Highly copper(II)-selective chelating ion-exchange resins based on bis(imidazole)-modified glycidyl methacrylate copolymers

The metal-ion uptake behaviour of poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate) polymers (GMT), modified with the bis(imidazole)-containing ligands bis(1,1-imidazol-2-yl)(4-imidazol-4(5)-yl)-2-aza-butane (biib), bis(1,1-imidazol-2-yl)(4-pyridine-2-yl)-2-aza-butane (bipyb) and bis(1,1-imidazol-2-yl)(7-[3,5-dimethylpyrazol-1-yl])-2-aza-5-thia-heptane (bidpth), was determined for Cu2+, Ni2+, Co2+, Cd2+, Zn2+ and Ca2+ as chlorides in buffered solutions in the pH range from 1.0 to 6.0. All three resins are very selective for Cu2+ under competitive conditions, as the uptake of the other metal ions tested was quite low. Full ligand occupation for Cu2+ under noncompetitive conditions was established for GMT-biib and GMT-bipyb, while only two-third ligand occupation was found for GMT-bidpth. The high values for the biib- and bipyb-modified resins are ascribed to the higher stability of the Cu2+ complexes in the polymer phase. This was confirmed by the relatively high values of log D obtained for these two resins. The high stability even at low pH of the Cu2+ complexes formed on the three resins, hampers the complete stripping, with 1.0 M H2SO4, of all Cu2+ ions from the resins.