Three adsorbents have been synthesized by immobilization of Schiff base ligands on the surface of SiO2-Al2O3 mixed oxides and evaluated for the removal of Cd(II) and Pb(II) from aqueous solutions. The contact time to attain equilibrium for maximum adsorption was 120 min. These heterogeneous Schiff base ligands were found to be effective adsorbents for the removal of heavy metal ions from solution, with Si/Al-pr-N=salicylaldehyde having a high adsorption capacity for Cd(II) ions and Si/Al-pr-N=pyridine-2-carbaldehyde having a high adsorption capacity for Pb(II) ions. The adsorption of heavy metal ions has been studied in terms of pseudo-first-order and pseudo-second-order kinetics, and the Freundlich, Langmuir, and Langmuir-Freundlich isotherm models have also been applied to the equilibrium adsorption data.