Photocatalytic Treatment of Waste Waters by stephan2

VIEWS: 189 PAGES: 12

									                                                  Symposium 4
                                   EXCITED STATE CATALYSIS


4-K-01   S. Malato, J. Blanco, A. Vidal, A. Campos, J. Cáceres, Large Scale Studies in Solar Photocatalytic Wastewater
         Treatment: Research Development, Applications and Conceptual Design of a Photocatalytic Plant
4-O-01   J. Sato, N. Saito, H. Nishiyama, and Y. Inoue, Photocatalytic Activity for Water Decomposition of RuO2-Combined
         MIn2O4 (M=Ca,Sr) with d10 Configuration
4-O-02   M.A. Aramendía , Chantal Guillard, J-M. Herrmann, A. Marinas, J. M. Marina and F. J. Urbano, Study of
         Photocatalytic Degradation of Pesticide-Acaricide Formetanate
4-O-03   S. Higashimoto, R. Tsumura, M. Matsuoka, H. Yamashita, M. Che and M. Anpo, Local Structures of Active Sites on
         Mo-MCM-41 Mesoporous Molecular Sieves and Their Photocatalytic Reactivity for the Decomposition of NOx
4-O-04   M. Bolte, G. Mailhot and M. Sarakha, Degradation of Pollutants by Homogeneous Photocatalysis with Iron (III)
         Aquacomplexes : a Comprehensive Investigation
4-O-05   J.-M. Herrmann Photocatalysis versus Catalysis : Differences, Similarities, Complementarités. Consequences for
         Environmental Concerns

4-P-01   M. Anpo and S. Dohshi, Investigations on the Photocatalytic Decomposition of NO and the Photo-induced
         Superhydrophilic Properties of Ti-B Binary Oxide Thin Film Photocatalysts
4-P-02   C. Guillard, C. Petreier, P. Pichat, P. Theron, Water Treatment by Simultaneously or Successively Using
         Sonication and TiO2-Based Photocatalysis
4-P-03   C. Guillard, E. Puzenat, K. Schoumacker , C. Geantet, M. Lacroix and J.-M. Herrmann, Photocatalytic Degradation of
         Methyl-tertio-butyl ether (MTBE) in Aqueous and Gas Phase. Reaction Mechanisms and Efficiencies of Various
         Industrial TiO2 Catalysts
4-P-04   M. Stylidi, D.I. Kondarides and X.E. Verykios, Investigation of the Photocatalytic Degradation of Aqueous Solutions
         of Acid Orange 7 over TiO2 Particles
4-P-05   G.Colón, J.A.Navío and H.Mansilla, Preparation, Characterisation and Photophysical Properties of CeO2-TiO2
4-P-06   J.M. Chovelon, E. Vulliet, C. Emmelin, J.M. Herrmann and C. Guillard, Photolytic and Photocatalytic Degradations
         of Sulfonylurea Herbicides: a Comparative Study
4-P-07   Z. Sojka, M. Che , Vibrational Excitation Mechanism for Electron Transfer Activation of Nitrous Oxide on
         Grafted MoOX/SiO2 Catalysts
4-P-08   Anita Rachel, M. Subrahmanyam, M. Sarakha and P. Boule, Photocatalytic Treatment of Waste Waters
4-P-09   M. Bowker, A. Dickinson, D. James and L Millard, The Photcatalytic Reforming of Methanol
4-P-10   Y. Krisnandi, S. Adesina and R. Howe, Photoreactivity of ETS-10
4-P-11   V. N. Snytnikov, Vlad. N. Snytnikov and V. O. Stoyanovsky, Methane Conversion with Vibrational-Excited Carbon
4-P-12   V. Augugliaro, S. Coluccia, E. García-López, V. Loddo, G. Martra, L. Palmisano and M. Schiavello, Vapour Phase
         Photocatalytic Oxidation of Ethanol and Toluene in a Continuous Spinning Basket Reactor
4-P-13   T.A. Khalyavka, V.V. Shimanovskaya, E.I. Kapinus, Photocatalytic Destruction of Tetradecylpyridinium on Titanium
         Dioxide in Aqueous Solutions.
4-P-14   J. Araña, O. González Díaz, M. Miranda Saracho, J. M. Doña Rodríguez*, J. A. Herrera Melián, and J. Pérez Peña,
         Photocatalytic Degradation of Organic Substances Using Fe/TiO2 Catalysts. A FTIR Study of the Role of Fe3+/
         Fe2+Ions in the Degradation Mechanism
4-P-15   J. Araña, R. González, E.L. Mendoza, J. M. D. Rodríguez, O.G. Díaz, J.P. Peña and J. A. Navío, FTIR
         Characterization of the TiO2 Photocatalytic Behaviour Modification Induced by Organic Adsorbates
4-P-16   A.J. Maira, J.M. Coronado, J. Soria, J. C. Conesa, V. Augugliaro, K.L. Yeung, Toluene Photocatalytic Degradation on
         TiO2 Nanoparticles: Activity and FTIR Studies
Symposium 4 Excited State Catalysis


  Large Scale Studies in Solar Photocatalytic Wastewater Treatment: Research Development, Applications and
                                  Conceptual Design of a Photocatalytic Plant

                                     S. Malato, J. Blanco, A. Vidal, A. Campos, J. Cáceres
                       CIEMAT-Plataforma Solar de Almería. P.O. Box. 22, 04200-Tabernas (Almería), Spain
                             Tel: 34-950387940; Fax: 34-950365015; e-mail:

      Mineralisation of organic water pollutants using interaction between ultraviolet radiation and semi-conductor catalysts has a
strong potential in the industrial destruction of toxic organics as it has been widely demonstrated in the recent years [1]. The Solar
Photocatalytic Detoxification Process consists on the utilisation of the near-ultraviolet part of the solar spectrum (wavelength shorter
than 400 nm.), to promote these reactions. Nevertheless, the specific solar technology to carry out the process does not presently exist
commercially. The Plataforma Solar de Almería (PSA), Large European Scientific Installation belonging to the Spanish Ministry of
Science and Technology and the largest European lab for Solar Energy Applications, is exploring the use of our oldest renewab le
source of energy to drive photocatalytic processes since the beginning of the nineties. This paper will summarize all these 10-years
efforts. A description will be given of how solar photocatalysis could become a significant segment of the wastewater treatment
technologies. It will outlines the decomposition of
organic and inorganic contaminants and different
examples will be also shown for better
comprehension of the ability of solar energy for
carrying out oxidation and reduction processes. It
will be described the experimental systems
necessary for performing pilot-plant-scale solar
photocatalytic experiments, the basic components
of these plants and the different possibilities for
operating them. Besides, some of the most up-to-
date scientific and technological results will be
given, including the design of a solar
photocatalytic detoxification treatment plant.
                                                                       PSA photocatalytic Pilot Plants (partial view).

[1] Malato S., Blanco J. and Herrmann J.M as Guest Editors (1999). Solar Photocatalysis for Water Decontamination. Catalysis
    Today, 54, 16 articles.


