ABSTRACT
In the practice of the environmental analytical chemistry of metal ions, particles play an important role. Adsorption kinetics of metal ions in disperse systems are usually considered on a more or less empirical level. In cases where convection is important, the basis of the metal ion transport is provided by liquid flow and diffusion simultaneously. For many different metal ions, the rate constants of complexation reactions are essentially independent of the nature of the substituting ligand. Metal ion desorption is provoked by addition of a certain competing ligand, usually one that yields a spectrophotometrically active complex. The crystal flow cell offers a method to determine adsorption and desorption of certain metal species. Colloid-bound metal ions are identified with “strongly adsorbed” metal that features only an “extremely slow release”. The bioavailability of metal ions in a flowing natural system may be limited by the characteristic hydrodynamic time constant of the system.
