The investigation of the competitive binding of metal ions to a biogenic material comprised of organic peat immobilized in a polysilicate matrix was undertaken. This material was packed into 5.0 mL bed-volume columns using 40-60 mesh size particles. Two separate mixtures of metal ions were studied by monitoring the solution pH and the concentration of each metal in the effluent as a function of the volume of influent introduced to the material. These mixtures contained either the metal ions Ca2+, Mg2+, and Cu2+ or the ions Cu2+, Hg2+, and Pb2+. A general order of binding affinities was determined to be Mg2+ < Ca2+ << Cu2+ < Pb2+, < Hg2+. Comparisons of amounts of metal ions bound and protons released indicated the initial release of two protons for each divalent metal ion bound. However, prolonged exposure of the material to the metal solutions yielded a molar ratio of 1:1. This suggests the involvement of ion exchange sites followed by that of sites using an alternate binding mechanism. The presence of binding sites with varied mechanisms and metal ion affinities was further illustrated through the initial binding and subsequent release of lower affinity metal ions (e.g., Mg2+ and Ca2+). (c) 2006 Elsevier B.V. All rights reserved.