In Situ Coprecipitation Formed Highly Water-Dispersible Magnetic Chitosan Nanopowder for Removal of Heavy Metals and Its Adsorption Mechanism

The requirement for enhanced, less expensive, and eco-friendly nanocomposites as an adsorbent is highly preferred for removal of heavy metals and in the major applications of environmental remediation. For widespread application prospects, a simple and cost-effective method for highly effective nanoadsorbent preparation is mainly studied. In this study, by using natural polymer chitosan (CS) and different iron ion precursors, a facile in situ one-step coprecipitation synthetic approach is used to develop water-dispersible chitosan/Fe₃O₄ nanocomposites. The physical and chemical properties of the synthesized magnetic chitosan nanopowder (MCNP) before and after adsorption were studied using FTIR, SEM, TEM, XRD, BET, and TGA instrumental methods. The adsorption efficiency was specifically studied by varying initial metal ion concentration, pH of the solution, and MCNP dosage for Pb(II) and Cu(II) as a model pollutant. The experimental data obtained are fitted by three adsorption isotherms and reaction kinetics models. The adsorption of Pb(II) and Cu(II) onto MCNP (1 g/L) followed a Langmuir adsorption isotherm with the highest adsorption capacity of 113.38 and 92.34 mg/g at pH = 5.5 and temperature 25 °C, respectively. The results of thermodynamic analysis show that the adsorption of Cu(II) on MCNP is endothermic, while the Pb ions are exothermic. MCNP nanocomposite is regenerated by the EDTA-2Na-washing method and exhibited greater stability with reusability over usage of five times. Overall, the synthesized water-dispersible MCNP presented regeneration capability and stability toward the aqueous phase and is an excellent adsorbent for heavy metals removal processes.