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 (<i>Rubus glaucus</i>) 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, ΔH° > 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.