SOLID-LIQUID EXTRACTION STUDIES OF DIVALENT METALS WITH IMPREGNATED RESINS CONTAINING MIXTURES OF ORGANOPHOSPHORUS EXTRACTANTS

The extraction of Zn(II), Cu(II) and Cd(TI) from nitrate solutions by impregnated resins containing mixtures of di(2-ethylhexyl)phosphoric a cid (DEHPA) and tri-n-octyl-phosphine oxide (TOPO) have been studied. Impregnated resins containing TOPO and mixtures of DEHPA and TOPO have been prepared by direct adsorption of both extractants into macroporo us supports, Amberlite XAD2. The adsorption of DEHPA and TOPO molecule s on the macroporous support is shown by FTIR spectroscopy to be resul t of only weak extractant-support interactions. The distribution coeff icients of Zn(II), Cu(II) and Cd(II) were determined as a function of pH and extractant concentration (DEHPA, TOPO) in the resin phase and t he data were analyzed graphically using the slope analysis method in t erms of synergistic effect. Analysis of the results showed that the ex traction of these metal ions can be explained assuming the formation o f metal complexes in the resin phase with a general composition MLp(NO 3)(t)S-s(HL)(q) where p, t, s, q take values depending on the metal an d the extractant concentration ratio in the resin phase ([HL](r)/[S](r )).