Thermodynamic and kinetic study for subcritical water extraction of PAHs

Four models were used to describe the subcritical water extraction’ (SCWE) kinetics of polycyclic aromatic hydrocarbons (PAHs) at elevated temperatures in this work. The subcritical water extraction profiles obtained at temperatures of 200 °C and 250 °C were fitted with four models to presume the extraction mechanism parameters which could provide conceptual design to develop scale up methodology from laboratory SCWE devices. Among the four models, the two-site kinetic desorption model gave the best description of SCWE of phenanthrene, fluoranthene, and pyrene. Both the model analysis and experimental results suggested that the first desorption step is more important than the volumetric mass transfer process in this study. The desorption activation energy attained for extraction of phenanthrene, fluoranthene, and pyrene in this study were calculated to be 57, 52, and 70 kJ/mol, respectively. Conclusively, the model analysis could give information on the controlling step of PAHs extraction in SCWE process.