masterThesis
Estudo, preparo e caracterização de nanocompósitos mesoporosos de Diatomita/Nb2O5/TiO2 para o tratamento de águas contaminadas
Fecha
2022-04-13Registro en:
FERNANDES, Yuri Leandro Rodrigues Lopes. Estudo, preparo e caracterização de nanocompósitos mesoporosos de Diatomita/Nb2O5/TiO2 para o tratamento de águas contaminadas. 2022. 134f. Dissertação (Mestrado em Ciência e Engenharia de Materiais) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2022.
Autor
Fernandes, Yuri Leandro Rodrigues Lopes
Resumen
The emerging need for more efficient water treatment methods has become a problem
beyond the scientific character: it covers ethical, economic and social issues. The
advancement of the understanding about the mechanisms of filtration and treatment of
contaminated water by porous matrix composites, such as diatomite, stimulated the
development of this work. In this study, white diatomite ceramic powder was used to
fabricate porous composites incorporated by Nb2O5 and TiO2 particles through the
Tape Casting technique. Four ceramic-polymer tapes of ceramic mass composition
(diatomite/TiO2/Nb2O5) were obtained: tape a (1/0/0); tape b (0.9/0.1/0); tape c
(0.9/0.05/0.05); and tape d (0.9/0/0.1). Finally, six-layer laminates were arranged,
thermo-pressed, calcined at 500 ºC and sintered at 1200 ºC, giving rise to the A - E
ceramic wafers. The thermal behavior of the tapes was determined by
thermogravimetric analysis (TG). Aiming to verify the effect of the processing route and
composition on the morphological characteristics, the composition of crystalline
phases, flexural strength, porosity profile and the adsorptive and photodegradation
properties, the wafers were characterized by X-ray diffraction, field emission scanning
electron microscopy, three-point bending test, N2 physisorption, photodegradation test
and Egap determination aided by UV-vis spectrophotometer. The resulting ceramic
composites were found to have high porosity morphologies and monolithic characters.
The crystalline phases cristobalite, quartz, anatase, rutile, and H-Nb2O5 were
identified; by which an evolution of the crystalline structure, elimination of the
amorphous zone, as well as the partial transformation of anatase-rutile phase was
noted in wafers B and C. The bending test demonstrated an increase of up to 225%
in strength through incorporation of the particles into the diatomite matrix, from 4.28
Mpa in wafer A to 13.90 Mpa in wafer C. The wafers exhibited a mesoporous structure,
with narrowing of the pore size distribution and surface areas between 6.161 m²/g and
3.6 m²/g. A decomposition of up to 87.3% of methylene blue was observed across the
composites, whose Egap values are in the range of 3.19 eV – 3.70 eV.