Facilitated transport of carbon dioxide through bicarbonate solution

Abstract

Facilitation effect due to bicarbonate ion on the transport of carbon dioxide through a liquid film has been investigated over a wide range of bicarbonate concentration and upstream partial pressure of carbon dioxide. The effect of arsenite ion, known as catalyst for carbon dioxide-bicarbonate reaction, has also been examined. Experiments were carried out by using a liquid film bound with silicone rubber membrane at both sides. The flux ratio, defined as the ratio of the actual flux to that by simple diffusion, increased with concentration of bicarbonate and decreased with upstream partial pressure of carbon dioxide. The boundary layer approximation was found in a reasonable correlation with the data. Addition of arsenite ion resulted in an unexpectedly high facilitation. The reason was discussed qualitatively by relating the buffer action of arsenious acid to the pH level and the pH profile along the membrane thickness.