Amino-functionalized core-shell magnetic mesoporous composite microspheres for Pb(II) and Cd(II) removal

Amino-functionalized Fe₃O₄@mesoporous SiO₂ core-shell composite microspheres NH₂-MS in created in multiple synthesis steps have been investigated for Pb(II) and Cd(II) adsorption. The microspheres were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), N₂ adsorption-desorption, zeta potential measurements and vibrating sample magnetometer. Batch adsorption tests indicated that NH₂-MS exhibited higher adsorption affinity toward Pb(II) and Cd(II) than MS did. The Langmuir model could fit the adsorption isotherm very well with maximum adsorption capacity of 128.21 and 51.81 mg/g for Pb(II) and Cd(II), respectively, implying that adsorption processes involved monolayer adsorption. Pb(II) and Cd(II) adsorption could be well described by the pseudo second-order kinetics model, and was found to be strongly dependent on pH and humic acid. The Pb(II)- and Cd(II)-loaded microspheres were effectively desorbed using 0.01 mol/L HCl or EDTA solution. NH₂-MS have promise for use as adsorbents in the removal of Pb(II) and Cd(II) in wastewater treatment processes.