Isotherm, kinetic and thermodynamic studies on the adsorption of 13-dehydroxybaccatin III from Taxus chinensis onto Sylopute

Batch experimental studies were carried out on the adsorption of 13-dehydroxybaccatin III (13-DHB III) using Sylopute while varying parameters such as initial 13-DHB III concentrations, contact times and adsorption temperatures. Out of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models, adsorption data with the highest accuracy were best described by the Langmuir isotherm. It was found that the adsorption capacity decreased with an increasing temperature and the adsorption of 13-DHB III onto Sylopute was favourable. The adsorption kinetics were well described by the pseudo-second-order kinetic model, while intraparticle diffusion and boundary layer diffusion did not play a dominant role in 13-DHB III adsorption according to the intraparticle diffusion model. Thermodynamic parameters revealed the exothermic, irreversible and non-spontaneous nature of adsorption. The isosteric heat of adsorption was constant even with variations in surface loading, indicating a heterogeneous surface. (C) 2017 Elsevier Ltd.