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Continuous bubble fractionation, a separation technique based on the enrichment of a solute on the surfaces of rising gas bubbles and subsequent removal of the concentrated liquid from the top where the busting bubbles accumulate the solute, has been investigated for the separation of a solute from a dilute solution. The solute concentration profile and effectiveness of the column have been studied using the height and diameter as variables. The implications of basic mechanisms involved in the solute transfer on the column performance were considered.

The performance of a bubble fractionation process was investigated experimentally using liquid flow rate and gas flow rate as variables. Based on an ideal model, the theoretical performance of the continuous bubble fractionation process was qualitatively evaluated. Experimental results indicate that an increase in the bottom effluent rate while keeping the overflow rate constant increases the solute concentration in the top overflow. An increase in overflow rate while keeping the bottom effluent rate constant decreases the solute concentrations of top overflow, but decreases insignificantly the bottom effluent's solute concentration. When the feed rate is constant, optimization of the bubble fractionation system can be achieved by regulating the top-to-bottom flow rate ratio. For practical engineering application, a meaningful combination of physical dimensional parameters into dimensionless operational charts can be useful for plant operators in operating the continuous bubble fractionation process.

The bubble fractionation process is one of a number of adsorptive bubble separation methods which involves the use of selective adsorption of surface-active solutes at the gas-liquid interfaces of the rising bubbles in a bubble column. It can be used as an advanced treatment method for certain industrial effluents or domestic sewage which contain surface-active substances. In this study, a theory for continuous operation of the bubble fractionation process was developed. The theory involves: (a) the adsorption of surface-active solutes at rising bubble surfaces; and (b) balancing flow in the bubble column against axial diffusion and the departure of solutes from the fractionation system. Theoretical analyses imply that the effectiveness of the continuous bubble fractionation system increases with increasing gas rate and the surface activity of the solute but decreases with increasing column cross-sectional area, axial diffusion and bubble size.

Theoretical equations developed in Part I of this paper1 have been evaluated experimentally using bubble size and gas flow rate as variables. Variations of bubble size and gas flow rate, which will affect the column performance of either batch or continuous bubble fractionation system, are predicted by the developed theory. Based on theoretical development and experimental verifications, several approaches for the improvement of the bubble fractionation system are suggested.