Abstract
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 (Fe(3)O(4), ZnO, CaO, MgO, and minor CaCO(3)) 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. Pb(2+) was almost completely removed (95-99%) within 15-30 min using 50-100 mg of nanoparticles, with ~80-90% efficiency at 75 mg. Cd(2+) 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 Pb(2+) adsorption followed the Langmuir model (R(2) = 0.982) with monolayer chemisorption, whereas Cd(2+) obeyed the Freundlich model (R(2) = 0.945), indicating heterogeneous multilayer adsorption. Pb(2+) removal fitted a pseudo-second-order model (R(2) = 0.991), while Cd(2+) followed a pseudo-first-order behavior (R(2) = 0.958). Thermodynamic parameters (ΔG° < 0, ΔH° > 0, ΔS° > 0) confirmed a spontaneous and endothermic process. Sugarcane-bagasse-derived Fe(3)O(4)-ZnO-CaO-MgO nanomaterials act as sustainable and effective adsorbents for marine heavy metal removal.