Equilibrium and mechanism of cobalt(II) extraction from chloride solution by hydrophobic 2-pyridineketoxime

• The 2-pyridyl ketoxime can efficiently extract Co(II) from chloride solutions.
• Extraction strongly depended on pH, contact time and ionic strength of solution.
• During the extraction, the oxidation of Co(II) to Co(III) is observed.
• As stripping agent a mixture of HCl and metal powder is proposed.

This work represents the results of detailed studies on cobalt(II) extraction from chloride solutions by 1-(2-pyridyl)tridecan-1-one oxime. The obtained results show that extraction of cobalt(II) ions strongly depended on pH, contact time and concentration of extractant, cobalt(II) and chloride ions. The slope analysis pointed that the cobalt(II) ions’ coordination by 2-pyridinektoxime occurs through a hydrogen exchange mechanism, forming mainly with CoCl+ and Co(NO3)+ a binuclear complex or higher agglomerates. Furthermore, during the extraction cobalt ions’ are also oxidised to the trivalent state, which in the next stage can be stripped off at argon atmosphere using HCl or HCl with metal powder as reductant.

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