SOLVENT-EXTRACTION OF 7 TRIVALENT METAL-IONS IN AQUEOUS PERCHLORATE SOLUTIONS WITH TRIOCTYLPHOSPHINE OXIDE IN HEXANE AND RAPID EXTRACTION OF CHROMIUM(III)

Solvent extraction of scandium(III), yttrium(III), lanthanum(III), eur opium(III), gallium(III), indium(III), and chromium(III) in weakly aci dified 1 mol dm(-3) NaClO4 solutions with trioctylphosphine oxide (TOP O) in hexane was studied. The extraction equilibrium was established b y the two phase agitation for within 3 min and the extracted species e xcept chromium(III) were found to be M(TOPO)(4)(3+)(ClO4-)(3). The ext raction of chromium(III) was also achieved by the two phase agitation for only a short time but, from the dependence of the extraction on th e TOPO concentration, the extracted species was assumed to be Cr(TOPO) (6)(3+)(ClO4-)(3). Since the inert Cr(H2O)(6)(3+) was SO rapidly extra cted and the solvation number was higher than that of the other metal ions, the TOPO molecules were assumed to combine with the hydrating wa ter molecules by hydrogen bonds which can be formed in a short time ev en when the metal ion was inert. The chromium(III) was also extracted rapidly from 1 mol dm(-3) NaSCN, NaNO3, NaBr, and NaCl solutions with TOPO in hexane and the extraction was better from NaSCN solution than from NaClO4 solution but it was not effective from the solutions of ot her salts.