Synthèse des poudres nanométriques de TiO2 et ZnO pures et dopées en vue de leur utilisation dans le domaine de la dépollution de l’eau.

Abstract

ZnO powders were synthesized by sol-gel route with ([Zn(OOCCH3)2.2H2O], > 99.9%) as precursor and at room temperature. The powders were annealed for 1 hour at temperatures between 500 and 900°C. The effects of aluminum doping have been studied. We also explored the effect of the thermal budget on the properties of pure and aluminum-doped ZnO nanostructures. The powders were analyzed by X-ray diffraction (XRD), Raman spectroscopy and the scanning electron microscopy techniques were used for the observations of agglomerates. The photocatalytic activities of ZnO powders were evaluated using the Methylene Blue (MB) degradation reaction. The results show that at 700°C, we have amalgamation of ZnO and aluminum. We observe the formation of the spinel phase for 10% and 20% aluminum doping. The photocatalytic activities of ZnO powders were evaluated using the Methylene Blue (MB) degradation reaction. The results show that for the case of nanoparticles calcined at 700°C the highest photocatalytic activity wich is obtained for pure ZnO then ZnO doped with 20% .The titanium oxide (TiO2) powders were synthesized by a solgel route with TiCl4 as precursor and at the ambient .The powders have been dried up at 100 0C during 12 h and annealed during 1h at temperatures between 400 and 800 0C. In the present work, the effects of dissolved ions (e.g. Na+, Cl- and F-) on the structural, particle morphology were investigated using various additives as NaCl, NaOH, HCl, and HF. The powders were analyzed by X-ray diffraction (XRD), Raman spectroscopy and the scanning electron microscopy techniques wer used for agglomerate observations. The photocatalytic activities of the TiO2 powders were evaluated using the degradation reaction of Methylene Blue (MB).The results show that the presence of Na+ accelerates the transition from anatase to rutile while that of Cl- and F- delays this transition. The additives modify the pH of the solution and as result the size of the spherical agglomerates, which are constituted of nanoparticles crystalline. These agglomerates are constituted of grain whose size depends on the temperature. A more acid solution leads to smaller agglomerates of 0.5 m size which is a solution that is more basic give bigger agglomerates. The better photoactivity is obtained in anatase/rutile mixture with high fraction of the rutile. Na+ in the TiO2 films affect the photocatalytic activity. The surface states on the metal oxide has a considerable influence on the photocatalytic activity with varying pH.