About
190
Publications
41,763
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
11,793
Citations
Publications
Publications (190)
This chapter considers the fundamental phenomena occurring when TiO2 is excited by photons. The focus is first on the formation and fate of the charges generated by the excitation. Then, the roles in photocatalytic reactions of water and oxygen which are almost always present are presented and discussed; the effects of adding ozone or hydrogen pero...
This brief overview focuses on three of the main basic phenomena limiting the applications of photocatalysis using semiconductors for the treatment of water, so that this technology has really not gone beyond the demonstration stage aside from niche applications. These phenomena are: the recombination of photogenerated charges; the adsorption of tr...
Titanium dioxide nanotubes (TNT) have mainly been used in dye sensitized solar cells, essentially because of a higher transport rate of electrons from the adsorbed photo-excited dye to the Ti electrode onto which TNT instead of TiO2 nanoparticles (TNP) are attached. The dimension ranges and the two main synthesis methods of TNT are briefly indicate...
This chapter begins with an overview of the fundamentals of heterogeneous photocatalysis to orient the readers. From these fundamentals are drawn special requirements for photocatalytic coatings relative to other types of coatings. The following sections indicate how the photocatalytic coating techniques may differ depending on (1) the three main a...
In the domain of semiconductor photocatalysis, infrared spectroscopy is a technique able to provide information inter alia upon: the generation, accumulation, scavenging and/or trapping of electronic charges under band-gap irradiation; the surface radicals existing during or after irradiation; the irradiation effects on the interactions of the surf...
A dual-phase material (DP-160) comprising hydrated titanate (H 2 Ti 3 O 7 . xH 2 O) and anatase (TiO 2) was synthesized in a low-temperature one-pot process in the presence of triethylamine (TEA) as the N-source. The unique structure exhibits strong visible light absorption. The chromophore is linked to Ti–N bonds derived from both surface sensitiz...
The photocatalytic degradation of butanedioic acid (BDA), hydroxybutanedioic acid (OH-BDA) and 2,3-dihydroxybutanedioic acid (diOH-BDA) (succinic acid, malic acid and tartaric acid, respectively) in a TiO2 aqueous suspension at pH 3 was investigated to determine the effects of hydroxyl substitution. Temporal variations in the concentrations of the...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
This overview of photocatalytic purification/deodorization of indoor air using TiO2 includes four parts. First, considering that TiO2 exposed to indoor air – which contains several thousands ppmv of water – is covered by layers of water molecules, it is suggested that: (i) the approach to the surface of pollutants at ppbv concentrations is hindered...
In the past, TiO2 particles have been considered non-toxic because of both their chemical inertness and the conclusions of epidemiological studies dealing with μm-sized particles. Recently, the assignment of diseases to inhalation of atmospheric particles, and the important industrial development of nm-sized particles - among which TiO2 particles a...
Charge recombination is the main drawback of heterogeneous photocatalysis; it considerably limits the applications. Consequently, it is of paramount importance to study this process. Time resolved microwave conductivity (TRMC) is an appropriate technique for that purpose since it allows measurements without electrical contacts. Here are presented a...
We have chosen 3-ethoxypropan-1-ol (EtOPrOH) as a typical short-carbon-chain ether–alcohol used as industrial solvent and
have analyzed the degradation products resulting from its attack by •OH radicals generated by the photo-Fenton reaction. The laboratory conditions were representative of those found in tropospheric
water droplets. Twelve product...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Ti-pillared and Ti/Cr-pillared montmorillonite have been prepared from natural bentonite and characterized by UV-Vis DRS and X-ray diffraction. The photocatalytic activities have been tested for the removal of 4-chlorophenol in water. The influence of the Ti/Cr ratio and the calcinations method on these activities has been investigated. It was foun...
We have investigated the effects of the TiO2 type and coating method, two important factors for TiO2-based photocatalytic purification/deodorization of air. First, two TiO2 powders (PC500 and 105) designed by Millennium Chemicals for photocatalysis were compared with Degussa P25 TiO2, a common reference, for removing methanol or n-octane in a flowi...
