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1.
Fe-doped TiO 2 was prepared by the calcination of Fe xTiS 2 ( x = 0, 0.002, 0.005, 0.008, 0.01) and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible diffuse reflectance spectra. All the Fe-doped TiO 2 were composed of an anatase crystal form and showed red shifts to a longer wavelength. The activity of the Fe-doped TiO 2 for the degradation of phenol was investigated by varying the iron content during UV (365 nm) and visible light (405 nm and 436 nm) irradiation. The degradation rate depended on the Fe content and the Fe-doped TiO 2 was responsive to the visible light as well as the elevated activity toward UV light. The molar ratio of 0.005 was the optimum for both the UV and visible light irradiations. The result was discussed on the basis of the balance of the excited electron–hole trap by the doped Fe 3+ and their charge recombination on the doped Fe 3+ level. The Fe-doped TiO 2 ( x = 0.005) was more active than P25 TiO 2 under solar light irradiation. The suspended Fe-doped TiO 2 spontaneously precipitated once the stirring of the reaction mixture was terminated. 相似文献
2.
The synthesis of TiO 2 and Fe–TiO 2 by sol–gel method is demonstrated and characterized. The characterization of TiO 2 and Fe–TiO 2 is performed with instruments, including TGA/DTA, FTIR, UV–Vis, N 2 adsorption and SEM. Dichloromethane is used for the photocatalytic activity test. From the results of dichloromethane photocatalyitc degradation, the calcined temperature of TiO 2 and the presence of water vapor influence the photocatalytic activity. The optimum doping amount of iron ions is 0.005 mol%, and this can enhance the photocatalytic activity, while too great an amount will make the iron ions become recombination centers for the electron–hole pairs and reduce the photocatalytic activity. UV–Vis diffuse reflectance spectra of Fe–TiO 2 show an increase in absorbency in the visible light region with the increase in iron ions doping concentration The intermediate of dichloromethane photodegradation includes CHCl 3, CCl 4, CH 2Cl 2 and COCl 2. The presence of iron ions may reduce the adsorption of Cl element on the surface of the photocatalyst. 相似文献
3.
The degradation of a common textile dye, Reactive-brilliant red X-3B, by several advanced oxidation technologies was studied in an air-saturated aqueous solution. The dye was resistant to the UV illumination (wavelength λ 320 nm), but was decolorized when one of Fe 3+, H 2O 2 and TiO 2 components was present. The decolorization rate was observed to be quite different for each system, and the relative order evaluated under comparable conditions followed the order of Fe 2+–H 2O 2–UV Fe 2+–H 2O 2 > Fe 3+–H 2O 2–UV > Fe 3+–H 2O 2 > Fe 3+–TiO 2–UV > TiO 2–UV > Fe 3+–UV > TiO 2–visible light ( λ 450 nm) > H 2O 2–UV > Fe 2+–UV. The mechanism for each process is discussed, and linked together for understanding the observed differences in reactivity. 相似文献
4.
The plasma–chemical degradation of Forafac 1110, a perfluorinated non-ionic surfactant, in aqueous solutions was investigated using TiO 2 catalysts. The considered plasma was the gliding arc in humid air, which results from an electric discharge at atmospheric pressure and quasi-ambient temperature. Two titanium dioxide powders were used and their synergistic effects on the Forafac degradation were compared. The results were discussed through the evolution of the pH, the conductivity, the fluoride ions concentration released in solutions, the surfactant concentration remaining after treatment and the chemical oxygen demand (COD) measurement. The combination of the plasma–chemical treatment with heterogeneous catalysis through the use of TiO2 accelerated the Forafac degradation, since only 60 min was sufficient to remove 96% instead of 360 min needed in the absence of TiO2. The use of anatase and rutile under the trade-name of Rhodia TiO2 and Merck TiO2, respectively, led to different results, because Rhodia TiO2 has proven to be more efficient. It would seem that the crystalline phase as well as the crystallite size, explain the efficiency of anatase. The advantage of the plasma-catalysis is due to the fact that there is a significant production of the OH• radicals not only generated by the gliding arc discharge but also by TiO2. 相似文献
5.
