Banca de DEFESA: ADRIELE DE OLIVEIRA BATISTA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : ADRIELE DE OLIVEIRA BATISTA
DATE: 01/10/2025
TIME: 09:00
LOCAL: Instituto de Química - PPGQ - Online
TITLE:

Photocatalytic degradation of Rhodamine 6G using silver-modified lithium niobate perovskite.

KEY WORDS:

heterogeneous photocatalysis, niobium perovskites, Rhodamine 6G, visible light.

PAGES: 95
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

The perovskite structure is recognized for its remarkable properties in solidmaterial chemistry. Recently, research has focused on high-performance photocatalytic technologies for environmental recovery and sustainable energy generation. Rhodamine 6G (Rh-6G) is a widely used synthetic dye, but it is poorly biodegradable and polluting. When released into water, it can harm aquatic fauna and flora. Due to its stability and toxicity, it is frequently studied in photodegradation to reduce environmental impacts. Interest in photocatalysis has driven studies of perovskites such as NaNbO₃, KNbO₃, and LiNbO₃, due to their photocatalytic properties and band gap tunability. In this work, the modification of LiNbO₃ with silver was evaluated on the photocatalytic efficiency to degrade Rhodamine 6G under visible light. The photocatalytic capabilities of LiNbO₃ and Li(1-x)Ag(x)NbO₃ perovskites with silver concentrations of 5%, 10%, 20%, 30% and 40% in mol were analyzed. Photodegradation of Rh-6G was performed under visible light, using a xenon lamp (300W, 400nm filter) or blue LED (10W, 440nm). The dye calibration curve was constructed to determine the molar absorptivity coefficient, with maximum absorbance at 526nm. A concentration of 10mgL⁻¹ was used, followed by adsorption in the dark for 2h. Photocatalysis occurred under visible light for 120min, with measurements every 15min. Modification of LiNbO₃ with silver increased the photocatalytic capacity, reducing the band gap from 4.10 eV to 2.65–2.82 eV, facilitating electronic excitation. The insertion of silver into the LiNbO₃ structure made the material more reactive, achieving approximately 76% degradation in 120 minutes under irradiation with a xenon lamp and approximately 97% with a blue LED, in the same time interval. The observed kinetics were pseudo-first order for all materials analyzed, with Ag30% being the most reactive in the established period, with values of k = 0.01093 min⁻¹ for irradiation with a 300 W xenon lamp and k = 0.03644 min⁻¹ for irradiation with a 10 W blue LED. Tests with reactive species scavengers showed that the superoxide radical exerts the greatest effect in preventing photodegradation, both for LiNbO₃ and Ag30%. Conduction-band electrons react with dissolved oxygen, forming superoxide radicals that oxidize the pollutant or generate secondary species that promote its conversion to CO₂ and water. Thus, modifying LiNbO₃ with silver proves an effective strategy for developing photocatalysts for the degradation of organic pollutants in water.

COMMITTEE MEMBERS:
Interno - 1144471 - IDIO ALVES DE SOUSA FILHO
Presidente - ***.460.177-** - JOSE CARLOS NETTO FERREIRA - UFRRJ
Externo à Instituição - JOSUÉ SEBASTIAN BELLO FORERO - UFRJ