Photocatalytic purifiers, which are in development for treating gaseous effluents at flow rates generally higher than several tens of m3 h−1, usually employ TiO2-coated materials either as planar or folded fibrous filters, or as honeycomb monoliths. Our primary objective was to compare the photocatalytic efficacy of two types of these materials usi...
The apparent first-order rate constant, k(app), of the Acid Blue 113 textile azo dye photocatalytic disappearance in aqueous suspensions of 4 commercialized TiO(2) samples (50 m(2) g(-1)-Degussa P25; 54 m(2) g(-1)-Millennium Chemicals PC50; 250-270 m(2) g(-1)-Sachtleben Chemie Hombikat UV100; 320 m(2) g(-1)-Ishihara ST01) was determined from the de...
Filtered air (relative humidity) 9-10%) containing methanol was flown through a cold plasma reactor connected to a photocatalytic reactor. The results showed a synergetic effect between the two purifying technologies, which is principally attributed to plasma-generated O 3 benefiting the photocatalytic process.
TiO2 and TiO2/SiO2 films were supported on polyester granules using a grafting procedure and controlled temperature deposition under the generated autogenous pressure. For the TiO2 films, tetraisopropyl orthotitanate, propan-2-ol and water were used; for the TiO2/SiO2 films titanium tetrachloride, propan-2-ol and silica were employed. The precursor...
TiO2 films on silica-coated glass plates were obtained through dip-coating and subsequent calcination at 753 K; this temperature and the proportions of the dip-coating solution components (tetraisopropyl orthotitanate, ethoxyethoxyethanol, propan-2-ol, α-terpineol, and a hydroxypropyl cellulose) were optimized. Depending on the number N (5 ≤ N ≤ 30...
Cet article présente les principes fondamentaux de la photocatalyse, ainsi que les avancées récentes dans ce domaine. Les principales applications commerciales ou industrielles pour la dépollution ou la désinfection de l'eau et de l'air sont développées. Mots-clés Photocatalyse, dioxyde de titane, semi-conducteur, dépollution, désinfection. Abstrac...
The main concepts of photocatalysis are described. The latest research developments in this field are reviewed, as well as the principal commercial and industrial applications for water and air depollution or disinfection.
Photocatalytic purification of indoor air requires devices that are compact and ensure good contact between the air flow and the photocatalyst-coated material with a minimal pressure drop. These three conditions lead to materials-destined to be coated by a photocatalyst-having complex shapes. Accordingly, modeling becomes essential in optimizing th...
TiO2 and TiO2/SiO2 films were supported on polyester granules using a grafting procedure and controlled temperature deposition under the generated autogenous pressure. For the TiO2 films, tetraisopropyl orthotitanate, propan-2-ol and water were used; for the TiO2/SiO2 films titanium tetrachloride, propan-2-ol and silica were employed. The precursor...
This article first indicates the various types of temperature-induced oxygen isotopic exchange (OIE) that can occur between
labeled gaseous O2 and solid oxides. Earlier main results of light-induced OIE with semiconductor oxides are then briefly reviewed. The core
of the article reports new results about the use of light-induced OIE to assess (i) t...
Our goal was to determine whether changes induced in TiO2 by sintering have a net effect on the photocatalytic removal rate of trace organics in water that depends on the organic. To that end, we have used (i) commercialized TiO2 samples prepared by varying the sintering temperature of the parent TiO2; (ii) several probe molecules: phenol, anisole,...
This paper outlines the basic events that occur when a semiconductor, in contact with aerated liquid water containing low concentrations of pollutants, is photoexcited. First, the factors favouring this recombination of photoproduced charges are recalled, and the difficulties in decreasing the recombination are underlined. Second, the formation and...
Fe-pillared montmorillonite has been used as a Fenton-type heterogeneous catalyst for the removal of cinnamic acid in water. The influences of the cinnamic acid, catalyst and H2O2 concentrations and pH on the removal rate of cinnamic acid have been studied. The results show that the efficiency of Fe-pillared montmorillonite is higher than that of t...
The sintering temperature is an important parameter in many TiO2 synthesis processes. Increasing this temperature (1) reduces the number of defect sites and, accordingly, the rate of electron–hole recombination, which improves photocatalytic rates and (2) decreases particle surface area, which a priori may be expected to reduce photocatalytic rates...
