Extraction of metals under Galvani potential control

Galvani potential established by a common ion at an interface between two immiscible electrolyte solutions (ITIES) can serve as a driving force and catalyse various biphasic reactions. Using potential determining ions provides a means to scale-up electrochemical processes at the ITIES from the laboratory, analytical scale – at least – to the preparative scale without relying on electrodes and an external power source. However, research on the applications of this phenomenon has been rather scarce. In this work, the effect of Galvani potential on the extraction of various metals with diphenylthiocarbazone (Dithizone) dissolved in 1,2-dichlorobenzene (DCB) was investigated using conventional 4-electrode cell cyclic voltammetry (CV) and extraction experiments in which the Galvani potential at the ITIES was controlled by a common ion. Especially, in the case of metals that do not spontaneously form a complex with the ligand, extraction was not detectable in the CV within the potential window provided by the supporting electrolytes. However, the extraction experiments show that the Galvani potential does enhance the extraction rate of these metals significantly, which indicates that the established potential exceeds the potential window of the CVs. Some of the metals were found to have affinity to the potential determining ions, and negative effect of additional electrolytes in the water phase on the extracted fraction was observed, which will have to be taken into account if potential determining ions were applied in extraction.