Sustainable Green Synthesis of RuO2 Nanoparticles Employing Murraya koenigii Leaf Extract: Catalytic Dye Degradation and Biological Assessment

The increasing discharge of persistent azo dyes from textile and allied industries poses serious environmental and health challenges, necessitating efficient and sustainable remediation strategies. In this study, green-synthesized ruthenium dioxide (RuO 2 ) nanoparticles were investigated for their catalytic, antifungal, and antioxidant performance. The catalytic activity of RuO 2 nanoparticles was evaluated for the oxidative degradation of two hazardous azo dyes, methyl orange (MO) and Congo red (CR), using hexacyanoferrate(III) ions as an environmentally benign oxidizing agent under alkaline conditions. Kinetic studies revealed that the degradation process follows pseudo-first-order kinetics and is strongly influenced by pH, oxidant concentration, dye concentration, catalyst loading, ionic strength, and temperature. Compared to uncatalyzed systems, RuO 2 nanoparticles significantly enhanced degradation rates and reduced activation energies, confirming their role in facilitating interfacial electron transfer and reactive oxygen species–mediated oxidation. Thermodynamic analysis indicated favorable reaction feasibility for the catalyzed pathway. The degradation mechanism was elucidated using UV–Vis spectroscopy, FTIR, and LC–MS analyses, confirming azo bond cleavage, aromatic ring disruption, and progressive mineralization of both dyes. Reusability studies demonstrated that RuO 2 nanoparticles retained substantial catalytic activity over multiple cycles, with XRD, SEM, and TGA analyses confirming their structural, morphological, and thermal stability after recovery. In addition, RuO 2 nanoparticles exhibited pronounced antifungal activity and significant antioxidant activity in the DPPH assay, with IC 50 values comparable to standard antioxidants. Overall, this study highlights the multifunctional potential of green-synthesized RuO 2 nanoparticles for wastewater remediation and related biomedical applications.