Showing papers on "Photocatalysis published in 2004"
TL;DR: In this paper, photo-induced superhydrophilicity was used on the surface of a wide-band gap semiconductor like titanium dioxide (TiO 2 ) for photocatalytic activity towards environmentally hazardous compounds.
4,241 citations
TL;DR: In this article, the photocatalytic degradation of azo dyes containing different functionalities has been reviewed using TiO2 as photocatalyst in aqueous solution under solar and UV irradiation.
Abstract: The photocatalytic degradation of azo dyes containing different functionalities has been reviewed using TiO2 as photocatalyst in aqueous solution under solar and UV irradiation. The mechanism of the photodegradation depends on the radiation used. Charge injection mechanism takes place under visible radiation whereas charge separation occurred under UV light radiation. The process is monitored by following either the decolorization rate and the formation of its end-products. Kinetic analyses indicate that the photodegradation rates of azo dyes can usually be approximated as pseudo-first-order kinetics for both degradation mechanisms, according to the Langmuir–Hinshelwood model. The degradation of dyes depend on several parameters such as pH, catalyst concentration, substrate concentration and the presence of electron acceptors such as hydrogen peroxide and ammonium persulphate besides molecular oxygen. The presence of other substances such as inorganic ions, humic acids and solvents commonly found in textile effluents is also discussed. The photocatalyzed degradation of pesticides does not occur instantaneously to form carbon dioxide, but through the formation of long-lived intermediate species. Thus, the study focuses also on the determination of the nature of the principal organic intermediates and the evolution of the mineralization as well as on the degradation pathways followed during the process. Major identified intermediates are hydroxylated derivatives, aromatic amines, naphthoquinone, phenolic compounds and several organic acids. By-products evaluation and toxicity measurements are the key-actions in order to assess the overall process.
3,692 citations
TL;DR: In this article, the authors have synthesized chemically modified titanium dioxide photocatalysts in which S (S4+) substitutes for some of the lattice titanium atoms, which showed strong absorption for visible light and high activities for degradation of methylene blue, 2-propanol in aqueous solution and partial oxidation of adamantane under irradiation at wavelengths longer than 440nm.
Abstract: Although titanium dioxide photocatalysts having anatase phase are a promising substrate for photodegradation of pollutants in water and air, their photocatalytic activities show only under ultraviolet (UV) light. For us to utilized a wide range of incident light such as solar light, development of the photocatalysts whose activities show under visible light is one of the most important strategies. We have synthesized chemically modified titanium dioxide photocatalysts in which S (S4+) substitutes for some of the lattice titanium atoms. They show strong absorption for visible light and high activities for degradation of methylene blue, 2-propanol in aqueous solution and partial oxidation of adamantane under irradiation at wavelengths longer than 440 nm. The oxidation state of the S atoms incorporated into the TiO2 particles is determined to be mainly S4+ from X-ray photoelectron spectra (XPS) spectra.
1,226 citations
TL;DR: In this article, a detailed investigation of photocatalytic degradation of acid red 14 (AR14) was presented, and it was shown that zinc oxide appears to be a suitable alternative to TiO2 for water treatment.
Abstract: The degradation of acid red 14 (AR14), commonly used as a textile dye, can be photocatalysed by ZnO. Using advanced oxidation processes (AOPs), zinc oxide appears to be a suitable alternative to TiO2 for water treatment. In this study, a detailed investigation of photocatalytic degradation of acid red 14 is presented. Photodegradation efficiency was small when the photolysis was carried out in the absence of ZnO and it was also negligible in the absence of UV light. The semi-log plot of dye concentration versus time was linear, suggesting first order reaction (K=0.0548 min−1). The effects of some parameters such as pH, amount of photocatalyst, hydrogen peroxide and ethanol concentration were also examined. The addition of proper amount of hydrogen peroxide improved the decolorization, while the excess hydrogen peroxide could quenched the formation of hydroxyl radicals ( OH). As our results indicated that ethanol inhibited the photodegradation of dye, we concluded from the inhibitive effect of ethanol that hydroxyl radicals played a significant role in the photodegradation of dye. This should not undermine direct oxidation caused by positive holes.
