2–NH2 composite nanofibers. 相似文献
17.
Photocatalytic oxidation using semiconductors is one of the advanced oxidation processes for degradation of organic pollutants in water and air. TiO 2 is an excellent photocatalyst that can mineralize a large range of organic pollutants such as pesticides and dyes. The main challenge is to improve the efficiency of the TiO 2 photocatalyst and to extend TiO 2 light absorption spectra to the visible region. A potential solution is to couple TiO 2 with a narrow band gap semiconductor possessing a higher conduction band such as bismuth oxide. Therefore, here we prepared Bi 2O 3/TiO 2 heterojunctions by the impregnation method with different Bi/Ti ratio. The prepared composites have been characterized by UV–Vis diffused reflectance spectra and X-ray diffraction. The photocatalytic activity of the heterojunction has been determined from the degradation of orange II under visible and UV light. Results show that Bi 2O 3/TiO 2 heterojunctions are more effective than pure TiO 2-anatase under UV-A irradiation, with an optimum for the Bi/Ti ratio of 5 %, for the photocatalytic degradation of Orange II. However, the photocatalytic activity under irradiation at λ higher than 420 nm is not much improved. Under UV–visible radiation, the two semiconductors are activated. We propose a mechanism explaining why our products are more effective under UV–visible irradiation. In this case the charge separation is enhanced because a part of photogenerated electrons from the conduction band of TiO 2 will go to the conduction band of bismuth oxide. In this composite, titanium dioxide is the main photocatalyst, while bismuth oxide acts as adsorbent photosensitizer under visible light. 相似文献
18.
A southern Italian area that is characterized by large outcrops of rocks that are rich in titanium oxide (TiO2) phases were investigated to determine the mineralogical risk induced by the natural dispersion of TiO2 minerals. Rock, sediment and surface water samples were collected to determine the physicochemical and mineralogical factors (i.e., size distribution, morphology and alteration) indicative of potential TiO2 toxicity. X-ray diffraction data suggested that titanium oxides were present as rutile and anatase. Scanning electron microscopy images showed elongated TiO2 morphologies; fibres were found as either isolated or embedded/enclosed in flake-like phyllosilicates. The concentration of fibres in stream water ranged from 1.7 to 4.6 million fibres per litre. The highest fibre amounts in the sediments were in the <8-µm fraction, while single fibres were primarily concentrated in the <2-µm fraction. The results indicate that titanium oxide minerals represent a natural source of environmental risk and that the geomineralogical characterization of rich TiO2 areas is indispensable for understanding their geoavailability, dispersion and distribution. 相似文献
19.
We report a facile approach for preparing mesoporous boron-doped TiO 2 materials by combining the sol?Cgel process with the dehydration of glucose. Specifically a high surface carbon material was formed by dehydration of glucose, then used as template. This material and the TiO 2 dry gel were calcinated to produce porous TiO 2. The as-synthesized boron-doped TiO 2 was in pure anatase crystallite phase with high surface area. X-ray photoelectron spectroscopy (XPS) results showed that boron was incorporated into the anatase TiO 2 lattice to form TiO 2?xB x. The absorption spectra of TiO 2?xB x extended into the visible region to 460?nm. The TiO 2?xB x exhibited much higher photocatalytic activity on phenol degradation than pure TiO 2. It showed that the phenol degradation by-products of TiO 2?xB x were different from that of pure TiO 2. Mechanism of the photocatalytic degradation of phenol at TiO 2?xB x was also proposed. 相似文献
20.
The occurrence of chlorinated pesticides in wellwaters is a major problem of public health in Ivory Coast and other African
countries. Here, we studied the photocatalytic degradation of the pesticide diuron in aqueous solution in presence of two
commercial TiO 2 catalysts, P25 and PC500. The capacity of diuron adsorption at the TiO 2 surface is lower for both photocatalysts. The efficiency of photocatalytic degradation of diuron, it is higher using P25
Degussa than PC500 Millenium TiO 2 catalyst. 相似文献
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