Separation of Iron and Cobalt from Sulphate Solutions by Solvent Exraction

Authors: Ercan AÇMA, Nizamettin KARAHAN

Abstract: The separation of cobalt and iron from sulphate solutions by solvent extraction was investigated in this experimental study. D2EHPA (Di-2-ethyl hexyl phosphoric acid) and Kelex 100 (7-(4-ethyl-1-methyloctil-8-hydroxyquinoline) were used as organic phases. Shell Jet Al is a suitable diluent for D2EHPA (20% D2EHPA + 80% Shell Jet Al), but the addition of Nonyl Fenol as a modifier phase is necessary for Kelex 100 (20% Kelex 100, 10% Nonyl Fenol, 70% Shell Jet Al). According to the experiments, Co and Fe were loaded in D2EHPA from single metal ion containing solutions at pH 5.95 and 4.83, respectively. When the Kelex 100 was used, the equilibrium pH values obtained were 8.83 for Co and 3.70 for Fe in the loading step. The optimal A/O ratio was 1. When t he initial iron concentration in solution increased, the loading efficiencies of this metal decreased for both of organic phases. The loading efficiency of Co decreased in D2EHPA when the cobalt ion concentration increased in initial solution. However, solutions containing upto 13 g.l-1 Co were treated with Kelex 100. The loading ratio of iron was higher than Co for the both organic phases. After loading step, Co was stripped with 150 g.l-1 H2SO4 solution from D2EHPA phase and 250 g.l-1 H2SO4 solution from Kelex 100 at maximum efficiency. For the stripping of iron from both organic phases, it was necessary to use 300 g.l-1 HCl solution. In the determined optimum conditions, the separation of Co and Fe from sulfate solutions by loading in Kelex 100 and by stripping with H2SO4 solution to aqueous phase was impossible. The separation of cobalt and iron was possible with the separation ratio of 400 from cobalt solutions containing upto 0.5-0.6 g.l-1 Fe by loading in D2EHPA and by stripping with H2SO4 solution. However, the use of both organics would be more suitable for the enrichment of dilute cobalt sulphate solutions containing no iron, because the above iron concentration could be reached by the chemical precipitation methods.

Keywords: Hydrometallurgical, D2EHPA, Kelex 100, Solvent Extraction, Cobalt, Iron