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Title: Mixtures of polymers and cholinium-based ionic liquids to tailor the phase diagrams and extraction efficiency of aqueous biphasic systems
Author: Dinis, Teresa B. V.
Barbosa, Luís
Neves, Catarina M. S. S.
Coutinho, João A. P.
Freire, Mara G.
Keywords: Selective extraction
Polymers mixture
Bio-based ionic liquids
Aqueous biphasic system
Issue Date: 2017
Publisher: National Center for Scientific Research
Abstract: Aqueous biphasic systems (ABS) are outstanding alternatives over conventional liquid-liquid extraction processes since it is avoided the use of volatile and hazardous organic solvents (VOCs). ABS are more biocompatible systems formed by two aqueous-rich phases that can be designed by combining different pairs of solutes (polymer-polymer, polymer-salt or salt-salt) above specific concentrations. In the past years, ABS have been studied as powerful techniques for purification, separation and extraction purposes. Ionic liquids (ILs) have been described as interesting fluids towards the development of more sustainable processes. Due to the ILs unique properties, their introduction in ABS led to systems with higher selectivity and extraction performance for a wide plethora of compounds. In fact, it was already shown that ILs allow to overcome the low hydrophilic-hydrophobic range of ABS composed of two polymers or one polymer and one inorganic salt. IL-based ABS formed with polyethylene glycol (PEG) polymers were recently introduced and a successful control of the phase polarities, through the manipulation of the IL chemical structure, was demonstrated. Lately, it was also demonstrated that a new class of natural-derived cholinium-based ILs are capable of undergoing two phase separation by the addition of PEGs with different molecular weights. In the present work, mixtures of PEGs with different molecular weights (400 and 2000 g/mol) were used to ascertain on the formation ability of ABS composed of water and cholinium-based ILs or salts. The results obtained indicate that the formation ability of these ABS increase with the content of PEG2000 over PEG400 (and follow a continuous increase), meaning that a close-fitting control on their phases polarity can be attained. These systems were then evaluated on their performance for extracting a series of alkaloids with different polarities, namely caffeine, theophylline, theobromine and nicotine. In general, the alkaloids partition extent to the most hydrophobic phase (PEG-rich) follows their polarity/hydrophobicity. In summary, it is here demonstrated that mixtures of polymers as phase-forming components of ABS allow to tailor the partition coefficients of different alkaloids and their use in the purification of added-value compounds from biomass extracts is straightforwardly foreseen.
Peer review: yes
Appears in Collections:CICECO - Comunicações

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