Metal-uptake behaviour by a novel pyrazole-containing ligand immobilised on to poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate)

The novel pyrazole-containing ligand 5-(3,5-dimethylpyrazol-1-yl)-3-thiapentylamine (dptpa) has been anchored on to poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate) by ring-opening reaction of the pendant epoxy groups with the amine. Batch metal-uptake capacities were determined for the chloride salts of Cu2+, Ni2+, Co2+, Cd2+, Zn2+ and Ca2+ in the pH range 0.9-6.0. The uptake capacity of the modified polymer, designated p(GMT)-dptpa, for Cu2+ increases rapidly with increasing pH. The resin shows a high uptake capacity (0.46 mmol/g) for Cu2+ and low uptake capacities for the other divalent metal ions around pH 6 under non-competitive conditions. Ar pH < 2.5 the resin shows a high affinity for Cd2+ and Zn2+ ions, 0.38 and 0.27 mmol/g, respectively. Under competitive conditions, p(GMT)-dptpa shows selectivity for Cu2+ over the other metal ions at pH > 3.5. Around pH 6 the ratio of the selectivity for Cu2+ over Cd2+ is 17:1. Distribution coefficients for Cu2+ indicate that the stability of the formed Cu2+ complexes decreases rapidly with decreasing pH, which is consistent with the results of the non-competitive and competitive uptake experiments. Kinetic experiments have shown that the uptake of Cu2+. is rapid, i.e. t(1/2) = 15 min. Regeneration experiments performed with H2SO4 as the stripping agent have shown that the resin, after an initial loss of 25% loading capacity, retains the same Cu2+-capacity after several regeneration cycles even after the use of 2.0 M H2SO4. Only very small amounts of Cu2+ are left on the resin after the stripping procedure. (C) 1997 Elsevier Science Ltd. All rights reserved.