The Separation of Platinum(II) and Palladium(II) by Surfactant Gel Extraction (Part II)

A surfactant solution of cetylpyridinium chloride (CPC) separates into two phases by cooling the solution or by the addition of salts. Platinum(II) and palladium(II) were reacted with chloride ions to form the stable complexes PtCl42- and PdCl42- respectively, and these were extracted into the CPC phase. The cationic surfactant CP+ and the CPC gel play the role of a counter ion and an extraction solvent for these anionic complexes. A decrease in extractability was observed at low metal concentrations and applied to remove a large excess of palladium(II) from platinum(II) or that of platinum(II) from palladium(II) as the ion-pair [PdCl42-](CP+)(2) or [PtCl42-](CP+)(2). The percent extraction was (98.7 +/- 0.4)% and (6.4 +/- 7.3)% for 1.0x10(-4) mol dm(-3) palladium(II) and 3.0x10(-7) mol dm(-3) platinum(II), respectively. A small amount of metals remained in the aqueous phase after extraction. The pre-concentration of metals was performed by their extraction as electrically neutral complexes with pyrrolidinedithiocarbamate which gave a constant and complete extractability at low metal concentrations. By a combination of these extractions, it is possible to achieve successive separations of the major base metals from the minor components in the Mixtures.