A mechanistic process model for aqueous two-phase flotation: Insights into enzyme transport mechanisms

Continuous aqueous two-phase flotation (ATPF) is an alternative downstream approach for the selective separation of enzymes from complex biosuspensions. Until now, mass transport across the phase interface has been assumed to be mainly due to accumulation of enzymes on the surface of rising gas bubbles (flotation), while theoretical studies are lacking. This work presents a mechanistic compartment model of the ATPF process that also includes mass transport by extraction, i.e. diffusion across the phase interface. The model is validated with ATPF experiments over a wide range of process parameters and reliably predicts the process behavior. The results indicate that extraction accounts for more than 80% of the integral mass transfer, while bubbles are still essential for phase mixing and the creation of a large interfacial area. Therefore, the proposed process model provides valuable insights into the enzyme transport mechanisms and enables future developments such as model predictive control.