Partitioning of reactive red-120, 4-(2-pyridylazo)-resorcinol, and methyl orange in ionic liquid-based aqueous biphasic systems

• Ionic liquid-based aqueous biphasic extraction is an efficient and suitable method for partitioning of dyes into ionic liquid phase.
• Efficient extraction time of dyes into ionic liquid phase was less than 1 min.
• Ionic liquid phase was recyclable.

In this paper partitioning behaviors of reactive red-120, 4-(2-pyridylazo)-resorcinol, and methyl orange as model azo dyes in ionic liquid-based aqueous biphasic systems were studied. For designing aqueous biphasic systems and investigating the partitioning of the model dyes, phase diagrams and binodal curves were obtained at 25 °C for [C4mim][Br]/salt systems at different pH values. It was found that the partition coefficients of the studied dyes depended on their chemical structures, pH of the aqueous phase, temperature and composition of the aqueous biphasic system. Ionic liquid-based aqueous biphasic extraction was an efficient and suitable method for partitioning of dyes into ionic liquid-rich top phase. Efficient extraction of dyes into IL phase was done within 1 min. The hydrophilic ionic liquid 1-butyl-3-methylimidazolium bromide, [C4mim][Br], in top phase was efficiently recovered by using the hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim][PF6]. In the recycling process, almost no dye was extracted into [C4mim][PF6] phase.

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