Kinetics and thermodynamics of microwave-assisted drying of paclitaxel for removal of residual methylene chloride

Abstract

Abstract This study investigated the removal efficiency of residual methylene chloride from paclitaxel according to the drying temperature in the case of microwave-assisted drying, and performed a kinetic and thermodynamic analysis of the drying process. At all the temperatures (35, 45, and 55 °C), a large amount of the residual solvent was initially removed during the drying, and the drying efficiency increased when increasing the drying temperature. Five drying models (Newton model, Page model, modified Page model, Henderson and Pabis model, Geometric model) were then used for the kinetic analysis, where the Page model and modified Page model showed the highest coefficient of determination ( r 2 ) and lowest root mean square deviation (RMSD), indicating that these models were the most suitable. Furthermore, in the thermodynamic analysis of the microwave-assisted drying, the activation energy ( E a ) was 46.21 kJ/mol and the standard Gibbs free energy change ( Δ G 0 ) was negative, whereas the standard enthalpy change ( Δ H 0 ) and standard entropy change ( Δ S 0 ) were both positive, indicating that the drying process was spontaneous, endothermic, and irreversible.