Assessment of the photocatalytic activity of scheelite CaWO4/g-C3N4 nanocomposites via rhodamine B degradation under visible light

Abstract

CaWO₄/g-C₃N₄ nanocomposites were synthesized via ultrasonication method using pre-synthesized CaWO₄ and g-C₃N₄ nanostructures. CaWO₄ and g-C₃N₄ are combined to prepare an eco-friendly photocatalyst with high chemical stability. Furthermore, the synergetic effect of the band alignment of CaWO₄ and g-C₃N₄ forms a heterojunction, which facilitates the separation of photogenerated charge carriers and thus enhances the overall photocatalytic performance of the nanocomposites. The synthesized nanostructures were characterized via X-ray diffraction (XRD), UV‒Vis diffuse reflectance spectroscopy (UV‒Vis DRS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity was assessed via degradation of Rhodamine-B (RhB) under visible light. In this study, the effects of reaction parameters such as initial pH, catalyst dosage, initial dye concentration, and contact time are explored. Under optimized conditions, (i.e., at pH=8, with 80 mg/L catalyst and 7.5 ppm RhB dye, the CaWO₄/g-C₃N₄ nanocomposites with 3% g-C₃N₄ (CC3) degrade nearly 98% of the RhB within 150 min. Among the various synthesized catalysts, CC3 has a high-rate constant of 27.03 × 10 ⁻³ min⁻¹. CC3 exhibited good cyclic stability and degradation efficiency even at the 5th cycle. Furthermore, trapping experiments revealed the importance of superoxide and holes during the photodegradation of RhB. In the present study, the photodegradation activity of CaWO₄/g-C₃N₄ nanocomposites was demonstrated, which may open new avenues for environmental remediation.