Adsorption of L-α-glycerophosphocholine on ion-exchange resin: Equilibrium, kinetic, and thermodynamic studies

The adsorption of L-alpha-glycerophosphocholine (GPC) by cation-exchange resin 001 x 7 was studied in a batch system. The adsorbent dosage, shaking speed, and adsorption temperature were investigated. An adsorption efficiency of more than 99.4% was obtained under optimal conditions. The kinetic data evaluated by the pseudo-second-order kinetic model fitted the experimental data better than those evaluated by the pseudo-first-order model. The rate constant k(2) increased when the temperature increased, indicating the adsorption was endothermic in nature. The Langmuir and Freundlich isotherm models were used to analyze the adsorption equilibrium data, and it was found that the experimental data well fitted the Langmuir isotherm model. The thermodynamic parameters, enthalpy change (Delta G(0)), free energy change (Delta H-0), and entropy change (Delta S-0), were calculated. The value of Delta G(0) was found to be in the range of -5.09 to -14.20 kJ mol(-1), indicating that the adsorption was spontaneous and basically physisorption, and the positive values of Delta H-0 and Delta S-0 exhibited that the adsorption was endothermic and the randomness of the system increased during the adsorption.