Eco-Friendly Synthesized Functionalized Magnetic Nanoparticles for the Trace Removal of Chromium Species: Kinetic and Isotherm Studies Coupled with Dual Detection via UV–Vis and ICP

This study explores the development and analysis of an eco-friendly one-step process for attaching iron oxide magnetic nanoparticles (MNPs) to a type of hyperbranched polyester commercially known as the "Boltorn H40" polymer. The research focuses on the application of this technique for extracting trace amounts of chromium ions [Cr(III) and Cr(VI)] with concentrations of less than 1 ppm. The elimination of Cr(VI) is of significant concern due to its severe toxicity and detrimental environmental impact. A systematic evaluation was conducted to investigate the influence of operational parameters, including adsorbent dosage, contact time, pH, and initial chromium concentration, on removal efficiency using synthetic aqueous solution. The adsorption behavior of the innovative BH40@Fe₃O₄ MNPs nanocomposite was found to follow both the Langmuir model and pseudo-second-order kinetics. For trace-level concentrations, the material achieved removal efficiencies of 99% for Cr(VI) and 98% for Cr(III), with Cr(VI) exhibiting faster and more effective adsorption. A UV-vis spectroscopy procedure was developed to enable real-time oxidation state-specific monitoring of chromium ions in aqueous systems. This method allows for the direct detection and quantification of Cr(VI) even in the presence of Cr(III), making it suitable for analyzing binary systems. This new approach provides a practical way to distinguish between chromium species in water, providing more insight into competitive adsorption mechanisms. Durability tests showed that the nanocomposite retained over 90% of its initial adsorption capacity even after four regeneration cycles, confirming its excellent reusability. This study presents a highly efficient, durable, and scalable material for removing trace-level chromium species, offering strong potential for real-world environmental remediation applications.