Banca de QUALIFICAÇÃO: ERIK ALEXANDER CUNHA FERREIRA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : ERIK ALEXANDER CUNHA FERREIRA
DATA : 28/05/2018
HORA: 14:00
LOCAL: Auditório do CCET
TÍTULO:

Study of pH variation in the synthesis and photocatalytic properties of silver molybdate obtained by the sleepchemical method.

PALAVRAS-CHAVES:

Silver molybdate, sleepchemical synthesis, photocatalysis, pH control.

PÁGINAS: 100
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

The structure and morphology of the nanostructured molybdates is strongly dependent on the preparation method and the reaction medium. In this work the influence of the H + concentration on the formation of silver molybdate structures through the sleepchemical method was studied. Silver molybdate powders were prepared by the sleepchemical method. Initially, an aqueous solution of silver nitrate and molybdic acid at controlled pH in the range of 1 to 9 was prepared. The synthesized samples were structurally characterized by X-ray diffraction (XRD) technique and morphologically by scanning electron microscopy technique. field emission (MEV-FEG). The optical properties of the synthesized silver molybdates were characterized by UV-Visible (UV-Vis) spectroscopy. The photocatalytic activity was evaluated by the degradation of methylene blue dye under UVA irradiation. The results of X-ray diffraction indicated the influence of pH on the formation of silver molybdates with the monoclinic Ag2Mo2O7 crystalline phase being obtained at pH 3 and pH 4, a mixture of the monoclinic Ag2Mo2O7 and Ag2MoO4 crystalline phases at pH 5 and crystalline phase Ag2MoO4 obtained at pH 6, pH7 and pH8. In the SEM-FEG analysis it was verified that the pH has control over the growth of the particles, with morphology of nanobastones of diameter smaller than 50 nm and length above 1 μm being obtained in the range of pH 1 to pH 5. Micrometric particles with morphology irregular and larger than 1 μm sizes were obtained in the range of pH 5 to pH 8. The band gap energy (Egap) varied 0.5 eV almost linearly as a function of the pH of the reaction medium, indicating that the H + concentration of the precursor solution directly influences the formation of silver molybdate structure. The results of the degradation of the methylene blue dye catalyzed by the silver molybdates showed to be efficient, presenting complete degradation of the dye in 120 minutes for the powders synthesized at pH 7, 110 minutes for the powders synthesized in reaction medium of pH 6 and 8 , 40 minutes for powders synthesized at pH 5, and complete adsorption of the dye by the synthesized powders in the range of pH 1 to pH 4 after 10 minutes in a sleepchemical bath without light incidence.

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