Extractive Recovery and Separation of Palladium(II) and Platinum(IV) from Chloride Solutions

The recovery and separation of Pd(II) and Pt(IV) from model solutions with high Cl– concentration (~300 g L–1) were studied. The behavior of Pd(II), Pt(IV), and matrix components was examined in relation to the model solution acidity, Cl– concentration, and kind of extractants and stripping agents. The mechanisms of the extraction of platinum metals with various extractants (trioctylamine, methyltrialkylammonium chloride, tri-n-octylphosphine oxide, dibutyl sulfoxide, tributyl phosphate) from chloride solutions are described. A quaternary ammonium salt, methyltrialkylammonium chloride, is suggested for simultaneous quantitative recovery of Pd(II) and Pt(IV) from solutions with the acidity varying in a wide range and with high Cl– concentrations. The subsequent selective separation of the platinum metals from the organic phase occurs in the course of stripping with a 0.3 М NH4OH + 0.1 M NH4Cl solution. The composition of scrubbing solutions allowing separation of matrix components such as Fe(III), Te(IV), Cu(II), Pb(II), and partially Se(IV) from Pd(II) and Pt(IV) and regeneration of the extractant after the extraction and stripping was chosen. The efficiency of the recovery of Pd(II) and Pt(IV), the number of stripping steps, and the purity and yield of the individual fractions depend mainly on the solution acidity and Cl– concentration.