The study of adsorption kinetic and thermodynamic of CTP on ion exchange resin

Duolite A-30 resin is adapted to separate CTP from the mixture of CTP, CDP and CMP basing on the adsorption capacity and selectivity on the different resins. Equilibrium data for the adsorption of CTP from aqueous solutions with Duolite A-30 resin had been researched, which is correlated with a langmuir-type of isotherm equation. The kinetics and thermodynamics of ion exchange between CTP and OH ions with Duolite A-30 resin were studied. Meanwhile, the corresponding determining-rate-steps are ascertained and diffusion coefficients were calculated. The results showed that the ion exchange rate between CTP and Duolite A-30 resin is controlled by particle diffusion control (PDC) if the concentration of CTP solution is larger than 7.5 g/L (D_i = 3.47 × l0^-7cm²/s), otherwise, controlled by film diffusion control (FDC) if the concentration of CTP solution is less than 1.0 g/L (K_f = 4.112 × 10^-4/s) within temperature range of 283.15~303.15K. The thermodynamics parameters are that the activation energy of adsorption (E_a) is 9.108 kJ/mol, the enthalpy of adsorption (ΔH) is 5.17 kJ/mol·K, the entropy of adsorption (ΔS_283.15K) is 80.28 J/mol·K.