Lanthanum-doped anatase TiO 2 thin films on glass prepared via a sol–gel process have been shown to have much higher photocatalytic activity for the degradation of gaseous benzene than pure anatase TiO 2 thin film. The photodecomposition of benzene on both types of TiO 2 films follows the first-order kinetics while the CO 2 and CO formation followed the zero-order kinetics. GC/MS identification of the intermediates produced during the photodegradation of benzene revealed that doping lanthanum into TiO 2 thin film favors a cleavage of benzene ring. An optimal lanthanum amount with respect to photocatalytic activity was about 2.5 wt% (La 2O 3/TiO 2). 相似文献
6.
The degradation of aniline solution in alkaline medium of pH 11.0 by electrocatalytic oxidation has been studied using an electrochemical reactor containing a SnO 2–Sb 2O 3–PtO anode and a Ti cathode, both of 54 cm 2 area. Hydroxyl radicals (HO √) are produced at the anode, being tested with the trace catcher salicylic acid and phenol by spectrophotometery and high performance liquid chromatography. Intermediates dianiline, 4-anilino phenol and azobenzol were detected by gas chromatography–mass spectrometry. The existence of HO √ produced in the aniline degradation was assayed with scavenger tertiary butanol. The results showed that electrocatalytic oxidation is an effective process for the degradation of aniline. A general reaction pathway that accounts for aniline degradation to CO 2 involving those intermediates is proposed. 相似文献
7.
Aqueous 4-nitrophenol solutions containing TiO 2 or Al 2O 3 nanoparticles were irradiated with electron beam. 4-nitrophenol was decomposed by the ionizing radiation process in the absence of the nanoparticles. The addition of TiO 2 or Al 2O 3 (2 g l −1) before irradiation improved the removal of 4-nitrophenol, total organic carbon (TOC) but also nitrogen (TN). To identify the origin of the loss (catalysis or simply adsorption), TiO 2 or Al 2O 3 nanoparticles were added after irradiation. Experiments show that the effect of the presence of TiO 2 or Al 2O 3 during irradiation is just due to adsorption. 相似文献
8.
Arsenic oxidation (As(III) to As(V)) and As(V) removal from water were assessed by using TiO 2 immobilized in PET (polyethylene terephthalate) bottles in the presence of natural sunlight and iron salts. The effect of many parameters was sequentially studied: TiO 2 concentration of the coating solution, Fe(II) concentration, pH, solar irradiation time; dissolved organic carbon concentration. The final conditions (TiO 2 concentration of the coating solution: 10%; Fe(II): 7.0 mg l −1; solar exposure time: 120 min) were applied to natural water samples spiked with 500 μg l −1 As(III) in order to verify the influence of natural water matrix. After treatment, As(III) and total As concentrations were lower than the limit of quantitation (2 μg l −1) of the voltammetric method used, showing a removal over 99%, and giving evidence that As(III) was effectively oxidized to As(V). The results obtained demonstrated that TiO 2 can be easily immobilized on a PET surface in order to perform As(III) oxidation in water and that this TiO 2 immobilization, combined with coprecipitation of arsenic on Fe(III) hydroxides(oxides) could be an efficient way for inorganic arsenic removal from groundwaters. 相似文献
9.
To sufficiently utilize chemically active species and enhance the degradation rate and removal efficiency of toxic and biorefractory organic pollutant para-chlorophenol ( para-CP), the introductions of iron metal ions (Fe 2+/Fe 3+) into either pulsed discharge plasma (PDP) process or the PDP process with TiO 2 photo-catalyst were tentatively performed. The experimental results showed that under the same experimental condition, the degradation rate and removal efficiency of para-CP were greatly enhanced by the introduction of iron ions (Fe 2+/Fe 3+) into the PDP process. Moreover, when iron ions and TiO 2 were added together in the PDP process, the degradation rate and removal energy of para-CP further improved. The possible mechanism was discussed that the obvious promoting effects were attributed to ferrous ions via plasma induced Fenton-like reactions by UV light irradiation excited and hydrogen peroxide formed in pulsed electrical discharge, resulting in a larger amount of hydroxyl radicals produced from the residual hydrogen peroxide. In addition, the regeneration of ferric ions to ferrous ions facilitates the progress of plasma induced Fenton-like reactions by photo-catalytic reduction of UV light, photo-catalytic reduction on TiO 2 surface and electron transfer of quinone intermediates, i.e. 1,4-hydroquinone and 1,4-benzoquinone. 相似文献
10.
