Removal of Cadmium and Lead from Tires Discarded in the Open Sea with Multicomponent Nanoparticles from Sugarcane Bagasse

This study addresses the environmental challenge of end-of-life tire accumulation, a major source of toxic metals such as lead and cadmium in marine ecosystems. As a sustainable solution, multicomponent metal-oxide nanoparticles (Fe3O4, ZnO, CaO, MgO, and minor CaCO3) were green-synthesized from sugarcane bagasse and stabilized with blackberry (Rubus glaucus) extract. Structural characterization (XRD, SEM, TEM, and EDS) confirmed their crystalline inorganic composition. Pb2+ was almost completely removed (95–99%) within 15–30 min using 50–100 mg of nanoparticles, with ~80–90% efficiency at 75 mg. Cd2+ removal showed dose-dependent kinetics: ~90% removal occurred within 10 min at 75 mg, while 50 and 100 mg reached ~60–70% after 60 min. Equilibrium, kinetic, and thermodynamic analyses revealed that Pb2+ adsorption followed the Langmuir model (R2 = 0.982) with monolayer chemisorption, whereas Cd2+ obeyed the Freundlich model (R2 = 0.945), indicating heterogeneous multilayer adsorption. Pb2+ removal fitted a pseudo-second-order model (R2 = 0.991), while Cd2+ followed a pseudo-first-order behavior (R2 = 0.958). Thermodynamic parameters (ΔG° 0, ΔS° > 0) confirmed a spontaneous and endothermic process. Sugarcane-bagasse-derived Fe3O4–ZnO–CaO–MgO nanomaterials act as sustainable and effective adsorbents for marine heavy metal removal.