Synthesis Design of TiO 2 Nanotubes and Nanowires and Photocatalytic Applications in the Degradation of Organic Pollutan
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Synthesis Design of TiO2 Nanotubes and Nanowires and Photocatalytic Applications in the Degradation of Organic Pollutants in the Presence or not of Microorganisms Asma Turki1,2, Pilar Fernández Ibáñez3, Abdelhamid Ghorbel1, Hafedh Kochkar1, Chantal Guillard2 and Gilles Berhault2 1 Laboratoire de Chimie des Matériaux et Catalyse, University El Manar, Tunis, Tunisia 2 Institut de Recherches sur la Catalyse et l’Environnement (IRCELYON), CNRS – University Lyon I, Villeurbanne, France 3 Plataforma Solar de Almería, Tabernas, Spain ABSTRACT 1 D TiO2 nanomaterials (nanotubes, nanowires) were synthesized through hydrothermal treatment of TiO2 powder (P25) in concentrated alkaline solutions (NaOH for nanotubes, KOH for nanowires) followed by calcination at varying temperatures between 400°C and 700°C. Samples were characterized by HRTEM, XRD, Raman spectroscopy, and N2 adsorptiondesorption isotherms. High surface area nanotubular TiO2 materials can maintain their 1D morphology up to a temperature of calcination of 400°C while changing their phase from hydrogenotitanate to anatase. The use of KOH leads to a retarded formation of anatase. Photocatalytic results showed that TiO2 anatase nanotubes calcined at 400°C can degrade formic acid with a rate constant four times higher than for P25. A direct correlation between surface area and photocatalytic activity explains the much higher activity of TiO2 anatase nanotubes. On the opposite, for the degradation of phenol, P25 remains more active. In the disinfection of water, contrary to P25, the high surface area of TiO2 nanotubes allows the simultaneous degradation of formic acid and the inactivation of pathogen fungus showing the interest of such materials for the treatment of wastewater. INTRODUCTION 1 D TiO2 nanomaterials have attracted great attention in the last years as potential candidates for highly efficient photocatalysts [1]. Indeed, these nanostructured materials present several interesting properties like an enhanced stability at high temperature, open mesoporous morphology, high surface area, high cationic exchange capacity, high proton conductivity and low rate of electron-hole recombination. These materials can be obtained using three general methods: using a chemical template, electrochemically or using a hydrothermal treatment. The hydrothermal treatment involves treating a TiO2 precursor in an autoclave using a concentrated alkaline solution [2]. This method presents the advantage to be simple, not expensive and easy to scale up. 1D TiO2 nanomaterials prepared by this technique are therefore ideal candidates as photocatalysts for wastewater treatments. In the present study, 1D TiO2 nanotubes and nanowires calcined at different temperatures will be compared to P25 to evaluate their potential interest for the degradation of common organic pollutants (formic acid and phenol). They will be also evaluated under real solar conditions for the inactivation of a pathogen fungus, Fusarium Solani in the presence or not of formic acid.
EXPERIMENT Titanate nanotubes were pr
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