Banca de QUALIFICAÇÃO: LUANA MÁRCIA BEZERRA BATISTA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : LUANA MÁRCIA BEZERRA BATISTA
DATA : 28/05/2018
HORA: 09:00
LOCAL: Auditório do química 3
TÍTULO:

SYNTHESIS, CHARACTERIZATION AND EVALUATION OF NIOBIUM COMPOUNDS AS CATALYSTS FOR WASTE RECYCLING AND WATER TREATMENT

PALAVRAS-CHAVES:

vermiculite, acid activation, niobium oxide, glycerol, niobium oxyhydroxide, methyl orange

PÁGINAS: 160
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Físico Química Inorgânica
RESUMO:

Brazil has the largest amount of niobium reserves on the planet, estimated at approximately 98%. Despite this, the government's interest in mineral exploration is limited, which has reduced the country's knowledge of numerous environmental and technological applications of niobium compounds. Thus, studies aimed at adding value to niobium and its compounds are essential. Therefore, this thesis evaluated the potential of different niobium compounds in the following applications: (I) valorization of the residue of biodiesel production (glycerol) and (II) water treatment. The results achieved were divided into the article format into two separate chapters. In Chapter 1, niobium catalysts supported on sodium vermiculite (Nb₂O₅/V0) and treated with hydrochloric acid (Nb₂O₅/V3) were prepared by the incipient impregnation method. For comparison, Nb₂O₅ was also synthesized. All catalysts were characterized by N2 adsorption and desorption, X-ray dispersive spectroscopy, X-ray diffractometry, diffuse reflectance spectroscopy in the visible ultraviolet region and raman spectroscopy. The characterization techniques evidenced the presence of Nb2O5 in the crystalline phase TT on the surface of the V0 support and in the amorphous phase on the surface of the support V3. The best dispersion of the niobium oxide was in the support V3 (S_BET = 464. 5 m² g^-1), due to its greater specific area compared to V0 (S_BET = 0.7 m² g^-1). Flash pyrolysis of the biodiesel production residue (glycerol) under the catalysts Nb₂O₅/V0, Nb₂O₅/V3 and Nb₂O₅ was investigated using the Py-GC-MS instrument. The results showed high conversion of glycerol to Nb₂O₅ (82.2%), with higher yields for oxygenated products, such as carboxylic acids (35.8%) and esters (23.7%). In the presence of the Nb₂O₅/V3 catalyst, higher deoxygenation (CO₂ = 6.4%) occurred, not identifying esters, favoring acids (31%) and aldehydes (10.8%). Nb₂O/V0 exerted the weakest influence on all identified products, similar to thermal pyrolysis. The different catalytic behaviors of the three catalysts can be attributed to their different acidity and textural properties. In Chapter 2, the niobium oxyhydroxide catalyst (NbO₂OH) was applied in the treatment of water, by means of discoloration of the orange methyl dye using solar photocatalysis. NbO₂OH was characterized by X-ray diffraction, N₂ adsorption and desorption, Fourier transform infrared spectroscopy, scanning electron microscopy, diffuse reflectance spectroscopy in the visible ultraviolet region and zero charge point. The characterization elucidated that the NbO₂OH is a material with amorphous structure, constituted by Nb-OH bonds and with a band gap equal to 3.6 eV, favoring its application in photocatalysis. The catalytic efficiency of NbO₂OH was evaluated by varying the concentrations of dye, H₂O₂, pH and NbO₂OH dosage. The best treatment conditions were 15 mg L^-1 dye, 0.1 M H₂O₂, pH = 4.0 and 1 g L^-1 NbO₂OH, resulting in complete discoloration of the dye after 10 minutes of treatment. NbO₂OH was reused and at the end of five treatment cycles, the efficiency remained unchanged, confirming its stability. The studied niobium compounds are promising catalysts for both applied applications, serving as a stimulus for the development of niobium technology in our country.

MEMBROS DA BANCA:
Presidente - 2140818 - AMANDA DUARTE GONDIM
Interno - 350509 - ANTONIO SOUZA DE ARAUJO
Externo ao Programa - 2011255 - ARUZZA MABEL DE MORAIS ARAUJO