Our purpose was to show that the sintering temperature of TiO(2) can have a different net effect (thought to arise from a decrease in surface area against a decrease in recombination rate of charge carriers) on the photocatalytic removal rate of various organic pollutants in water. For that, we have chosen four chlorinated pollutants, viz. 4-chloro...
The influence of the halogen upon the TiO(2) photocatalytic degradation of p-halophenols in water has been investigated. Phenol was used as the reference compound. Compared with its value for phenol, the apparent first-order rate constant of removal, k, was slightly but significantly higher for p-fluorophenol and p-chlorophenol, and slightly but si...
The non-biodegradability of textile wastewaters is mainly due to the presence of synthetic dyes. We have studied the photocatalytic degradation of four commercial (i.e. containing additives) azo dyes (viz. Yellow Cibacron FN-2R, Red Cibacron FN-R, Navy Erionyl R 180%, Everdirect Black VSF) in aqueous suspensions of TiO2 Degussa P25 under irradiatio...
TiO2 photocatalysis is based on the photoexcitation of electrons from the valence band to the conduction band. Increasing the rate of photocatalytic reactions requires decreasing the rate r at which the electrons are de-excited back to the valence band. Ozone was expected to be a good candidate to lower r on the basis that it is a much better elect...
The developments in TiO2-based materials, and applications including continuing progress in longstanding uses such as photocatalytic water or air treatment are discussed. Self-cleaning surfaces are attracting significant industrial interest and are already well on there way toward widespread commercialization. Indoor air treatment also seems to be...
Heterogeneous photocatalysis could be alternative remediation technology for water since it does not need the addition of any chemicals and it is suitable for treating low concentrations of pollutant. Although the TiO2 Degussa P 25 is most used photocatalyst its photonic efficiency still low and its recovery from water is considered as an awkward p...
We studied the photocatalytic activity of Ti-montmorillonite. The highest activity was found for a Ti/bentonite ratio of 10mmol/g, prepared using HCl and calcined by microwaves. This mixture is less active than TiO2 P-25 for 4-chlorophenol removal in water, but more active for methanol removal in air.
The aim of this study was to assess in a vineyard the effect of purifying by solar photocatalysis the title rinse waters (currently most often rejected) in terms of efficacy and on-site practicality for the wine grower. The on-site, self-functioning, solar purifying unit included a corrugated-steel inclined plate of area S = 1 m2 onto which a TiO2-...
Laboratory tests of photocatalytic air purifiers are usually performed with a single pollutant, in the parts per million by volume domain and at airflow rates < or =0.1 m3/hr. Clearly, it is necessary to probe photocatalytic materials and apparatuses under real conditions or conditions closely mimicking reality. Photocatalytic prototypes were place...
Heterogeneous photocatalysis could be alternative remediation technology for water since it does not need the addition of any chemicals and it is suitable for treating low concentrations of pollutant. Although the TiO2 Degussa P 25 is most used photocatalyst its photonic efficiency still low and its recovery from water is considered as an awkward p...
The objective was to assess in a vineyard the effect of purifying by solar photocatalysis the title rinse waters (presently rejected or, extremely rarely, cleaned in specific installations) in terms of efficacy and on-site ease-of-use for the wine grower. The on-site, self-functioning, solar purifying unit included a corrugated-steel inclined plate...
The objective was to assess in a vineyard the effect of purifying by solar photocatalysis the title rinse waters (presently rejected or, extremely rarely, cleaned in specific installations) in terms of efficacy and on-site ease-of-use for the wine grower. The on-site, self-functioning, solar purifying unit included a corrugated-steel inclined plate...
Nanocrystalline bicomponent TiO2–In2O3 powders with various Ti/In ratio have been prepared by the sol–gel technique and calcined at 473 and 723 K. Their crystalline structure, surface area, surface acidity, sorption properties with respect to 2-chlorophenol, and optical absorption were determined by appropriate techniques (XRD, BET, FTIR, and UV-Vi...
The photocatalytic removal rates r of dichloroacetic acid (DCAA), 4-chlorobenzoic acid (4-CBA) and 4-chlorophenol (4-CP) in water were compared for TiO2 samples used either as a powder or as a coating on a fiber glass tissue, SiO2 being the binder. From SEM-EDX measurements it was deduced that SiO2 prevails over TiO2 in the coating top layers and 1...
