Role of water in the mechanism of the salt extraction to the organic solvent

Abstract

A two-electrode cell comprising a liquid/liquid interface is used to study the water clusters formation in the organic solvent phase following the extraction of tetraalkylammonium chloride (TAACl) from the aqueous phase. The change in the concentration of the common TAA+ ion on the aqueous side of the interface is monitored by the open circuit potential measurements. It is shown that the amount of TAACl extracted into the organic phase exceeds considerably the limit determined by the concentration of Cl− in the organic phase at a given interfacial potential difference and the electroneutrality condition. A mechanism is proposed including an accumulation of the excess TAACl in the water clusters formed from the hydration shell of the Cl− ions, water already dissolved in the organic phase, and additional water extracted from the aqueous phase. At higher concentration of TAACl in the aqueous phase this process leads to the formation of emulsion in the organic phase. Theoretical expressions describing the extraction of TAACl to the organic solvent phase are derived.