Kinetic study of the speciation of copper(II) bound to a hydrous ferric oxide
The equilibrium distribution of metal ions over distinguishable sites of a heterogeneous complexant may be determined by monitoring the rate of reaction of the equilibrated system with a ligand capable of stripping the metal ion off the various sites. This kinetic speciation method has the advantage that it indicates not only the equilibrium distribution but also the relative lability of complexes. It may also reveal lability differences among complexes of very similar thermodynamic stability. This kinetic method has been applied to the speciation of Cu-(II) in the presence of a hydrous ferric oxide colloid using a copper-selective color-forming chelating ligand. The pH (4.5-1.0) range spans the region over which an «adsorption edge» is observed in conventional isotherm measurements