Reactive Transport of Protons in Electro-Osmotic Displacements with Electrolyte Concentration Difference in a Microcapillary.

In this work, we model electro-osmotic displacement with electrolyte concentration difference in a microcapillary by incorporating proton transport coupled with surface complexation reaction and carbonate equilibrium. The hysteretic effect observed in experiments is well-captured by the model. By deriving the semianalytical solution of the nonlinear transport equation using method of characteristics, we elucidate the transport mechanism of protons by classifying their nonlinear transport behavior (shock/rarefaction/discontinuity) into several regimes depending on the concentration ratio and the pH. The model can be used to predict pH variation and characterizes surface property in electro-osmotic experiments.