SYNTHESIS, CHARACTERIZATION AND THEORETICAL CALCULATIONS OF ZNTIO3 FOR THE ADSORPTION AND PHOTOCATALYTIC REMOVAL OF METHYLENE BLUE DYE
Currently, nanomaterials have aroused great interest for environmental applications, such as the removal of colorants in wastewater. The purpose of this thesis was the preparation of structured materials with adsorbent and photocatalytic properties for the removal of the cationic methylene blue (MB) dye in aqueous solutions. To do this, initially, several Ecuadorian clays were collected and characterized, which were used as supports for photocatalysts prepared based on zinc and titanium. The photocatalysts ZnTiO3/TiO2, ZnTiO3/TiO2/La and TiO2 (anatase phase) were synthesized by the sol-gel method. G-Clay and R-Clay clays were used as raw material sources to synthesize FAU and LTA zeolites, respectively, by alkaline fusion and hydrothermal method. The zeolites were combined with their precursor clays and with the photocatalysts to prepare pellets that were successfully used in MB removal tests in aqueous solutions. The experimental isotherms were adjusted to the Langmuir model and the experimental kinetics to the pseudo-second-order model, which showed monolayer adsorption on a surface that contained an infinite number of identical sites, maintaining a constant adsorption rate during the process. Finally, a comparative study was carried out using computational simulation to determine the MB adsorption mechanism on the surfaces (101) of ZnTiO3 and TiO2 (anatase phase). The DFT calculations were developed using the VASP code. The results showed that the adsorption of MB on the surface (101) of ZnTiO3 is stronger than on the surface (101) of TiO2. The large bandgap calculated also showed that ZnTiO3 can potentially be used as a photocatalyst, which would allow complete degradation of MB after being adsorbed. In this way, the feasibility of using ZnTiO3 as an adsorbent and photocatalytic material for the removal of methylene blue in aqueous systems was experimentally and computationally corroborated.
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