Photocatalytic Activity for Water Decomposition of RuO2-Combined MIn2O4 (M=Ca,Sr) with d10 Configuration

                                        J. Sato, N. Saito, H. Nishiyama, and Y. Inoue
                      Department of Chemistry, Nagaoka University of Technology, Nagaoka 940-2188, Japan

       For overall splitting of water to produce hydrogen and oxygen, RuO2–combined MIn2O4 (M=Ca,Sr) was found to be a new
photocatalyst, and their photocatalytic properties were investigated in detail. The feature of MIn 2O4 (M=Ca, Sr) is that the oxides
are composed of a p-block In3+ ion with d10 configuration which is different from the d 0 configuration of the metal ions (Ti4+, Zr4+,
Nb5+ and Ta5+) of so far developed conventional transition metal oxide photocatalysts.
       MIn2O4 (M=Ca,Sr) powder was synthesized by a solid state reaction at high temperatures and impregnated up to incipient
wetness with ruthenium carbonyl complex, Ru 3(CO)12, in THF, dried at 353 K and oxidized in air at 673 K to prepare a RuO 2-loaded
MIn2O4 photocatalyst. The photocatalyst in water was illuminated with a Xe lamp operated at 400 W. The products were analyzed
by an online gas chromatograph.
       Upon lamp irradiation of 1 wt% RuO2-loaded MIn2O4 (M=Ca,Sr), hydrogen and oxygen were produced from pure water and
increased nearly in proportion to illumination time. In a repeated run after evacuation of the gas phase products, little degradation of
photocatalytic activity was observed. The photocatalytic activity of RuO 2-combined CaIn2O4 increased with increasing loading of
RuO2, passed through a maximum at 1wt % and slowly decreased. Instead of M=Ca and Sr, BaIn 2O4was employed as an indate, but
little photocatalytic activity was observed. Light absorption of MIn 2O4 (M=Ca,Sr) occurred at around 450 nm, increased
monotonously with shorter wavelength and reached the maximum level at 300 nm.
       MIn2O4 (M=Ca, Sr) with an orthorhombic structure has a pentagonal-prism-like tunnel structure. In previous studies, we have
shown that BaTi4O9 with a pentagonal prism tunnel makes a good photocatalyst for water decomposition when fine RuO 2 particles
were loaded on the titanate1,2. The role of the tunnel structures in photoexcited charge formation was demonstrated, and it is
interesting to note that photocatalytically active MIn 2O4 (M=Ca, Sr) has similar tunnel structures. The present study has clearly
demonstrated that the p-block metal oxides of octahedrally coordinated In3+ with d10 configuration make a new photocatalyst for
water decomposition.

[1]   M. Kohno, T. Kaneko, S. Ogura, K. Sato, and Y. Inoue, J. Chem. Soc. Faraday Trans. 94, 89 (1998).
[2]   S. Ogura, M. Kohno, K. Sato, and Y. Inoue, Phys. Chem. Chem. Phys. 1, 179 (1999).

Symposium 4 Excited State Catalysis


                         Study of Photocatalytic Degradation of Pesticide-Acaricide Formetanate

 M.A. Aramendíaa , Chantal Guillardb,Jean-Marie Herrmannb ,Alberto Marinasa,b, José M. Marinasa and Francisco J. Urbanoa
   Departamento de Química Orgánica. Facultad de Ciencias. Campus Universitario de Rabanales. Edificio C3, E-14004, Córdoba, Spain.
                                        Fax: (+34) 957212066. E-mail:
   Laboratoire de Photocatalyse, Catalyse et Environnement LPCE, (IFoS UMR CNRS n°5621) ; Ecole Centrale de Lyon, B.P. 163,
                                                   69131 Ecully-cédex, France

       Formetanate (FMT) is an pesticide-acaricide widely used in agriculture. This aspect together with its inhibiting character with
respect to acetylcholinesterase, makes necessary a study of its degradation. In the present work, its photocatalytic degradation was
studied using different titania-containing catalysts. The disappearance of formetanate was proved to follow a half order kinetics
(evidence for a dissociative adsorption). In our conditions, complete mineralization of 20 ppm of pure formetanate occurred within
125 min of UV-radiation            100
when Degussa P25 or
TiO24VAC were used as               90
                                                                                                                       P25 Degussa
catalysts (see Fig. 1). In                                                                                             ZrTi5
order to make working               80

conditions as close as
possible to those of the
real world, the influence
                                 mineralization %

of the presence of (i)
formulation agents and (ii)         50

of humic acids was
studied. Both of them
seemed to have an
inhibiting effect on the
initial rate. In conclusion,        20

photocatalysis proved to
be an excellent new                 10

Advanced           Oxidation
Technology (AOT) to                     0         50       100       150         200        250       300         350          400         450
eliminate        formetanate                                                      time (min)
residues present in surface         Fig.1 CO2 evolution during mineralization of 20 ppm or pure formatanate for different titania-containing
and ground waters.                          catalysts.


     Local Structures of Active Sites on Mo-MCM-41 Mesoporous Molecular Sieves and Their Photocatalytic
                                      Reactivity for the Decomposition of NOx

         Shinya Higashimoto, Rie Tsumura, Masaya Matsuoka, Hiromi Yamashita, Michel Che*,and Masakazu Anpo
  Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka
                                                         599-8531 (Japan)
*Laboratoire de Réactivité de Surface, Université P. et M. Curie, UMR7609, CNRS, 4 Place Jussieu, 75252 Paris Cedex 05 (France)

    The design of highly active and efficient photocatalysts encapsulated or incorporated within zeolite cavities and frameworks is a
promising approach in the development of applicable photocatalytic systems. The present study deals with the in-situ
characterization of the local structures on Mo-oxides of Mo-MCM-41 and their photocatalytic reactivity for the decomposition of NO
into N2 by the coexistence of propane or CO by applying dynamic photoluminescence, UV-Vis and XAFS techniques along with an
analysis of the reaction products.
    The results of XRD and UV-Vis analyses indicated that Mo-MCM-41 has the same framework structure of MCM-41 molecular
sieves and no aggregated Mo-oxides are formed. The XAFS (XANES and EXAFS) spectra indicated that Mo-oxides are highly
dispersed with a tetrahedral coordination in Mo-MCM-41 (1.0 Mo wt%), having two shorter Mo-O bonds and two longer ones, while
in Mo-MCM-41 (4.0 Mo wt%), tetrahedrally coordinated Mo-oxides (MoO42-)n with an additional Mo-O-Mo bond could be
      Mo-MCM-41 (1.0 Mo wt%) exhibits a phosphorescence spectrum at around 400-600 nm upon excitation at around 295 nm,
which is attributed to the radiative decay from the charge transfer excited triplet state of the highly dispersed tetrahedrally
coordinated Mo-oxides. The increase of Mo content, from 1.0 to 4.0 Mo wt%, leads to the formation of two types of tetrahedrally
coordinated Mo-oxides at highly dispersed levels and (MoO42-)n probably induced by Mo-Mo interactions via oxygen ions (Mo-O-
Mo). The addition of propane, NO, or CO onto Mo-MCM-41 (1.0 Mo wt%) led to an efficient quenching of the phosphorescence
and its lifetime was shortened depending on the pressure. On the other hand, in Mo-MCM-41 (4.0 Mo wt%), the addition of NO or
propane also led to the quenching of two types of tetrahedrally coordinated Mo-oxides at highly dispersed levels and (MoO 42-)n,
having a more efficient quenching for the former Mo-oxides. The photocatalytic decomposition reactions of NO were found to
proceed efficiently on Mo-MCM-41 by the coexistence of propane and CO, leading to the formation of N2, and corresponding
oxygen-containing products such as acetone, and CO2 with a good stoichiometry, respectively. Relationship between the local
structures of Mo-oxides and their photocatalytic reactivity as well as reaction mechanism will also be discussed.

