Lead (Pb2+) contamination in aquatic environments poses a serious risk to human health and ecosystems, necessitating the development of efficient, sustainable, and regenerable adsorbent materials. In this study, a carbon-based magnetic nanocomposite (AC/MnFe2O4) derived from orange peel waste was synthesized and systematically evaluated for Pb2+ removal from aqueous solutions. The structural, morphological, elemental, and magnetic properties of the synthesized materials were characterized using SEM, EDX, XRD, and VSM, confirming successful immobilization of MnFe2O4 nanoparticles onto the porous activated carbon matrix and sufficient magnetic separability. The effects of key operational parameters, including solution pH (2–10), initial Pb2+ concentration, adsorbent dosage, temperature (25–60°C), and contact time, were systematically investigated. Adsorption kinetics were analyzed using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. Equilibrium data were evaluated using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) isotherm models. The Langmuir model exhibited excellent agreement with experimental data, yielding a high maximum adsorption capacity of 129.87 mg/g and a favorable separation factor (RL=0.023). The low mean adsorption energy obtained from the D–R model (E = 3.79 kJ/mol) suggests that Pb2+ adsorption is predominantly governed by physisorption mechanisms. Thermodynamic analysis revealed negative Gibbs free energy values (ΔG°=−6.72 to − 0.45 kJ/mol) at lower temperatures, confirming the spontaneous nature of Pb2+ adsorption, while the negative enthalpy change (ΔH°=−60.75 kJ/mol) indicates an exothermic process. Reusability studies demonstrated that the AC/MnFe2O4 nanocomposite retained over 66% of its initial adsorption efficiency after nine adsorption–desorption cycles. The combination of high adsorption capacity, favorable kinetics, magnetic recoverability, and good regeneration performance highlights the AC/MnFe2O4 nanocomposite as a promising and sustainable adsorbent for Pb2+ remediation in water treatment applications.