Utilization of magnetic hydrogels in the separation of toxic metal ions from aqueous environments

We report the synthesis of poly(2-acrylamido-2-methyl-1-propansulfonic acid-co-vinylimidazole), p(AMPS-c-VI) hydrogels from various amounts of 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) and N-vinylimidazole (VI) monomers by photo-polymerization technique. Hydrogel composites with magnetic properties were synthesized in situ by incorporating Fe(II) and Fe(III) ions into p(AMPS-c-VI) hydrogels network and then reducing them with alkaline solution. Hydrogels swellings were performed for both bare and magnetic hydrogels. The selective removal capability of toxic metal ions, Cu(II), Cd(II), Fe(II), and Pb(II) by these hydrogels was studied in aqueous medium. Desorption studies were also performed in weakly acidic media to observe whether these hydrogel composites can be utilized as reusable tool for the toxic metal ion removal. The effects of the gel amount, contact time with metal ions, metal species and metal ion concentrations on absorption phenomena were evaluated. The equilibrium removal process of metal ions by the composite hydrogels complies well with the Langmuir adsorption isotherm model.