Separation of Palladium(II) and Platinum(IV) by Bulk Liquid Membranes during Electrodialysis

Abstract

The process of PdCl₄ ²⁻ and PtCl₆ ²⁻ separation extracting from binary hydrochloric mixtures as well as palladium(II) extraction from individual solutions by bulk liquid membranes containing diphenylthiourea and di‐o‐tolylthiourea in 1,2‐dichloroethane is studied at galvanostatic electrodialysis. The effects of the current density, the composition of the liquid membrane and of aqueous solutions on the rate of the metal transport are determined. It is shown that an effective separation of Pt(IV) from Pd(II) is achieved in the presence of an excess of the carrier. Maximum separation factor β_Pt/Pd of 380 is obtained in 1 hour of electrodialysis under optimal conditions. The transport of platinum(IV) is supposed to occur in the form of ionic associates (PdL₄Cl)₂PtCl₆. Platinum(IV) concentration and composition of the strip solution do not exert a considerable influence on the separation factor.

Keywords:

• Liquid membrane
• electrodialysis
• platinum metals
• diphenylthiourea
• di‐o‐tolylthiourea
• separation

Acknowledgement

The author is grateful to Dr. A.N. Popov for helpful discussions and assistance with the voltammetric experiments.