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

Magnetic polymethylmethacrylate (mPMMA) microbeads carrying ethylene diamin e (EDA) were prepared for the removal of heavy metal ions (i.e., copper, le ad, cadmium, and mercury) from aqueous solutions containing different amoun t of these ions (5-700 mg/L) and at different pH values (2.0-8.0). Adsorpti on 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 he avy 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 7 9.8 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 wa s found to be Cu(II) > Pb(II) > Cd(II) > Hg(II) for both under noncompetiti ve and competitive conditions. The adsorption of heavy metal ions increased with increasing PH and reached a plateau value at around pH 5.0. The optim al pH range for heavy metal removal was shown to be from 5.0 to 8.0. Desorp tion 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 f or more than five adsorption-desorption cycles without considerable loss of adsorption capacity. (C) 2000 John Wiley & Sons, Inc.