Desenvolvimento de semicondutores à base de Nióbio para ativação fotoassistida de Peroximonossulfato para fotodegradação do Ácido Cafeico

Abstract

The presence of phenolic compounds in agro-industrial effluents poses a significant environmental challenge due to their low biodegradability, phytotoxicity, and contribution to the chemical oxygen demand (COD). Caffeic acid, one of the main representatives of this class, was employed in this study as a model compound for the evaluation of remediation processes. In this context, Advanced Oxidation Processes (AOPs), particularly heterogeneous photocatalysis, have emerged as promising alternatives. Accordingly, this work aimed to develop and characterize Nb₂O₅-based semiconductors synthesized via the peroxo-oxidant method (OPM) and subjected to different calcination temperatures (200 °C and 400 °C), targeting their application in the photodegradation of caffeic acid through photoassisted activation of peroxymonosulfate (PMS) under visible light irradiation. The materials were characterized using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS), Raman Spectroscopy, Thermogravimetric and Differential Scanning Calorimetry Analyses (TG/DSC), Electron Paramagnetic Resonance (EPR), and specific surface area measurements (SBET), highlighting the impact of thermal treatment on the structural, morphological, and optical properties of the materials. Photocatalytic tests revealed that the sample calcined at 200 °C exhibited superior performance, achieving over 90% degradation of caffeic acid within 5 minutes, along with good stability and reusability. Furthermore, the generation of reactive oxygen species (ROS), particularly hydroxyl radicals (•OH), was confirmed by EPR, emphasizing the role of PMS activation in the process efficiency. Overall, the results underscore the potential of Nb₂O₅ as a sustainable photocatalyst, offering advantages such as chemical stability, the absence of noble metals, and reusability, thereby contributing to the development of wastewater treatment technologies aligned with the principles of green chemistry and the use of abundant resources in Brazil.