Banca de DEFESA: EMANOEL HOTTES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : EMANOEL HOTTES
DATE: 05/08/2021
TIME: 14:00
LOCAL: PPGQ
TITLE:

Application of Lamellar Double Hydroxides on the adsorption and slow liberation of glyphosate herbicide in an aqueous medium

 

KEY WORDS:

glyphosate, LDHs, LDOs, adsorption, kinetics, slow release

PAGES: 131
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SPECIALTY: Físico Química Inorgânica
SUMMARY:

The widespread use of pesticides in agriculture has contributed significantly to the increase of environmental contamination. In Brazil, where glyphosate (GPS) responds to the majority of the herbicide consumption, GPS is associated to the contamination of soil and hydric bodies. The Layered Double Hydroxides (LDHs), materials of the anionic clay family, present a high capacity of anions intercalation and they can be used in different segments, such as in the adsorption process and slow release of chemical compounds. Therefore, the aim of this paper was to study the adsorption of the glyphosate pesticide, using calcined LDHs – the so-called Layered Double Oxydes (LDOs) and their process of release by the hybrid material. The studies of glyphosate adsorption in pH 10, using LDO in the proportion 2:1 de Mg/Al, indicated that the process follows a pseudo first-order kinetic, being the Langmuir isotherm model the one that best presented adjustment when compared to the Freundlich and Temkin models. The negative values of ΔG° and positive ΔS° indicate the spontaneity of the adsorptive process. The glyphosate/adsorption interaction mechanism was studied through the powder XRD, ATR-FTIR and NMR of solid 13C and 31P. The 7,4 Å value obtained to the interlamellar spacing suggests that the adsorption does not involve the intercalation of glyphosate, but it does for the hydroxide anion. The band shift in ATR-FTIR, from carboxylate and phosphate portions, to lower numbers of wave on the hybrid compound face the non-adsorbed glyphosate, indicates that these groups are involved in the interaction process of glyphosate/layered of the LDH. As of the 13C {1H} CP-MAS and 31P{1H} CP-MAS spectra, it was possible to infer that the glyphosate is possibly found complexed to the present metals in the LDH lamellas. The study of anionic competition indicates that the increase on the carbonate concentration leads to a significant reduction on the glyphosate adsorption, reaching up to less than 15% when the carbonate concentration is 200 μg/mL. For the release studies, LDHs were synthesized on the Mg-Al-glyphosate system (metallic reason 2:1) by the direct co-precipitation method, followed by reflux and by the reconstruction method, followed by the hydrothermal treatment. The analysis of powder XRD of hybrid compounds suggested that the synthesized material by reconstruction presents a less amorphous character than the one synthesized by co-precipitation and the basal spacing value of 7,8 Å is an indication of interspersed glyphosates on the vertical position. The analysis of ATR-FTIR and NMR of hybrid compounds indicated that the glyphosate interacts with the layered through the carboxylate and phosphate groups, as in the adsorption. To a 48 hour contact time, the glyphosate release was more effective to the pH values equal to 8 and 10, being superior to 70%. To the acid pH 6 and 4, the values were inferior to 60%. A comparative analysis of the glyphosate release face to solutions of nitrate anions, carbonate and chloride, all of them in the concentration of 5 x 10-3 M, indicated that more than 60% of the present glyphosate on the hybrid compound was released after 15 hours when in presence of carbonate. In the solution of the other anions, the release did not exceed 35% on the same period of time. It was observed that, in an aqueous medium, the glyphosate release is directly proportional to the carbonate concentration.

BANKING MEMBERS:
Presidente - 1475121 - MARCELO HAWRYLAK HERBST
Externa ao Programa - 1898760 - RENATA NUNES OLIVEIRA
Externo ao Programa - 1399485 - ANDRES CALDERIN GARCIA
Externo ao Programa - 1809123 - ANDRE MARQUES DOS SANTOS
Externa à Instituição - JUSSARA LOPES DE MIRANDA - UFRJ
Externa à Instituição - JAQUELINE DIAS SENRA - UERJ
Externa à Instituição - ROSANE AGUIAR DA SILVA SANGIL - UFRJ