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

Abstract

The novel pyrazole-containing ligand 5-(3,5-dimethylpyrazol-l-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 Cu 2+, Ni 2+, Co 2+, Cd 2+, Zn 2+ and Ca 2+ in the pH range 0.9-6.0. The uptake capacity of the modified polymer, designated p(GMT)-dptpa, for Cu 2+ increases rapidly with increasing pH. The resin shows a high uptake capacity ( 0.46 mmol g ) for Cu 2+ and low uptake capacities for the other divalent metal ions around pH 6 under non-competitive conditions. At pH < 2.5 the resin shows a high affinity for Cd 2+ and Zn 2+ ions, 0.38 and 0.27 mmol g , respectively. Under competitive conditions, p(GMT)-dptpa shows selectivity for Cu 2+ over the other metal ions at pH > 3.5. Around pH 6 the ratio of the selectivity for Cu 2+ over Cd 2+ is 17:1. Distribution coefficients for Cu 2+ indicate that the stability of the formed Cu 2+ 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 Cu 2+ is rapid, i.e. t 1 2 = 15 min . Regeneration experiments performed with H 2SO 4 as the stripping agent have shown that the resin, after an initial loss of 25% loading capacity, retains the same Cu 2+-capacity after several regeneration cycles even after the use of 2.0 M H 2SO 4. Only very small amounts of Cu 2+ are left on the resin after the stripping procedure.