Extraction equilibrium of ytterbium(III) with sulfoxides and their mixtures

The extraction equilibria of¹⁷⁵Yb from thiocyanate solutions with di-n-pentyl sulfoxide (DPSO), di-n-octyl sulfoxide (DOSO), tri-n-octylphosphine oxide (TOPO) and their mixtures in carbon tetrachloride has been investigated. A relatively small synergistic enhancement has been observed with mixtures of dialkyl sulfoxides (DPSO+DOSO) and also with mixtures of DPSO+TOPO. These extraction data have been analyzed with the aid of a computer by taking into account complexation of the metal in the aqueous phase by inorganic ligands and assuming a set of product species in the organic phase and adjusting their formation constants through an iterative non-linear least-squares procedure to obtain the best fit to the data. The extraction of the metal is inversely and linearly dependent upon the dielectric constant of the solvent and temperature of the system.