Two new chelate-forming polymers, poly[8-hydroxyquinoline-5,7-diyl(piperazine-N, N'-bismethylene)] (Polymer I) and poly[8-hydroxyquinoline-5,7-diyl(N, N'-dimethylethylenediamine N, N'-bismethylene)] (Polymer II) were prepared through a Mannich-type condensation of 8-hydroxyquinoline with formaldehyde and piperazine or N,N'-dimethylethylenediamine, respectively. The chelation properties of these polymers toward the divalent metal-ions, Mg2+, Ca2+, Ni2+, Cu2+, Zn2+, and Cd2+ were studied by a static batch equilibration technique at 25 degreesC as a function of contact time and pH. Polymers I and II exhibited faster rates of metal-ion uptake and highly improved capacities than their parent phenol-formaldehyde system, poly(8-hydroxyquinoline-5,7-diylmethylene). Polymer I exhibited higher capacities and a more pronounced selectivity towards Cu2+ than Polymer II. The nature and rigidity of the spacer group was found to play a paramount role in determining the chelation characteristics of the chelating polymer; the use of piperazine as a spacer group was found to considerably enhance the capacity and selectivity of this class of chelating polymers toward divalent metal ions. (C) 2004 Elsevier B.V. All rights reserved.