Migration experiments focused on the relationship between sorption mechanism and chemical form of cobalt were carried out by means of column method. Adsorbents packed in the column were natural sand and artificial materials, for instance, charcoal. The experimental results were compared with three different migration models based on ion exchange, filtration, and adsorption, respectively.
Cobalt existed as cation in the low pH region, where the migration behavior of cobalt was described by the ion exchange model. Cationic and colloidal species of cobalt coexisted in the pH 8.5 solution. The migration behavior of cobalt in this solution was satisfactorily described by the coupled model of the ion exchange and the filtration. Chelated anionic cobalt was not retained on the sand but retained on the charcoal and the other artificial materials to considerable extent. Breakthrough curves of cobalt in the charcoal column were successfully described by the adsorption model. Chelated cobalt was retained on the charcoal better than cationic cobalt. Distribution coefficients of chelated cobalt and cationic one were 670 ml/g and 130 ml/g, respectively.