A microcapsule containing chelating resin selective for cadmium (II)

Ion exchange and solvent extraction technologies have been widely used for uptake and recovery of heavy metals from aqueous phases. However, different problems have been encountered on applying these techniques. Alternative to overcome these limitations is the microcapsulation of extractants within a functionalized polymeric shell. A chelating resin was prepared by treating Ceralite IR 400 with chromotropic acid and characterized by FTIR spectrum and sulphur analysis. Then, polystyrene microcapsules containing chelating resin were prepared by interfacial copolymerization of w/o/w emulsions. The adsorption of Zn(II), Cd(II), Ni(II), Co(II), Cu(II) and Pb(II) into microcapsule was studied by batch experiments. The effect of pH and counter ions on adsorption behavior has been investigated. Maximum uptake of Cd(II) into microcapsule was found in the presence of I ions and remained unchanged in the pH range 1-7 and the Cd(II) ions remained unaffected in the microcapsule even in 1 M HCl solution. The selectivity for Cd(II) was over four times greater than the other investigated metal ions. The breakthrough capacity for Cd(II) was 2.68 m mol/g microcapsule. The microcapsule packed mini-column has been applied for separation of Cd(II) from Zn(II), Pb(II), Cu(II), Ni(II) and Co(II). The microcapsule has also been tested for selective recovery of Cd(II) from river water.