1,218 citations
TL;DR: The potential of a common semiconductor, ZnO, has been explored as an effective catalyst for the photodegradation of two model dyes: Methylene Blue and Eosin Y and substantial reduction of COD was achieved.
1,049 citations
TL;DR: Pt, Au and Pd deposited TiO2 have been prepared and characterised by surface analytical methods such as surface area, XRD, and scanning electron micrograph and photophysical characterisation by diffuse reflectance spectroscopy.
816 citations
TL;DR: In this article, the basic principles of photocatalysis, focusing in particular on important mechanistic and kinetic aspects as well as on some requirements for efficient photocatalysts, are discussed.
791 citations
TL;DR: In this article, Mn-, Ru-, Rh-, and Ir-doped SrTiO3 possessed intense absorption bands in the visible light region due to excitation from the discontinuous levels formed by the dopants to the conduction band of the host.
Abstract: Mn-, Ru-, Rh-, and Ir-doped SrTiO3 possessed intense absorption bands in the visible light region due to excitation from the discontinuous levels formed by the dopants to the conduction band of the SrTiO3 host. Mn- and Ru-doped SrTiO3 showed photocatalytic activities for O2 evolution from an aqueous silver nitrate solution while Ru-, Rh-, and Ir-doped SrTiO3 loaded with Pt cocatalysts produced H2 from an aqueous methanol solution under visible light irradiation (λ > 440 nm). The Rh(1%)-doped SrTiO3 photocatalyst loaded with a Pt cocatalyst (0.1 wt %) gave 5.2% of the quantum yield at 420 nm for the H2 evolution reaction.
788 citations
TL;DR: It was suggested that the specific surface nanostructure was effective for the suppression of recombination between photogenerated electrons and holes and for the separation of H(2) evolution sites from oxidation reaction sites.
Abstract: (AgIn)xZn2(1-x)S2 solid solutions between ZnS photocatalyst with a wide band gap and AgInS2 with a narrow band gap showed photocatalytic activities for H2 evolution from aqueous solutions containing sacrificial reagents, SO32- and S2-, under visible-light irradiation (λ ≥ 420 nm) even without Pt cocatalysts. Loading of the Pt cocatalysts improved the photocatalytic activity. Pt (3 wt %)-loaded (AgIn)0.22Zn1.56S2 with a 2.3 eV band gap showed the highest activity for H2 evolution, and the apparent quantum yield at 420 nm amounted to 20%. H2 gas evolved at a rate of 3.3 L m-2·h-1 under irradiation using a solar simulator (AM 1.5). The diffuse reflection and the photoluminescence spectra of the solid solutions shifted monotonically to a long wavelength side as the ratio of AgInS2 to ZnS increased in the solid solutions. The photocatalytic H2 evolution depended on the compositions as well as the photophysical properties. The dependence of the photophysical and photocatalytic properties upon the composition wa...
758 citations
TL;DR: In this article, nitrogen-doped titania photocatalysts were obtained from titanium tetraisopropoxide or titanium tetrachloride and thiourea.
Abstract: Nitrogen-doped titania photocatalysts were prepared from titanium tetraisopropoxide or titanium tetrachloride and thiourea. The yellow powders obtained after calcination at 400−600 °C photocatalyze the mineralization of 4-chlorophenol by visible light (λ ≥ 455 nm). Different from previously published data these materials do not contain sulfur but instead nitrogen as the doping component inducing visible light photocatalysis. The measured band gap narrowing of 40−80 meV and the anodic shift of the quasi Fermi potential of 40−90 mV are in agreement with recent results on nitrogen-doped titania.
