Mass transfer coefficients from pendant water drop measurements in compressed carbon dioxide

Mass transfer coefficients were determined in the two-phase system of water/compressed carbon dioxide at three temperatures of 297, 313 and 335 K, and in the pressure range of 6–25 MPa. Mutual Mass transfer of the two components, water and carbon dioxide was investigated in the binary system, and extraction of phenol from an aqueous droplet by carbon dioxide was studied in a ternary system. In all systems a pendant water drop was formed at the tip of a capillary and was exposed to the quiescent surrounding carbon dioxide for a definite time. To obtain mass transfer coefficients from experimental data, such as drop volume and phenol concentration as a function of contact time, a model was used that divides the transport process into three steps: transport towards the interface, passage through the interface, transport straight away from the interface. Depending on the particular system, only one or two of these steps were considered to have a rate-determining function.