(601a) Diffusioosmosis over a Reactive Surface

Diffusioosmosis, the deterministic fluid motion generated by a solute concentration gradient over a surface, is central to the fluid and mass transport that underlies metamorphic transformation. Existing models of diffusioosmosis have assumed a pH-independent surface charge density and neglected the surface reactions that regulate the surface charge density via deprotonation and protonation. Such an assumption leads to questionable predictions, since acids or bases shift the reaction equilibria so that the surface charge density varies with the solution pH. Here, considering a thin electric double layer, we calculate the diffusioosmotic mobility of an electrolyte over a reactive, charge-regulated surface. We analyze how the physical properties of the surface and the electrolyte, such as the surface material and ion diffusivity, affect the diffusioosmotic flow. The model developed from this work can be utilized to understand and predict diffusioosmosis in natural phenomena such as metamorphism, in addition to that in applications such as enhanced oil recovery and geological carbon sequestration.