Preparation and characterization of magnetic polymethylmethacrylate microbeads carrying ethylene diamine for removal of Cu(II), Cd(II), Pb(II), and Hg(II) from aqueous solutions

Abstract

Magnetic polymethylmethacrylate (mPMMA) microbeads carrying ethylene diamine (EDA) were prepared for the removal of heavy metal ions (i.e., copper, lead, cadmium, and mercury) from aqueous solutions containing different amount of these ions (5-700 mg/L) and at different pH values (2.0-8.0). Adsorption of heavy metal ions on the unmodified mPMMA microbeads was very low (3.6 mu mol/g for Cu(II), 4.2 mu mol/g for Pb(II), 4.6 mu mol/g for Cd(II), and 2.9 mu mol/g for Hg(II)). EDA-incorporation significantly increased the heavy metal adsorption (201 mu mol/g for Cu(II), 186 mu mol/g for Pb(II), 162 mu mol/g for Cd(II), and 150 mu mol/g for Hg(II)). Competitive adsorption capacities tin the case of adsorption from mixture) were determined to be 79.8 mu mol/g for Cu(II), 58.7 mu mol/g for Pb(II), 52.4 mu mol/g for Cd(II), and 45.3 mu mol/g for Hg(II),The observed affinity order in adsorption was found to be Cu(II) > Pb(II) > Cd(II) > Hg(II) for both under noncompetitive and competitive conditions. The adsorption of heavy metal ions increased with increasing PH and reached a plateau value at around pH 5.0. The optimal pH range for heavy metal removal was shown to be from 5.0 to 8.0. Desorption of heavy-metal ions was achieved using 0.1 M HNO3. The maximum elution value was as high as 98%. These microbeads are suitable for repeated use for more than five adsorption-desorption cycles without considerable loss of adsorption capacity. (C) 2000 John Wiley & Sons, Inc.