INFLUENCE OF THE AMINE NATURE ON THE COMPOSITION OF PALLADIUM COMPLEXES IN SOLVENT-EXTRACTION SYSTEM

The extraction of palladium chloro complexes by di-n-octylamine and di amines of various structure as function of the composition of the aque ous and organic phases has been studied. The compositions of the extra cted species are indicated and the mechanisms of their distribution ar e described. It was shown that from 1 to 3 M HCl solutions. complexes such as (R2NH2)(2)PdCl4 solvated by molecules of dioctylamine chloride are extracted. With increasing the initial concentrations of palladiu m or decreasing acidity of the aqueous phase, a direct coordination ta kes place, first of one and then two molecules of amine to atom of pal ladium with the formation of extracted compounds such as (R2NH2)[Pd(R2 NH)Cl-3] and Pd(R2NH)(2)Cl-2 in the organic phase. The extraction of p alladium by tri-n-octylamine from weakly acidic and neutral solutions results in the formation of Pd(R3N)(2)Cl-2 in the organic phase. Tetra octylalkylenediamines have been found to be more effective extractants in comparison with dioctylamine and trioctylamine. The extraction of palladium by tetraoctylalkylenediamine chlorides proceeds with the for mation of monomeric (Am'H-2)PdCl4 and dimeric (Am'H-2)Pd2Cl6 extracted species. From solutions with high concentration of HCl and an excess of the extractant, the extraction occurs according to an anion-exchang e mechanism forming ionic associates which contain the complex anion P dCl42-. The proportion of dimeric species of the extracted compounds i ncreases with decreasing the chloride ion and free extractant concentr ation. and with increasing the concentration of palladium in the organ ic phase. For the system with tetraoctylethylenediamine, the formation of extracted complex with direct coordination of diamine molecules to the palladium atom has been shown. Using as an example the system wit h tetraoctylbutylenediamine, calculations of the constants of extracti on and dimerization of extracted compounds have been carried out. A qu antitative description of the extraction equilibria for different comp ositions of this system has been made.