The water-soluble polymers poly(styrene sulfonic acid-co-maleic acid) and poly(acrylic acid-co-maleic acid) were investigated with respect to their metal-ion-binding ability with ultrafiltration. The studied metal ions included Ag(I), Cu(II), Ni(II), Co(II), Ca(II), Mg(II), Pb(II), Cd(II), Zn(II), AI(III), and Cr(Ill) ions. The retention properties of the polyelectrolytes for the metal ions depended strongly on the ligand type. As for the carboxylate ligands, with increasing concentration and pH, the metal-binding affinity increased. (C) 2005 Wiley Periodicals, Inc.