Extraction of Copper by Selective Ion Exchangers with Pendent Ethyleneimine Groups—Investigation of Active States

Abstract

Abstract Selective ion exchangers with pendent ethyleneimine groups of the type -(NHC2H4)n · NH2, where n = 1 to 5, have been prepared, and their ability to extract cationic and anionic-chelated copper(II) ions has been evaluated. Copper has been extracted from aqueous solution, and the equilibrium capacities of extraction vary according to the active sites in the selective ion exchangers. The poor exchange properties of selective ion exchangers with short pendent groups have been related to the nature of the active coordination sites. The active sites on these selective ion exchangers change from two nitrogen atoms and two oxygen atoms (N2O2) with short chains (n = 1) to four nitrogens when n = 2 to 5. Those which have N4 active sites appear to extract cationic copper(II) efficiently, but those with N2O2 sites have low capacities and copper is easily leached from the resin even when the loading of the resin is low. When copper is complexed to EDTA to form an anionic complex, a side chain like pentaethylene hexamine is required to extract the copper from aqueous solution. A macroporous polystyrene resin had a lower capacity for anionic chelated copper than a polystyrene gel resin with the same functional groups due to the poorer accessibility of the active (N4) sites to the large anion.