The metal transport protein transferrin, when immobilized to Sepharose, can serve as an affinity media for the selective removal and subsequent release of heavy metal ions from aqueous solution. The material is stable over the pH range of 2-10, is self-indicating for the binding of certain metal ions, and maintains its integrity towards metal-binding capacity for long periods of time. In one step heavy metal ion concentrations can be reduced by at least five orders of magnitude to, at most, part per billion levels. The findings here presented suggest a novel practical method for the decontamination and/or recovery of metals ions from very dilute solutions and represent the first efforts to extend the concept of affinity chromatography to metal ions.