Banca de DEFESA: ONÉCIMA BIATRIZ DE MEDEIROS RAMALHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ONÉCIMA BIATRIZ DE MEDEIROS RAMALHO
DATE: 30/04/2024
TIME: 09:00
LOCAL: Sala virtual
TITLE:

OBTAINING THE CdMo1-XWXO4 SOLID SOLUTION AND STUDYING ITS PHOTOCATALYTIC PROPERTIES

KEY WORDS:

cadmium molybdate, cadmium tungstate, solid solutions, photoluminescence, photocatalysis.

PAGES: 101
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

Materials from the molybdate and tungstate families, with ABO₄ type structures, have been studied in recent times due to their good photoluminescent and photocatalytic properties, including cadmium molybdate (CdMoO₄) and cadmium tungstate (CdWO₄). Solid solutions of CdMo_1-xW_xO₄, with x = 0; 0.25; 0.5; 0.75 and 1% mol, were synthesized using the microwave-assisted hydrothermal method, using two solvents: deionized water and PEG-400. The structure of the samples was characterized by x-ray diffraction (XRD), the morphology analyzed by field emission scanning electron microscopy (SEM-FEG). The optical properties were evaluated through UV-Vis analysis, Raman spectroscopy and photoluminescence (FL) and the photocatalytic activity was evaluated through the degradation of methylene blue and methyl orange dyes, as well as the mixture between them. The XRD patterns showed that the samples with x = 0 and x = 1, for the hydrothermal method with deionized water, have scheelite and wolframite structures, respectively, and the intermediate compositions are a mixture of the two phases. For the samples obtained with the PEG-400 solvent, a continuous solid solution with a scheelite structure is formed up to the composition x = 0.75. Raman spectroscopy showed changes in local order-disorder when tungsten was added to the structure in both methods. The SEM-FEG analysis showed that the morphology of the samples is polyhedra and rod-shaped for the samples with deionized water, and irregular for the samples with PEG-400. The band gap energy varied between 3.46 and 4.03 eV, and this value decreased as the tungsten atoms were inserted into the CdMoO₄ structure, in both methods. The photoluminescent spectra of the samples have a broadband behavior, and most of the powders have emission in the orange-red region. The photocatalytic activity was evaluated against methylene blue and methyl orange, this showed that the samples present good photocatalytic activity for the methylene blue dye and the same occurred in the mix of dyes, corroborating with the zeta potential analysis that showed a surface with negative charges. Reuse showed that the crystalline structure of the solid solution remained stable after four cycles, making it possible to reuse it without losing efficiency.

COMMITTEE MEMBERS:
Presidente - 1802888 - FABIANA VILLELA DA MOTTA
Interno - 1883170 - MAURICIO ROBERTO BOMIO DELMONTE
Externo à Instituição - LUÍS PRESLEY SEREJO DOS SANTOS - UNIFESP
Externa à Instituição - RENATA CRISTINA DE LIMA - UFU
Externa à Instituição - VIVIANE DA SILVA PINHEIRO - IFRN