The effect of Ag photodeposition on the rate of photocatalytic degradation of 2-chlorophenol (2-CP) in aqueous suspensions of Degussa P 25 titanium dioxide has been studied using HPLC. For Ag contents between 5 x 10(-6) and 1.6 x 10(-4) wt%, the rate was slowest int he absence of Ag and increased with increasing Ag content. For a Ag content of 6 x...
The aim of this study was to obtain information about the degradation of t-butyl methyl ether (MTBE; (CH(3))(3)C-O-CH(3)) in atmospheric water droplets (rain, clouds, fog). These water droplets contain hydrogen peroxide and iron ions, which are a source of the powerful oxidising radical OH degrees, particularly under solar irradiation (photo-Fenton...
Self-cleaning coatings on glass plates covered with a thin silica barrier layer were formed from anatase nanoparticles mixed with Ti and Si organic salts, and subsequent calcination. UV irradiation of these coatings exposed to O2 produced either a gradual increase or decrease in O2 pressure P (1–120 Pa). For each coating the initial P value, Psat,...
Solid-phase micro-extraction has been used for identifying, quantifying and following the evolution of intermediate products of octanol degradation by two advanced oxidation treatments (AOTs), photocatalytic and ultrasound processes, inducing mainly the same active species. Headspace extraction enabled direct extraction of the organic compounds in...
In an attempt to improve the understanding of the basic mechanisms on the degradation of pollutants in water by TiO2 photocatalysis, we discussed the primary degradation mechanism of three triazolidine derivatives, such as 1,2,4-triazolidine-3,5-dione (TRIANE), 4-hydroxy-1,2,4-triazolidine-3,5-dione (OH-TRIANE) and 4-phenyl-1,2,4-triazolidine-3,5-d...
To expand the still-rare studies about the effect of humic acids (HA) on the photocatalytic removal of water organic pollutants over TiO2, quinoline was selected, considering the previously investigated aromatics. Dark adsorption measurements have shown that the amount of quinoline (initial concentration (CQ)o = 0.17 mmol L-1) adsorbed at equilibri...
TiO2 photocatalysis and ultrasound are advanced oxidation processes for water treatment. Our study aimed at showing, via the purposely chosen title compounds, that these techniques can be complementary. For C6H5COCF3 (PTMK), the photocatalytic removal rate was higher than the ultrasonic (515 kHz) removal rate in the presence of TiO2 in the dark, wh...
Our objective was to further assess the capabilities of TiO2 to purify/deodorize indoor air and industrial gaseous effluents. Using a laboratory photoreactor including a lamp emitting around 365 nm and a TiO2-coated fiber glass mesh, we first determined that the removal rate of three very different pollutants (CO, n-octane, pyridine) was 5–10 μmol...
Heterogeneous photocatalysis with TiO2 nanoparticles for the detoxification of waste-waters and other media is typically achieved by oxidative pathways involving ultimately photogenerated surface-trapped holes (i.e. surface-bound OH radicals). However, reductive pathways may coexist. The degradation of 2,4-dichlorophenol (2,4-DCP) and pentachloroph...
To explain the differences between the product distributions obtained when quinoline (Q) in water is degraded by TiO2 photocatalysis and by the photo-Fenton process, we have proposed a mechanism based on the reaction between superoxide and
quinoline radical-cation (Q·+), both species resulting from electron transfers at the TiO2 surface (J. Phys. C...
UV irradiation of TiO2 promotes electrons from the valence band to the conduction band. The capabilities of the resulting redox system to degrade
organic pollutants in water and the variety of products formed is illustrated here by the case of 2,3-dimethylpyrazine. Two
debated questions, viz. (i) which electron-donors are implicated to fill in the...
Malic acid, a model molecule for partially oxidized products found either in biomass or in various degradative processes, could totally be mineralized by photocatalytic degradation. Laboratory experiments enabled one to determine the identity of 15 intermediates, logically presented in four parallel degradation pathways. The major one is initiated...