Symposium 4 Excited State Catalysis


  Degradation of Pollutants by Homogeneous Photocatalysis with Iron (III) Aquacomplexes : a Comprehensive

                                 Michèle BOLTE, Gilles MAILHOT and Mohamed SARAKHA
   Laboratoire de Photochimie Moléculaire et Macromoléculaire, UMR CNRS Université Blaise Pascal, F-63177 Aubière cedex France

      Beside the heterogeneous advanced oxidation processes using photocatalysts and the homogeneous Fenton or photoFenton
reaction, iron (III) complexes can also play the role of photoinducer. The excitation of iron (III) hydroxy-complexes in mildly acidic
medium (pH<5) leads by a photoredox process to the formation of HO radicals and to iron (II).
      In our laboratory, the excitation of iron (III) hydroxy-complexes has been used in order to promote the degradation of
pollutants in aqueous solution since the early nineties. The process was proved to be efficient with artificial light and with solar light.
In addition a reoxidation takes place that regenerates the photoactive species and permits the mineralization of the pollutan t. The
most likely way of reoxidation of iron (II) is through the reaction with OH radicals which has been largely reported in the literature :
the rate constant of the reaction Fe2+ + OH  Fe3+ + OH ranges from 1.4 to 4.3x108 mol-1.L.s-1.
      The process was shown to be quite efficient leading in most cases to the complete mineralization but great care had to be given
to iron (III) speciation. Among iron (III) aquacomplexes, FeOH 2+ (which refers to FeOH(H2O)52+, the water molecules being
omitted) present in mildly acidic solution 3<pH<4-5 is photolysed with the highest quantum yield. It has been clearly shown that
FeOH2+ is the main responsible of the degradation if not the only one. So the mechanism can be described as follows :
                                                    Fe(OH2+)  Fe2+ + OH
               P                                                                P = pollutant
       OH                                                        2+
                                                            Fe        ...
                 2+              2+       h
            Fe          FeOH                                                         degradation              mineralization
                                                            OH + P ...

      In addition, iron, due to its redox properties can react with the intermediates, stable species or transients, all along the process.
      The experiments under artificial light were generally performed upon irradiation at 365nm, this wavelength being present in the
solar emission and energetic enough to cause the desired photoredox reaction. The degradation process of different molecules, all
representative of the major families of pollutants were investigated and will be presented. More emphasis will be given on 4-
chlorophenol, diuron and isoproturon and tributyltin.


Photocatalysis versus Catalysis : Differences, Similarities, Complementarités. Consequences for Environmental Concerns

                                                       Jean-Marie HERRMANN
  Laboratoire de Photocatalyse, Catalyse et Environnement, UMR CNRS (IfoS), Ecole Centrale de Lyon, BP 163, 69 131 ECULLY Cedex.
                                               e- mail :

       Heterogeneous photocatalysis is a sub-discipline of catalysis, whose originality results from the mode of activation of the
catalyst : As indicated by its, the activation mode results from the absorption of photons by the solid. As photocatalysts are generally
chalcogenides, i.e. oxides and sulfides, they are semiconductors which become photoconductors when the photon energy is at least
equal to or greater than the energy band gap EG. This light absorption induces the formation of electron-hole pairs which
subsequently dissociate into free electrons e- and holes p+. If e- and p+ do not recombine, they can separately reach the surface at
which they can react with acceptor adsorbates (O 2, NO, H+) and with donor ones (OH-, R-COO-, …). A subsequent redox process
originates, independent of temperature. By contrast to conventional catalysis, the activation by phonons has been replaced by that by
photons. There results that (i) photocatalytic activity a vs  follows the adsorption curve of the solid and (ii) that a varies
proprotionally to the light flux  (in W/m2) in optimal conditions and as  1/2 if the flux is too intense, which causes a predominant
sterile electron-hole recombination. Otherwise, photocatalysis follows the same basic laws as conventional catalysis. The activity is
proportional to the coverage , which varies as = KP/(1+KP) in gas phase, whereas, in liquid phase, C/(1+KC). The activity
increases proprotionally to the mass of catalyst, i.e. to the total number of active sites as in conventional catalysis. This means that
the system is truely catalytic and that there is no photochemistry neither in adsorbed nor in fluid phase. However, for a given
photoreactor design, there exists an optimal mass above which the activity levels off, indicating that some solid particles remain in
the shade of the others.
       The applications are multiple. Initially, it has been shown that photocatalysis is able to selectively oxidize hydrocarbons into
CO-containing molecules :
      (CH3)3 – C6H4 – CH3 + O2  (CH3)C – C6H4 – CHO (100%) + H2O
or to generate hydrogen from hydroxylated compounds.
       However, the main applications concern environmental catalysis at room temperature under artificial or solar light since the sun
spectrum contains 3% near-UV beams. Both air and water can be purified with a total mineralization of pollutants and poisons. The
paramount advantage of photocatalysis concerns water treatment, since no need of heating is required. The final results are identical
to those obtained by water calcination, which is excessively energy-wasting because of the high heat capacity of water. Various
pesticides (herbicides, insecticides), dyes and toxic products have been successfully eliminated and will be examplified. One of the
main application is « helio-photocatalysis » used in solar purification and potabilisation of water, which concerns semi-arid countries,
rich in solar bearing but poor in water.

Symposium 4 Excited State Catalysis


Investigations on the Photocatalytic Decomposition of NO and the Photo-induced Superhydrophilic Properties of
                                  Ti-B Binary Oxide Thin Film Photocatalysts

                                                    M. Anpo* and S. Dohshi
             Department of Applied Chemistry, Osaka prefecture University, Gakuen-cho, Sakai, Osaka 599-8531, JAPAN
                                   Fax: -81-722-54-9910; E-mail: anpo@

      Transparent TiO2 thin film photocatalysts have been investigated in many fields not only for their high photocatalytic reactivity
but also for their superhydrophilic properties. We have reported that such transparent TiO 2 thin film photocatalysts can be prepared
not only by a conventional sol-gel method as a wet process but also by the ionized cluster beam (ICB) method as a dry process.1)
      In the present study, we have prepared Ti-B binary oxide thin film photocatalysts of differing Ti content by the ICB method
using multi-ion sources and investigated their photocatalytic reactivity and photo-induced superhydrophilic properties for the design
and development of unique and effective photofunctional materials.
      UV-Vis absorption and XAFS (XANES and FT-EXAFS) investigations of the Ti-B binary oxide thin film photocatalysts have
indicated that these photocatalysts are composed of ultra fine nano-particles of TiO2 with high transparency. UV irradiation of these
Ti-B binary oxide thin films in the presence of NO led to the decomposition of NO into N2 and O2 with a high efficiency and
selectivity. Moreover, these Ti-B binary oxide thin films showed high superhydrophilic properties, achieving a water contact angle of
0 degree under UV light irradiation. Such photocatalytic reactivity and photo-induced superhydrophilic properties were found to be
strongly dependent on the Ti-content of these Ti-B binary oxide thin films and interestingly, we have found that these properties are
remarkably enhanced on films having low Ti-content due to the high photoreactivity observed on smaller TiO 2 nano-particles in the
binary oxides.

