Optimizing the Gas Absorption/Chemical Reaction Method for Measuring Air – Water Interfacial Area in Porous Media

The gas absorption/chemical reaction (GACR) method developed in chemical engineering to measure gas–fluid interface in reactor systems is adapted for natural porous geologic media. Several series of column experiments were conducted using model glass beads and a natural sand to determine optimal operational conditions for measuring air–water interfacial area with the adapted method. The impacts of operational variables were investigated, including liquid and gas volumetric flow rates, solution concentration, and temperature. The results show that the magnitude of the measured air–water interfacial area is dependent upon all of these variables to greater or lesser degrees. Larger fluid flow rates promote distribution and mixing of the fluids, enhancing absorption and reaction. Increasing the concentration of NaOH in solution reduced the relative utilization of NaOH, promoting pseudo-first-order reaction conditions. The results elucidate the optimal operational conditions for application of the method to geomedia systems.