Sorption behavior of cobalt in sulfuric acid solutions

Interaction of cobalt(II) ions with functional groups of sorbents based on amines, which additionally contain carboxyl (ANKB-35) and hydroxyl (SB-1, AN-31) fragments, is investigated. It is shown that the form of existence of the sorbent exerts an insignificant effect on cobalt absorption with ampholyte ANKB-35. Alternatively, anion exchangers AN-31 and SB-1 sorb cobalt in noticeable amounts only in the deprotonated form (OH−). The analysis of obtained results on the cobalt sorption in equilibrium conditions as well as the IR spectroscopy provides clarification of specific features of the process. It is found that cobalt is adsorbed owing to the complex formation with nitrogen of amino groups of sorbents with the additional formation of bonds with carboxyl (ANKB-35) and hydroxyl (AN-31, SB-1) groups. In addition, the process is complicated by precipitation in the phase of sorbents according to the scheme Co2+ → Co(OH)2 → Co(OH)3. This effect is especially characteristic of the SB-1 anion exchanger, which contains a considerable amount of hydroxyl groups. The obtained data provide a justified choice of the ion exchanger and conditions of its use to concentrate Co2+ from solutions of sulfuric acid leaching of various cobalt-containing raw materials.