[1] M. Takeuchi, H. Yamashita, M. Matsuoka, M. Anpo, T. Hirao, N. Itoh and N. Iwamoto, Catal Lett., 66 (2000) 185-187 and 67
    (2000) 135.


        Water Treatment by Simultaneously or Successively Using Sonication and TiO 2-Based Photocatalysis

                         Chantal GUILLARDa, Christian PETRIERb, Pierre PICHATa, Philippe THERONa
       “Photocatalyse, Catalyse et Environnement”, CNRS UMR “IFoS”, Ecole Centrale de Lyon, 69131 ECULLY CEDEX, France
                                      Fax : 33 (0) 4 78 33 03 37 – E :
                  “Chimie Moléculaire et Environnement”, Université de Savoie du-LAC, France, 73376 LE BOURGET

      These studies are aimed (i) at evaluating the potentialities of the simultaneous or successive use of photocatalysis and
ultrasounds to eliminate and mineralize organic pollutants in water, (ii) at comparing the intermediate degradation products generated
by both techniques and (iii) at investigating the influence of ultrasonic frequency.
Phenyltrifluoromethylketone (PTMK), which contains a CF3 group as many pesticides, forms trifluoroacetic acid (TFA), a stable
end-product, by photocatalysis. Octan-1-ol, susceptible of forming micro-emulsions like fatty acids, can stay away from the TiO 2
surface, which should inhibit its photocatalytic degradation. But both compounds, which are hydrophobic, can enter ultrasonic
cavitation bubbles to be pyrolyzed, unlike phenol which was selected for its hydrophilicity.
      For the three compounds, (PTMK, Octan-1-ol and phenol), it was found that 515 kHz-ultrasound was more efficient than 30
kHz-ultrasound. In all cases photocatalysis was found more efficient than sonication if 30 KHz was used. However, Ultrasound at
515 KHz was better than photocatalysis for the degradation of Octan-1-ol while photocatalysis remained more efficient for the
disappearance of PTMK and similar for the degradation of phenol.
 Concerning the simultaneous use of photocatalysis and ultrasound, a synergy was observed at 30 kHz with the ultrasound probe
employed, and it was explained by a OH° radical photocatalytic production from sonochemically formed H2O2. This synergy was not
found for hydrophilic compounds or in presence of 515 kHz-ultrasound, at least with the ultrasound probe used.
We proved the ultrasonic pyrolysis of PTMK and octan-1-ol by comparing the photocatalytic and ultrasonic intermediate degradation
products. In particular, ultrasonic degradation of PTMK avoids TFA formation by pyrolysis of the CF 3 group. Octan-1-ol, for which
more than 20 intermediate degradation products have been quantified for each technique thanks to SPME, produces only small
amounts of acid by photocatalysis or by the simultaneous use.

Symposium 4 Excited State Catalysis


      Photocatalytic Degradation of Methyl-tertio-butyl ether (MTBE) in Aqueous and Gas Phase. Reaction
                       Mechanisms and Efficiencies of Various Industrial TiO2 Catalysts
  Chantal GUILLARD (a), Eric PUZENAT(a), Karine SCHOUMACKER(a,b) , Christophe GEANTET(b), Michel LACROIX(b) and
                                                      Jean-Marie HERRMANN(a)
      “Photocatalyse, Catalyse et Environnement”, CNRS UMR “IFoS”, Ecole Centrale de Lyon, 69131 ECULLY CEDEX, France
                                              Fax : 33 (0) 4 78 33 03 37 – E :
                        “Institut de Recherches sur la Catalyse”, 2 Avenue A. Einstein 69626 Villeurbanne Cedex
                                       Fax : 33 (0)4 72 44 53 99,
      This study is aimed at comparing the reaction mechanism, both in aqueous and in gas phase, of the photocatalytic degradation
of methyl-tertio-butyl ether (MTBE), a volatile organic compound (VOC) used as a substitute for tetraethyl-lead in gasoline and now
often found in the atmosphere and in ground waters around gas stations. The efficiencies of different industrial TiO 2 catalysts were
also determined for both phases.
      Two successive attacks of MTBE by OH° radicals and then by HO 2° can explain the major formation of tertiobutyl formate and
the minor one of acetone and methylacetate observed in aqueous phase according to the following mechanism for the major product:
      (TiO2) + hυ  e- + p+
      O2 (g) + e-  O2-(ads)
      H2O H+ + OH-
      OH- + p+  OH°
     O2°-(ads) + H+  HO2°(ads)
     (CH3)3C_O_CH3 + OH°  (CH3)3C_O_CH2° + H2O
     (CH3)3C_O_CH2° + HO2°  (CH3)3C_O_CH2_OOH  (CH3)3C_O_CO_H
       By contrast, superoxyde (O2°-) adsorbed species, holes and HO2° radicals formed in situ at the surface of titania in contact with
a gas phase instead of water were determined as the main active species. They can account for the major formation of acetone and
methylacetate and the minor formation of tertiobutanol according to the following mechanism:
       (TiO2) + hυ  e- + p+
       O2 (g) + e-  O2-(ads)
       CH3_O_C(CH3)2_CH3 + O2°-  CH3_O_C(CH3)2_CH2- + HO2°
       CH3_O_C(CH3)2_CH2- + p+  CH3_O_C(CH3)2_CH2°
       CH3_O_C(CH3)2_CH2° + HO2°  CH3_O_C(CH3)2_CH2OOH
       CH3_O_C(CH3)2_CH2OOH  molozonide  ozonide
       Ozonide  acetone + formic acid
                  methylacetate + formaldehyde
       For the same structure (anatase), the higher the crystallite size, the higher the photocatalytic efficiency. This behaviour seems
to be linked to UV-absorption properties of the photocatalysts. Could the presence of 20% of rutile in the Degussa P-25 sample be at
the origin of its better efficiency?

