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See detailSol-gel preparation and characterisation of SnO2 powders employed as catalyst for phenol photodegradation
Benhebal, Hadj; Chaib, Messaoud; Léonard, Angélique ULg et al

in Scientia Iranica (2013), 20(6), 1891-1898

Crystallized pure SnO2 powders were prepared by the sol-gel process and were used as photocatalyst for the degradation of phenol under UV light at pH 6.5 and a temperature of 20°C. The physical properties ... [more ▼]

Crystallized pure SnO2 powders were prepared by the sol-gel process and were used as photocatalyst for the degradation of phenol under UV light at pH 6.5 and a temperature of 20°C. The physical properties of photocatalyst were characterized by X-ray diffraction, Scanning Electron Microscopy, nitrogen adsorption-desorption and Ultraviolet-visible diffuse reflectance spectroscopy. The influences of different operating variables such as the pH, the photocatalyst loading, the initial concentration of phenol, were studied to improve the efficiency of phenol degradation. [less ▲]

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See detailDegradation of p-nitrophenol and bacteria with TiO2 xerogels sensitized in situ with tetra(4-carboxyphenyl)porphyrins
Tasseroul, Ludivine ULg; Lambert, Stéphanie ULg; Eskenazi, David ULg et al

in Journal of Photochemistry and Photobiology A : Chemistry (2013), 272

TiO2-based materials doped with porphyrins have been prepared using a sol-gel process. To stabilize the TiO2-dye interactions, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl ... [more ▼]

TiO2-based materials doped with porphyrins have been prepared using a sol-gel process. To stabilize the TiO2-dye interactions, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl) porphyrin were introduced in situ into the TiO2 matrix during the sol-gel process rather than by grafting. Samples were thoroughly characterized by TEM, X-ray diffraction, FT-IR, DR-UV/vis and their texture has been examined by nitrogen adsorption-desorption at 77 K. The low thermal treatment allows obtaining anatase-TiO2 particles with high specific surface area without porphyrin degradation. A significant improvement of the photoactivity under visible light of porphyrin doped-TiO2 xerogels was observed for p-nitrophenol and for bacterial degradation. © 2013 Elsevier B.V. All rights reserved. [less ▲]

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See detailDéveloppement d'un photocatalyseur à base d'oxyde de titane pour l'élimination de polluants et de bactéries en milieu aqueux
Tasseroul, Ludivine ULg

Doctoral thesis (2012)

Dans le cadre de la réutilisation des eaux usées et de l’accès limité à l’eau potable dans certaines régions du globe, de nouvelles techniques d’épuration nécessitant de faibles consommations d’énergie ... [more ▼]

