Selective and rapid uptake of Cu(II) by bis(benzimidazole) modified oxirane and thiirane resins

The benzimidazole containing ligand 1,3-bis(benzimidazol-2-yl)propylamine (bbpaH) was anchored onto poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate) (GMT) and onto the thiirane analogue of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (GME-S). Abbreviations of the modified polymers are GMT-bbpaH and GME-S-bbpaH. A multistep synthesis was applied in an attempt to increase the ligand concentration on the polymer GMT, This resulted in the resin GMT-bbpaH(ind) of which the solid state CP MAS ¹³C-NMR data showed that in this case only a monobenzimidazole was formed, i.e. only the 3-benzimidazole group was formed.Batch extraction capacities were determined for the chloride salts of Cu²⁺, Ni²⁺, Co²⁺, Cd²⁺, Zn²⁺ and Ca²⁺ in the pH range 0.9–6.0 in buffered solutions at room temperature. All three resins show a high selectivity for Cu²⁺ under competitive conditions, with maximum ligand occupations of 54%, 64% and 27% for GMT-bbpaH, GME-S-bbpaH and GMT-bbpaH(ind), respectively. The resin GMT-bbpaH also takes up some Zn²⁺ ions at pH > 4.5, the maximum ligand occupation being 17%. The resin GME-S-bbpaH shows some affinity for Zn²⁺ and Cd²⁺ ions in this pH range, with ligand occupations of 17% and 7%, respectively. Only GMT-bbpaH(ind) shows complete selectivity for Cu(II) at pH > 3, although the maximum Cu²⁺-uptake capacity is rather low.Kinetic experiments showed that the oxirane derivative exhibits a faster uptake kinetics compared with the thiirane analogue. Incomplete stripping of the Cu(II)-loaded ion-exchange resins and loss of Cu(II)-uptake capacity was observed during the regeneration experiments.