726 citations
TL;DR: In this article, the authors focused on the treatment of hazardous wastewater (bearing heavy metals and organic compounds) by photocatalysis and the effects of various parameters such as pH, light intensity, dissolved oxygen, etc.
Abstract: Photocatalysis has been a widely studied technology since the 1970s. Many investigations have been carried out with the aim of understanding the fundamental processes and enhancing photocatalytic efficiencies especially for water, air, and soil pollution control. In this comprehensive paper, studies focused on the treatment of hazardous wastewater (bearing heavy metals and organic compounds) by photocatalysis and the effects of various parameters such as pH, light intensity, dissolved oxygen, etc., are reviewed. In addition, the design features and efficiencies of various photoreactors used for this process are discussed. Some studies on the economic analysis of photocatalytic systems are also included. It can be concluded that the photocatalysis process is suitable for the treatment of drinking water and industrial wastewater. Also, harvesting the energy of the sun for photoreactions would make it a cleaner and more cost-effective treatment method.
TL;DR: In this paper, the effect of reductants such as methanol, SCN, Br-, I-, and hydroquinone on the photocurrent action spectrum of anatase TiO2 powder was investigated.
Abstract: Nitrogen doping of anatase TiO2 powder extended the photocurrent action spectrum for water oxidation from the UV-light region (≤400 nm) to the visible-light region (≤ ∼550 nm), as reported. Investigations of the effect of the addition of reductants such as methanol, SCN-, Br-, I-, and hydroquinone to the electrolyte have for the first time given clear experimental evidence to the mechanism that visible-light responses for N-doped TiO2 arise from an N-induced midgap level, formed slightly above the top of the (O-2p) valence band. The investigations, in combination with the above mechanism, have also shown that photocatalytic oxidation of organic compounds on N-doped TiO2 under visible illumination mainly proceed via reactions with surface intermediates of water oxidation or oxygen reduction, not by direct reactions with holes trapped at the N-induced midgap level.
TL;DR: In this article, the photocatalytic degradation of a model azo-dye (Acid Orange, AO7) in aerated aqueous TiO2 dispersion has been studied under visible light (λ>400 nm) irradiation.
Abstract: The photocatalytic degradation of a model azo-dye (Acid Orange, AO7) in aerated aqueous TiO2 dispersion has been studied under visible light (λ>400 nm) irradiation. The presence and role of oxidative species, such as singlet oxygen ( 1 O 2 ), superoxide (O2− ) and hydroperoxy (HO2 ) radicals was examined with the use of appropriate quenchers of these species. The reaction pathway of dye degradation was also investigated by monitoring the temporal evolution of intermediates and final products on both the photocatalyst surface and in solution, with the use of a variety of techniques, including GC–MS, FTIR and UV-Vis spectroscopies. It has been found that complete decolorization of the solution may be achieved, accompanied by a substantial decrease of the chemical oxygen demand (COD) of the solution. Evidence is presented that the main oxidative species is O2− (or HO2 ), while singlet oxygen, when formed, is also active. The adsorbed dye molecule is initially cleaved in the vicinity of the azo-bond and the resulting fragments are oxidized toward compounds of progressively lower molecular weight and, eventually, to CO2 and inorganic ions. However, when the solution is bleached, formation of active oxidative species does not take place, oxidation reactions cease and the concentrations of the dye intermediates remain practically stable upon further exposure to visible light irradiation. Formation of photoinduced hydrogen peroxide, which is also generated under the present conditions, also stops when the dye concentration in solution drops to very low levels. This behavior has been explained evoking the photosensitization mechanism of wide band-gap semiconductors, according to which the reaction is triggered by excitation of the dye molecule by visible light photons, followed by charge injection to the conduction band of the semiconductor and subsequent production of active oxygen radicals. Formation of the latter oxidizing species is possible only in the presence of visible light-absorbing compounds and cannot take place after fragmentation of the parent AO7 molecule in the vicinity of the azo-bond and decolorization.
