Kinetics and thermodynamics of the adsorption of copper(II) onto chelating resin

The kinetics and thermodynamics of copper(II) adsorption onto D401 chelating resin were studied as for removal of copper(II) from enzymatic synthesis of L-theanine using glutamine-copper(II) as donor substrate. The structures of copper loaded resin were confirmed by infrared spectroscopy. Adsorption capacity of copper(II) increased with increasing initial metal ion concentration and temperature. And its highest value was 1.887 mmol/g at pH 5.6. Experimental data fitted well to the Langmuir model at all temperatures studied. The thermodynamic equilibrium functions were also determined. ΔG<0, ΔH=21.5 kJ/mol, ΔS>0, so the adsorption was spontaneous, endothermic and entropy increasing. The kinetic experimental data were correlated with pseudo-second-order kinetic model. The adsorption rate was controlled by film diffusion and particle diffusion simultaneously throughout the entire adsorption period. The resin could be applied to the removal of copper(II) from theanine-copper complexes by enzymatic synthesis under wide pH range, with a good selectivity with copper(II).