1. The gaseous pollutant diffuses from the bulk area of the gas phase to the gas–liquid interface.
2. The gas moves (transfers) across the interface to the liquid phase. This step occurs extremely
rapidly once the gas molecules (pollutants) arrive at the interface area.
3. The gas diffuses into the bulk area of the liquid, thus making room for additional gas molecules to be absorbed. The rate of absorption (mass transfer of the pollutant from the gas phase to the liquid phase) depends on the diffusion rates of the pollutant in the gas phase (first step) and in the liquid phase (third step).
To enhance gas diffusion, and therefore absorption, steps include:
• Providing a large interfacial contact area between the gas and liquid phases
• Providing good mixing of the gas and liquid phases (turbulence)
• Allowing sufficient “residence” or “contact” time between the phases for adsorption to occur