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Poly(methyl methacrylate) (PMMA) microspheres carrying poly(ethylene imine) (PEI) were prepared for the removal of heavy-metal ions (copper, cadmium, and lead) from aqueous solutions with different amounts of these ions (50 -600 mg/L) and different pH values (3.0 -7.0). Ester groups in the PMMA structures were converted to imine groups in a reaction with PEI as a metal-chelating ligand in the presence of NaH. The adsorption of heavy-metal ions on the unmodified PMMA microspheres was very low [3.6 mol/g for Cu(II), 4.6 mol/g for Cd(II), and 4.2 mol/g for Pb(II)]. PEI immobilization significantly increased the heavy-metal adsorption [0.224 mmol/g for Cu(II), 0.276 mmol/g for Cd(II), and 0.126 mmol/g for Pb(II)]. The affinity order of adsorption (in moles) was Cd(II) Ͼ Cu(II) Ͼ Pb(II). The adsorption of heavy-metal ions increased with increasing pH and reached a plateau value around pH 5.5. Their adsorption behavior was approximately described with the Langmuir equation.

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