Two, three dihydroxybenzoic acid (DHBA), a portion of the metal chelating domain of enterobactin, was immobilized on crosslinked organic polymer polyallylamine (PAAm) and used as a chelating agent for iron removal from aqueous solutions. The swelling behavior of PAAm and PAAm hydrogels conjugated with dihydroxybenzoic acid and the effect of contact time on the swelling and binding capacity of the hydrogel was investigated at several pH values to define the absorption mechanism. Iron uptake kinetics followed the pseudosecond order Ho model and equilibrium was described by either Temkin or Freundlich isotherms. Maximum chelating capacities of the hydrogels were found to be 500-1500 mg Fe(3+) g(-1) and 1500-2500 mg Fe(2+) g(-1) for PAAm and PAAm/DHBA hydrogels, respectively, depending on the pH of the media. The selectivity of the conjugate hydrogel toward ferric ions was studied at several different pH values. At every pH ranging from 2 to 7.5, the conjugate hydrogel showed relatively high binding affinity for ferric ions. The selective and rapid, high affinity binding of iron by this siderophore-mimetic hydrogel offers potential application as a nonabsorbed chelator for iron in the gastrointestinal tract of patients suffering from iron overload diseases. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1384-1392, 2011