TiO2 photocatalysis and ultrasound are emerging technologies for the mineralization of pollutants in water. To further investigate these technologies and to assess whether advantages and synergy can be expected from their differences, phenyltrifluoromethylketone (PTMK) was selected as a test compound for pollutants generating CF3COOH, an undesirabl...
Self-cleaning glass can be obtained by coating glass with a transparent, thin layer of TiO2 nanoparticles. To test the self-cleaning properties, fluoranthenethe most abundant polycyclic aromatic hydrocarbon in the atmospheric particulate matterwas sprayed over the glass. Under solar-like UV light, not only was fluoranthene removed at a rate of ca....
Self-cleaning glass was prepared by depositing anatase nanoparticles as a transparent film onto glass previously coated by a barrier layer. A photoreactor was built to evaluate the efficiency. Palmitic acid, chosen as a compound representing stains from various sources and sprayed over these plates to form an uniform layer of ca. 580 nm thickness,...
The self-cleaning property of glass arises from a thin transparent TiO2 coating. Under solar UV light, TiO2 becomes capable of degrading organics at its surface. Our objectives were : to assess the self-cleaning efficiency with respect to the removal of compounds representative of organic deposits ; to identify and, if possible, quantify the interm...
The phototransformations of thin layers of pentachlorophenol (PCP), an insectide and herbicide, have been investigated in the laboratory in open air under irradiation at wavelengths >290nm, i.e. corresponding to the sunlight UV region. The PCP disappearance rate was much higher when a 50v/v% methanol/water mixture instead of pure methanol was used...
Photocatalytic oxidations of toluene and benzene in air were carried out over water (TiO2/H2O) and HCl (TiO2/HCl) pretreated TiO2 as this latter pretreatment enhances the toluene removal rate. The main purpose was to identify intermediate products. No gas-phase by-products were detected by direct GC/FID analysis under our conditions despite the hig...
The detoxification of water has been performed at a pilot scale under solar irradiation at the Plataforma Solar de Almeria (Spain). The photoreactor consisted of a tank (247l) connected to compound parabolic collectors (CPCs) (147l), through which the aqueous suspension of titania (0.2g/l of TiO2 Degussa P-25) was circulated at a flow-rate of 3.5m3...
V2O5/TiO2 aerogels were made by a two-step sol-gel process characterized by surface area measurements, X-ray diffraction, Raman and infrared spectroscopies and high resolution electron microscopy. Catalytic performance in the selective reduction of NO by propane was found to be significantly better than those of their homologues prepared by a conve...
Pyridine, 1-2-dimethoxybenzene, morpholine and lindane are mineralized by the TiO2-UV process. In the studies briefly reviewed here, their intermediate products, in particular the aliphatics, were identified both to determine what are the compounds that may be left in the treated water and to increase our understanding of the photocatalytic pathway...
Effects of methanol, formamide, acetone and acetate ions on the TiO2 photocatalytic degradation of phenol in water at equal initial concentrations (∼1 mmol L−1) have been studied. The amount of phenol adsorbed in the dark and the apparent first-order rate constant of phenol disappearance remained the same within experimental accuracy. The temporal...
In an attempt to improve our understanding of the basic mechanisms of the degradation of aromatic pollutants in water by TiO2 photocatalysis, quinoline (benzo[b]pyridine) was selected as a molecular probe, principally because of the difference in electron density over its two rings. This study was based on the identification and quantification of t...
1,1,1-Trichloroethane (TCA) has been chosen for the study of the reducing versus oxidizing steps of carbon, involved in the
degradation, in UV-irradiated TiO2 aqueous suspensions, of chlorinated alkanes containing two C atoms. At wavelengths > 290 nm, TCA disappearance rate was largely
increased in the presence of TiO2. The corresponding apparent f...
In an earlier study [Pichat et al. (1993) Photocatalytic Purification and Treatment of Water and Air, pp. 207–223. Elsevier, Amsterdam] the photocatalytic degradability over TiO2 of some chlorophenols in water was correlated to the 1-octanol-water partition coefficient (Kow) and to the Hammett constant (σ) of these compounds. To determine whether a...
