Banca de QUALIFICAÇÃO: JOYCE MARINA PAIVA DA SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : JOYCE MARINA PAIVA DA SILVA
DATE: 17/11/2021
TIME: 14:00
LOCAL: Sala virtual (videoconferência)
TITLE:

SYNTHESIS AND CHARACTERIZATION OF AG2Cr1-xMoxO4 AND Ag2Cr1-yWyO4 PARTICLES WITH PHOTOCATALYTIC PROPERTIES

KEY WORDS:

Ag₂CrO₄, Ag₂MoO₄, Ag₂WO_4, heterostructures, coprecipitation, photocatalysis.

PAGES: 77
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

Improper disposal of organic pollutants into the environment has been increasing interest in materials with photocatalytic properties. These materials are capable of degrading different components, such as dyes present in effluents.  In this work, the coprecipitation synthesis method was used to obtain particles of Ag₂Cr_1-xMo_xO₄ and Ag₂Cr_1-yW_yO₄, where x and y = 0; 0.25; 0.5; 0.75 and 1 mol%. The nanoparticles obtained were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and visible ultraviolet spectroscopy (UV-Vis). For photocatalytic properties, tests were performed against methylene blue dye and against a mixture of dyes (methylene blue, methyl orange and rhodamine-B). The XRD results showed that the synthesis by coprecipitation was efficient to obtain the pure phases and samples with intermediate composition, and Raman spectroscopy confirmed the presence of two phases in the samples with intermediate composition, indicating the formation of heterostructures. The images obtained by SEM indicated that the samples of intermediate compositions showed a mixture of the morphologies of pure phases, with an irregular morphology for the Ag₂CrO₄ sample, in coral shape for the Ag₂MoO₄ sample and rod-shaped morphology for the sample of Ag₂WO₄. All intermediate composition showed absorption for longer wavelengths and lower gap energies, when compared to the pure phases of Ag₂MoO₄ and Ag₂WO₄. Photocatalysis indicated that all samples showed good catalytic activity against methylene blue, all intermediate composition being more efficient than the pure phases of Ag₂MoO₄ and Ag₂WO_4, with 95% and 99% efficiency, respectively. Reuse cycles indicated high potential for practical application in wastewater, due to the ability of consecutive cycles for photodegradation. Furthermore, the test against the mixture of dyes indicated that the efficiency of the photocatalytic activity will depend on the complexity of the molecules involved.

BANKING MEMBERS:
Presidente - 1802888 - FABIANA VILLELA DA MOTTA
Interno - 1883170 - MAURICIO ROBERTO BOMIO DELMONTE
Externo à Instituição - MARIO GODINHO JUNIOR - UFG