BINARY EXTRACTION OF PLATINUM METALS

The equations describing the regularities of interphase distribution o f platinum metals as their chloro complex acids in systems containing binary extractants have been derived. The dependencies of distribution coefficients of platinum metals on the composition of both phases, an d their aqueous acidity have been determined when both binary extracti on and a combination of anion-exchange and binary extraction occurred. The interrelation of the binary extraction constant of chloro complex acids of platinum metals with the extraction constant of hydrochloric acid and the anion-exchange constant is described. We studied platinu m metal extraction by salts of organic acids and organic bases and sho wed that in the systems involving binary extractants, such as salts of quaternary ammonium bases, the distribution of platinum metals procee ds via either anion-exchange or binary mechanisms depending on the com position of the system. With increasing pH, the distribution coefficie nts of platinum metals decrease according to the regularities of binar y extraction due to forming thermodynamically stable binary extractant s, R(4)NA. When the anion-exchange extraction occurs, the distribution of complex acids of platinum metals in the systems containing binary extractants is affected by interactions of the extractants and the ext racted compounds with the organic acids. Interactions between extracta nts in the chloride form and the molecules of organic acids have been shown to be largely responsible for the extraction characteristics. Th e binary extractant systems are preferred in the development of solven t extraction processes for the recovery and the stripping of platinum metals.