Banca de DEFESA: GABRIEL JOAQUIM SANTOS SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GABRIEL JOAQUIM SANTOS SILVA
DATE: 03/07/2025
TIME: 15:00
LOCAL: Auditório do NUPPRAR
TITLE:

Green synthesis of magnetite (Fe₃O₄) nanoparticles from coconut fiber (Cocos nucifera) applied in the electro-decarboxylation of fatty acids.

KEY WORDS:

Magnetite; Nanoparticles; Green Synthesis; Decarboxylation

PAGES: 122
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SPECIALTY: Físico Química Inorgânica
SUMMARY:

The growing demand for sustainable and efficient technologies in sectors such as environmental remediation, energy storage, and biomedicine has stimulated interest in the development of nanomaterials compatible with these processes. Among these materials, magnetite (Fe₃O₄) stands out due to its unique physicochemical properties and broad applicability in advanced technological systems. However, its conventional synthesis commonly employs toxic reagents such as ammonium nitrate and hydrazine, which are used to reduce Fe³⁺ to Fe²⁺ during the formation process. The use of these substances raises environmental concerns due to their toxic nature and the generation of harmful byproducts. As an alternative, this study proposed the green synthesis of magnetite using coconut fiber extract (Cocos nucifera), exploring reducing compounds present in the biomass, such as catechin, to provide the electrons needed for iron reduction and accelerate nanoparticle formation. XRD analysis confirmed the presence of magnetite and maghemite (γ-Fe₂O₃) phases, while Rietveld refinement indicated a lattice parameter typical of magnetite (~8.39 Å) and an average particle diameter of 9.6 ± 1.5 nm. FTIR identified hydroxyl, carboxyl, and aromatic groups, confirming the chemisorption of coconut-derived functional groups on the nanoparticle surface. Additionally, the band gap ranged from 1.47 to 2.05 eV, indicating semiconductor behavior. TEM images showed well-dispersed nanoparticles, suggesting controlled nucleation. Mössbauer spectroscopy of the best sample indicated 33% Fe²⁺ and 67% Fe³⁺, close to the ideal magnetite stoichiometry, a result further supported by magnetic analyses, which confirmed properties consistent with those described in the literature for Fe₃O₄ nanoparticles. In electro-decarboxylation tests, the MNT 01 sample (synthesized with coconut extract) achieved 64.2% hydrocarbon selectivity in the decarboxylation of lauric acid, outperforming both the catalyst-free reaction (53.7%) and the control sample without extract, MNT CTL 01 (61.7%). The magnetite-based catalysts also reached an average conversion of 71.2%, demonstrating efficient catalytic performance. Regarding product distribution, 1-undecene was identified as the major compound, evidencing effective decarboxylation. Furthermore, the use of functionalized magnetite significantly reduced the formation of oxygenated byproducts, improving hydrocarbon selectivity.

COMMITTEE MEMBERS:
Presidente - 2140818 - AMANDA DUARTE GONDIM
Externo à Instituição - ERNANI DIAS DA SILVA FILHO - UFRN
Externo ao Programa - 1674707 - MARCO ANTONIO MORALES TORRES - nullInterno - 2087667 - TIAGO PINHEIRO BRAGA