Isotherm, kinetic and thermodynamic characteristics of adsorption of paclitaxel onto Diaion HP-20

Batch experiment studies were carried out on the adsorption of the anticancer agent paclitaxel using Diaion HP-20 while varying parameters such as initial paclitaxel concentration, contact time and adsorption temperature. The experimental data were fitted to the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. Comparison of results revealed that the Langmuir isotherm model could account for the adsorption isotherm data with the highest accuracy among the four isotherm models considered. From the analysis of adsorption isotherms, it was found that adsorption capacity increased with increasing temperature and the adsorption of paclitaxel onto HP-20 was favorable and process could be physical in nature. The obtained kinetics data for paclitaxel adsorption onto HP-20 agreed well with the pseudo-second-order model, and intraparticle diffusion played a dominated role in pacltaxel adsorption according to the intraparticle diffusion model. Thermodynamic parameters, such as standard enthalpy (Delta H degrees), standard entropy (Delta S degrees) and standard Gibbs free energy (Delta G degrees) change, were investigated. The results indicated that the process of paclitaxel adsorption onto HP-20 was endothermic, irreversible, spontaneous and by hydrophobic interaction. (C) 2016 Elsevier Ltd. All rights reserved.