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This work aims at exploring new sustainable separation processes based on ionic liquids. Aqueous biphasic systems (ABS) based on poly(ethylene glycol) (PEG) with low molecular weight (600 and 4000 g mol −1 ) and choliniumbased ionic liquids and salts containing anions derived from carboxylic acids (oxalate, malonate, succinate, L-malate, fumarate, glutarate and citrate), available in natural compounds, are here presented. Contrary to common ionic liquids, the cholinium-based ionic liquids used in this work are biodegradable, nontoxic, cheap, and simple to prepare, and PEG is also a cheap and nontoxic phase promoter agent. The data reported in this work allows novel insights into the phase splitting mechanism of these ABSs regarding the influence of alkyl chain length of the anion and the presence of substituent groups in the anion. The effect of PEG molecular weight in the ABS was also addressed. Furthermore, the possible application of these systems for the extraction/separation of antioxidants, namely, tert-butylhydroquinone (TBHQ), was evaluated.

Aqueous biphasic systems (ABS) using ionic liquids (ILs) offer an alternative approach for the extraction, recovery, and purification of biomolecules through their partitioning between two aqueous liquid phases. In this work, the ability of a wide range of ILs to form ABS with aqueous solutions of Na2 CO3 was evaluated. The ABS formed by IL + water + Na2 CO3 were determined at 25°C, and the respective solubility curves, tie-lines, and tie-line lengths are reported. The studied ILs share the common chloride anion, allowing the IL cation core, the cation isomerism, the presence of functionalized groups, and alkyl side chain length effects to be evaluated. An increase in the cation side alkyl chain length leads to a higher ability for liquid-liquid demixing whereas different positional isomers and the presence of an allyl group have no major influence in the phase diagrams behavior. Quaternary phosphonium- and ammonium-based fluids are more able to form an ABS when compared with imidazolium-, pyridinium-, pyrrolidinium-, and piperidium-based ILs. Moreover, the presence of an aromatic cation core has no major contribution to the formation of ABS when compared to the respective nonaromatic counterparts. Finally, to appraise on the systems applicability in downstream processing, selected systems were used for the partitioning of tetracyclines (neutral and salt forms) - a class of antibiotics produced by bacteria fermentation. Single-step extraction efficiencies for the IL-rich phase were always higher than 99% and confirm the great potential of ILs to be applied in the biotechnological field.

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