Banca de DEFESA: EDUARDO BATISTA GUIMARAES NUNES DOS SANTOS
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.DISCENTE : EDUARDO BATISTA GUIMARAES NUNES DOS SANTOS
DATA : 05/07/2019
HORA: 14:00
LOCAL: Instituto de Química
TÍTULO:
Exploring solid phase of Al(OH)3 produced in situ by homogeneous precipitation assisted by microwaves radiation for fast extraction of chemical species
PALAVRAS-CHAVES:
Microwave-assisted homogeneous precipitation
Solid phase extraction
In situ adsorbent generation
Coprecipitation
Adsorption
PÁGINAS: 108
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Separação
RESUMO:
The aluminum hydroxide precipitation in homogeneous solution assisted by microwave radiation for the extraction of organic compounds, coprecipitation of metallic ions and inorganic anion species removal were studied. Unlike what occurs in conventional precipitations, where the precipitant is added, facilitating the production of colloids, precipitation in homogeneous solution produces more pure crystals that are rapidly agglomerate, speeding up the filtration of solids. When irradiating with microwaves, the urea solutions in the presence of aluminum ions leads to the formation of overheating zones and the fast decomposition of urea causes a local pH increasing and the production of Al(OH)3 in situ, which aids to separate other chemical species from the solution. In order to investigate the ability to organic compounds separation with the solid phase produced in situ, some experiments were carried out to extract neutral and electrically charged dyes. The results showed that the Al(OH)3 had a strong affinity for neutral organic compounds, with extraction rates higher than 80% for Congo red dye, betacarotene, humic acid and curcumin. The extraction of phenolic compounds by the proposed separation process was studied and the removal capacities for quercetin, quercitrin, morin, kaempferol, rutin, caffeic acid, ferulic acid, dopamine, L-dopa and chlorogenic acid from aqueous solutions were estimated. As, only quercetin was quantitatively removed with the precipitate (> 99%), an alternative process was developed for the separation and preconcentration of quercetin in aqueous extracts of onion sample without using organic solvents. Studies about the coprecipitation of metallic cations and anions separations during the Al3+ in situ precipitation process were carried out. The coprecipitation of metals by homogeneous precipitation of microwave assisted Al(OH)3 was evaluated in aqueous solutions and brines. Higher recovery rates (> 70%) were obtained for Cr, Fe, Pb and Cu, allowing the determination of Cr and Fe contents in brine samples by atomic spectrometric techniques without the interference of sodium. The proposed irradiation coprecipitation process was applied to evaluate the feasibility of trace metal determination in commercial samples of special salts for culinary uses (black salt, flakes of flower of salt and Himalayan pink salt). Higher separation rates for Cr and Fe were estimated for flower of salt and pink salt samples due to the high sulfur content characteristic of the black salts. Finally, the transfer of large inorganic anions (phosphate and dichromate) from aqueous solutions to the Al(OH)3 produced from homogeneous microwave-assisted precipitation was evaluated and an efficient phosphate extraction to Al(OH)3 solid phase in solutions without chloride and nitrate ions was obtained (> 99%). Phosphate ions determination in fertilized vegetal soil samples and cola soft drink were evaluated and the results indicated strong matrix effects due to competition between organic compounds and inorganic anion. The effect of dichromate ion presence in aqueous and brine solutions were also evaluated.
MEMBROS DA BANCA:
Interno - 039.199.838-23 - MAURO KORN - USP
Interno - 1698441 - RENNAN GEOVANNY OLIVEIRA ARAUJO
Interno - 2721446 - DANIELE CRISTINA MUNIZ BATISTA DOS SANTOS
Externo à Instituição - WAGNA PILER CARVALHO DOS SANTOS - IFBA
Externo à Instituição - MADSON DE GODOI PEREIRA - UNEB