SOLVENT-IMPREGNATED RESINS CONTAINING DI-(2,4,4-TRIMETHYLPENTYL)PHOSPHINIC 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 ionic strength by impregnated resins containing di-(2,4,4-trimethy lpentyl)phosphinic acid (HL) has been studied at 25-degrees-C. The dis tribution coefficient of the metal ion was determined as a function of both pH and extractant concentration in the resin phase, and the data were analyzed graphically using the slope analysis method and numeric ally using the program LETA-GROP-DISTR. Analysis of the results showed that the extraction of these metal ions can be explained by the forma tion of metal complexes in the resin phase with a general composition ML2(HL)q where the value of q depends on the metal. Extractions reacti ons are proposed and the extraction constants of these reactions are p resented. Finally, a comparison between the extraction of Zn(II), Cu(I I) and Cd(II) with di-(2,4,4-trimethylpentyl) phosphinic acid sorbed i nto Amberlite XAD-2 and the extraction using an organic solvent as Iso par H has been made.