TL;DR: In this article, the formation of surface fluorides on TiO2 (F−TiO2), which can be easily attained by a simple addition of F- to aqueous TiO 2 suspensions, uniquely affects both photocatalytic reactions and photoelectrochemical behaviors.
Abstract: The formation of surface fluorides on TiO2 (F−TiO2), which can be easily attained by a simple addition of F- to aqueous TiO2 suspensions, uniquely affects both photocatalytic reactions and photoelectrochemical behaviors. The fluoride adsorption is favored at acidic pH and greatly reduces the positive surface charge on TiO2 by replacing ⋮Ti−OH2+ by ⋮Ti−F species. Effects of surface fluorination on the photocatalytic reactivities are very different depending on the kind of substrates to be degraded. F−TiO2 is more effective than pure TiO2 for the photocatalytic oxidation of Acid Orange 7 and phenol, but less effective for the degradation of dichloroacetate. It is proposed that the OH radical mediated oxidation pathways are enhanced on F−TiO2, whereas the hole transfer mediated oxidations are largely inhibited due to the hindered adsorption (or complexation) of substrates on F−TiO2. As for the photocatalytic reduction, the dechlorination of trichloroacetate is much reduced on F−TiO2. The photocurrents collec...
TL;DR: In this paper, the photocatalytic degradation of 4-nitrophenol under UV and solar exposure was investigated with Ti1-xMxO2±δ.
Abstract: The W, V, Ce, Zr, Fe, and Cu metal ion substituted nanocrystalline anatase TiO2 was prepared by solution combustion method and characterized by XRD, Raman, BET, EPR, XPS, IR TGA, UV absorption, and photoluminescence measurements The structural studies indicate that the solid solution formation was limited to a narrow range of concentrations of the dopant ions The photocatalytic degradation of 4-nitrophenol under UV and solar exposure was investigated with Ti1-xMxO2±δ The degradation rates of 4-nitrophenol with these catalysts were lesser than the degradation rates of 4-nitrophenol with undoped TiO2 both with UV exposure and solar radiation However, the photocatalytic activities of most metal ion doped TiO2 are higher than the activity of the commercial TiO2, Degussa P25 The decrease in photocatalytic activity is correlated with decrease in photoluminescence due to electron states of metal ions within the band gap of TiO2
Metz1
TL;DR: In this paper, a photocatalytic experiment was performed under UV-Vis illumination and the photoactivity of the junctions was found to be strongly dependent on the substrate, and a part of charge recombination that can take place when both semiconductors are excited was observed.
Abstract: Bi2S3/TiO2 and CdS/TiO2 heterojunctions were prepared by direct mixture of both constituents and by precipitation of the sensitizer with commercial TiO2 at different concentrations. UV-Vis spectroscopy analysis showed that the junctions-based Bi2S3 and CdS are able to absorb a large part of visible light (respectively up to 800 and 600 nm). This fact was confirmed by photocatalytic experiment performed under visible light. A part of charge recombination that can take place when both semiconductors are excited was observed when photocatalytic experiment was performed under UV-Vis illumination. Orange II, 4-hydroxybenzoique acid (4-HBZ) and benzamide (BZ) were used as pollutants. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena taking place in each case are discussed.
TL;DR: A novel photocatalyst, PbBi2Nb2O9 has been discovered that shows high activities for degradation of organic pollutants, generation of photocurrent, and water decomposition into O2 or H2, all under visible right irradiation (lambda >/= 420 nm).
Abstract: A novel photocatalyst, PbBi2Nb2O9 has been discovered that shows high activities for degradation of organic pollutants, generation of photocurrent, and water decomposition into O2 or H2, all under visible right irradiation (λ ≥ 420 nm). This is the first example of an undoped, single-phase oxide photocatalyst that shows such reactivity. Its quantum yields are much higher than those for most of the previously reported materials, especially in water decomposition to generate oxygen (29%). Since it is an oxide, there is much less concern for stability under light irradiation.
