Microfluidic mass transfer of supercritical CO2 in brine

In the context of carbon sequestration in saline aquifers, we investigate CO2 transport dynamics in brine under reservoir-like conditions (P = 8 MPa, T = 50∘C) using microfluidics. We quantify the mass transfer of supercritical CO2 in brine across a range of concentrations (0–1 M) and liquid flow rates (15–60 μL/min) for the first time. We find the volumetric mass transfer coefficient kLa ranges from 50.3 to 144.0 s−1, increasing with flow rate and, to a lesser extent, with salinity. More importantly, the kLa value for supercritical CO2 in brine at a higher temperature shows a significant enhancement of >50% compared to gas and liquid CO2 in water. Our analysis, incorporating a theoretical mass transfer model, points to a dominant contribution from the liquid film to the overall kLa, nearly doubling that of the emulsion caps, attributed to the thin film's larger surface area and dynamic renewal. •Microfluidic mass transfer of segmented supercritical CO2 flow in brine is quantified.•Microfluidic experiments are performed for various salinities and at a high pressure.•The volumetric mass transfer coefficient (kLa) values are between 50.3 and 144.0 s−1.•The kLa values for supercritical CO2 are greater than gas/liquid CO2 in water by 50%.•A model shows a greater kLa contribution from the liquid film than bubble caps by 2×.