Amine-functionalized cobalt ferrite nanoparticles as efficient magnetically separable adsorbents for Pb(II) and E. coli

Amine-functionalized cobalt ferrite (CoFe 2 O 4 –NH 2 ) nanoparticles were synthesized via a polyol-based solvothermal route and compared with non-functionalized CoFe 2 O 4 prepared by a sonochemical–combustion method as magnetically separable adsorbents. Structural and physicochemical properties were characterized by HRTEM, SAED, XRD, FTIR, VSM, N 2 and CO 2 adsorption. The functionalized material formed porous spherical aggregates (51 ± 8 nm) composed of 4–8 nm crystallites, exhibiting a significantly enhanced specific surface area compared to pristine CoFe 2 O 4 . Both samples displayed ferrimagnetic behaviour with high saturation magnetization, enabling rapid magnetic separation. Adsorption studies toward Pb(II), Cd(II), and Ni(II) revealed strongly ion-dependent behaviour. Langmuir modelling yielded a maximum adsorption capacity of 86.4 ± 1.5 mg g −1 for Pb(II) on CoFe 2 O 4 –NH 2 , more than twice that of the non-functionalized analogue. Furthermore, CoFe 2 O 4 –NH 2 achieved complete removal (100%) of Escherichia coli (10 2 cfu/mL) at 3–30 mg/mL and retained full efficiency after five reuse cycles. The results demonstrate that amine functionalization markedly enhances adsorption performance while preserving magnetic separability, highlighting the potential of CoFe 2 O 4 –NH 2 as a multifunctional platform for water remediation.