The aerobic visible-light-photosensitised irradiation of methanolic solutions of either of the phenolic-type contaminants model compounds (ArOH) p-phenylphenol (PP), p-nitrophenol (NP) and phenol (Ph), and for two additional phenolic derivatives, namely p-chlorophenol (ClP) and p-methoxyphenol (MeOP), used in some experiments, was carried out. Employing the natural pigment riboflavin (Rf) as a sensitiser, the degradation of both the ArOH and the very sensitiser was observed. A complex mechanism, common for all the ArOH studied, operates. It involves superoxide radical anion (O 2√−) and singlet molecular oxygen (O 2( 1Δ g)) reactions. Maintaining Rf in sensitising concentrations levels (≈0.02 mM), the mechanism is highly dependent on the concentration of the ArOH. Kinetic experiments of oxygen and substrate consumption, static fluorescence, laser flash photolysis and time-resolved phosophorescence detection of O 2( 1Δ g) demonstrate that at ArOH concentrations in the order of 10 mM, no chemical transformation occurs due to the complete quenching of Rf singlet excited state. When ArOH is present in concentrations in the order of mM or lower, O 2√− is generated from the corresponding Rf radical anion, which is produced by electron transfer reaction from the ArOH to triplet excited Rf. The determined reaction rate constants for this step show a fairly good correlation with the electron-donor capabilities for Ph, PP, NP, ClP and MeOP. In this context, the main oxidative species is O 2√−, since O 2( 1Δ g) is quenched in an exclusive physical fashion by the ArOH. The production of O 2√− regenerates Rf impeding the total degradation of the sensitiser. This kinetic scheme could partially model the fate of ArOH in aquatic media containing natural photosensitisers, under environmental conditions. 相似文献
11.
TiO 2 powder-containing paper composites, called TiO 2 paper, were prepared by a papermaking technique, and their photocatalytic efficiency was investigated. The TiO 2 paper has a porous structure originating from the layered pulp fiber network, with TiO 2 powders scattered on the fiber matrix. Under UV irradiation, the TiO 2 paper decomposed gaseous acetaldehyde more effectively than powdery TiO 2 and a pulp/TiO 2 mixture not in paper form. Scanning electron microscopy and mercury intrusion analysis revealed that the TiO 2 paper had characteristic unique voids ca. 10 μm in diameter, which might have contributed to the improved photocatalytic performance. TiO 2 paper composites having different void structures were prepared by using beaten pulp fibers with different degrees of freeness and/or ceramic fibers. The photodecomposition efficiency was affected by the void structure of the photocatalyst paper, and the initial degradation rate of acetaldehyde increased with an increase in the total pore volume of TiO 2 paper. The paper voids presumably provided suitable conditions for TiO 2 catalysis, resulting in higher photocatalytic performance by TiO 2 paper than by TiO 2 powder and a pulp/TiO 2 mixture not in paper form. 相似文献
12.
The photocatalytic inactivation (PCI) of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) was performed using polyoxometalate (POM) as a homogeneous photocatalyst and compared with that of heterogeneous TiO 2 photocatalyst. Aqueous suspensions of the microorganisms (10 7–10 8 cfu ml −1) and POM (or TiO 2) were irradiated with black light lamps. The POM-PCI was faster than (or comparable to) TiO 2-PCI under the experimental conditions employed in this study. The relative efficiency of POM-PCI was species-dependent. Among three POMs (H 3PW 12O 40, H 3PMo 12O 40, and H 4SiW 12O 40) tested in this study, the inactivation of E. coli was fastest with H 4SiW 12O 40 while that of B. subtilis was the most efficient with H 3PW 12O 40. Although the biocidal action of TiO 2 photocatalyst has been commonly ascribed to the role of photogenerated reactive oxygen species such as hydroxyl radicals and superoxides, the cell death mechanism with POM seems to be different from TiO 2-PCI. While TiO 2 caused the cell membrane disruption, POM did not induce the cell lysis. When methanol was added to the POM solution, not only the PCI of E. coli was enhanced (contrary to the case of TiO 2-PCI) but also the dark inactivation was observed. This was ascribed to the in situ production of formaldehyde from the oxidation of methanol. The interesting biocidal property of POM photocatalyst might be utilized as a potential disinfectant technology. 相似文献
13.
