Banca de DEFESA: LUANA MÁRCIA BEZERRA BATISTA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : LUANA MÁRCIA BEZERRA BATISTA
DATA : 19/10/2018
HORA: 10:00
LOCAL: Sala 3F1
TÍTULO:

SYNTHESIS, CHARACTERIZATION AND EVALUATION OF NIOBIUM COMPOUNDS AS CATALYTIC AGENTS FOR WATER TREATMENT AND GLYCEROL REUSE

PALAVRAS-CHAVES:

niobium compounds, water treatment, glycerol reuse, photocatalysis, pyrolysis

PÁGINAS: 135
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Físico Química Inorgânica
RESUMO:

The largest amount of Niobium reserves of the planet is available at Brazil, which is estimated at approximately 98%. Despite that, the interest of the government in exploiting Niobium is limited, what caused a reduction of the awareness of new environmental and technological applications of niobium-based compounds. Thus, studies focusing on niobium compounds are necessary. Therefore, this research aimed to evaluate the applicability potential of niobium compounds in water treatment and recovery of waste from biodiesel production (glycerol). The results obtained were divided into two different chapters in the format of an article. Regarding water treatment, the use of niobium oxyhydroxide (NbO₂OH) was applied as a catalytic agent in the discoloration of methyl orange using solar photocatalysis. The NbO₂OH was characterized by X-ray diffractometer (XRD), N₂ adsorption and desorption, Fourier-transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV DRS) and point of zero charge (pzc). The characterizations showed that NbO₂OH is a material with amorphous structure, composed of Nb-OH bonds and presents a band-gap of 3.6 eV, which fosters the application of Niobium in photocatalysis. The catalytic efficiency of NbO₂OH was assessed in experiments with different concentrations of methyl orange, H₂O₂, pH and NbO₂OH. The best treatment conditions occurred with the use of 15 mg L^-1of methyl orange, 0.1 M of H₂O₂, pH = 4.0 and 1 g L^-1 of NbO₂OH, resulting in the complete discoloration of the coloring after 10 minutes of treatment. The NbO₂OH was reused and, after five cycles of treatment, the efficiency remained unchanged, which confirms the stability of the niobium compound. Subsequently, Niobium catalysts supported in sodium vermiculite (Nb₂O₅/V0) and in vermiculite treated with 3 mol L^-1 of hydrochloric acid (Nb₂O₅/V3) were prepared using incipient impregnation method. Also, Nb₂O₅ was synthesized to comparison. All catalysts were characterized by N₂ adsorption and desorption, X-ray dispersive spectroscopy (EDS), X-ray diffractometer (XRD), spectroscopy of diffuse reflectance in the visible ultraviolet region (UV DRS) and Raman spectroscopy. The techniques of characterization evidenced the existence of Nb₂O₅ in the TT crystal phase at the surface of V0 support and in the amorphous phase at the surface of V3 support. The best dispersion of niobium oxide occurred in V3 support (S_BET = 464.5 m² g^-1) due to its bigger specific area compared to V0 (S_BET = 0.7 m² g^-1). The glycerol fast pyrolysis using Nb₂O₅/V0, Nb₂O₅/V3 and Nb₂O₅ catalysts was investigated with Py-GC-MS. The results indicated high glycerol conversion using Nb₂O₅ (82.2%), presenting higher yield for oxygenated compounds such as acids (25.1%), alcohols (19.8%) and esters (23.7%). In comparison, a higher deoxygenation occurred in the presence of the catalyst Nb₂O₅/V3 (CO₂ = 6.4%), observing the presence of acids (15.9%), alcohols (19.7%) and aldehydes (10.8%), while esters were not identified. The Nb₂O₅/V0 showed the least influence over all the observed products similarly to the thermal pyrolysis. The distinct behaviors of the three catalysts can be attributed to different levels of acidity and textural properties. The Niobium compounds analyzed are potentially indicated catalysts for the applications addressed in this study, stimulating the development of technologies that use Niobium in Brazil.

MEMBROS DA BANCA:
Presidente - 2140818 - AMANDA DUARTE GONDIM
Interno - 350509 - ANTONIO SOUZA DE ARAUJO
Externo ao Programa - 2011255 - ARUZZA MABEL DE MORAIS ARAUJO
Externo à Instituição - EDJANE FABIULA BURITI DA SILVA - Estácio
Externo à Instituição - NATALY ALBUQUERQUE DOS SANTOS - UFPB