Ionic Liquid-Nonionic Surfactant Aqueous Two-Phase System

Cloud point system is usually applied for extraction of neutral organic compounds.Thus,ionizable compounds can be extracted into the coacervate phase by cloud point extraction at their molecular state while back-extracted at their ionized state by simple adjustment of pH.However,some ionized solutes with a relatively weak polarity can also be solubilized in nonionic surfactant micelles.Isolation of those ionizable compounds from nonionic surfactant micelle aqueous solution becomes challengeable.Ionic liquid as a novel solvent can replace water to mediate nonionic surfactant forming cloud point system.The effect of ionic liquid type,nonionic surfactant HLB(hydrophile-lipophile balance),and water content on cloud point of nonionic surfactant in ionic liquid aqueous solution was examined,in which the lowest cloud point at a relatively high ionic liquid faction was observed.Phase diagram of nonionic surfactant-ionic liquid-water ternary system exhibited a two-phase region: a nonionic surfactant-rich aqueous phase and an ionic liquid-rich aqueous phase at high ionic liquid fraction,which was known as ionic liquid-nonionic surfactant aqueous two-phase system.Setting the ionic dyes as model compounds,the partitioning behavior in conventional cloud point system and ionic liquid-nonionic surfactant aqueous two-phase system was studied comparatively.Organic compounds,especially anionic compounds,had been transferred from nonionic surfactant micelle aqueous solution into ionic liquid aqueous solution by the ionic liquid-nonionic surfactant aqueous two-phase system.Thus,ionic liquid-nonionic surfactant aqueous two-phase system provides a novel strategy for recovery of anionic compounds from nonionic surfactant micelle aqueous solution.Red Monascus pigments can be existed as cation,neutral molecule,and anion depending on their molecular structure of amine residue as well as their environmental condition(such as pH).Using excess MSG(monosodium glutamine)as the sole nitrogen source,several kinds of red Monascus pigments were produced by extractive fermentation in a nonionic surfactant micelle aqueous solution.Most of red pigments were concentrated in the coacervate phase within experimental pH range during cloud point extraction.By application of the novel aqueous two-phase system,red Monascus pigments were transferred from coacervate phase into ionic liquid-rich aqueous phase.Thus,the challengeable downstream processing of extractive fermentation,i.e.,recovery of red Monascus pigments from nonionic surfactant aqueous solution,was converted to the relatively easy separation between red Monascus pigments and water-miscible ionic liquid.And then,chloroform-ionic liquid aqueous solution two-phase system was used to separate anionic red pigments from water-miscible ionic liquid due to the preferable partitioning of [Bmim]Cl in the water phase of water-chloroform two-phase phase.The aqueous solution(pH=7)was further isolated by evaporation of solvent and precipitation of pigments via addition of acidic water(pH=1).The experimental result also indicated that several kinds of red Monascus pigments were produced during extractive fermentation using excess glutamic acid as the sole nitrogen source.