Hydrogen titanate (H-titanate) nanowires were prepared via a hydrothermal reaction of TiO 2 powders (P25) in KOH solutions and then calcined at various temperatures. The phase structure, crystallite size, morphology, specific surface area, and pore structures of the calcined H-titanate nanowires at various temperatures were characterized with field emission scanning electron microscope, X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption isotherms, and their photocatalytic activities were evaluated by photocatalytic oxidation of acetone in air. With increasing calcination temperature, the specific surface area and porosity of the calcined samples steadily decreased. At a calcination temperature range of 400–600 °C, the calcined H-titanate nanowires showed higher photocatalytic activity than P25 powders for photocatalytic oxidation of acetone. Especially, at 500 °C, the calcined H-titanate nanowires showed the highest photocatalytic activity, which exceeded that of P25 by a factor of about 1.8 times. This can be attributed to the synergetic effect of larger specific surface area, higher pore volume and the presence of brookite TiO 2. With further increase in the calcination temperature (700–900 °C), the photocatalytic activity of the samples decreased obviously owing to the growth of TiO 2 crystallites. 相似文献
14.
将Fe3+负载在活性炭上制得载铁催化剂Fe/AC,并研究了该催化剂对邻苯二甲酸二甲酯(DMP)的催化降解性能。通过正交实验和单因素实验,探讨了催化剂投加量、H2O2投加量、溶液pH值和反应温度对水中DMP降解率的影响,同时对DMP矿化度进行了分析。实验结果表明,制得的载铁催化剂具有较高的催化活性;降解效果的影响顺序是反应温度〉催化剂投加量〉H2O2投加量〉溶液pH值;在反应温度为80℃、催化剂投加量为4 g/L、H2O2投加量为20 mL/L和溶液pH值为3的条件下反应120 min后,质量浓度为10 mg/L的DMP降解率最高可达97.73%;在优化的实验条件下反应150 min,DMP矿化度可达62.73%;催化剂反复使用5次仍具有较好的催化活性,DMP降解率仍可达到77%以上;反应过程中溶液Fe3+浓度的变化维持在1.07 mg/L左右,且可推测催化降解DMP主要是由非均相和均相催化氧化反应共同作用的。 相似文献
15.
In this study, the rates of degradation of organic compounds by several AOPs (H 2O 2/UV, Fe(III)/UV, Fe(III)/H 2O 2/UV, Fe(II)/H 2O 2 and Fe(III)/H 2O 2) have been compared. Experiments were carried out at pH ≈ 3 (perchloric acid / sodium perchlorate solutions) and with UV reactors equipped with a low-pressure mercury vapour lamp (emission at 253.7 run). The data obtained with atrazine ([Atrazine] o = 100 μg/L) showed that the rate of degradation of atrazine in very dilute aqueous solution is much more rapid with Fe(III)/UV than with H 2O 2/UV. Photo-Fenton process (Fe(III)/H 2O 2/UV) was found to be more efficient than H 2O 2/UV and Fe(II)/H 2O 2 for the mineralization of acetone ([Acetone] o = 1 mM). 相似文献
16.
The photocatalytic removal of humic acid (HA) using TiO 2 under UVA irradiation was examined by monitoring changes in the UV 254 absorbance, dissolved organic carbon (DOC) concentration, apparent molecular weight distribution, and trihalomethane formation potentials (THMFPs) over treatment time. A resin fractionation technique in which the samples were fractionated into four components: very hydrophobic acids (VHA), slightly hydrophobic acids, hydrophilic charged (CHA) and hydrophilic neutral (NEU) was also employed to elucidate the changes in the chemical nature of the HA components during treatment. The UVA/TiO 2 process was found to be effective in removing more than 80% DOC and 90% UV 254 absorbance. The THMFPs of samples were decreased to below 20 μg l −1 after treatments, which demonstrate the potential to meet increasingly stringent regulatory level of trihalomethanes in water. Resin fractionation analysis showed that the VHA fraction was decreased considerably as a result of photocatalytic treatments, forming CHA intermediates which were further degraded with increased irradiation time. The NEU fraction, which comprised of non-UV-absorbing low molecular weight compounds, was found to be the most persistent component. 相似文献
17.
