Isotherm and Kinetic Studies on Adsorption of Yellow Azo Dyes (Sunset Yellow, Tartrazine) using <i>Kigelia africana</i> (Lam.) Benth., Leaf Extract Mediated Iron Nanoparticles

Abstract

Sunset yellow and tartrazine are commonly used azo dyes extensively employed in beverages and food products such as soda, fruit juices, confectionery, and cakes. These dyes hold the distinction of being the second and third most frequently utilized colour additives in a wide array of beverage products. The discharge of these synthetic food dyes into industrial wastewater can lead to significant environmental and health issues. Due to its aromatic structure, this dye is resistant to breaking down into harmless compounds, and its removal through effective adsorption presents an economical and efficient solution. The use of renewable bioresources for the eco-friendly production of metallic nanoparticles represents a recent and growing trend in nanotechnology research, offering enhanced environmental safety. In this current research, we achieved the green and cost-effective synthesis of monodispersed Iron Nanoparticles (FeNPs) with exceptional stability by utilizing an aqueous extract of Kigelia africana (Lam.) Benth is the primary bioresource for this synthesis. The FeNPs were noticed to be uniformly distributed spherical-shaped particles having smooth surfaces with a 26-34 nm size range and an average particle size of 28 ± 0.86 nm. The XRD results confirm that the FeNPs were rhombohedral phase structures with 71.43% of elemental iron. These synthesized nanoparticles were applied for the removal of sunset yellow and tartrazine dyes were investigated and more than 90% were removed. The adsorption isotherm study was best fitted with the Langmuir model, and the maximal adsorption capacity was found to be 76.29 and 47.22 mg/g for sunset yellow and tartrazine respectively. The adsorption reaction follows pseudo-first-order kinetics with a high correlation coefficient. Repeated cycles of regeneration, reuse and stability showed very high removal efficiency and stability. In conclusion, the biosynthesis of metal nanoparticles demonstrates substantial promise for applications in environmental protection.