Biosynthesis of Silver Nanoparticles Using Rhubarb Seed Extract for the Effective Removal of Organic Dyes from Aqueous Media: Insights into Isotherm and Kinetics Models

ّImproper disposal of synthetic dyes like methylene blue (MB), methyl orange (MO), and acid red 18 (AR18) poses a significant threat to aquatic environments and human health, highlighting the need for efficient and sustainable remediation strategies. This study introduces a novel, green synthesis of silver nanoparticles (AgNPs) using Rhubarb seed extract. It provides a cost-effective, eco-friendly, and rapid method to produce functional adsorbents for treating dye-contaminated wastewater. Thorough characterization confirmed the morphology and composition of the biosynthesized AgNPs through UV-Vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analysis (XRD). Batch adsorption experiments showed outstanding maximum removal efficiencies exceeding 95% for MB, MO, and AR18 under optimal conditions (pH 11, 9, and 5, respectively; 0.8 g adsorbent; 20 minutes contact time; 30 mg/L dye concentration). The adsorption process followed the Langmuir isotherm (R2 = 0.9998 for MB, 0.9994 for MO, 0.9999 for AR18) and pseudo-second-order kinetics (R2 = 0.9998, 0.9992, and 0.9991, respectively), with maximum adsorption capacities (qmax) of 40.16, 50.76, and 44.64 mg/g. The innovation of this research lies in using Rhubarb seed extract for AgNP biosynthesis, showcasing high performance even for complex dye mixtures while promoting environmental sustainability and economic viability compared to conventional chemical methods. These findings establish Rhubarb seed-derived AgNPs as an effective and innovative platform for advanced wastewater purification.