Urea-Modified Fe ₃ O ₄ @Polypyrrole and Its Adsorption on Heavy Metals Mn(VII) and Dyes (Methylene Blue and Malachite Green)

The rapid development of textile, dyeing, and metallurgical industries has led to the discharge of large volumes of wastewater contaminated with dyes and heavy metal ions, posing significant environmental challenges. To address this issue, we developed a novel urea-modified magnetic PPy nanocomposites (Fe 3 O 4 @PPy-CM) via silane modification for the efficient removal of Mn(VII), methylene blue (MB), and malachite green (MG). A uniform PPy layer was successfully coated onto Fe 3 O 4 nanoparticles through in situ polymerization, which increased the material’s specific surface area and adsorption capacity. The grafted urea moiety serves as a key functional component, providing abundant nitrogen-based active sites for binding the target contaminants. Adsorption efficiency evaluations at 308.15 K demonstrated high removal rates exceeding 90% for both Mn(VII) and MB and 85% for MG. Kinetic studies confirmed a chemisorption-dominated process, with Mn(VII) uptake following pseudo-first-order kinetics and MB/MG adsorption adhering to pseudo-second-order kinetics. The equilibrium data for all contaminants were accurately described by the Langmuir isotherm model, indicating monolayer adsorption. Remarkably, the composite maintained excellent stability and adsorption performance over five consecutive adsorption-desorption cycles, underscoring its strong potential for practical wastewater treatment applications.