Síntese do compósito vanadato de cério (CeVO4) e nitreto de carbono grafítico (g-C3N4) para degradação de poluentes por meio da fotocatálise

Abstract

Rare earth elements (RE), consisting of the lanthanides, scandium, and yttrium, exhibit remarkable physicochemical properties such as magnetism, phosphorescence, and catalytic activity. They are widely applied in modern technologies and have more recently gained prominence in environmental photocatalysis, particularly for pollutant degradation and antibacterial action. Among the studied compounds, rare earth orthovanadates (REVO₄) stand out for their stability, redox properties, and potential as catalysts under UV and visible light. In this context, the present study aimed to synthesize cerium vanadate (CeVO₄) composites with graphitic carbon nitride (g-C₃N₄) using a microwave-assisted hydrothermal method. The research focused on analyzing the influence of different CeVO₄/g-C₃N₄ ratios in synthetic effluents, as well as investigating their structural properties and potential applications, with emphasis on developing controlled morphology and environmentally sustainable materials. The materials were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), which enabled vibrational analysis of the chemical bonds present in the compounds. Morphological analysis was performed using scanning electron microscopy (SEM). Ultraviolet–visible spectroscopy (UV–Vis) was employed to determine the light absorption capacity of the materials, while photocatalytic tests evaluated their efficiency in degrading Rhodamine B (RhB) and methylene blue (MB) dyes under visible light irradiation. The results showed that pure CeVO₄ synthesized at pH 4 (50 mg) and g-C₃N₄ exhibited higher efficiency in RhB degradation, reaching 48%, whereas CeVO₄ synthesized at pH 9 was more efficient in MB degradation, achieving 49.61%. The CeVO₄/g-C₃N₄ heterostructures synthesized at pH 4 demonstrated superior performance compared to pure samples, with the catalyst containing 50 mg achieving 50.50% degradation for RhB (CeVO₄ pH 4/g-C₃N₄) and the 100 mg catalyst reaching 75.90% degradation for MB (CeVO₄ pH 9/g-C₃N₄). Scavenger tests revealed that hydroxyl radicals (•OH) are the main oxidative species responsible for the degradation of RhB and MB, as evidenced by the significant efficiency reduction in the presence of tert-butyl alcohol. Reusability tests demonstrated high stability and efficiency of the catalyst over three cycles, maintaining consistent performance.