Dans le cadre de la réutilisation des eaux usées et de l’accès limité à l’eau potable dans certaines régions du globe, de nouvelles techniques d’épuration nécessitant de faibles consommations d’énergie sont étudiées. Parmi ces nouvelles techniques, la photocatalyse hétérogène utilise des réactions d’oxydation et de réduction pour la dégradation de polluants organiques et de micro-organismes. Le photocatalyseur le plus employé est le TiO2. Lorsqu’il est illuminé par un rayonnement UV, des paires électron/trou sont générées et réagissent avec l’eau et l’oxygène pour former des radicaux libres qui vont dégrader les polluants. Le procédé sol-gel permet de contrôler facilement la texture, la cristallinité, l’introduction de dopants et la mise en forme de matériaux. Il a été utilisé dans ce travail pour la synthèse de photocatalyseurs à base de TiO2, (xérogels). À partir de sols en cours de gélification, des films de TiO2 ont été déposés par spin-coating. Après calcination, ces films sont actifs pour la dégradation du bleu de méthylène sous UV-A. Afin d’améliorer l’activité photocatalytique de xérogels de TiO2, des particules d’argent ont été introduites dans la matrice par cogélification. Ces particules d’argent améliorent l’activité du TiO2 pour la dégradation du bleu de méthylène sous UV-A. En plus de l’amélioration de l’activité photocatalytique, l’extension de l’activation du TiO2 au domaine visible du spectre solaire a été étudiée par sensibilisation avec des porphyrines. Ces porphyrines sont introduites d’une part, par greffage sur le catalyseur Degussa P25 et d’autre part, in situ dans la matrice de xérogels de TiO2. Le greffage des porphyrines ne permet pas l’activation du catalyseur Degussa P25 sous lumière halogène. Par contre, l’introduction in situ des porphyrines permet l’activation du TiO2 avec des longueurs d’onde du domaine visible et améliore ainsi l’activité des xérogels sous lumière halogène pour la dégradation du p-nitrophénol. L’activité antibactérienne de plusieurs catalyseurs préparés au cours de la thèse a également été évaluée pour la dégradation de deux espèces de bactéries : Escherichia coli et Lactobacillus rhamnosus. Cette activité antibactérienne est corrélée à l’activité dépolluante des photocatalyseurs. L’étude cinétique de la dégradation du p-nitrophénol sur un xérogel de TiO2 dopé in situ avec une porphyrine a été réalisée. Cette étude montre que la dégradation implique un type de site actif correspondant aux trous h+ créés lorsque le TiO2 est exposé à la lumière. L’étape limitante correspond à la réaction de surface entre le p-nitrophénol adsorbé et les radicaux OH• adsorbés. Cette étude cinétique utilise une loi sigmoïdale plutôt que linéaire pour modéliser les courbes de dégradation du p-nitrophénol. [less ▲]

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See detailKinetic study of p-nitrophenol photodegradation with modified TiO2 xerogels
Tasseroul, Ludivine ULg; Pirard, Sophie ULg; Lambert, Stéphanie ULg et al

in Chemical Engineering Journal (2012), 191

TiO2 xerogels were sensitized in one step by the in situ introduction of nickel (II) tetra(4-carboxyphenyl)porphyrin (TCPPNi) into the TiO2 matrix during sol–gel synthesis. Crystalline photoactive phase ... [more ▼]

TiO2 xerogels were sensitized in one step by the in situ introduction of nickel (II) tetra(4-carboxyphenyl)porphyrin (TCPPNi) into the TiO2 matrix during sol–gel synthesis. Crystalline photoactive phase TiO2-anatase was obtained without high thermal treatments and was determined by X-ray diffraction. The presence of TCPPNi in TiO2 xerogels was established by DR-UV/Vis and FT-IR spectroscopy. The introduction of porphyrin led to a diminution of the specific surface area of TiO2 xerogels, and this diminution was analyzed by nitrogen adsorption–desorption. The particle size was estimated by SEM. The xerogel surface charge state, which influences the interactions between pollutant and TiO2, was determined by measurement of the point of zero charge. The photoactivity of xerogels was evaluated for p-nitrophenol degradation in aqueous medium at 20 ◦C. Results showed that porphyrin doped TiO2 degraded more than 40% of the p-nitrophenol whereas non doped TiO2 xerogel degraded only 10% of the compound. Moreover, porphyrin was found to improve the photoactivity of TiO2 xerogels in a similar way to UV-A pretreatment. A kinetic study of p-nitrophenol degradation was then performed. Results showed that one type of active site corresponding to the hole of electron–hole pairs was created at the TiO2 surface by light and that the rate determining step was the reaction between the adsorbed p-nitrophenol molecule and the adsorbed OH• radical. The apparent activation energy was found to be equal to 12 kJ mol−1. [less ▲]

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See detailSynthesis by the sol-gel process of visible light sensitive-TiO2 for the degradation of pollutants and microorganisms
Tasseroul, Ludivine ULg; Lambert, Stéphanie ULg; Páez Martínez, Carlos ULg et al

in Récents Progrès en Génie des Procédés, Lavoisier Technique et Documentation, Volume 101, 6 p. (CD-ROM) (2011, November 29)

