Development and optimization of ionic liquid-based emulsion liquid membrane process for efficient recovery of lactic acid from aqueous streams

Abstract

Development of ionic liquid-based emulsion membranes (ILEMs) has emerged as potential alternatives to organic solvent-based emulsion membranes for the extraction and recovery of biologically active compounds from aqueous streams. Hence, present study aims to develop novel ILEMs for the removal of bioactive lactic acid (LA) from aqueous streams using 100% vegetable oil as diluent. A series of ILEMs were prepared using three different ionic liquids (ILs) namely tetramethylammonium chloride [TMAm][Cl], tetramethylammonium acetate [TMAm][Ac] and tributylmethylammonium chloride [TBMAm][Cl] as a carrier. Besides, olive oil used as diluent, NaOH used as stripping agent, Tween 80 and Span 20 were employed as emulsifier in ILEMs preparation. The visual static stability of ILEMs was observed and the ILEM extraction efficiency was fully optimized in terms of various process parameters. The results showed that short-chain acetate based quaternary ammonium IL [TMAm][Ac] provided greater efficiency compared to chloride based ILs [TMAm][Cl] and [TBMAm][Cl]. A maximum of 94.50% LA removal was obtained with [TMAm][Ac] at optimized conditions of 0.05 M LA, 1.0 wt.% Span 20, 0.3 M NaOH, 0.3 wt.% [TMAm][Ac], 0.3 ratio of internal phase to diluent phase and 3:1 treat ratio (ratio of external phase to membrane phase) at a stirring speed of 250 rpm for 25 min. The emulsion was found stable for 134 min at the optimized conditions. Overall, this newly developed ILEM could be effectively used for the LA removal and other bioactive compounds from aqueous streams.