Banca de DEFESA: JOYCE MARINA PAIVA DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JOYCE MARINA PAIVA DA SILVA
DATE: 18/02/2022
TIME: 14:00
LOCAL: Sala virtual (videoconferência)
TITLE:

Synthesis and characterization of Ag₂CrO4:Ag₂MoO₄ and Ag₂CrO₄:Ag₂WO₄ heterostructures with photocatalytic properties

KEY WORDS:

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

PAGES: 92
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

The incorrect disposal of organic pollutants into the environment has been increasing interest in materials with photocatalytic properties that are capable of degrading different components, such as dyes present in effluents. In this work, the synthesis method by coprecipitation at 70ºC was used to obtain heterostructures of Ag₂CrO₄:Ag₂MoO₄ and Ag₂CrO₄:Ag₂WO₄, in which Mo and W were inserted in the proportions of 0; 0.25; 0.5; 0.75 and 1 mol%. The nanoparticles obtained were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (SEM-FEG) and ultraviolet visible spectroscopy (UV-Vis). For the 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 confirmed the achievement of the investigated phases, indicating the efficiency of the synthesis by coprecipitation for the samples obtained. Raman spectroscopy revealed significant changes in the local order-disorder as a function of the gradual replacement of the lattice former. The images obtained by SEM-FEG indicated that the samples composed of two phases presented a morphology formed by the mixture of the respective pure phases. All heterostructures obtained showed absorption for longer wavelengths, and lower gap energies, when compared to pure Ag₂MoO₄ and Ag₂WO₄ phases. The photocatalytic activity was investigated and the results indicated that all samples showed good catalytic activity against methylene blue, and all heterostructured samples were more efficient than pure Ag₂MoO₄ and Ag₂WO₄ phases, with efficiency of 95% and 99%, respectively. The reuse cycles indicated high potential for practical application in wastewater, due to the capacity of consecutive cycles for photodegradation. Furthermore, the test against the dye mixture indicated that the efficiency of the photocatalytic activity will be dependent on the complexity of the molecules involved.

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