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR ... [more ▼]

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR and FT-IR spectroscopies were performed to establish the interaction between porphyrins and TiO2. Cristallinity and specific surface area were performed by XRD and nitrogen adsorption-desorption measurements. The photoactivity of doped-TiO2 xerogels was evaluated for p-nitrophenol and Escherichia coli degradation. Under visible light, the samples allowed the degradation of 40% of p-nitrophenol in 6 h and the elimination of 108 CFU/mL of E. coli in 48 h. [less ▲]

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See detailSynthesis by sol-gel process of visible light sensitive-TiO2 for the degradation of pollutants and microorganisms
Tasseroul, Ludivine ULg; Lambert, Stéphanie ULg; Páez Martínez, Carlos ULg et al

Poster (2011)

Since the discovery of photocatalytic decomposition of water on TiO2 electrodes by Fujishima and Honda [1], heterogenous photocatalysis has been widely studied for environmental applications ... [more ▼]

Since the discovery of photocatalytic decomposition of water on TiO2 electrodes by Fujishima and Honda [1], heterogenous photocatalysis has been widely studied for environmental applications. Photocatalytic processes are new technologies for waste water treatment because new compounds (alkanes, pesticides, dyes, etc.) in effluents are not readily degraded by the conventional treatments [2]. Oxidative processes can completely destroy organic pollutants [3] or microorganisms (bacteria, viruses, fungi, etc.) [4,5]. At this moment, the commercial Degussa P25 is the mostly used photocatalyst. Nevertheless, it requires UV light to be activated, that is why scientists try to activate TiO2 under visible light. The aim of this study is to synthesize photocatalysts activated by visible light and to evaluate their activity for the degradation of pollutants and microorganisms. The sol-gel process allows the direct introduction of visible light sensitive species like porphyrins inside the TiO2 matrix during the synthesis [6]. Two tetracarboxyphenyl porphyrins are synthesized for the sensitization of TiO2 to visible light : the metal free tetracarboxyphenyl porphyrin and the nickel tetracarboxyphenyl porphyrin. These porphyrins are characterized by 1H NMR, FT-IR and UV/Vis spectroscopies. They are introduced during the sol-gel synthesis of TiO2 matrix. Diffuse reflectance and FT-IR spectroscopies are used to ensure that porphyrins are incorporated inside the matrix of TiO2. Indeed, characteristic porphyrins peaks appear on spectra. The cristallinity and specific surfaces of catalysts are also determined by XRD and nitrogen adsorption-desorption measurements respectively. The depolluting efficiency of photocatalysts is evaluated for the degradation in water of p-nitrophenol, which is listed as one of the 114 organic pollutants by the Environmental Protection Agency in the US. After 6 h under visible light, 40 % of p-nitrophenol are degraded with some catalysts. The activity is influenced by i) the presence of porphyrins : the photoactivity increases with the amount of porphyrins ; ii) the nature of porphyrins : nickel porphyrins are more active than free metal porphyrins ; and iii) the crystallinity of catalysts : amorphous catalysts are less active than crystallized samples. The photocatalysts with the highest degradation rating of dyes will be selected for the degradation in water of Escherichia coli and Lactobacillus acidophilus. [1] A. Fujishima, K. Honda, Nature 238, 37-38 (1972) [2] P. Gogate, A. Pandit, Advances in Environmental Research 8, 501-551 (2004). [3] D. Chen, A. Ray, Water Research 32, 3223-3234 (1998) [4] R. Watts, S. Kong, M. Orr, G. Miller, B. Henry, Water Research 29, 95-100 (1995). [5] J. Hong, M. Otaki, Journal of Bioscience and Bioengineering 101, 185-189 (2006). [6] C. Wang, J. Li, G. Mele, G.M. Yang, F.-X. Zhang, L. Palmisano, G. Vasapollo, Applied catalysis 78, 218-226 (2007). [less ▲]

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