Innovative Green Synthesis of New Waste‐Derived Chitosan‐Based Biocomposite via Initiator‐Free Gamma Irradiation: Mechanistic Insight Into Rare Earth Element Adsorption

ABSTRACT

Wastewaters containing rare earth elements (REEs) represent both an environmental concern and a valuable secondary resource for the recovery of economically important elements The development of sustainable and reusable adsorbents using synthesis approaches that minimize the need for chemical initiators is therefore of considerable interest. In this study, a chitosan–maleic acid–glycine (Cs‐MA‐Gly) biocomposite was prepared from commercially available chitosan using an initiator‐free gamma irradiation process. The resulting material was characterized by Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), and degree‐of‐deacetylation analysis. Batch adsorption experiments were performed to evaluate the removal of La(III), Ce(III), and Nd(III) ions from aqueous solutions. The highest adsorption performance was obtained at pH 5, with an equilibrium contact time of 140 min. The Langmuir maximum adsorption capacities q _max were 96.8, 100.5, and 105.7 mg g ⁻¹ for La(III), Ce(III), and Nd(III), respectively. The kinetic data were best described by the pseudo‐second‐order model, whereas the Langmuir isotherm provided the best fit to the equilibrium data, yielding correlation coefficients R ² of 0.995, 0.997, and 0.998 for La(III), Ce(III), and Nd(III), respectively. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic under the investigated conditions. Electrostatic attraction, ion exchange, and coordination involving functional groups within the biocomposite may contribute to the adsorption process. Furthermore, the material retained more than 92% of its initial adsorption capacity after five consecutive adsorption–desorption cycles, demonstrating promising reusability under the tested conditions. Overall, this study demonstrates the potential of initiator‐free gamma irradiation for preparing a reusable chitosan‐based biocomposite for REE recovery from aqueous solutions.