Formation of Ether-Functionalized Ionic-Liquid-Based Aqueous Two-Phase Systems and Their Application in Separation of Protein and Saccharides

Ionic-liquid (IL)-based aqueous two-phase systems (ATPSs) have attracted much attention in the separation technology. In this work, we synthesized five novel ether-functionalized ILs and studied their applications in ATPS formation. The phase diagrams for several systems were determined at 298.15 K. An as-prepared IL (1-(2-butoxy-ethyl)-3-methylimidazolium chloride) was chosen as a representative to construct ATPSs for separation of bovine serum albumin (BSA) from aqueous saccharide solutions. Results showed that 76.1-94.3% of BSA was enriched into the IL-rich top phase and almost all the saccharides were extracted into the salt-rich bottom phase in a one-step separation process. The main factors affecting the separation process, such as kinds of saccharides and the amount of inorganic salts, were discussed. Furthermore, the size distributions of aggregates in the IL-rich top phase were determined by dynamic light scattering (DLS), and accordingly the possible mechanism for the separation was investigated.