Liquid-liquid extraction of group IB metal ions by thioethers

Liquid-liquid extraction of metal ions by means of organic extractants possessing divalent sulfur (thioethers) is discussed. it is shown that 1,2-bis(hexylthio)ethane (BHTE) and 13,14-benzo-1,4,8,11-tetrathiacyclopentadecane (TTX) are powerful extractants for soft metal ions such as copper(I), Silver(I), and gold(I). The same is true for the trivalent phosphorus compounds, triphenylphosphine and phosphite tristers, which were studied for comparison. Copper(II) and gold(III) are efficiently extracted with thioethers in combination with reducing agents. From an equilibrium study for the extraction of copper(I) and silver(I) by BHTE (L), a complex of the type ML₂X (M⁺, metal ion; X^?, anion) was proved to be extracted. In the extraction of gold, the combined use of a thioether and phosphite enhanced the extractability of the metal, compared with the independent use of these extractants; the synergism is discussed. Further, the reductive extractions of copper(II) and gold(III) were coupled with a photo-redox reaction, leading to light-induced extraction of these metal ions.