Elucidating coupling dynamics of mass transfer and chemical absorption in slug-flow microchannels with tuned wall wettability

The wettability of the channel walls plays a crucial role in determining the flow hydrodynamics and mass transfer characteristics of gas–liquid two-phase flows in microchannel reactors. However, the dynamics of mass transfer coupled with chemical absorption remain to be fully understood. In this study, PMMA-made microchannels were modified to achieve contact angles of 10°, 40° and 70° under optimized conditions, and their effects on gas bubble formation, length, and flow velocity were characterized. This was followed by a quantitative analysis of mass transfer in both CO 2 -MEA and CO 2 -H 2 O systems. It was found that bubble length increased with greater channel wettability and lower liquid-phase flow rate, while also becoming longer with higher gas-phase flow rates. Bubble velocity decreased with increasing channel wettability at any given position along the channel, and in the CO 2 -H 2 O system it remained significantly greater than in the CO 2 -MEA system downstream of the main channel. Based on experimental observations and Higbie’s unsteady state diffusion theory, a novel semi-empirical model was developed to quantitatively characterize the dynamics of gas–liquid mass transfer in slug flow coupled with chemical absorption along microchannels. The calculated values of the overall volumetric liquid phase mass transfer coefficient showed good agreement with the experimental results. This work provides valuable insights for the design and optimization of compact, high-efficiency gas–liquid contactors, which are critical for advancing next-generation CO₂ capture technologies.