pH-Dependence and Contributions of The Carbonic Species To Co2 Flux Across The Gas/Liquid Interface

Abstract

The purpose of this article is to expand the available knowledge on CO2 transfer across the gas/liquid interface in two ways: (1) propose a new mathematical model to describe the pH dependence of CO2 flux across the gas/liquid interface; and (2) propose new relationships that quantitatively describe the contributions of each of the carbonate species ( 2 3 H CO , − 3 HCO , and 2− 3 CO ) to total flux across the gas/liquid interface. The new
model was based on accounting for the difference between the pH in the liquid phase at any time during gas
transfer and the pH of the liquid phase at equilibrium when net gas transfer stops. The article also proposes a
correction to the currently in-use mathematical model, which was found to apply in the special change and in
unlikely cases in which the initial pH does not change. The theoretical and experimental work presented in this
article present clear theoretical and mathematical understanding of the process of gas transfer involving acidbase ionization reactions. Numerous batch and continuous-flow countercurrent reactors CO2 stripping
experiments were conducted at different initial pH values to verify the proposed model. The experiments included runs in which the pH was allowed to change as a result of CO2 transfer and experiments involving buffered solutions in which the pH did not change significantly. In all cases, the experimental results matched the theory in an excellent manner.