   Investigation of the Photocatalytic Degradation of Aqueous Solutions of Acid Orange 7 over TiO 2 Particles
                                         M. Stylidi, D.I. Kondarides and X.E. Verykios
                       Department of Chemical Engineering, University of Patras, GR-26500 Patras, Greece
                             Tel./Fax. No: +30 (61) 991 527; e-mail:

      Azo dyes are an abundant class of synthetic, colored, organic compounds that comprise half of the textile dyestuffs used today.
It is estimated that a large amount of these dyes release into the environment without proper treatment. Together with the
environmental pollution, some of these dyes have documented health hazards. The toxicity and mass production of these dyes leads
to the necessity of treatment. The major difficulty in treating textile azo dyes is the ineffectiveness of biological process es, while
physical processes, merely transfer the pollutants to other media and cause secondary pollution. During the past two decades,
photocatalytic processes involving TiO2 semiconductor particles have been shown to be potentially advantageous and useful in
recalcitrant azo dyes degradation.
      The photocatalytic degradation of a model hydroxyazo dye, Acid Orange 7 (AO7), has been investigated over TiO2 particles
(Degussa P-25) irradiated with a light source simulating solar light. The extent of degradation of AO7 has been determined by UV-
vis spectrophotometry and chemical oxygen demand (COD) method. Intermediates and final products have been identified during the
course of degradation by means of HPLC and GC-MS analysis. It has been found that the dye initially decomposes into colorless
aromatic intermediates, which undergo further photocatalytic oxidation, leading to low acids and CO2 formation. Investigation of the
by-products indicates that the first step of the degradation leads to the breaking of the C=N bond of the hydrazone form of AO7. This
dye is known to undergo a tautomeric equilibrium in aqueous solutions which favors the hydrazone form. Moreover, FTIR
spectroscopy was used to follow the progress of the reaction of AO7 absorbed on TiO 2 surface. The changes in the spectra indicated
the degradation of absorbed AO7.
      The TiO2-assisted photodegradation of the azo dye was also achieved employing home made titanium dioxide prepared using
different methods, with titanium isopropoxide or titanium tetrachloride as precursors. These materials were pretreated at various
temperatures in order to modify their morphological and physicochemical characteristics. The crystal structure and the specific
surface area of these samples were determined by means of XRD and BET techniques. The photocatalytic activity of the home-made
TiO2 powders for the AO7 photodegradation was investigated as a function of the crystalline mode (anatase-rutile content) and the
specific surface area and compared to the that of commercial TiO 2 (Degussa P-25).

Symposium 4 Excited State Catalysis


                    Preparation, Characterisation and Photophysical Properties of CeO 2-TiO2 System

                                                 G.Colón1, J.A.Navío1 and H.Mansilla2
    Instituto de Ciencia de Materiales. Centro Mixto CSIC-Universidad de Sevilla. Avda. Americo Vespucio s/n. 41092 Sevilla (Spain).
      Laboratorio de Recursos Renovables. Facultad de Ciencias Químicas. Universidad de Concepción. Casilla 160-C. Concepción (Chile).

       CeO2-TiO2 mixed oxide is a promising system to be used in electrochromic devices, due to their electro-optical performance 1.
Generally we find this mixed oxide system in the form of thin films or coatings for application as counter electrodes. It is also
reported that CeO2-TiO2 coatings deposited on glass by the sol-gel method show UV absorption, high reflectance and interference
coloring 2. However, there is not any information about the possibility to use this system for photocatalytic applications.
       We have prepared CeO2-TiO2 system by coprecipitation method, using Ce(NO 3)3 and commercial TiO2 (Degussa P25). CeO2
contents varying from 0 to 10% mol. Wide characterisation of the system (TGA/DTA, XRD, SEM-EDX, IR, UV-vis) show the
influence of CeO2 presence in the TiO2. At higher cerium loadings certain segregation it is observed from XRD. Thermal evolution
of the precursor can be followed by TGA analysis. We can notice that weight losses takes place up to 400ºC, after which, slight
increase in weight it is observed and due probably to Ce3+ oxidation. From UV-vis spectra slight differences can be drawn with
respect to TiO2 Degussa P25. Mixed oxides present absorptions in the UV region, shifting toward higher wavelengths for CeO2.
       Photocatalytic behaviour of mixed oxides have been tested for the photooxidation of phenol, using UV and solar light.
Conversions this reaction decreases as CeO 2 content increases. Best activities can be observed for CeO 2-TiO2 (1% mol). Using solar
light, conversions do not experiment a better behaviour with respect to TiO 2. Therefore, we can deduce that this preparation method
is not adequate for obtaining photocatalytically active Ce-Ti system. CeO2 segregation observed could be a negative fact that make
decrease the photoactivity of commercial TiO2, in spite that it is well know the capability of cerium to adsorb and interchange
oxygen, point that it is very important in heterogeneous photocatalysis.

[1]     C.O.Avellaneda and A.Pawlicka, Thin Solid Films, 335, (1998), 245.
[2]     T.Morimoto, H.Tomonaga and A.Mitani, Thin Solid Films, 351, (1999), 65.


             Photolytic and Photocatalytic Degradations of Sulfonylurea Herbicides: a Comparative Study

                            J.M. Chovelon*, E. Vulliet*, C. Emmelin*, J.M. Herrmann**, C. Guillard**
                          * LACE, UMR 5634, University Claude Bernard Lyon 1, 69622 Villeurbanne Cedex
                                  ** IFoS, UMR 5621, Ecole Centrale de Lyon, 69131 Ecully Cedex

      The photodegradation of pollutants in aqueous solutions is attracting considerable attention for application to environmental
problems (identification of the main photoproducts and assessment of their toxicity, detoxication of polluted waters, etc).
      The photodegradation pathways include either direct or indirect reactions. Direct photodegradation involves the photoexcitation
of the pollutants after exposure to visible or to ultraviolet light followed by the dissipation of excess energy through molecular
restructurations leading to the formation of smaller metabolites. Under indirect photodegradation, the light energy is absorbed by the
photosensitizers and can either be indirectly transferred to the pollutants or be used to produce reactive species such as OH°. Even if
both processes utilise the same source of energy, mechanisms of transformation, quantum yields, and photoproducts can be different.
      This paper reports on a comparative study of two photodegradation processes : direct photolysis, and indirect photodegradatio n
using TiO2 as a photocatalyst (Degussa P-25). Sulfonylurea herbicides (see Fig.1) used to control broadleaf weeds and some grasses
in cereal crops have been selected as pollutants.
      Pathways of photochemical degradations as well as the kinetics were determined and compared.
      Quantum efficiencies were determined using polychromatic light. Conclusions were drawn from the results obtained.

                                               OCH3                                                              OCH3
                                       N                                                                    N
                      SO2NHCONH                N                                    SO2NHCONH                    N
                                       N                                                                    N
                   OCH2CH2OCH3                 OCH3                             OCH2CH Cl
                                                                                      2                           CH3

                     Cinosulfuron                                                            Triasulfuron

                                           Fig.1 Formulae of herbicides used in this study

[1]     C.O. Avellaneda and A. Pawlicka, Thin Solid Films, 335, (1998), 245.
[2]     T. Morimoto, H. Tomonaga and A. Mitani, Thin Solid Films, 351, (1999), 65.

