MATRIX EFFECTS ON PALLADIUM(II) CHELATION BY 2 MACROPOROUS POLYSTYRENE RESINS WITH 2,6-BIS(METHYLTHIOMETHYL)PYRIDINE GROUPS

Two commercially available macroporous polystyrenes (3% DVB) with different physical characteristics, Janssen-MPs and XAD-2, have been chloromethylated and subsequently reacted with the terdentate ligand 2,6-bis(methylthiomethyl)-3-hydroxypyridine. The level of functionalization as well as the sorption ability of the resulting chelating resins (MPs-SNS and XAD-2-SNS) towards Pd(II) from acidic chloride aqueous solutions strongly depend on the morphology of the polymeric matrices. Despite a lower functionalization degree, the XAD-2 based chelating resin, derived from a polymeric support with higher surface area and lower pore average diameter, showed higher performances. Both uptake of Pd(II) and stripping of the sorbed Pd(II) were fairly rapid, indicating a better accessibility to the chelating sites. The saturation capacity suggests the formation of a 1 : 1 complex. In addition, the XAD-2 based resin displays superior selectivity in the extraction of Pd(II) from mixtures of Pd(II)-Cu(II) at pH 1, essentially quantitative separation of Pd(II) being achieved even with Cu(II) present in 150-fold excess. The sorption levels of Fe(III), Co(II), Ni(II) and Zn(II) at pH 1 were not detectable.