LIQUID-LIQUID-EXTRACTION OF METAL-IONS WITH A CYCLIC MONOAZATETRATHIOETHER

A new cyclic monoazetetrathioether, 1-aza-4,7,11,14-tetrathiacyclohexadecane (ATCH), was synthesized. The liquid-liquid partition of ATCH between water and l,2-dichloroethane was examined. It was shown that ATCH transferred from dichloroethane to water below pH 5.5. The values of the protonation constant (Kb) and the distribution constant (K-DR) of ATCH were estimated to be log K-b=5.8 and log K-DR= 1.7. Provided in the presence of picrate ion, the protonated ATCH in the aqueous phase formed an ion pair, with the picrate ion and was extracted into the organic phase. The liquid-liquid extraction of metal ions with ATCH in the presence of the picrate ion was examined. Soft metals such as Ag(I), Cu(I) and Hg(II), except for Cd(II), were well extracted in the presence of picrate. On the other hand, hard and the intermediate metals such as Mg(II), Zn(II), Mn(II), Ni(II) and Co(II) were not extracted at all, except for Cu(II). The compositions of the extracted species were in the ratio 1 : 1 : 1 (M : L : Pic) for Ag(I) and Cu(I) and 1 : 1 :2 for Hg(II). The extraction constants of Ag(I), Cu(I) and Hg(II) were evaluated as follows: log K-ex=9.8 for Ag(I), 8.9 for Cu(I) and 12.3 for Hg(II). The extractability and selectivity of ATCH is similar to that of 1,4,8,11-tetrathiacyclotetradecane (TTCT).