Extraction studies of Zn(II), Cu(II) and Cd(II) with impregnated and Levextrel resins containing di(2-ethylhexyl) phosphoric acid (Lewatit 1026 Oc)

Abstract

Impregnated resins are an alternative approach to the usual techniques for the recovery of metal ions, such as solvent extraction and ion exchange resins. This paper presents the results of the extraction of Zn(II), Cu(II) and Cd(II) from nitrate and chloride solutions at 0.1 M ionic strength and 25°C by the Levextrel impregnated resin Lewatit 1026 Oc containing di(2-ethylhexyl)-phosphoric acid (DEHPA). The distribution coefficients were determined as a function of both pH and ionic medium and the data were analyzed graphically, using the slope analysis method, and numerically using the program letagrop-distr. Analysis of the results shows that the extraction of these metal ions can be explained assuming the formation of metal complexes in the resin phase have a general composition ML 2(HL) q where q takes different values depending on the metal. An extraction reaction is proposed and the extraction constants of the species are given. The adsorption of DEHPA molecules on the styrene/divinyl benzene macroporous support is due to weak extractant-support interactions, as indicated by FTIR spectroscopy. Furthermore, it is also shown that the ability of the extractant towards Zn(II), Cu(II) and Cd(II) changes in the solid support, in comparison with organic solvents. Finally, a comparison is made between the extraction of Zn(II), Cu(II) and Cd(II) with Lewatit 1026 Oc resins and impregnated resins prepared by direct adsorption of DEHPA into Amberlite XAD2 (XAD2-DEHPA resins).