Two new chelating/ion-exchange resins have been obtained by amination of vinylbenzyl chloride-styrene-divinylbenzene copolymer, bearing ethoxycarbonylethyl phosphonate, with ethylenediamine and diethylenetriamine. The effect of close proximity of acidic and basic sites of ligand on chelating/ion-exchange of four divalent metal cations has been studied. In order to explain the behavior of the synthesized resins, a series of reference resins has been obtained. These resins have same types of functional groups--phosphonic acid and N-substituted amide of carboxylic acid but deposited randomly within polymer material. It has been found that close proximity of both acidic and basic sites, interacting with each other, gave antagonistic effect at pH 3.7 and 5.6 and suppressed uptake of Cu(II), Cd(II), Ni(II) and Zn(II) from weakly acidic solutions. For example Resins 1 and 2 with carbamylethylenephosphonates displayed at pH 3.7 log K-d CU(II) 2.10 and 3.06, whereas reference Resins 3 and 4 had log K-d Cu(II) 2.83 and 4.50, respectively. EPR studies of Cu(II) complexes formed in each case were used to explain the observed effect. (C) 2000 Elsevier Science Ltd. All rights reserved.