The quantum yield Φ is crucial in homogeneous photochemistry; in heterogeneous photocatalysis this term remains elusive since the number of absorbed photons remains experimentally difficult to asses. A comprehensive method to standardize and compare process efficiencies in heterogeneous photocatalysis was proposed earlier by describing the relative...
The photocatalytic purification of water containing fenitrothion has been performed in TiO2 aqueous suspensions. The mineralization into CO2, H2PO4−, SO42−, NO3− was achieved. Several intermediates have been identified by HPLC and GC/MS. They illustrate the transformation of PS into PO, the splitting between the phosphorous part and the aromatic...
Differences in photocatalytic degradations arising from oxidative cleavage of a peptide bond and a quaternary nitrogen moiety in a TiO2-illuminated suspension are described to elucidate the routes to mineralization of two amphoteric stufactants and one nonionic surfactant, namely, sodium N′-dodecylamidopropyl-N, N-dimethyl ammonium acetate (C12-ami...
Elimination from water of lindane, a common soil insecticide whose occurrence in groundwaters used as sources of drinking water is of great concern, was shown to be achieved by the TiO2-UV system. Gas chromatography-mass spectrometry analyses of a photocatalytically treated aqueous solution initially containing 3.44 mmol/L (=1g/L) lindane indicated...
Photocatalytic treatment of dichlorophenols (DCPs) leads to the formation of condensation products. These products were identified as polyhydroxyPCBs. Depending on the initial DCP isomer, different extents and yields of polyhydroxyPCB formation (up to 1%) and different types of polyhydroxyPCBs were observed. The formation of dehalogenated hydroxyph...
These laboratory studies were aimed at distinguishing the relative importance of released or added ferric ions and of ferric oxide particles for the photodegradation of oxalic acid in natural waters. The parameters whose effects were determined for this purpose included the pH, the irradiation wavelength, the concentrations of the various species a...
Catalase, which catalyses the dismutation of H2O2 into H2O and O2, and Cu, Zn-super-oxide dismutase (SOD), which catalyses the dismutation of O2o− and H2O2, have been used to assess the importance of the role of these species formed in situ in TiO2 or ZnO aqueous suspensions. Variations in the apparent first-order rate constant, kapp, of the disapp...
Morpholine has been chosen for the study of the TiO2 photocatalytic degradation of saturated heterocyclic compounds in water because it is found in a number of industrial effluents. Its disappearance rate was observed to be much greater with, than without, TiO2 in the UV spectral range. Furthermore, comparison with a variety of aromatic pollutants...
The photocatalysed oxidation of phenol, 2-chlorophenol and pentachlorophenol was re-examined under conditions in which TiO2 anatase was sensitized by CdS in air-equilibrated aqueous media; this was to assess whether or not the interparticle electron transfer pathway, first discovered a decade ago (N. Serpone, E. Borgarello and M. Gratzel, J. Chem....
2,3-Benzofuran (BZF), a mutagenic and carcinogenic compound, was chosen as a model water pollutant to study the TiO2 photocatalytic degradation of molecules which have two aromatic rings and a built-in oxygen heteroatom. For BZF and its two main degradation intermediates, salicylaldehyde (SA) and 2-coumaranone (2-CO), a relatively good correlation...
In an attempt to answer the as yet unsolved question of the structures of the aliphatic compounds resulting from the ring
opening of aromatic pollutants in water during a photocatalytic treatment, we have carried out a GC-MS study (with or without
silylation) of aqueous solutions of each of the dimethoxybenzenes (DMBs) UV-irradiated in the presence...
Lindane is a common soil insecticide. Despite its low solubility, it is found in groundwaters which are used as sources of drinking water at some sites. Therefore, it is a pollutant of great concern as it may reasonably be anticipated to be a carcinogen. Its destruction by various oxidants has been studied and lindane has been found to be recalcitr...
Pyridine (Pyr), a noxious chemical whose ring is part of the chemical structure of many pesticides, is more rapidly eliminated in water by photocatalysis over TiO2 than benzamide, whose nucleus has also a relatively low electron density and whose extent of adsorption is equivalent. Hydroxylation of Pyr first occurs only at position 2. Beside acetat...