TL;DR: In this paper, the effect of different chemical parameters on photocatalytic inactivation of E. coli K12 was discussed, and it was shown that the presence of some inorganic ions (0.2 mmol/l) like HCO3-, HPO42-, Cl-, NO3- and SO42- to the suspension affects the sensitivity of bacteria to sunlight in the presence and in absence of TiO2.
Abstract: The effect of different chemical parameters on photocatalytic inactivation of E. coli K12 is discussed. Illumination was produced by a solar lamp and suspended TiO2 P-25 Degussa was used as catalyst. Modifications of initial pH between 4.0 and 9.0 do not affect the inactivation rate in the absence or presence of the catalyst. Addition of H2O2 affects positively the E. coli inactivation rate of both photolytic (only light) and photocatalytic (light Plus TiO2) disinfection processes. Addition of some inorganic ions (0.2 mmol/l) like HCO3-, HPO42-, Cl-. NO3- and SO42- to the suspension affects the sensitivity of bacteria to sunlight in the presence and in absence of TiO2. Addition of HCO3- and HPO42- resulted in a meaningful decrease in photocatalytic bactericidal effect while it was noted a weak influence of Cl-, SO42- and NO3-. The effect of counter ion (Na+ and K-) is not negligible and can modify the photocatalytic process as the anions. Bacteria inactivation was affected even at low concentrations (0.2 mmol/l) of SO42- and HCO3- but the same concentration does not affect the resorcinol photodegradation, suggesting that disinfection is more sensitive to the presence of natural anions than photocatalytic degradation of organic compounds. The presence of organic substances naturally present in water like dihydroxybenzenes isomers shows a negative effect on photocatalytic disinfection. The effect of a mixture of chemical substances on photocatalytic disinfection was also studied by adding to the bacterial suspension nutrient broth, phosphate buffer and tap water. (C) 2004 Elsevier B.V. All rights reserved.
TL;DR: The blue shift in the absorption onset confirms the size quantization of MS2 nanoclusters, which act as effective and stable sensitizers, making it possible to utilize visible light in photocatalysis.
Abstract: A new approach has been developed for the fabrication of visible light photocatalysts. Nanoclusters of MoS2 and WS2 are coupled to TiO2 by an in situ photoreduction deposition method taking advantage of the reducing power of the photogenerated electrons from TiO2 particles. The photocatalytic degradation of methylene blue and 4-chlorophenol in aqueous suspension has been employed to evaluate the visible light photocatalytic activity of the powders. The blue shift in the absorption onset confirms the size quantization of MS2 nanoclusters, which act as effective and stable sensitizers, making it possible to utilize visible light in photocatalysis. Quantum size effects alter the energy levels of the conduction and valence band edges in the coupled semiconductor systems, which favors the interparticle electron transfer. In addition, the coupled systems are believed to act in a cooperative manner by increasing the degree of charge carrier separation, which effectively reduces recombination.
TL;DR: It was concluded that the primary factor for the enhanced activity of combustion-synthesized catalyst is a larger amount of surface hydroxyl groups and a lowered band gap.
Abstract: Nanocrystalline TiO2 was synthesized by the solution combustion method using titanyl nitrate and various fuels such as glycine, hexamethylenetetramine, and oxalyldihydrazide. These catalysts are active under visible light, have optical absorption wavelengths below 600 nm, and show superior photocatalytic activity for the degradation of methylene blue and phenol under UV and solar conditions compared to commercial TiO2, Degussa P-25. The higher photocatalytic activity is attributed to the structure of the catalyst. Various studies such as X-ray diffraction, Raman spectroscopy, Brunauer−Emmett−Teller surface area, thermogravimetric−differential thermal analysis, FT-IR spectroscopy, NMR, UV−vis spectroscopy, and surface acidity measurements were conducted. It was concluded that the primary factor for the enhanced activity of combustion-synthesized catalyst is a larger amount of surface hydroxyl groups and a lowered band gap. The lower band gap can be attributed to the carbon inclusion into the TiO2 giving Ti...
