Síntese e aplicação de catalizadores sólidos em reações de fotodegradação do corante índigo de carmina

Abstract

Industrial activities are quite polluting, one of them is those that use dyes to produce their products, mainly contaminating water. To solve this type of contamination, this work aims to synthesize Si/Zn mixed oxides, characterize and apply them in photodegradation reactions of the indigo carmine dye. The Si/Zn mixed oxides were produced in a hydrothermal system via the sol gel method. The solids were synthesized with different amounts of zinc acetate, producing three photocatalysts named respectively SiZn1, SiZn2 and SiZn3. These were characterized spectroscopically by infrared (FT-IR), X-ray diffraction (DRX), scanning electron microscopy (SEM) and diffuse reflectance spectroscopy. The FT-IR and DRX characterizations confirmed the presence of ZnO and Zn2SiO4 Willemite in the three materials produced. In SEM and DRX it showed a more defined crystalline phase in SiZn3. Diffuse reflectance spectroscopy estimated the band gap of 3.05 eV for SiZn2 and 3.00 eV for SiZn3, which are good values ​​for semiconductors that are applied in photodegradation. These photocatalysts were applied in heterogeneous photodegradation in solutions, containing carmine indigo dye, taking advantage of the semiconductance property of zinc oxide. Photocatalytic tests were carried out in a photoreactor, using 30 ppm dye solutions. The suspensions were kept under magnetic stirring and irradiation with a 125 W mercury vapor lamp. 2.0 mL aliquots were collected at different periods of time until the reactions completed 3 h. The amount of degraded dye was determined by UV/visible spectroscopy, showing a degradation percentage of 53.53% in 3 hours of reaction for SiZn1, 99.05% degradation in 1 hour and 30 minutes for SiZn2 and 94% within 3 hours of reaction for SiZn3. The SiZn2 photocatalyst was recovered and reused six more times, and it maintained its photocatalytic activity, which proves the great versatility and viability of this solid. With this, we intend to make the treatment of effluents from the most varied branches of the chemical industry more accessible and cheaper, providing a more effective removal of different types of contaminants released into the environment.