Testing of silica-chitosan decorated NiFe2O4 magnetic nano-adsorbents for adsorption of Pb(II), Zn(II), and Cd(II) ions from aqueous solution

Water contamination with toxic heavy metals such as Pb(II), Zn(II), and Cd(II) poses a serious environmental and health challenge. This study aims to develop efficient and reusable nanoadsorbents for wastewater treatment. Chitosan-functionalized NiFe2O4@SiO2 (NiFe2O4@SiO2-chitosan) core–shell nanospheres were synthesized using a co-precipitation method to produce NiFe2O4 nanoparticles, followed by silica coating and surface modification with chitosan. The functionalized nanocomposites demonstrated high adsorption capacities of 258.39 mg/g for Pb(II), 246.91 mg/g for Zn(II), and 224.21 mg/g for Cd(II). The adsorption behavior aligned with the Langmuir isotherm model, indicating monolayer coverage, while the kinetics followed a pseudo-second-order model, confirming chemisorption via coordination with the amino groups. The nanospheres also exhibited superparamagnetic behavior with a magnetization (Ms) of 12.41 emu/g, enabling rapid magnetic separation, and retained a removal efficiency of 77%–81% after five regeneration cycles. Overall, NiFe2O4@SiO2-chitosan nanocomposites demonstrate strong potential as sustainable, reusable, and magnetically separable adsorbents for the effective removal of heavy metals from wastewater.