Banca de QUALIFICAÇÃO: ISLANNY LARISSA OURIQUES BRASILEIRO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : ISLANNY LARISSA OURIQUES BRASILEIRO
DATA : 30/11/2018
HORA: 14:00
LOCAL: Sala de aula do NUPEG
TÍTULO:

"Synthesis of mixed oxides of a-Fe₂O₃/Nb₂O₅ and its application as catalysts in oxidation reactions"

 

PALAVRAS-CHAVES:
PÁGINAS: 126
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Química
RESUMO:

Develop new catalysts with high efficiency for the degradation of organic compounds in effluents, mediated by sunlight and that are stable, has been a great challenge. The textile industry highlights as one of the main sources of environmental pollution by the generation of high volumes of effluents containing synthetic dyes. In this context, Advanced Oxidative Processes, such as heterogeneous photocatalysis and heterogeneous Fenton process, are a promising alternative for these contaminants degradation. In this work, mixed oxides of a-Fe₂O₃/Nb₂O₅ were prepared from a Pechini sol-gel route, with two different mass ratios (a-Fe₂O₃ and Nb₂O₅ (60/40 and 80/20, respectively) and calcination temperatures between 500 and 800 ° C. The influence of these parameters was investigated on the materials structural, morphological, optical and photocatalytic properties. These catalysts were submitted to methylene blue (MB) degradation tests by both photocatalysis and photo-Fenton reaction. The best performing sample in these initial tests was used in the following tests to optimize the process operating conditions. An experimental design was used for a preliminary investigation of the variables behavior that affect the system and its possible interactions. The catalytic reaction mechanism, the limiting step, the reaction rate law and the catalyst stability were also evaluated.Crystalline nanoparticles were obtained with significant differences in their properties and in the degradation efficiency of the methylene blue dye under UV-Vis radiation. Calcination temperatures between 500 and 800 °C led to the formation of different crystalline phases, including: a-Fe₂O₃, Nb₂O₅, FeNbO₄ and FeNb₂O₆; as well as the formation of materials with multigap behavior. High temperatures caused the increase of the particle size and the agglomerative state of the material. The sample composed of 60 % a-Fe₂O₃ and 40 % of Nb₂O₅ and calcined at 500 ºC (0,6-Fe/Nb-1) presented the highest catalytic activity and was then used in the following tests in photo-Fenton-like reactions. According to the experimental design 2⁴ performed, the variables that presented a significant effect on the response were: AM, catalyst and H₂O₂ concentrations. The proposed mechanism followed an LH type kinetics, with the highest removal percentage obtained at 85 % after 4 h of experiment, under the optimum operating conditions found. Compared to a-Fe₂O₃ and Nb₂O₅, removal percentages were increased by 62 and 15 %, respectively. The catalyst was stable even after 5 consecutive cycles of reaction, unlike Nb₂O₅, suggesting its potential application in the treatment of environmental pollutants.

MEMBROS DA BANCA:
Interno - 2929066 - ANDRE LUIS LOPES MORIYAMA
Presidente - 349801 - CARLSON PEREIRA DE SOUZA
Interno - 2275848 - ELISAMA VIEIRA DOS SANTOS
Externo à Instituição - MAITÊ MEDEIROS DE SANTANA E SILVA - UFRN
Externo à Instituição - VIVIAN STUMPF MADEIRA - UFPB