Treatment of Pb(II) and Cd(II) Pollutants in Aqueous Solution Using RSM‐Statistically Optimized Adsorption Over Fe 3 O 4 @mSiO 2 @Chitosan Magnetic Nanoadsorbents

ABSTRACT In this study, magnetic Fe 3 O 4 adsorbent was synthesized and functionalized with mesoporous silica‐chitosan to create a multifunctional Fe 3 O 4 @mSiO 2 @Chitosan for the removal of heavy metal ions from aqueous solution through adsorption. Box‐Behnken Design, an RSM tool, was used to create an experimental design for adsorption trials with 3 independent variables: pH of the solution, contact time, and concentration of metal ions. The mesoporous SiO 2 shell, with a negative zeta potential of −42.2 mV, prevents aggregation and maintains a high surface area. Chitosan functionalization adds –NH 2 and –OH groups to the adsorbent surface, providing strong chelation sites for Pb 2+ and Cd 2+ . The positive zeta potential (+28.1 mV) of the chitosan coating enhances electrostatic attraction to partially hydrolyzed metal species. The optimized adsorption design for Fe 3 O 4 @mSiO 2 @Chitosan achieved 96% removal efficiency for Cd(II) and 95% removal efficiency for Pb(II). An isotherm study confirmed that the adsorption data were best described by the Langmuir isotherm model with R 2 values ranging from 0.95 to 0.98. A shift from monolayer to multilayer adsorption was observed after functionalization of Fe 3 O 4 with @mSiO 2 @Chitosan. An inert layer on silica‐stabilized nanoparticles prevents their leaching and aggregation. The Fe 3 O 4 @mSiO 2 @chitosan adsorbent showed a 30% increase in adsorption capacity compared to pristine Fe 3 O 4 .