Countercurrent extraction separation of some platinum group metals: part III

Abstract

The bromo complexes of platinum(IV), palladium(II), rhodium(III), and iridium(IV) were prepared and studies were made on their distribution between hydrobromic acid solutions and various common solvents. The solvents employed were n-tributyl phosphate (TBP), methyl isobutyl ketone, amyl acetate, and various TBP-benzene mixtures. Distribution coefficients as a function of HBr concentration are given for each metal for each solvent system. A careful study of the measured distribution coefficients clearly showed that a number of binary and ternary mixtures of the metals can be resolved with a Craig countercurrent distribution apparatus. Rh-Pt and Rh-Pd mixtures in 4.38 M HBr solutions were quantitatively separated on a Io-stage Craig apparatus using a 90% TBP-10% benzene solvent. Rh-Ir mixtures in 4.38 M HBr were resolved by 3 consecutive batch extractions with 90% TBP-10% benzene. Mixtures of Pd, Rh, and Ir in 4.38 M HBr were resolved in 90 stages using methyl isobutyl ketone as the solvent. Pd, Rh and Ir were recovered in 97.0, 87.6 and 94.5% yields, respectively. Mixtures of Pd, Rh and Pt in 4.38 M HBr were resolved in 90 stages using amyl acetate and methyl isobutyl ketone as solvents. Pd, Rh and Pt were recovered in 90.0, 96.0 and 94.0% yields, respectively. Two computer programs for the IBM 1620 Computer are given ; these facilitate the comparison of theoretical and actual solute distributions.