Propionic acid extraction in a microfluidic system: simultaneous effects of channel diameter and fluid flow rate on the flow regime and mass transfer

In this work, extraction of propionic acid from the aqueous phase to the organic phase (1-octanol) was performed in T-junction microchannels, and effects of channel diameter and fluid flow rate on the mass transfer characteristics were investigated. The two-phase flow patterns in the studied microchannels with 0.4 and 0.8 mm diameters were observed. Weber number and surface-to-volume ratio were calculated for evaluating flow patterns. Moreover, the effects of volumetric flow rates on the extraction efficiency, volumetric mass transfer coefficient, and pressure drop were examined. Results showed that the pressure drop in the microchannel with 0.4 mm diameter was 2-2.7 times higher than that in the microchannel with 0.8 mm diameter. In both microchannels, with an increase in the flow rate, the extraction efficiency first increased and, then, decreased. In addition, at high flow rates (2.4, 4.5, and 6 mL/min), the extraction efficiency in the microchannel with 0.8 mm diameter increased up to the range of 7-14.9 % compared with that in the microchannel with 0.4 mm diameter.