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Title: Mechanisms ruling the partition of solutes in ionic-liquid-based aqueous biphasic systems: the multiple effects of ionic liquids
Author: Passos, Helena
Dinis, Teresa B. V.
Capela, Emanuel V.
Quental, Maria V.
Gomes, Joana
Resende, Judite
Madeira, Pedro P.
Freire, Mara G.
Coutinho, João A. P.
Issue Date: 7-Apr-2018
Publisher: Royal Society of Chemistry
Abstract: In the past decade, the remarkable potential of ionic-liquid-based aqueous biphasic systems (IL-based ABSs) to extract and purify a large range of valued-added biocompounds has been demonstrated. However, the translation of lab-scale experiments to an industrial scale has been precluded by a poor understanding of the molecular-level mechanisms ruling the separation or partition of target compounds between the coexisting phases. To overcome this limitation, we carried out a systematic evaluation of specific interactions, induced by ILs and several salts used as phase-forming components, and their impact on the partition of several solutes in IL-based ABSs. To this end, the physicochemical characterization of ABSs composed of imidazolium-based ILs, three salts (Na2SO4, K2CO3 and K3C6H5O7) and water was performed. The ability of the coexisting phases to participate in different solute-solvent interactions (where "solvent" corresponds to each ABS phase) was estimated based on the Gibbs free energy of transfer of a methylene group between the phases in equilibrium, ΔG(CH2), and on the Kamlet-Taft parameters - dipolarity/polarizability (π*), hydrogen-bonding donor acidity (α) and hydrogen-bonding acceptor basicity (β) - of the coexisting phases. Relationships between the partition coefficients, the phase properties expressed as Kamlet-Taft parameters and COSMO-RS descriptors were established, highlighting the ability of ILs to establish specific interactions with given solutes. The assembled results clearly support the idea that the partition of solutes in IL-based ABSs is due to multiple effects resulting from both global solute-solvent and specific solute-IL interactions. Solute-IL specific interactions are often dominant in IL-based ABSs, explaining the higher partition coefficients, extraction efficiencies and selectivities observed with these systems when compared to more traditional ones majorly composed of polymers.
Peer review: yes
DOI: 10.1039/c8cp00383a
ISSN: 1463-9076
Appears in Collections:CICECO - Artigos
DQ - Artigos

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