Banca de DEFESA: MICHAEL SEGUNDO SENA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : MICHAEL SEGUNDO SENA
DATA : 08/09/2016
HORA: 14:00
LOCAL: AUDITÓRIO DO NUPEG
TÍTULO:

Evaluation of Photocatalytic Potential of Cerium Molybdate Obtained from EDTA-Citrate Method on Methylene Blue Degradation

PALAVRAS-CHAVES:

Cerium Molybdate, Synthesis, EDTA/Citrate, Experimental Design, Photocatalysis, Methylene Blue

PÁGINAS: 98
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Química
RESUMO:

In this work, Cerium Molybdate (Ce₂(MoO₄)₃) was synthesized and characterized, obtained with the method of combined complexation EDTA-Citrate. The synthesis parameters were investigated to evaluate the influence of pH (5, 7,5 and 10), calcining time (3, 4 and 5h) and heating rate (5, 7 and 10°C.min^-1) on phase formation, average crystallite size and the material band gap. The samples obtained were characterized by TG/DSC, XRD, EDX, SEM and DRS analysis. With the curve of TG/DSC analysis, it was found decomposition temperature of volatiles until 600 °C, this temperature was chosen to calcine the precursors. The XRD patterns of the samples were all indexed to JCPDS (Joint Committee on Powder Diffraction Standards) card no. 01-070-1382 with a single-phase monoclinic structure of Scheelite type and space group C2/c, secondary phases were not identified. The XRD patterns were refined by the Rietveld method, whereby the lattice parameters and the unit cell volume were obtained. Regarding to the EDX analysis (atomic %), it was noted that there are small differences between the theoretical atomic percentages of Ce and Mo and synthesized samples. By means of the SEM images, it was observed that generally the powders are formed by large agglomerated particles of rounded shape, forming a porous material. The crystallite size of the study was made based on the interpretation of data from diffractograms estimated by Halder-Wagner-Langford (HWL) and Scherrer methods, observing an average crystallite size ranges between 11.67 to 32.75 nm. The optical properties of the nanoparticles were evaluated using DRS- UV/Vis analysis whereby the optical band gap were measured, ranging between 2.33-2.43 eV and are classified as semiconductor materials with potential photocatalytic application using the visible light as the radiation source. An experimental design 2³ with three replications in central point was performed and the effects of synthesis parameters in crystallite size were evaluated. The synthesis method used was efficient for the production of a crystalline, single phase and nanosized material, and it was found that the synthesis performed with the reaction parameters on the point 1 of the experimental design is the most suitable for production of the material with the desired characteristics of crystallite size and band gap. With the photocatalysis tests, it was observed that in the conditions discussed in this work the material has high removal performance of blue methylene dye even without light irradiation, reaching a decrease in absorbance of 98% dye after 6 hours contact with an initial dye concentration of 30 ppm using cerium molybdate in a concentration of 125 mg/L. It was found through adsorption kinetics studies of methylene blue on cerium molybdate particles that the pseudo-second-order kinetic model describes well the system on the experimental conditions discussed in the work.

MEMBROS DA BANCA:
Externo à Instituição - ANDARAIR GOMES DOS SANTOS - UFERSA
Externo ao Programa - 2929066 - ANDRE LUIS LOPES MORIYAMA
Presidente - 349801 - CARLSON PEREIRA DE SOUZA
Externo à Instituição - FRANCISCO KLEBSON GOMES DOS SANTOS - UFERSA