NiFe₂O₄@SiO₂-NH-cellulose-protein composite biopolymer as a modified cysteine-rich protein structure for heavy metals...

In this study, a multifunctional nanocomposite, NiFe₂O₄@SiO₂-NH-cellulose-protein, was successfully synthesized through a multi-step process involving surface modification, biopolymer integration, and protein functionalization. The sample was characterized using various analytical techniques. FT-IR spectra confirmed the successful functionalization. XRD analysis showed that the NiFe₂O₄ spinel structure remained intact, with crystallite sizes ranging from 9.45 nm (Scherrer method). TGA analysis of the sample revealed a significant weight loss of 72.1 % at 385 °C. The EDX and ICP results indicated the presence of 42.68 % oxygen, 31.34 % carbon, 2.98 % nickel, 5.63 % iron, 7.59 % silicon, 2.89 % sulfur, and 6.89 % nitrogen in the composite. The adsorbent exhibited excellent performance for Cd(II), Ni(II), and Pb(II) removal from aqueous solutions. Adsorption was highly pH-dependent, with optimal removal efficiencies (Cd: 89 %, Ni: 87 %, Pb: 91 %) achieved at pH 6. Increasing adsorbent dosage enhanced removal up to 1 g/L, beyond which aggregation reduced efficiency. Adsorption capacity increased with metal ion concentration up to 600 mg/L, following a Langmuir-type monolayer behavior with maximum capacities of 833, 909, and 714 mg/g for Cd(II), Ni(II), and Pb(II), respectively. Kinetic studies revealed rapid adsorption within 60 min, reaching equilibrium at 120 min, best described by the Elovich model, indicating complex chemisorption. FT-IR analysis confirmed the involvement of amine, thiol, and carbonyl groups in metal ion binding. These results highlight the material's strong potential for efficient heavy metal remediation.