Adsorption Performance and Modeling of Pb(II) on Magnetically Functionalized TiO2 Nanoflowers

Heavy metal contamination, particularly lead, poses significant environmental and health risks. In this study, a multifunctional TiO2@PLDOPA@Fe3O4 (TPF) nanocomposite was synthesized and evaluated as a reusable adsorbent for lead ion (Pb(II)) removal from aqueous solutions. Batch adsorption experiments were conducted to examine the effects of contact time, temperature, solution pH, adsorbent dosage, and shaking speed on adsorption performance. A high Pb(II) removal efficiency of 84% and an equilibrium adsorption capacity of 72.38 mg g−1 were obtained under optimized conditions. Kinetic analysis revealed that Pb(II) adsorption followed a pseudo-second-order model, indicating surface-controlled interactions. Thermodynamic analysis suggested a spontaneous and endothermic adsorption process dominated by physical interactions and electrostatic attraction Equilibrium data were better fitted by the Freundlich model, suggesting heterogeneous multilayer adsorption on the functionalized composite surface. The maximum monolayer adsorption capacity of TPF reached 263.16 mg g−1, exceeding those of pristine TiO2 and Fe3O4. Regeneration studies showed that the TPF nanocomposite retained approximately 87% of its initial adsorption capacity after five adsorption-desorption cycles, demonstrating good stability and reusability. The integration of hierarchical TiO2, magnetic Fe3O4, and bio-inspired PLDOPA functionalization provides a promising and sustainable strategy for heavy metal removal and highlights the potential of multifunctional nanocomposites in circular and resource-efficient water treatment systems.