The cross-linked polyaminocarboxylates for the removal of metal ions from aqueous solutions of the present invention are cross-linked anionic polyelectrolytes CAPE 6 and CAPE 9, containing pH-responsive amino acid residues. The cross-linked anionic polyelectrolytes have been synthesized via cycloco-polymerization and ter-polymerization of a diallylammonioethanoate monomer (90 mol %) and a cross-linker, 1,1,4,4-tetraallylpiperazinium dichloride (10 mol %) in the absence of SO2 (CAPE 6) and in the presence of SO2 (CAPE 9), respectively. For the sorbents CAPE 6 and CAPE 9, the efficiency of Cu2+ removal at an initial metal concentration of 200 ppb was found to be 77.5% and 99.4%, respectively. Treatment of real wastewater samples spiked with Cu2+ ions showed the excellent ability of the cross-linked anionic polyelectrolytes to adsorb metal ions.