Distribution studies of Zn(II), Cu(II) and Cd(II) with Levextrel resins containing di(2,4,4-trimethylpentyl)phosphinic acid (Lewatit TP807'84)

The use of physically immobilized reagents on macroporous polymeric supports has been presented as an alternative approach, for the recovery of metal ions, to the usual techniques such as solvent extraction and ion exchange. 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 degrees C by Levextrel impregnated resin Lewatit TP807'84 containing di(2,4,4-trimethylpentyl)phosphinic acid (DTMPPA). The distribution coefficient was 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 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(2)(HL)(q), where q takes different values depending on the metal studied. An extraction reaction is proposed and the extraction constants of the species are given. The adsorption of DTMPPA molecules on the styrene/divinyl benzene macroporous support seems to be the result of weak extractant-support interactions, as evidenced by FTIR spectroscopy. Nevertheless, it is also shown that the extraction ability of the extractant towards Zn(II), Cu(II) and Cd(II) does not suffer from the presence of the solid support, in comparison with its ability to extract these metals using organic solvents. Finally, a comparison between the extraction of Zn(II), Cu(II) and Cd(II) by Amberlite XAD2-DTMPP resins and using Lewatit TP807'84 resins is made.