Mass transfer from dispersed bubbles to electrolyte solution in packed beds

The measurement of gas‐liquid interfacial areas and mass transfer coefficients in concurrent upward bubbly flow (u_G from 0.02 to 0.16 m/s, u_L from 0.0051 to 0.056 m/s) over a packed bed consisting of 1.2 mm glassy carbon particles is described. Specific surface areas were measured by chemical absorption of O₂ into Na₂SO₃ solutions; volumetric mass transfer coefficients were measured by physical desorption of O₂ into N₂ bubbles. Surface areas were obtained in the range of 4 × 10³ to 2 × 10⁵ m⁻¹, much higher than have been previously reported. High areas are related to the use of electrolytes and small packing particles. Bubble size was found to depend primarily on liquid velocity. Volumetric mass transfer coefficients k_La_G are also high (0.1 < k_La_G < 2.3 s⁻¹), primarily as a result of high gas‐liquid interfacial areas. Mass transfer coefficients k_L are small, however. For the smaller bubble dispersions, mass transport is controlled by diffusion rather than by convection.