REACTIVE & FUNCTIONAL POLYMERS Reactive & Functional Polymers 32 (1997) 221-229 Solid-liquid extraction studies of divalent metals with impregnated resins containing mixtures of organophosphorus extractants J.L. Cortina *, N. Miralles, A.M. Sastre, M. Aguilar Chemical Engineering Department, ETSEIB, Universitat Politknica de Catalunya, Diagonal 647, E-08028, Barcelona, Spain Received 18 January 1996; revised version received 4 June 1996; accepted 3 October 1996 Abstract The extraction of Zn(II), CL@) and Cd(R) from nitrate solutions by impregnated resins containing mixtures of di(2-ethylhexyl)phosphoric acid (DEHPA) and tri-n-octyl-phosphine oxide (TOPO) have been studied. Impregnated resins containing TOP0 and mixtures of DEHPA and TOP0 have been prepared by direct adsorption of both extractants into macroporous supports, Amberlite XAD2. The adsorption of DEHPA and TOP0 molecules on the macroporous support is shown by FTIR spectroscopy to be result of only weak extractant-support interactions. The distribution coefficients of Zn(II), Cu(I1) and Cd(II) were determined as a function of pH and extractant concentration (DEHPA, TOPO) in the resin phase and the data were analyzed graphically using the slope analysis method in terms of synergistic effect. Analysis of the results showed that the extraction of these metal ions can be explained assuming the formation of metal complexes in the resin phase with a general composition ML,(N03),S,(HL), where p, t, s, q take values depending on the metal and the extractant concentration ratio in the resin phase ([HL],/[S],). Keywords: Impregnated resins; Divalent metal extraction; Organophosphorus extractants 1. Introduction Impregnated resins bridge the gap between solvent extraction and ion exchange [1,2] be- cause they combine the advantages of solid ion exchange for processing very dilute solutions with the specific extraction properties of extrac- tants. They also combine the fast mass transfer rates, high distribution and selectivity factors dis- tinctive to the extractants dissolved in a liquid organic phase, with simplicity of equipment and operation distinctive to solid-ion-exchange tech- nology. The development and application of these * Corresponding author. systems in metal extraction processes has been intensively investigated for the purpose of ap- plications on metal separation and recovery pro- cesses [3-61. In the last years, we have started the develop- ment of impregnated resins by direct adsorption of organophosphorus extractants into high sur- face polymeric supports. In previous papers the extraction of Zn, Cu and Cd by acidic organophos- phorus extractants di(2-ethylhexy1)phosphoi-k acid (DEHPA) [7], di(2,4,4&imethylpentyl)- phosphinic acid (DTMPPA) [8], and O-methyl- dihexyl-phosphine oxide O’-hexyl-2-ethyl phos- phoric acid [9] adsorbed into Amberlite XAD2 has been studied. The extraction of the above 1381-5148/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved PZZS1381-5148(96)00083-l