Abstract
Aqueous biphasic system (ABS) has been proposed as an alternative technique for the extraction, separation and/or purification of diverse biomolecules. ABS composed of polyethylene glycol (PEG) and sodium salts, using ILs ([Cnmim]Cl) as additives were studied. Phase diagrams of PEG 800+sodium salts (Na2HPO4, Na3C6H5O7, Na2CO3, Na2SO4, NaH2PO4)+H2O+5wt% [C4mim]Cl at 298.15 K were used to study the effect of different salts on the ABS. Binodal curves for the ABS composed of PEG (molecular weights of 400, 600, 800, 1000 and 2000g·mol−1)+Na2SO4+H2O+5wt% IL ([C2mim]Cl, [C4mim]Cl, [C6mim]Cl, [C8mim]Cl, [C10mim]Cl) at 298.15 K were determined to study the effect of the polymer size and the IL alkyl side chain length on ABS. Ability of the various salts to form ABS follows the trend: Na3C6H5O7>Na2HPO4>Na2CO3>Na2SO4>NaH2PO4. The increase in the molecular weight of PEG increases the phase separation ability of the system. [C6mim]Cl shows the best phase separation at PEG400+Na2SO4. [C8mim]Cl and [C10mim]Cl improves the phase separation of PEG-Na2SO4. The phase diagram is not affected at 288.15–308.15 K. The phase separation increases at 318.15–328.15 K and decreases at >318.15 K. These results illustrate the ability of the IL to tune the polarity of the PEG-rich phase. PEG–Salt–IL ABS could be an interesting advance in separation processes and could lay the basis for future studies in extraction processes.
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•Phase diagrams of PEG-Salt-ILs additives of ABS were investigated.•Effect of salt on phase separation of ABS obeys Hofmeister series.•Phase separation improves with increasing polyethylene glycol (PEG) size.•Imidazolium-based ILs with C8 and C10 show best phase-forming ability.•The impact of temperature on ATPS is not significant but could not be neglected.