The sustainable valorization of agricultural residues into high-performance adsorbents offers an environmentally responsible solution for heavy metal remediation. In this study, cotton straw was successfully converted into nanocellulose (NC) and further modified with aluminium oxide to develop a nanocomposite (NC@Al₂O₃) for efficient Pb(II) removal from aqueous media. Structural and morphological characterization using FTIR, XRD, FESEM, and TEM confirmed successful nanocellulose isolation and uniform Al₂O₃ deposition. The synthesized NC exhibited a crystallinity index of 82.38%, which decreased to 31.32% after Al₂O₃ modification, indicating surface coating effects. Zeta potential analysis demonstrated a strong negative surface charge for NC (− 51.3 mV), reduced to − 20 mV after modification, facilitating enhanced electrostatic interaction with Pb²⁺ ions. Batch adsorption studies revealed maximum Pb²⁺ removal efficiencies of 92% (NC) and 94% (NC@Al₂O₃) at pH 5, 0.5 g dosage, 75–135 min contact time, 30 °C, and 2 mg L⁻¹ initial concentration. Isotherm analysis showed excellent agreement with the Langmuir model (R² = 0.99), confirming monolayer adsorption, with favourable separation factors. Kinetic evaluation indicated pseudo-second-order behaviour for NC, while intraparticle diffusion significantly influenced NC@Al₂O₃ adsorption. Thermodynamic parameters revealed exothermic adsorption for NC and weakly endothermic behaviour (ΔH° = 2.85 kJ mol⁻¹) for NC@Al₂O₃. Regeneration studies demonstrated high reusability, achieving 76.87% (NC) and 90.69% (NC@Al₂O₃) desorption at 0.1 M HCl. Overall, the study establishes cotton straw-derived nanocellulose composites as scalable, eco-friendly, and cost-effective adsorbents for sustainable heavy metal remediation.
Sheetal et al. (Fri,) studied this question.