Recovery of cobalt from dilute aqueous solutions using activated carbon–alginate composite spheres impregnated with Cyanex 272

A novel adsorbent was designed for selective recovery of cobalt(ii) from synthetic binary cobalt(ii)-nickel(ii) and cobalt(ii)-manganese(ii) solutions, a synthetic multi-element solution and a real aqueous waste stream from the petrochemical sector. The adsorbent consisted of shaped activated carbon-alginate spheres impregnated with Cyanex 272. The synthesis was followed by characterisation using SEM, infrared spectroscopy, BET analysis and elemental analysis. Good selectivity for cobalt(ii) over nickel(ii) could be achieved during adsorption, while this was not the case for cobalt(ii) over manganese(ii). Cobalt(ii) and manganese(ii) were therefore fully adsorbed and stripped using a dilute sulphuric acid solution. The adsorbent was shown to be reusable in a column setup. Finally, the adsorbent material was used for the purification of a real aqueous waste stream from the petrochemical sector.