Effect of the nature of the crosslinking agent on the metal-ion complexation characteristics of 4 mol % DVB- and NNMBA-crosslinked polyacrylamide-supported glycines

Abstract

Metal-ion complexation behavior of glycine functions supported on divinylbenzene (DVB)- and N,N'-methylene bisacrylamide (NNMBA)-crosslinked polyacrylamide was carried out toward Co(II), Ni(II), Cu(II), and Zn(II) ions. The polymeric ligands and the derived metal complexes were characterized by IR, UV, and EPR spectra and by SEM. The metal-ion complexation of the rigid DVB-crosslinked system is lower than that of the semirigid NNMBA-crosslinked system. The glycine ligands renervated after the desorption of the metal ions showed an unusual specificity toward the desorbed metal ion. The low degree of crosslinking makes the desorption process simple and shows fast rebinding kinetics. The metal-ion-desorbed polymeric ligands would have pockets or holes characteristic of the desorbed metal ion, resulting in its specific rebinding. The rigidity of the crosslinking also determines the kinetics of metal-ion rebinding. The specificity and selectivity characteristics of the crosslinked polymeric ligand was found to be increased as the crosslinking agent changes from semirigid NNMBA to rigid and hydrophobic DVB. Thus, copper-desorbed resins showed an increased specificity toward copper ions and selectively binds copper ions from a mixture of copper and cobalt ions. The metal-ion specificity and selectivity characteristics of the metal-ion-desorbed system is exploited for the concentration of desorbed metal ions from a mixture of metal ions. The resin is amenable for a continuous process and can be regenerated several times.