Banca de DEFESA: ERIK ALEXANDER CUNHA FERREIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : ERIK ALEXANDER CUNHA FERREIRA
DATA : 31/08/2018
HORA: 14:00
LOCAL: Auditório do CCET
TÍTULO:

Study of the influence of pH on the production of silver molybdates modified by the sleepchemical method.

PALAVRAS-CHAVES:

Silver molybdate; sonochemical method; methylene blue; catalysis

PÁGINAS: 100
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
ESPECIALIDADE: Cerâmicos
RESUMO:

Silver-based semiconductors have attracted significant attention because of their unique photosensitivity which provides these materials with excellent photocatalytic activity due, among other factors, to the effects of plasmon resonance. Silver molybdates are a family of semiconductor materials belonging to the group of transition metal oxides with high technological value due to their diverse applications, among which are those of catalysis. In this dissertation, the study of the structural and morphological properties of silver molybdates was carried out, as well as their influence on the degradation of the methylene blue dye. Silver molybdates were obtained by coprecipitation of solutions in a controlled chemical environment in the range of pH 2 to pH 7, followed by sonochemical treatment. For a reaction medium of pH 1 and pH 8, no precipitation is observed, with powders being formed only after the sonochemical synthesis. Through the X-Ray Diffraction Technique, it was observed that the synthesized materials crystallize in the structures indexed to the crystallographic cards Ag₂Mo₃O₁₀•2H₂O, Ag₂Mo₂O₇ and Ag₂MoO₄, as a function of the pH of the reaction medium. Field Emission Electron Microscopy analysis showed that the Ag₂Mo₃O₁₀•2H₂O and Ag₂Mo₂O₇ structures exhibit nanorods morphology, while the Ag₂MoO₄ structures show irregular morphology, with both morphologies obtained after the sonochemical treatment, presenting a high number of silver precipitates on the surface. UV-Visible spectroscopy analysis by diffuse reflectance was performed to estimate the optical band-gap value. The degradability of the methylene blue dye (MB) as well as stability for the reuse of the synthesized materials were evaluated. Complete discoloration of the MB dye containing solution was observed after 5 minutes exposure of the Ag₂Mo₃O₁₀•2H₂O powders and 15 minutes exposure of Ag₂Mo₂O₇ without external irradiation and without loss of efficiency after 3 cycles of adsorption. The degradation of methylene blue dye under UV irradiation was observed for Ag₂MoO₄ structure, where complete discoloration of MB dye was observed after 60 minutes, with stable semiconductor result in reuse.

MEMBROS DA BANCA:
Interno - 1802888 - FABIANA VILLELA DA MOTTA
Externo à Instituição - MARIO GODINHO JUNIOR - UFG
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO