Solvent extraction of copper(I) and (II) as thiocyanate complexes with tetrabutylammonium ions into chloroform and with trioctylphosphine oxide into hexane

The solvent extraction of copper(II) in 1 mol dm(-3) Na(SCN, NO3), in which the thiocyanate concentration was 0.01 to 1 mol dm(-3), with tetrabutylammonium ions (tba(+)) into chloroform and with trioctylphosphine oxide (TOPO) into hexane was studied. Also, the solvent extraction of copper(I), which was formed by reducing copper(II) by ascorbic acid in these aqueous solutions, was studied. By a statistical analysis of the extraction data, it was concluded that copper(I) was extracted as tba(+)Cu(I)(SCN)(2)(-) and (CuSCN)-S-I(TOPO)(3), and copper(II) was extracted as (tba(+))(2)CUII(SCN)(4)(2-) and Cu-II(SCN)(2)(TOPO)(3). Although copper(I) was extracted with both extractants better than copper(II) in the lower thiocyanate concentration range, copper(II) was extracted better in the higher thiocyanate concentration range. This was concluded to be due to better extraction of the extractable species of copper(I) than those of copper(II); however, copper(I) formed unextractable complexes much more than did copper(II) in the higher thiocyanate concentration range in the aqueous phase.