Synthèse et Caractérisation des Nanocomposites TiO /SiO et TiO /SiO / 22 22 (Ag ou Cu) : application à la Minéralisation Photocatalytique du Diclofénac de sodium en solution aqueuse

Abstract

The present work in the fields of nanotechnology and heterogeneous photocatalysis focuses on the development of a sol-gel method for the synthesis of binary TiO /SiO and ternary TiO /SiO /(Ag or Cu) nanomaterial composites. This method is centered on the surface reduction of Ti ions to Ti , which advocates the creation of electronic states below the TiO2 3+ 3+ conduction band and oxygen vacancies. Ti ions act as a sub-band gap to reduce the rate of recombination of photogenerated electron/hole pairs. SEM analysis showed that the synthesis method proposed in this work resulted in very homogeneous composites, with good dispersion of the silica nanoparticles on the surface of the TiO2 nanoparticles, and consequently avoid any particle agglomeration effect. The BET analysis showed that grafting the silica nanoparticles on the surface of the TiO2 nanoparticles increased the specific surface area of the nanocomposites synthesized. The ATG/DSC and XRD analysis showed clear thermal stability, high crystallinity, with anatase as the predominant phase. XPS and UV-visible reflectance showed a surface reduction of Ti ions to Ti , and the presence of Silver or Copper on the surface of the materials increased the absorption capacity of TiO2 in the visible region. The study of the photocatalytic mineralization of diclofenac under UV irradiation showed an excellent degradation capacity of the TiO /SiO 20 % composite with 4+ 3+ 22 a percentage of 97.03 %, and excellent photocatalytic mineralization compared with commercial TiO2-P25 (83.68 % after 120 min irradiation). The diclofenac mineralization study under solar irradiation by ternary composites showed that the addition of Silver or Copper within the binary composite improved the mineralization efficiency with a percentage of 85.33 and 86.43 % for the material doped with Silver and Copper respectively. Reusing of ternary catalysts showed that the Copper-doped composite is a suitable material for the degradation of sodium diclofenac under solar irradiation, especially because it is the composite with the less expensive and most stable metal that could be used successfully for five successive cycles without any noticeable loss of performance. This work has enabled us to valorise Cameroon’s local resources: agricultural waste, in particular rice husks, adding to use the solar potential.