Accounting for interface behaviour in multi-stage aqueous two-phase extraction

Aqueous two-phase extraction (ATPE) is an alternative, cheaper and continuous protein purification technique. For ATPE to be used in industry, it must compete with current batch purification procedures, which can be achieved using multi-stage operation. To design extraction processes using ATPE appropriate process models must be developed. In this study, experimentally determined single-stage equilibrium data was used to generate a model to describe the behaviour of protein in multi-stage counter-current ATPE. Two distribution systems are considered: liquid-liquid (LL) and liquid-interface-liquid (LIL) distribution. The LIL model considers material which precipitates at the interface of the system. These models were then both compared against a three-stage experimental case study ATPE. The LIL model described the case study system better than the LL model, reducing the error from 40 % to 11 %. With this significant increase in accuracy, the LIL model represents an important tool with which to design multi-stage ATPE processes.