A Study of Cobalt Speciation Using a Sorption Method

The effect of cobalt(II) speciation on the parameters of its interphase distribution was studied for different types of sorbents. Inorganic sorbents based on the hydrolyzable elements have shown the highest selectivity for Co in neutral and alkaline media (pH 7–10). The experiments on the cobalt sorption onto KU-2 strong acid cation-exchange resin at pH 3–5 have shown the presence of Co2+, which shows a high affinity for all the sorbents studied. In the neutral and low alkaline media, the inorganic sorbents adsorbed Co(OH)+ and Co(OH)2 hydroxo complexes due to heterogeneous ion-exchange reaction (surface complex formation). The appearance of the S–pH dependences for the inorganic sorbents suggests higher stability of cobalt hydroxo complexes at microconcentrations as compared to the literature data. In the whole pH range studied, cobalt(II) showed a behavior of an inert sorbate with all the inorganic sorbents studied.