Banca de DEFESA: MÁRCIA MICHELLY VIEIRA DE MENDONÇA
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.DISCENTE : MÁRCIA MICHELLY VIEIRA DE MENDONÇA
DATA : 25/08/2023
HORA: 14:30
LOCAL: https://meet.google.com/qdg-nsxf-txj
TÍTULO:
SYNTHESIS, CHARACTERIZATION AND PHOTOCATALYTIC APPLICATION OF ZINC OXIDE AND ZINC CERIOUS OXINITIDE.
PALAVRAS-CHAVES:
Oxynitrides; photocatalytic degradation; losartan potassium degradation; hydroxychloroquine degradation.
PÁGINAS: 94
GRANDE ÁREA: Outra
ÁREA: Ciências Ambientais
RESUMO:
The presence of drugs in effluents and aquatic matrices causes great concern, because even at low concentrations they can cause adverse effects on human health and natural ecosystems. Hence the need to develop new processes or improve existing treatment techniques, such as photocatalysis, for the degradation of pollutants. In this work, the semiconductors ZnO and zinc cerium oxynitride (ZnCeON) were synthesized, and their photocatalytic activities were evaluated in relation to the degradation of hydroxychloroquine (HCQ) and Losartan Potassium (LP), respectively. The synthesis method was the reaction of combustion in solution, through the exothermic reaction between the oxidants (zinc nitrate and cerium nitrate) and the organic fuel (urea); each material was produced in three different fuel/oxidant ratios (Ø). The photocatalysts were characterized by thermogravimetric analysis (TGA), x-ray diffraction (DRX), diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM). For the photocatalytic tests, a mercury vapor lamp was used and the process was monitored by spectrophotometry in the UV-Vis region, comparing it with photolysis results. The effects of photocatalyst concentration and initial solution pH were evaluated. The HCQ mineralization was evaluated by means of total organic carbon removal and the formed short-chain organic acids were identified by ion chromatography. TGA showed that ZnO had low mass loss, indicating thermal stability, and that ZnCeON had impurities and large mass loss, requiring calcinations at 400 °C for 2h30min for all Ø. XRD showed the formation of the hexagonal wurtzite structure for all materials; FTIR showed the purity of the calcined ZnCeON in all Ø and the presence of bands corresponding to Zn-O, Ce-O and Zn-N bonds; ERD showed redshift for all ZnO Ø and band gap between 3.05 and 3.10 eV; SEM showed that at all Ø, ZnO presented nanoflower morphology, but the ZnO-1.1 sample also showed nanowires and nanorods on its surface. The degradation of HCQ over ZnO was influenced by the concentration of the catalyst and the pH of the initial solution. The concentrations of 500 and 1000 ppm of ZnO had similar performances, 84.74% and 87.46%, respectively, so that the use of 500 ppm promotes an economy of 50% in mass of the catalyst; the process corresponded to a pseudo-second order reaction with rate constants (k) of 1.89 x 10-4 min-1 and 1.41 x 10-4 min-1, for 500 and 1000 ppm, respectively. The pH study indicated that the best performances were obtained at pH 6.4, corroborated with a mineralization of 29.86%. Studies with ZnCeON showed that 30 min is enough to guarantee LP adsorption/desorption balance in the photocatalyst and that the catalyst with Ø = 5 has the best performance in photodegradation of LP (removal of 63.64%). The catalyst concentration and pH also influenced the process. The best results were obtained with 250 and 500 ppm of the catalyst, removing 44.84% (k = 1.89 x 10-4 min-1) and 64.30% (k = 1.41 x 10-4 min-1) of LP, respectively. The neutral medium (pH 6.8) provided a more efficient degradation of the LP, both in terms of absorbance removal (44.84%) and mineralization (34.4%). Both semiconductors are promising alternatives for the photodegradation of drugs in environmental matrices.
MEMBROS DA BANCA:
Presidente - 2470 - SUELY SOUZA LEAL DE CASTRO
Interna - 7961 - ANNE GABRIELLA DIAS SANTOS CALDEIRA
Externo à Instituição - CARLOS ALBERTO MARTINEZ HUITLE