always encountering during extraction of organic compound from
nonionic surfactant by Winsor I microemulsion [33].
Replacement of organic solvent in organic solvent–nonionic
surfactant–water ternary system with hydrophobic IL [Bmim]PF6
forms a novel ionic liquid based Winsor I microemulsion [34]. In
our previous work, this novel ionic liquid based Winsor I
microemulsion extraction was developed for recovery of ionizable
red Monascus pigments from nonionic surfactant aqueous solution,
in which red Monascus pigments were transferred from nonionic
surfactant aqueous solution to ionic liquid phase by this IL based
Winsor I microemulsion extraction and the ionizable red
Monascus pigments in the IL phase were back-extracted by IL–water
two-phase system via adjustment of pH [17]. In the present
work, nonionizable Monascus pigments (yellow ones and orange
ones as shown in Fig. 1) had also been transferred successfully
from nonionic surfactant micelle aqueous solution to ionic liquid
phase by IL based Winsor I microemulsion (Fig. 2). However,
back-extraction of nonionizable Monascus pigments by adjustment
of pH in IL–water two-phase system is impossible [35,36]. Organic
solvent–ionic liquid two-phase extraction was tried as an alternative
strategy (Table 1). Tert-butanol was chosen as organic solvent
and the operation parameter of organic solvent–ionic liquid
two-phase extraction was further optimized (Fig. 3).