title: Nonmonotonic Rayleigh-Taylor instabilities driven by gas-liquid CO2 chemisorption.
abstract: Density variations induced by gas absorption in reactive aqueous solutions often trigger buoyancy-induced motions, generally in the form of plumes monotonically sinking into the bulk liquid and enhancing the absorption rate. Here, we contrast two types of CO2-absorbing alkaline solutions, studying their dynamics inside a vertical Hele-Shaw cell by interferometry. While the first one indeed behaves as expected, the second one leads to a quite unusual oscillatory (phase-slipping) dynamics of convective plumes, which moreover does not lead to a significant transfer enhancement. Thanks to a simplified model of momentum and species transport, we show that this particular dynamics is related to a nonmonotonic density stratification, resulting in a stagnant layer close to the interface. Conditions for this to occur are highlighted in terms of the ratios of species' diffusivities and their contribution to density, a classification deemed to be useful for optimizing chemisorption (e.g., for CO2 capture or sequestration) processes.
authors.affiliation: Université Libre de Bruxelles (ULB) , Transfers, Interfaces and Processes (TIPs), av. F.D. Roosevelt 50, CP 165/67, 1050 Brussels, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Wylock
authors.forename: A
authors.initials: A
authors.lastname: Rednikov
authors.forename: B
authors.initials: B
authors.lastname: Haut
authors.forename: P
authors.initials: P
authors.lastname: Colinet