Effects of kinetics of adsorption and coalescence on continuous foam concentration of proteins: Comparison of experimental results with model predictions.

Protein enrichment and recovery were measured in a continuous foam concentration column for bovine serum albumin (BSA) for different pool heights, foam heights, superficial gas velocities, bubble sizes, feed flow rates, pH, and ionic strengths. Protein enrichment was found to decrease with an increase in pool height for low pool heights, reach a minimum at an intermediate pool height, and subsequently increase with pool height for sufficiently large pool heights eventually approaching an asymptotic value. Such a behavior was due to the combined effects of kinetics of adsorption of protein and coalescence. The increase in protein enrichment with pool height was due to the predominant effect of kinetics of adsorption of protein, whereas the opposite behavior at low pool heights was due to the predominant effect of coalescence in the foam. Protein enrichment was found to be higher for smaller feed concentrations, smaller gas velocities, larger bubble sizes, and larger foam heights. Enrichment at pH values different from the isoelectric point was found to be higher because of more coalescence. A model for foam concentration of proteins was employed to predict enrichment and recovery. The model predictions agreed well with the experimental data. (c) 1996 John Wiley & Sons, Inc.