Thermodynamic Analysis of Trace Cobalt(II) Extraction from Cobalt Chloride Aqueous Solution Using Cyanex 272 in Kerosene

Abstract

In this study, it was researched that the extraction of Co(II) from CoCl2 aqueous solutions using Cyanex 272 (bis(2,4,4-trimethylpentyl) phosphonic acid) in kerosene and determined the effects of the equilibrium pH value, extractant concentration and chloride ion concentration on the extraction of cobalt at different temperatures. The results indicate that the distribution ratio of cobalt increases as the equilibrium pH value, extractant concentration and extraction temperature increase. However, the cobalt distribution ratio decreases as the chloride ion concentration increases. We calculated the equilibrium constants (AH9, AG9, and AS9) for a range of temperatures and investigated the relationship between AG9 and T. The extraction reaction of cobalt was determined to be an endothermic reaction; thus, raising the temperature was beneficial to the reaction.