Visible Light Driven Photocatalytic Degradation of Congo Red Dye Using Biogenic Silver Nanoparticles

Abstract

In response to growing environmental concerns related to water scarcity and industrial pollution, particularly from the textile sector, this study explores a green and sustainable method for synthesizing silver nanoparticles (Ag NPs) using Eucalyptus globulus leaf extract. The biosynthesized Ag NPs were applied for the degradation of Congo Red, a widely used but toxic azo dye. This approach not only offers an eco-friendly alternative to conventional wastewater treatment methods but also demonstrates the potential of plant-based NP synthesis in environmental remediation. The synthesized Ag NPs were thoroughly characterized to confirm their structure, composition, and morphology. UV-Vis spectroscopy indicated the presence of surface plasmon resonance band (405 nm), while STEM analyses revealed spherical NPs ranging around ⁓6 nm in size. EDX confirmed the silver content and XRD demonstrated the crystalline and metallic nature of the Ag NPs. FTIR analysis identified functional groups responsible for the bio reduction, capping, and stabilization, indicating successful green synthesis using Eucalyptus globulus extract. The biosynthesized Ag NPs demonstrated excellent photocatalytic activity, achieving up to 98.9% degradation of Congo Red (CR) dye within 8 min under visible light and 97.8% degradation within 55 under sun light irradiation. Optimization of parameters such as initial dye concentration, catalyst (Ag NP) dose, and light exposure time confirmed the efficiency of the process, which followed a pseudo-first-order kinetic model. These findings demonstrate that green-synthesized Ag NPs are highly effective for dye removal and hold significant potential for environmental and pharmaceutical applications.