Magnetic polymethylmethacrylate microbeads carrying amine functional groups for removal of Pb(II) from aqueous solutions

Magnetic polymethylmethacrylate [mPMMA] microbeads (150-200 mum in diameter) carrying hexamethylene diamine (HMDA) were prepared for the removal of Pb(II) ions from aqueous solutions containing different amounts of Pb(II) ions (5-100 mg/L) and at different pH values (2.0-6.0). Adsorption rates were observed as high at the beginning of the adsorption process, and then equilibrium was reached in about 20 minutes. Adsorption of Pb(II) ions on the unmodified mPMMA microbeads was negligible (4.2 mu mol/g). While HMDA-incorporation significantly increased the Pb(II) adsorption was (128 mu mol/g). The adsorption of Pb(II) ions increased with an increasing pH, and reached a plateau value at around pH 5.0. The optimal pH range for Pb(II) removal was shown to be from 5.0 to 6.0. Desorption of Pb(II) ions was achieved using 0.1 M HNO3. The maximum desorption value was as high as 98%. These microbeads are suitable for repeated use for more than five adsorption-desorption cycles without a considerable loss of adsorption capacity.