Nanoarchitectured Biocomposites: Synergistic Halloysite-Chitin Magnets for Sustainable Cadmium (II) Mitigation in Water

A novel functionalized halloysite-nanochitin magnetic biocomposite, NiFe₂O₄-HNTs-chitin, was synthesized to effectively remove Cd (II) ions from aqueous media. The morphology and structure of the nanoadsorbent were analyzed using TEM, SEM, XRD, FT-IR, BET, EDS, and VSM. The adsorption studies demonstrated a peak Cd (II) adsorption capacity of 400.00 mg/g under conditions of 25°C, pH 6, using 0.05 g/100 mL of NiFe₂O₄-HNTs-chitin, with equilibrium achieved within just 10 min. Adsorption kinetics follow a pseudo-second-order model, and the isothermal data corresponded with the Langmuir model, suggesting monolayer adsorption on the adsorbent surface and a chemically controlled rate-determining step. The thermodynamic analysis showed that the uptake process is both spontaneous and exothermic (ΔH = −511.028 kJ/mol, ΔG = −32.78 kJ/mol). Remarkably, the adsorbent maintained high uptake and release effectiveness even after four cycles, with the primary mechanism of Cd (II) removal attributed to chelation through oxygen (O) and nitrogen (N) atoms. These results demonstrate that NiFe₂O₄-HNTs-chitin is a highly efficient and recyclable sorbent for removing Cd (II) ions from water, with significant practical applicability.