Metal uptake by N, N′-bis(2-benzimidazolylmethyl) amine immobilized on poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)

Abstract

N,N′-bis(2-benzimidazolylmethyl)amine (bbaH) has been anchored to poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (GMA). GMA resins with various glycidyl methacrylate: ethylene glycol dimethacrylate ratios were used. Two ways of attachment were investigated. Direct coupling of the aliphatic amine of bbaH to GMA yields resins (GB) containing 0.6–0.8 mmol of the ligand per gram of resin. In contrast, a three-step reaction yields resins (GAB) containing 1.2–1.6 mmol of the ligand per gram of resin. The resin structures were confirmed by solid-state cross polarization and magic-angle spinning nuclear magnetic resonance spectroscopy, infrared spectroscopy, and elemental analyses. The metal-uptake capacities of the resins for Cu 2+ are high: 0.63 mmol Cu 2+/g of resin for GB8/2-I and 1.25 mmol Cu 2+/g of resin for GAB8/2-II at pH 5.8. The capacities for Ca 2+, Co 2+, Ni 2+, Zn 2+ and Cd 2+ are lower. For 0.08 M CuCl 2 solutions in concentrated hydrochloric acid (pH −1) the Cu 2+ capacity is still reasonably high: 0.26 and 0.43 mmol/g for GB8/2-I and GAB8/2-II, respectively. Metal-uptake experiments under competitive conditions confirm the high selectivity for Cu 2+ . Elemental analyses and spectroscopic data suggest that 1:1 (metal:ligand) complexes are formed on the polymer matrix. Ligand field and EPR spectra are consistent with a distorted square pyramidal coordination geometry of the Cu 2+ and Co 2+ complexes and a distorted octahedral coordination geometry of the Ni 2+ complex. The kinetic performance of the resins was found to depend on the resin particle size and the amount of ethylene glycol dimethacrylate in the copolymer. The method of ligand attachment, however, does not affect the kinetic properties. H 2SO 4 (1 M) was tested for its stripping potential. Stripping of Cu 2+ was found to be quite fast and dependent on the GMA used. Complete removal of Cu 2+ over 99 %), however, could only be affected for some of the resins after prolonged acid treatment, the difficulties being caused by the relatively high Cu 2+ capacities at pH 0.