TL;DR: In this paper, pure and La doped TiO 2 nanoparticles with different La content were prepared by a sol-gel process using Ti (OC 4 H 9 ) 4 as raw material, and also were characterized by XRD, TG-DTA, TEM, XPS, DRS and Photoluminescence (PL) spectra.
TL;DR: In this paper, the photocatalytic activity of those catalysts was investigated for the liquid phase photocatatlytic degradation of active yellow XRG dye diluted in water under UV and visible light irradiation.
Abstract: Iron-ion-doped anatase titanium (IV) dioxide (TiO2) samples were prepared by hydrothermal hydrolysis and crystallization in octanol-water solution. The samples were characterized by X-ray diffraction, BET-specific surface area determination, UV-Vis diffuse reflectance spectroscopy and electron paramagnetic resonance spectroscopy. UV-Vis diffuse reflectance spectra showed a slight shift to longer wavelengths and an extension of the absorption in the visible region for almost all the ion-doped samples, compared to the non-doped sample. The photocatalytic activity of those catalysts was investigated for the liquid phase photocatatlytic degradation of active yellow XRG dye diluted in water under UV and visible light irradiation. It was found that the catalysts doped with FeCl3 have better catalytic activity for photodegradation of XRG than those doped with FeCl2. The amount of doped iron ion plays a significant role in affecting its photocatalytic activity and iron doped with optimum content can enhance photocatalytic activity, especially under visible light irradiation.
TL;DR: An oxide photocatalyst Bi2WO6 with corner-shared WO6 octahedral layered structure was synthesized and its band gap was determined to be 2.69 eV from UV-vis diffuse reflectance spectra as discussed by the authors.
Abstract: An oxide photocatalyst Bi2WO6 with corner-shared WO6 octahedral layered structure was synthesized. Its band gap was determined to be 2.69 eV from UV–vis diffuse reflectance spectra. The photocatalyst showed not only the activity for photocatalytic O2 evolution with the initial evolution rate of 2.0 μmol/h but also the activity of mineralizing both CHCl3 and CH3CHO contaminants under visible light irradiation. Meanwhile, wavelength dependence of CH3CHO decomposition was observed, which indicated that the photocatalytic activity of the photocatalyst was in good agreement with its light-absorption ability.
TL;DR: In this article, the microstructural and chemical properties of TiO2, obtained by a sol-gel procedure, were investigated by using X-ray diffraction (XRD) and electron spectroscopy for chemical analysis.
TL;DR: In this paper, the photocatalytic decolorization of Remazol Red RR, a commercial azo-reactive textile dye, in the presence of various semiconductor powder suspensions has been investigated in a quartz batch reactor with the use of artificial light sources (UV-C).
Abstract: The photocatalytic decolorization of aqueous solutions of Remazol Red RR, a commercial azo-reactive textile dye, in the presence of various semiconductor powder suspensions has been investigated in a quartz batch reactor with the use of artificial light sources (UV-C). ZnO and TiO2 have been found the most active photocatalysts; however ZnO indicated slightly higher efficiency. The effects of various process variables on decolorization performance of the process have been investigated. The results showed that the decolorization efficiency increases with increase in pH, attaining maximum value at pH 10 for ZnO. The zero-point charge for ZnO is 9.0 above which ZnO surface is negatively charged by adsorbed OH− ions, favoring the formation of strong oxidant OH radicals. The efficiency is inversely related to the dye concentration; increasing dye concentration enhances dye adsorption on the active sites of the catalyst surface, and consequently hinders OH− adsorption on the same sites, this results with a decreasing OH formation rate.