Symposium 4 Excited State Catalysis


 Vibrational Excitation Mechanism for Electron Transfer Activation of Nitrous Oxide on Grafted MoOX/SiO2 Catalysts

                                                            Z. Sojka1, M. Che2,3
                             Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Cracow, Poland
  Laboratoire de Réactivité de Surface , UMR 7609-CNRS, Université Pierre et Marie Curie, 4, Place Jussieu, 75252 Paris-Cedex 05, France
                                                    Institut Universitaire de France

       The chemical activation of reactants through their coordination to surface transition metal ions determines the primary step of
catalytic transformations For most reactants, adding or subtracting an electron may drastically alter their reactivity. The electron (or
the hole) supplied to trigger the activation is usually returned to the active center directly or indirectly in a subsequent step of the
reaction thus giving rise to electron transfer (ET) catalysis.
       Redistribution of the electron density within the metal-adligand moiety may result not merely from the bonding but also from
the deformation of the nuclear configuration of the activated molecule caused by its vibronic excitation. This may provide a new
pathway of lower energy along which the bound molecule can be specifically activated. Such a mechanism is particularly important
for triatomic molecules since excitation of the bending mode results in dramatic enhancement of their electron affinity, making the
ET thermodynamically feasible. This process can also be driven by electrostatic interactions with highly io nic surfaces like that of
MgO because the Coulombic term can compensate the unfavorable negative electron affinity of N 2O.
       In the present work we have analyzed the activation of N2O on MoOx/SiO2 catalysts which occurs through dissociative electron
transfer triggered by vibrational excitation. The reaction was followed by CW-EPR techniques using naturally abundant and 95Mo-
enriched molybdenum. The dynamics of the N–O bond cleavage is discussed in terms of a two-dimensional Morse-type potential
energy surface. To reach the Frank-Condon region, N2O needs to be excited to the v = 3 level. The overlap between the 3* and the
dxy redox orbitals provides the pathway for electron transfer, which occurs with an activation energy of 20 4 kJ/mol in the range of
323-393 K.

Acknowledgments. Z.S. is grateful to the Université P. et M. Curie, Paris VI for an invited Professorship.

                                            Photocatalytic Treatment of Waste Waters

                                Anita Rachel*, M. Subrahmanyam**, M. Sarakha* and Pierre Boule*
     * Laboratoire de Photochimie Moléculaire et Macromoléculair, UMR CNRS Université Blaise Pascal, F – 63177 Aubière cedex France
                                 **Indian Institute of Chemical Technology Hyderabad – 500007 India

      Titanium dioxide (anatase form) has well known photocatalytic properties. The use of suspended form of TiO 2 when exposed
to sunlight or artificial UV light (300-400 nm), was proposed for the elimination of non-biodegradable organic pollutants from waste
waters. The active species are the positive holes and OH radicals formed on TiO2 which are highly efficient oxidizers. Recovering
and recycling of the catalyst is the main problem encountered in this method and this limits its use. Hence immobilization of TiO 2
seems to be a possible solution, but most often it drastically reduces the efficiency of photochemical process.
      Experimental devices were set up for the comparison of TiO2 suspended (different types of TiO2, dispersed on zeolites) and
TiO2 immobilized on various supports such as glass, bricks, cement and inorganic fibres. Different methods of coating were used :
deposition by sputtering and calcination at 450°C to convert TiO2 into anatase and sol-gel technique by dip-coating method on
supports like glass,bricks and cement. Photocatalytic efficiencies were was compared under sunlight and artificial UV light (300-
400 nm) at different concentrations using sulfonic acids such as 2,5-anilinedisulfonic acid, 3-nitrobenzenesulfonic acid and 4-
nitrotoluene-sulfonic acid as models for pollutants from dye industry.
      Concerning immobilized TiO2, supported catalysts like glass, bricks or cement coated by classical dip-coating of TiO2 with
sol-gel technique, are a little more efficient than those obtained by sputtering technique, but they are not as efficient as susp ended
TiO2. Better results were obtained with TiO2 fixed on inorganic fibres (patented method), but fibres are more appropriate for the
treatment of air than for waste water. Designing of a photochemical device appropriate to the treatment of waste water as well as the
study of some other types of solid catalyst involving TiO 2 is in progress.

Acknowledgement: The work described herein was supported by Indo-French Centre for the Promotion of Advanced Research
(IFCPAR project 2205-2)

Symposium 4 Excited State Catalysis


                                             The Photcatalytic Reforming of Methanol

                                            M. Bowker, A. Dickinson, D. James, and L Millard
                Centre for Surface Science and Catalysis, Univ. Reading, Reading RG6 6AD, UK.

      We have studied the room temperature reforming of methanol under anaerobic conditions with Pd/TiO 2 catalysts and using a
solar simulator light source. The reaction occurs in an aqueous environment with water as the net oxidant of methanol (CH 3OH+H2O
 CO2+3H2). The reaction is poisoned in the absence of light, due to methanol decomposition on the Pd particles to leave CO
strongly adsorbed. Light induces band gap excitation (>3.2 eV) of the TiO2 to create Ti3+ and a highly reactive oxygen species which
removes the CO at the periphery of the Pd particles. Steady state reaction is achieved under these conditions by methanol re-
adsorption at the Pd vacancy, lierating 2 moles of H2 and water adsorption healing the anion vacancy in the TiO 2. Careful variation of
the loading of Pd has conclusively shown that both TiO 2 and Pd must be present in the surface layer and that the reaction only takes
place at the interface sites between the two.


                                                      Photoreactivity of ETS-10

                                            Yuni Krisnandia, Soji Adesinab and Russell Howec
      a                          b
          School of Chemistry and School of Chemical Engineering and Industrial Chemistry, University of New South Wales, Sydney
                                                          Australia 2052, and
                           Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK

       ETS-10 is a titanosilicate zeolite consisting of linear chains of TiO 6 octahedra surrounded by SiO4 tetrahedra, containing a three
dimensional pore structure defined by 12-rings. The TiO6 chains have been shown to behave as one dimensional semiconducting
wires with a band gap slightly larger than that of anatase. [1] This paper describes an investigation of the photoreactivity of ETS-10
and a comparison of its photocatalytic activity for the oxidation of gaseous ethene with that of a conventional anatase photocatalyst.
       Two forms of ETS-10 were investigated: a commercial sample in the hydrogen exchanged form, and a sample synthesized in-
house in which Na+ and K+ cations provided charge balance. These two forms behaved very differently. Irradiation of the commercial
sample with UV light in the presence of ethene caused photoreduction, and the growth of an intense EPR signal due to Ti 3+.
Subsequent admission of oxygen removed the Ti3+ signal and formed superoxide ions. Photoreduction also occurs when anatase is
irradiated in the presence of ethene. On the other hand, no photoreduction could be detected under the same conditions with t he
synthetic ETS-10 material. In-situ infrared experiments showed that irradiation of the synthetic ETS-10 in the presence of ethene and
wet oxygen caused partial oxidation of ethene to acetaldehyde and acetic acid. Commercial ETS-10 also gave significant amounts of
complete oxidation products CO and CO2. In a fluidized bed continuous flow microreactor only commercial ETS-10 gave gaseous
oxidation products (CO2) similar to a conventional anatase photocatalyst.
       These results will be discussed in terms of the structures of the commercial and synthetic ETS-10, and the various reaction
pathways possible for adsorbed ethene and oxygen. It will be argued that lattice defects and extraframework Ti 4+ ions in the
commercial ETS-10 give this material a photoreactivity not unlike that of anatase. Photoreduction of the synthetic ETS-10 , on the
other hand, is not observed, but there is nevertheless clear evidence that photocatalytic partial oxidation of ethene adsorbed in the
pores does occur. This evidence for communication between holes and electrons generated in the semiconducting wires and
molecules adsorbed in the pores confirms the novelty of ETS-10 as a microporous photocatalyst.

