Bactericidal action of TiO2 photocatalysis. Identification of preferential bacterial targets

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TiO2 photocatalysis under UV-A and UV-C radiations applied to water desinfection.

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TiO2 photocatalysis under UV-A and UV-C radiations applied to water desinfection.

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Study of Bioaerosols In Photocatalytic Filters

International @ EAU+FSI:CGUInternational audienceNon

Photocatalytic Inactivation of Bacteria and Fungi Performance and Mechanism

International @ EAU+CGU:STHInternational audienceNon

Comparison of initial photocatalytic degradation pathway of aromatic and linear amino acids

Elsellami, L. Pigeot-Remy, S. Dappozze, F. Vocanson, F. Houas, A. Guillard, C. Sp. Iss. SIInternational audienceAmino acids are at the origin of the formation of odourous compounds after chlorination treatment. Our objectives were to test the efficiency of a photocatalytic process to remove these types of compounds. Five amino acids (AA) - phenylalanine, tyrosine, tryptophan, glycine and alanine - have been chosen as model molecules. The photocatalytic degradation has been investigated in aqueous solutions containing TiO2 suspensions as photocatalysts, in order to assess the adsorption, the disappearance rate and the mechanism of degradation. Results showed that only a small amount of amino acid is adsorbed corresponding to less than 1% of OH covered for aromatic amino acids and about 10% for linear amino acids. A comparison of disappearance rate, total organic carbon (TOC) removal and intermediate for these five amino acids are presented and discussed, taking into account their nature

Comparison of Initial Photocatalytic Degradation Pathway of Aromatic and Linear Amino Acids.

International audienc

Photocatalysis and disinfection of water: Identification of potential bacterial targets

3-4 Pigeot-Remy, S. Simonet, F. Errazuriz-Cerda, E. Lazzaroni, J. C. Atlan, D. Guillard, C.In order to identify some of the potential bacterial targets, the effects of TiO2 nanoparticles on bacteria in aqueous suspension were assessed in the dark and under UV-A (lambda > 340 nm) radiation exposure, using the microorganism model Escherichia coli K-12. Illumination was produced with a HPK 125W lamp and suspended TiO2 Degussa P-25 was used as the photocatalyst, absorbing all the incident UV-A radiations. The impact of the photocatalyst on the bacteria was investigated by monitoring cell cultivability, cell wall integrity and nucleic acid stability. The contact of TiO2 particles with bacteria in the dark increased the bacterial sensitivity to membrane-perturbing agents, suggesting an increase in outer membrane permeability. In contrast, the contact between SiO2 particles, with an average particle size similar to that of TiO2 P-25, and bacteria did not induce any alteration of the cell permeability. The TiO2 deleterious action on the envelope integrity continued during the UV-A radiations exposure. Impacts on bacterial permeability precede the total loss of cultivability. After 2.5 h of photocatalytic treatment at 3.45 mW/cm(2), bacteria were no longer cultivable on their standard growth medium. However, some of them could become cultivable again under specific environmental conditions appropriate to their survival. These resilient bacteria exposed again to UV-A photocatalysis were more resistant to the treatment. Some chemical by-products released during photocatalytic inactivation of the bacteria were also monitored. The appearance of oxamic and oxalic acids as well as ammonium cations, sulfate and nitrate anions were observed. Transmission electron microscopy (TEM) was used to study the morphological damages to E. coli structure during the photocatalytic inactivation of the microorganisms. After 1.5 h of treatment, bacteria showed disorganized membrane structures, while bacteria were still visible although they were no longer cultivable after a longer exposure time. These results were correlated with damages of nucleic acids at in vivo level. An analysis by electrophoresis revealed that bacterial DNA and RNA molecules completely disappeared after 7 h of photocatalytic treatment. (C) 2011 Published by Elsevier B.V

Photocatalysis and disinfection of water.

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Photocatalysis and disinfection of water.

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