SOLVENT IMPREGNATED RESINS CONTAINING DI(2-ETHYL-HEXYL) PHOSPHORIC-ACID .2. STUDY OF THE DISTRIBUTION EQUILIBRIA OF ZN(II), CU(II) AND CD(II)

The extraction of Zn(II), Cu(II) and Cd(II) from nitrate solutions at 0.1 M ionic strength by impregnated resins containing di(2-ethylhexyl) phosphoric acid has been studied at 25-degrees-C. The distribution coe fficient was determined as a function of both pH and extractant concen tration in the resin phase. The data were analyzed graphically using t he slope analysis method, and numerically using the program LETAGROP-D ISTR. The composition of the extracted species in the resin phase has been determined. Analysis of the results showed that the extraction of these metal ions can be explained assuming the formation of metal com plexes in the resin phase with a general composition ML2(HL)q where q takes different values depending on the metal. An extraction reaction is proposed and the extraction constants of these species are given. F inally, a comparison between the extraction of Zn(II), Cu(II) and Cd(I I) by di(2-ethylhexyl)phosphoric acid into Amberlite XAD2 and the extr action using organic solvents has been made.