Banca de DEFESA: FERNANDA KAROLINE DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : FERNANDA KAROLINE DA SILVA
DATE: 26/02/2024
TIME: 14:00
LOCAL: Auditório do Departamento de Química
TITLE:

LOW-COST PHOTOCATALYTIC MATERIALS APPLIED TO TEXTILE EFFLUENT TREATMENT

KEY WORDS:

photocatalysis; titanium dioxide; silicon dioxide; sol-gel; bacterial cellulose.

PAGES: 69
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SPECIALTY: Foto-Química Inorgânica
SUMMARY:

The textile industry is among the most polluting in the world, producing large volumes of effluents contaminated with dyes. When released into aquatic environments without proper treatment, these effluents have impacts on ecosystems and human health. An effective solution involves the application of photochemical processes, such as photocatalysis. In this context, titanium dioxide (TiO₂) stands out for being chemically stable, cost-effective, insoluble in water, and non-toxic. However, the activation process of TiO₂ requires energy in the order of 3.2 eV, corresponding to ultraviolet radiation. Thus, this study aims to develop a new, low-cost photocatalytic material for treating wastewater from textile industries. Consequently, a hybrid photocatalyst of titanium dioxide and silica was developed to enhance the photocatalytic activity of TiO₂, activated by solar radiation. The addition of SiO₂ contributes to increasing the stability of the anatase phase of TiO₂, reducing particle size, and increasing specific surface area. Although the use of photocatalysts allows for the decolorization and mineralization of these dyes, additional filtration steps are still needed to remove the oxide after treatment, increasing the process cost. In this scenario, bacterial cellulose emerges as a good support alternative due to its properties. The methodology involved the production of hybrid photocatalysts of titanium dioxide and silica synthesized in different proportions, along with pure oxides through the sol-gel method. These were tested for their photocatalytic capacity, followed by the modification of bacterial cellulose membranes produced in the laboratory by Gluconacetobacter xylinus, used as a support for impregnating titanium dioxide. Two modifications were made to the bacterial cellulose using the titanium dioxide precursor, with variation in reaction time, namely, 24 hours and 5 days, respectively. Materials were characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), confirming membrane modifications and hybrid formation. FTIR results revealed a band at 650 cm^-1 characteristics of Ti-O-Ti, a band at 425 cm^-1 related to Si-O-Si, and XRD showed standard TiO₂ peaks in the anatase phase. The absence of the typical diffraction peak of the crystalline phase of SiO₂ suggests that the species in the hybrid are in an amorphous form. XRD analysis also revealed the preservation of the crystalline structure of bacterial cellulose after modification with TiO₂ precursor. Photocatalytic tests were conducted with methylene blue under solar radiation for 60 minutes. The discoloration rate was evaluated through electronic absorption spectroscopy, analyzing the decrease in absorbance after the test. All hybrid photocatalysts demonstrated higher activity compared to pure TiO₂. The highest activity was recorded for Ti-Si(60:40) samples, with a discoloration rate of 95% in 60 minutes of testing. The experiments showed the photocatalytic efficiency of the synthesized materials due to a significant reduction in absorbance values. In addition to being active in solar radiation, this results in lower industrial costs as it does not require electrical energy during the photocatalytic process.

COMMITTEE MEMBERS:
Externa à Instituição - LIDIANE MACEDO ALVES DE LIMA
Presidente - MONICA FREIRE BELIAN
Interno - WAGNER EDUARDO DA SILVA