A novel paper-based material containing titanium dioxide (TiO 2) photocatalyst was successfully prepared by a papermaking technique with the internal addition of inorganic fibers on which TiO 2 particles were supported. Photodegradation performance of acetaldehyde gas, an indoor pollutant, and the durability of the TiO 2-containing papers were investigated under UV irradiation. Ceramic fiber suspension and polydiallyldimethylammonium chloride as a cationic flocculant were mixed, followed by the addition of TiO 2 suspension and anionic polyacrylamide. Subsequently, the inorganic mixture was poured into a pulp suspension, and TiO 2 handsheets then prepared by a papermaking method. The tensile strength of TiO 2-containing paper without a ceramic carrier decreased by more than 30% after 240-h UV irradiation (2 mW/cm 2), although the strength of the TiO 2 sheet with ceramic fibers remained reasonably stable. The efficiency of acetaldehyde decomposition by the TiO 2 paper containing an inorganic carrier was nearly equal to that of the carrier-free TiO 2 paper. Scanning electron microscopic observation suggested that most TiO 2 particles were predominantly supported on the inorganic fiber matrix, and were mostly out of contact with organic pulp fibers. The TiO 2 paper with an inorganic carrier demonstrated both excellent photocatalytic performance and durability, which before had been mutually incompatible for organic materials containing TiO 2 photocatalyst. The two-stage mixing procedure for TiO 2 sheet-making is promising for the simple manufacture of high performance paper with photocatalytic ability. 相似文献
18.
The Ti0 2-mediated photomineralization of 8–1000 ppm of methanoic acid, of 6–100 ppm of ethanoic acid, of 6–180 ppm of propanoic acid, and of 6–90 ppm of n-decanoic acid in aqueous solutions was studied at 296± 2 K or 308 ± 2 K, with low and high pressure mercury arc lamps (radiant power in the absorption range 8 and 145 W respectively), using PHOTOPERM® CPP/313 membranes containing immobilized 30±3 wt.% Ti0 2, and, in parallel runs, 7 wt.% of a synergic mixture of tri( t-butyl)- and tri-( i-propyl) vanadate(V) as photocatalytic promoter. Stoichiometric H 20 2 was used or, in some of the runs, 0 3, at saturation, as oxygen suppliers. Disappearance of total organic carbon (TOC) was followed as a function of time. To fit kinetic curves up to complete photomineralization, a kinetic model was employed, already used successfully in previous studies, which considers appearance and disappearance of all intermediates, as if they were represented by a hypothetical single molecule, mediating all of them. The photocatalytic activity of trialkyl vanadates was evaluated from quantum yields at “infinite” concentration, with respect to the maximum allowable efficiencies. When using O 3, a dark catalysis effect clearly appeared towards intermediate species produced during the photocatalysed degradation. 相似文献
19.
In the present paper we investigated the effects of sub-lethal concentrations of Cu 2+ in the growth and metabolism of Scenedesmus incrassatulus. We found that the effect of Cu 2+ on growth, photosynthetic pigments (chlorophylls and carotenoids) and metabolism do not follow the same pattern. Photosynthesis was more sensitive than respiration. The analysis of chlorophyll a fluorescence transient shows that the effect of sub-lethal Cu 2+ concentration in vivo, causes a reduction of the active PSII reaction centers and the primary charge separation, decreasing the quantum yield of PSII, the electron transport rate and the photosynthetic O 2 evolution. The order of sensitivity found was: Growth > photosynthetic pigments content = photosynthetic O 2 evolution > photosynthetic electron transport > respiration. The uncoupled relationship between growth and metabolism is discussed. 相似文献
20.
The photodegradation of polychlorinated dibenzo-p-dioxins (PCDDs), which include tetra- to octa-CDDs (TeCDD, PeCDD, HxCDD, HpCDD and OCDD), was carried out in the presence of Fe(II) and H2O2 mixed reagent. The degradation efficiency was strongly influenced by UV irradiation, and the initial concentrations of H2O2 and Fe(II). An initial TeCDD concentration of 10 ng l(-1) was completely degraded within 20 min under the optimum conditions. All PCDDs tested were successfully degraded by Fe(II)/H2O2/UV treatment and complete degradation of TeCDD, PeCDD and HxCDD was achieved within 120 min. PCDD photodegradation rates decreased with the number of chlorine atoms. The degradation process of TeCDD by this system seems to be initiated by an oxidative reaction (OH* radical attack) because less chlorinated DDs as intermediate products were not detected. From the Frontier electron density calculation, the first OH* radical attack positions on TeCDD were found to be four C atoms neighboring two O atoms. The decomposition of TeCDD gave 4,5-dichlorocatechol as an intermediate product. A TeCDD degradation scheme was proposed based on the identified intermediate and the values of Frontier electron density. Based on these results, Fe(II)/H2O2/UV system could be useful technology for the treatment of wastewater containing persistent pollutants such as dioxins and polychlorinated biphenyls. 相似文献
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