[1]        S. Bordiga, G.T. Palomino, A. Zecchina, G. Ranghino, E. Giamello and C. Lamberti, J.Chem.Phys. 112 (2000) 3859.

Symposium 4 Excited State Catalysis


                                Methane Conversion with Vibrational-Excited Carbon Dioxide

                                      V. N. Snytnikov, Vlad. N. Snytnikov and V. O. Stoyanovsky
                            Boreskov Institute of Catalysis of Siberian Branch of Russian Academy of Sciences
                           Pr. Akad. Lavrentieva, 5, Novosibirsk 630090, Russia, e-mail:

      The problems of CO2 utilization and methane activation are essential for the modern chemistry. Methane conversion with
carbon dioxide may provide a solution to both of these problems. This process can be used for the industrial H 2 production, it is basic
for the synthesis of hydrocarbons and other valuable products. High temperatures and intensive heat flows are necessary for t his
endothermic reaction. Among the catalysts of methane conversion with carbon dioxide, nickel and platinu m metals supported on
aluminum and zirconium oxides are of particular interest.
      In our experiments, methane conversion with carbon dioxide over Ni/Al2O3 and other catalysts was studied upon feeding to the
heated catalyst the gas mixture, in which more than a half of CO2 molecules were vibration-excited. In experiments, the reaction
temperature varies from 400 to 800oC, the gas mixture pressure is in the range from 0.4 to 1.2 bar. The reactor is divided into two
zones. In the first zone, the gases are mixed and heated, and vibrational levels of CO2 are excited. The resulting mixture is fed to the
catalyst of volume 1-5 cm3. Analysis of the gaseous reaction products is made chromatographically. Products with a low boiling
point are adsorbed at the support and are further analyzed by the IR spectroscopy methods.
      It was shown experimentally that activation of the reaction gas mixture via excitation of vibrational-rotational levels of CO2
molecules results in considerable changes of the conversion products composition. In particular, at temperatures up to 700oC an
increased yield of heavy hydrocarbons C8-C10 is observed.


       Vapour Phase Photocatalytic Oxidation of Ethanol and Toluene in a Continuous Spinning Basket Reactor

Vincenzo Augugliaro a, Salvatore Coluccia b, Elisa García-Lópeza, Vittorio Loddoa, Gianmario Martra b, Leonardo Palmisano a and
                                                        Mario Schiavelloa
  Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, University of Palermo, Viale delle Scienze, 90128 Palermo, I taly
                        Dipartimento di Chimica IFM, Università di Torino, Via P. Giuria 7, I-10125 Torino, Italy

    Volatile organic compounds, VOC's, are an important class of air pollutants usually found in the atmosphere of urban and
industrial areas. Heterogeneous photocatalysis has been found to be effective to destroy these contaminants in dilute systems [1].
Many organic compounds have been successfully oxidised at room temperature on polycrystalline TiO 2 catalyst in the presence of
near-UV radiation [2,3].
      A continuous spinning basket photoreactor (Carberry-type reactor) of cubic shape and of stainless steel was used for
performing the experimental runs. The catalyst used was polycrystalline anatase TiO 2 and it was placed on the blades of the impeller.
Pyrex windows on the vertical walls of the reactor allowed the irradiation of the catalyst by means of medium pressure Mercury
lamps or actinic fluorescent tubes. Fluid dynamic characterisation of the photoreactor was carried out with the stimulus -response
technique. The photoreactor was fed by a mixture of air, contaminant (ethanol or toluene) and water in various molar ratios. The
influence of contaminant concentration, gas flow rate, temperature and water presence on the photoprocess performance was
      Ethanol photo-oxidation, which mainly produced acetaldehyde, was carried out with this configuration. On the basis of this
study the geometry of the reactor was modified and experiments were performed by using toluene. In this case CO 2 was the main
oxidation product and benzaldehyde was detected as the main intermediate.
      A FTIR study was carried out by simulating the experimental conditions used for the photoreactivity tests of toluene photo-oxidation.

[1]     Ollis D. F. and Al-Ekabi H. (1993), Photocatalytic Purification and Treatment of Water and Air, Elsevier, Amsterdam.
[2]     Augugliaro V., Coluccia S., Loddo V., Marchese L., Martra G., Palmisano L., Schiavello. M. (1999) Photocatalytic oxidation
        of Gaseous Toluene on Anatase TiO2 Catalyst. Mechanistic Aspects and FTIR Investigation. Appl. Cat. B: Environ. 20, 15-27.
[3]     Martra G., Augugliaro V., Coluccia S., García-López E., Loddo V., Marchese L., Palmisano L., Schiavello M. (2000)
        Photocatalytic oxidation of Gaseous Toluene on polycrystalline TiO 2 Catalyst: FT-IR investigation of surface reactivity of
        different types of catalyst. Studies on Surf. Sci. and Catal. 130, 665-670.

Symposium 4 Excited State Catalysis


          Photocatalytic Destruction of Tetradecylpyridinium on Titanium Dioxide in Aqueous Solutions.

                                         T.A. Khalyavka, V.V. Shimanovskaya, E.I. Kapinus.
     Institute for Sorption and Problems of Endoecology, NAS of Ukraine, 13, General Naumov St., Kyev-164, 03 680, Ukraine,

       The present work deals with influence of the crystalline structure of finely divided titanium dioxide on its activity in destruction
of tetradecylpyridinium chloride (TDPyCl), a cationic surfactant, in aqueous solutions. The spectral-grade anatase, rutile, TiO2 with
two-phase structure of the particles as well as anatase, promoted by Fe3+, Ni2+, Co2+, were used as photocatalytic agents.
       The samples of the spectral-grade titanium dioxide were obtained by thermal hydrolysis of titanium tetrachloride in the
presence of the corresponding nucleus. Cation admixture in the TiO2 samples did not exceed 10-5 %. The titanium dioxide constituted
spherical particles 1-5 m in diameter, which were formed by nanocrystalline aggregates with size of 10-60 nm. Specific surface of
the samples ranged between 3 and 200 m 2/g.
       Irradiation of TiO2 with UV light in aqueous TDPyCl solutions in the presence of oxygen results in oxidizing destruction of
this surfactant. The IR, UV and 1H NMR spectra demonstrate that the most part of the surfactant undergoes total mineralization.
Aliphatic alcohols, ketones and aldehydes were also found among the products of the photocatalytic reaction. The photocatalytic
oxidation of TDPyCl follows the first order kinetic equation. In the investigated systems, observed rate constants can differ in order
of magnitude depending on content of impurities, crystalline structure, nature of surface groups etc. Incorporation of Fe 3+, Ni2+, Co2+
into TiO2 extends the spectral range of photosensitivity of the system although the all ions inhibit the photocatalytic process. That is
why the spectral-grade samples show higher photocatalytic activity as compared with commercial-grade titanium dioxide.
       For the spectral-grade samples of titanium dioxide, the effective rate constants for the photocatalytic reaction under discussion
are closely allied and they do not depend on specific surface and porosity of the samples. The rate constants rise with increase of
temperature of the TiO2 thermal treatment. The effective rate constants for the two-phases samples are less than those for anatase by
factors 2-5 when these samples contain more than 50 % rutile. The sample containing 65% anatase demonstrates the highest catalytic
activity among the all TiO2 two-phases samples. The photocatalytic oxidation of TDPyCl in the presence of alcohols obeys second
order kinetic low.
      The -irradiated titanium dioxide demonstrates noticeable higher photocatalytic activity that could be caused by the formation
of additional defects in the crystalline lattice of the material. The irradiated samples did not change their photocatalytic activity after
storage during few weeks.


