Adsorptions of heavy metal ions by a magnetic chelating resin containing hydroxy and iminodiacetate groups

A magnetic Fe3O4–glycidyl methacrylate–iminodiacetic acid–styrene–divinyl benzene resin (MPGI) was synthesized by the polymerization of glycidyl methacrylate–iminodiacetic acid (GMA–IDA), divinyl benzene and styrene in the presence of magnetic Fe3O4 for the removal of Cu(II), Cd(II) and Pb(II) from aqueous solutions. The weight fractions of Fe3O4 and GMA–IDA within MPGI were analyzed by potentiometric titration of carboxylic acids and thermogravimetric analyzer. The equilibrium adsorption capacities of MPGI from their single-metal ion solutions were 0.88 mmol/g for Cu(II), 0.81 mmol/g for Pb(II) and 0.78 mmol/g for Cd(II). Increasing the concentration (0–0.3 M) of KCl, NaCl, MgCl2 and CaCl2 in Cu(II) or Pb(II) solution affected the adsorption behavior slightly. As the salt concentrations in Cd(II) solution increased, the adsorption capacities of Cd(II) decreased in the order: Mg2+ > Ca2+ > Na+ > K+. Within the pH range of 2–5, decreasing the pH of the Cu(II) solution did not produce remarkable changes in the equilibrium adsorption capacities. However, significant decrements occurred for the adsorptions of Pb(II) or Cd(II) when the pH values of the solutions were less than 3. The competitive adsorption tests verified that this resin had good adsorption selectivity for Cu(II) with the coexistence of Pb(II) and Cd(II).