Biofotocatalisadores a partir de microalgas e tio2 dopado com n para aplicação em fotocatálise solar

Abstract

The growing concern over the environmental impacts caused by industrial effluents has driven the search for cleaner technologies¹. In this context, the development of biophotocatalysts based on Scenedesmus microalgae coated with TiO₂ and nitrogen-doped TiO₂ (TiO₂-N) stands out as a promising approach for application in solar-driven heterogeneous photocatalysis². The resulting composites were applied to the degradation of Ponceau 4R dye, aiming to achieve energy efficiency and economic feasibility³. The methodology involved the synthesis of the catalysts (TiO₂ and TiO₂-N) and the cultivation of microalgae in BG-11 medium. The analyses followed a four-day protocol involving sample collection, pH and temperature measurements, spectrophotometric analysis (200–800 nm), preparation of microscope slides, and cell counting⁴. The samples were classified into control groups (CI–CIII), pure TiO₂ groups (PI–PIX), and TiO₂-N groups (DI–DIX), using different catalyst amounts (15, 25, and 35 mg). Analysis of variance (factorial ANOVA) revealed a significant effect of the treatments on pH, absorbance (680 nm), transmittance (750 nm), and cell count (p < 0.05), highlighting the effectiveness of the catalysts. The results showed an average pH close to 10, with temperatures ranging from 26 °C to 28 °C. In the control samples, an increase in absorbance was observed, indicating cell growth. For the adsorption analysis, a TiO₂-N sample was used, and its spectrum showed only slight variations in absorbance among the samples, with no significant changes or evidence of chemical degradation. Under the experimental conditions investigated, direct photolysis was not sufficient to promote the degradation of Ponceau 4R dye, although the absorbance of the aliquots decreased over time. In the photocatalytic experiments using 25 mg and 35 mg of TiO₂-N, the absorbance spectra indicated degradation efficiencies of 80.33% for TiO₂-N (25 mg) and 87.64% for TiO₂-N (35 mg), demonstrating that higher photocatalyst loading was more effective at this stage and reinforcing the superior performance of nitrogen doping. Thus, the results support the feasibility of using biophotocatalysts for the sustainable and efficient removal of organic contaminants.