A study of the hydrogenation of diphenylacetylene (tolane) over UV-irradiated metal/TiO2 powders in alcoholic media has been performed at room temperature. The nature of the alcohol exerts a net influence on the activity and selectivity toward cis- and trans-diphenylethylene (stilbene) formation, presumably because of the influence of alcohol on th...
The effects of two antioxidant enzymes on the rate of disappearance, r, of the pollutant 1,2-dimethoxybenzene (1,2-DMB) in
UV-irradiated (λ > 340 nm) TiO2 or ZnO aqueous suspensions have been determined. Catalase, which catalyzes the overall reaction 2H2O2 →> 2H2O + O2, caused a relatively moderate decrease in r in the case of TiO2 and no effect in...
Chlorobenzoic acids(CBA) are completely mineralized into CO2 and Cl-over UV-illuminated TiO2 in water according to the following reactivity order : 4-CBA〈2-CBA〈3-CBA. The identification of various intermediates of 2-CBA shows the decarboxylation and the progressive hydroxylation of the aromatic ring. This study confirms the potentialities of photoc...
(Zr, Ti)O2 gels as precursors of zirconium titanate (ZT) powders were prepared by the sol-gel method, which involves hydrolysis of ZrClO2+TiCl4 in the presence or absence of hydrogen peroxide, in twopH ranges, 8–9 or 11–12. Thermal evolution of these precursors has been studied by DTA, BET surface area, XRD and SEM. Differences
in DTA curves, surfa...
The photosensitivity of a ZrTiO4 sample (33 m2/g) prepared by a sol-gel method has been assessed in the presence of O2 by both photoconductance and oxygen isotope exchange (OIE) measurements at room temperature at wavelengths > 290 nm. For oxygen pressures
PO2 P_{O_2 }
< ca. 13.3 Pa, the steady-state photoconductance PO2 P_{O_2 }
, which indicated...
Three dimethoxybenzenes (DMBs) have been chosen to further assess the capabilities of the TiO2‐UV system to destroy substituted aromatic pollutants in water. At λ > 290 nm and pH = 3, the disappearance of DMB (0.145 mM) is much more rapid in the presence of TiO2 (Degussa P‐25; 2.5 g/L) than by direct photolysis; the intermediates generated by both...
The photocatalytic degradation of six dichlorophenols (DCPs) and three trichlorophenols (TCPs) in TiO2 aqueous suspensions was studied. The apparent first-order rate constants kapp of disappearance of these CPs and monochlorophenols (MCPs) were found to correlate with their Hammett constants λ and their 1-octanol-water partition coefficients Kow: k...
Heterogeneous photocatalysis is capable of destroying many organic micropollutants in aqueous medium. The principle of the method and a brief survey of the relevant literature are presented. On the basis of studies on the degradation of various substituted aromatics in UV-irradiated TiO2 aqueous suspensions carried out principally in our laboratory...
To more precisely assess the destruction of organic micropollu‐tants in water by UV‐illuminated TiO2 in the presence of oxygen (air), we have studied the degradation of chlorophenols (CPs), 2,4‐dichlorophenoxyethanoic acid (2,4‐D), benzamide (BZA) and nitrobenzene (NBz) as typical monoaromatic pollutants containing chlorine or nitrogen atoms. The b...
The photodegradation of naphthalene (NPH), chosen as a model of polynuclear aromatic pollutants, has been studied in the presence of a layer of four water-insoluble inorganic solids which can be found in the troposphere (TiO2, Fe2O3, muscovite, and a fly ash sample). Direct photolysis of NPH is negligible at >340 nm. Dark adsorption of NPH on TiO2...
Three dimethoxybenzenes (DMBs) have been chosen to further assess the capabilities of the TiO2-UV system to destroy substituted aromatic pollutants in water. At λ > 290 nm and pH = 3, the disappearance of DMB (0.145 mM) is much more rapid in the presence of TiO2 (Degussa P-25; 2.5 g/L) than by direct photolysis; the intermediates generated by both...
Alumina-based aerogels were made by supercritical drying of alcogels obtained by hydrolysis of organic derivatives of Al, Ce, La and Ba. Palladium catalysts supported on these aerogels were tested in the reaction CO+NO+O2. The effects of the Pd precursor, oxide additive, preparation procedure and thermal treatment on catalytic performance were exam...
