Banca de QUALIFICAÇÃO: LAZARO HERICLES FREITAS DA SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : LAZARO HERICLES FREITAS DA SILVA
DATE: 01/04/2026
TIME: 14:00
LOCAL: Auditório do IQ3
TITLE:

Photodegradation of Paracetamol Using Ag/CoFe₂O₄/SBA-15-Based Catalysts: Preferential Attack of Oxidizing Radicals.

KEY WORDS:

Degradation; Paracetamol; Photocatalyst; Cobalt ferrite; Silver

PAGES: 37
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Físico-Química
SPECIALTY: Cinética Química e Catálise
SUMMARY:

The contamination of aquatic ecosystems by residual pharmaceuticals, particularly paracetamol—one of the most widely consumed drugs worldwide—represents a growing threat to environmental quality and public health. In this context, an advanced heterogeneous photocatalyst based on Ag/CoFe₂O₄/SBA-15 was developed and characterized for the degradation of paracetamol under light irradiation. X-ray diffraction (XRD) results confirmed the formation of the spinel phase of cobalt ferrite (CoFe₂O₄) while preserving the mesoporous structure of the SBA-15 silica support, whereas Raman spectroscopy corroborated the formation of the CoFe₂O₄ phase through the identification of characteristic vibrational modes. X-ray photoelectron spectroscopy (XPS) confirmed the presence of all expected elements (Si, O, Ag, Fe, and Co) and revealed that silver was predominantly in its metallic state (Ag⁰) on the catalyst surface, establishing electronically active interfaces with cobalt ferrite. Diffuse reflectance measurements indicated band gap energy values around 2.6 eV, with no significant changes observed after silver impregnation. Photocatalytic activity tests showed that the sample containing 3% silver (denominated Ag3) exhibited the best performance, achieving 100% degradation within 5 h and following a pseudo-first-order kinetic model. This catalyst displayed good stability, maintaining degradation efficiency above 90% after two consecutive reuse cycles. A plausible reaction mechanism was proposed, consistent with theoretical DFT studies based on thermodynamic and kinetic data, which indicated that the photodegradation of paracetamol is predominantly driven by the attack of hydroxyl radicals (•OH) on the phenyl group, leading to the formation of the phenoxyl radical.

COMMITTEE MEMBERS:
Interno - 1959889 - DAVI SERRADELLA VIEIRA
Externo à Instituição - RÔMULO BATISTA VIEIRA - UNILAB
Presidente - 2087667 - TIAGO PINHEIRO BRAGA