Nonequilibrium facilitated transport of carbon dioxide in bicarbonate and bovine albumin solutions.

The nonlinear diffusion-reaction equations describing the nonequilibrium transport of CO2 through flat layers of complex but homogeneous aqueous media were solved by an approximate analytical method called the "Combined Damköhler Number" (CDN) technique. Unlike other approximate analytical solutions, the CDN technique is valid for the full range of Damköhler numbers, i.e., for any layer thickness. The present theoretical treatment uses as a basis the equilibrium approach of Stroeve, Hoofd, and Kreuzer which accounts for any species in the solution except for possible carbamate formation (binding of CO2 by the protein). The nonequilibrium model developed here for CO2 transport is the most general technique currently available in the literature. Theoretical results were compared to experimental data from the literature for diffusion in bicarbonate and albumin solutions and were generally in good agreement. Results obtained from numerical calculations were also compared and were found to be in excellent agreement with the CDN results.