 Photocatalytic Degradation of Organic Substances Using Fe/TiO2 Catalysts. A FTIR Study of the Role of Fe3+/ Fe2+Ions
                                           in the Degradation Mechanism

     J. Araña, O. González Díaz, M. Miranda Saracho, J. M. Doña Rodríguez*, J. A. Herrera Melián, and J. Pérez Peña.
  Departamento de Química. Universidad de Las Palmas de Gran Canaria, Campus de Tafira., E- 35017. Gran Canaria. España.
                         Tef. +34-928-45-44-37, Fax + 34-928-45-29-22, e-mail:

       The photocatalytic degradation of organic compounds by Fe-doped TiO2 has been studied. Results suggest that Fe is extracted
through the formation of a [Fe-organic species]2+ complexes by which organic substances degrade. Fe 2+ ions that remain in solution
after degradation go back to the catalyst surface and are oxidized by photogenerated holes. In this way the catalyst is react ivated
becoming ready for a new degradation process. The formation of hydrogen-carbonates on the TiO 2 catalyst through ·OH radicals
insertion has been detected by FTIR. This way the organics degradation by ·OH insertion is inhibited and the formation of [Fe-
organic species]2+ complexes is favored. This way, Fe doped TiO 2 shows a similar catalytic behavior as Fe2+ /Fe3+ in the photo-
Fenton reaction but when degradation is finished Fe turns back to the catalyst surface and excited TiO 2 substitutes H2O2 as ·OH
       The influence of the temperature used during the Fe impregnation of the catalysts and the catalysts Fe content, on the
photocatalytic behavior have been studied. On the other hand, FTIR and FTIR-ATR have been used to identify the adsorbed or
dissolved intermediates formed during the degradation process.

Keywords: Photocatalysis, mixed catalysts, degradation mechanism, FTIR, complexes, Fe, TiO2.

Symposium 4 Excited State Catalysis


      FTIR Characterization of the TiO2 Photocatalytic Behaviour Modification Induced by Organic Adsorbates

               J. Araña, R. González, E. López Mendoza, J. M. Doña Rodríguez, O. González Díaz and J. Pérez Peña.
              Departamento de Química. Universidad de Las Palmas de Gran Canaria, Campus de Tafira - 35017, Spain.
                              Tlf. +34-928-45-44-37, Fax + 34-928-45-29-22, e-mail:
                                                              J. A. Navío,
       Instituto de Ciencias de Materiales, Centro de Investigaciones Científicas “Isla de la Cartuja”, Av. Américo Vespucio, sn,
                                                Isla de la Cartuja, 41092-Sevilla, Spain.

      Modifications of the TiO2 ability to degrade organic substances when determined organic molecules are adsorbed on its surface
have been studied. Different catalysts have been prepared by TiO 2 impregnation with different aromatic and aliphatic organic
substances. Also, different organic substances have been used as substrates in order to study the influence the organic adsorbate-
organic substrate interactions on the photocatalytic behavior of TiO 2
      According to the different catalyst treatments distinct chemical species such as phenoxides, alcoxides, peroxo compounds,
acetates and orthophormiates, have identified by using FTIR spectroscopy. It has been observed that the presence of these species
modifies the catalyst surface area and the distribution of hydroxylic groups on the catalyst surface and enhances the adsorption of
water molecules. Also, depending on the type of TiO2-adsorbed species the organic substrate interaction with the catalyst will result
different affecting the organic substrate degradation.


                Toluene Photocatalytic Degradation on TiO 2 Nanoparticles: Activity and FTIR Studies

                         A.J. Maira*, J.M. Coronado*, J. Soria*, J. C. Conesa*, V. Augugliaro#, K.L. Yeung+
                       Inst. de Catálisis y Petroleoquímica, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain
         Dip. Di Ingegneria Chimica dei Processi e dei Materiali, Università di Palermo,V. delle Scienze, 90128 Palermo, Italy
          Dept. of Chem. Engineering, The Hong Kong Univ. of Science and Technology,Clear water bay, Kowloon, Hong Kong

      TiO2 nanoparticles prepared with solvothermal methods have shown in some cases higher activity in photocatalytic oxidation
of gaseous pollutants than commercial or laboratory materials prepared through high temperature calcinations [1,2]. Here the
performance of samples of both types in photocatalytic toluene vapor degradation is examined, and the differences between materials
with the same particle size are studied with the help of FTIR spectroscopy.
      In the photocatalytic oxidation of toluene under UV irradiation at near-ambient temperature, the activity of solvothermally
prepared TiO2 powders, which may be made as homodispersed particles with primary sizes as low as 3 nm, and their resistance to
deactivation (both in the presence and absence of water vapor) are always better than those of calcined specimens, in particu lar when
comparing photocatalysts of the same particle size and BET area. The selectivity to total mineralization (instead of to the formation
of partial oxidation products such as harmful benzaldehyde) is also higher; the data indicate that this is not due to a lower rate of
benzaldehyde formation, but to a higher activity for full oxidation.
      FTIR data obtained after separate stages of the process (room temperature outgassing, toluene adsorption, UV irradiation,
product desorption) show the formation of both toluene, which is only weakly adsorbed on both kind of samples, and benzaldehyde
species, which are adsorbed more strongly on the solvothermally prepared material. In this latter type of photocatalyst, H-bonded
surface OH groups exist in higher amounts, and are also more stable; it is proposed that they constitute the main active sites for
complete oxidation, while isolated OH groups, present in both types of TiO 2 samples, would be the primary sites for benzaldehyde
formation (probably via end-on toluene adsorption).

Acknowledgement- This work was made with financial support from the ECSC (contracts 7220-ED/093 and 7220-EB/004). J.M.C.
thanks the C.A.M. for a post-doctoral grant.

[1]    A.J. Maira, K.L. Yeung, C.Y. Lee, P.L. Yue, C.K. Chan, J. Catalysis 192 (2000) 185
[2]    A.J. Maira, K.L. Yeung, J. Soria, J.M. Coronado, C. Belver, C.Y. Lee, V. augugliaro, Appl. Catal. B: Environm. 29 (2001) 327.


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