Solvent extraction of copper(I) anionic thiocyanate complex into chloroform and 4-methyl-2-pentanone as ion-pairs with tetrabutylammonium

The study concerns the solvent extraction of 10(-5) to 10(-4) mol dm(-3) copper originally in the divalent state in 0.1 mol dm(-3) sodium nitrate solutions containing 10(-5) to 10(-3) mol dm(-3) thiocyanate, ascorbic acid and tetrabutylammonium ions (tba(+)) into chloroform or 4-methyl-2-pentanone (MIBK). The extraction of copper was quantitative in the highest thiocyanate concentration range in the presence of ascorbic acid and 10(-3) mol dm(-3) tba(+); no extraction was found in the absence of this reducing reagent. In all the thiocyanate concentrations, the extracted species was found to be in the form of tba(+)Cu(I)(SCN)(2)(-) but the copper in the aqueous phase containing this reducing reagent and thiocyanate was found to be still predominantly in the divalent state. The results indicate approximately complete dissociation of the extracted ion-pairs in MIBK, but negligible dissociation in chloroform.