Studies of equilibrium, kinetics simulation and thermodynamics of cAMP adsorption onto an anion-exchange resin

In a batch equilibrium system, the maximum adsorption capacity of cAMP onto an anion-exchange resin reached 0.1718, 0.1956, 0.2764 and 0.3437 g g−1 at 283, 293, 303 and 313 K, respectively. The adsorption data obtained were well described by the Langmuir isotherm. In the batch kinetic system, Fick diffusion, pseudo first-order and pseudo second-order models were applied to simulate the experimental kinetic data. The results revealed that the Fick model best described the adsorption process, and clearly predicted the intraparticle distribution of the concentration. The effective diffusion coefficients (De) for 283, 293, 303 and 313 K were 0.37 × 10−10, 0.51 × 10−10, 0.86 × 10−10 and 1.41 × 10−10 m2 s−1, respectively. The thermodynamic parameters such as ΔG0, which were all negative, indicated that the adsorption of cAMP onto the anion-exchange resin was spontaneous and the positive value of ΔH0 (+8.66 kJ mol−1) showed that the adsorption was an endothermic reaction.