TL;DR: In this article, the photocatalytic degradation of rhodamine B (RB) dye in the aqueous suspensions of TiO2 (∼17 nm) and Ag-deposited nanoparticles under visible and UV light irradiation was investigated.
Abstract: We investigated the photocatalytic degradation of rhodamine B (RB) dye in the aqueous suspensions of TiO2 (∼17 nm) and Ag-deposited TiO2 nanoparticles under visible and UV light irradiation in order to evaluate and distinguish various effects of the Ag deposition on the TiO2 photocatalytic activity. The TiO2 and Ag–TiO2 photocatalysts were characterized by XRD, TEM, XPS, UV-visible absorption and photon correlation spectroscopy. For comparison, the RB photodegradation was carried out in Degussa P25 TiO2 and Ag-deposited P25 suspensions under the same condition. In the RB/Ag–TiO2 system, Ag deposits significantly enhanced the RB photodegradation under visible light irradiation whereas the RB photodegradation under UV irradiation was slightly enhanced. The significant enhancement in the Ag–TiO2 photoactivity under visible light irradiation can be ascribed to simultaneous effects of Ag deposits by both acting as electron traps and enhancing the RB adsorption on the Ag–TiO2 surface. © 2004 Elsevier B.V. All rights reserved.
TL;DR: In this article, a series of vanadium-doped TiO 2 catalysts were synthesized by two modified sol-gel methods, and the TEM micrographs showed the sizes of primary particles were in the range of 6-20nm.
Abstract: A series of vanadium-doped TiO 2 catalysts were synthesized by two modified sol–gel methods. V-doped TiO 2 was found to be mainly preserved its anatase phase after calcination at 400 °C. The TEM micrographs showed the sizes of primary particles were in the range of 6–20 nm. The increase of vanadium doping promoted the particle growth, and enhanced “red-shift” in the UV-Vis absorption spectra. The XPS (X-ray photoelectron spectroscopy) could not detect vanadium indicating negligible vanadium on the surface of catalysts, furthermore, there were also no peak of vanadium oxide in the XRD patterns. XAS (X-ray absorption spectroscopy) analysis indicating V 4+ instead of V 5+ implied that vanadium either substituted Ti 4+ site or embedded in the vacancy of TiO 2 structure. Therefore, vanadium was concluded to be highly dispersed inside the TiO 2 structure. The photocatalytic activity was evaluated by the degradation of crystal violet (CV) and methylene blue (MB) under visible light irradiation. The degradation rate of CV and MB on V-doped TiO 2 were higher than those of pure TiO 2 . As the results, V-doped TiO 2 possessed better absorption ability of visible light.
TL;DR: In this article, a modified sol-gel process was used to synthesize copper-loaded titania (Cu/TiO2) catalysts for CO 2 photocatalytic reduction and the yield of methanol was evaluated.
TL;DR: Gas chromatography/mass spectrometry measurements showed no trace of environmentally undesirable species such as CF4, which has a very high global-warming potential.
Abstract: The decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water by UV−visible light irradiation, by H2O2 with UV−visible light irradiation, and by a tungstic heteropolyacid photocatalyst was examined to develop a technique to counteract stationary sources of PFOA. Direct photolysis proceeded slowly to produce CO2, F-, and short-chain perfluorocarboxylic acids. Compared to the direct photolysis, H2O2 was less effective in PFOA decomposition. On the other hand, the heteropolyacid photocatalyst led to efficient PFOA decomposition and the production of F- ions and CO2. The photocatalyst also suppressed the accumulation of short-chain perfluorocarboxylic acids in the reaction solution. PFOA in the concentrations of 0.34−3.35 mM, typical of those in wastewaters after an emulsifying process in fluoropolymer manufacture, was completely decomposed by the catalyst within 24 h of irradiation from a 200-W xenon−mercury lamp, with no accompanying catalyst degradation, permitting the catalyst...