Investigation of the effects of ionic liquid as diluent in separation of lactic acid from aqueous media by reactive extraction

Abstract

The fact that fossil fuels will be depleted in near future and the increase of environmental awareness in humans causes biotechnology to seek new and develop existing processes constantly. That is why researchers have turned to work in this field in recent years. In this study, the separation of lactic acid, an industrially important organic acid, from aqueous solutions by reactive extraction method where tripropylamine (TPA) has been used as an extractant and hydrophobic ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) as a diluent was investigated. Six different traditional organic solvents (n-pentane, toluene, 2-octanone 1-octanol, methyl isobutyl ketone (MIBK), dimethyl phthalate (DMP)) have been chosen to compare the efficiency of the selected ionic liquid. The batch physical and reactive extraction experiment results were presented as distribution coefficient (D), loading factor (Z), and extraction efficiency (E). All experiments were performed at 298.15 K with an initial lactic acid concentration of 1.28 mol·L-1 (10.275% w/w). In reactive extraction experiments, the effect of different TPA concentrations (0.35–1.4 mol·L-1) on extraction efficiency was investigated. While the extraction efficiency in physical extraction varied between 5.55 and 14.06%, ionic liquid has the highest extraction efficiency. In the reactive extraction results, it was seen that the ionic liquid has 99.61% extraction efficiency at 1.40 mol·L-1 TPA concentration. According to this result, the use of (TPA + 1-butyl-3-methylimidazolium hexafluorophosphate) organic mixtures is a suitable alternative to separate lactic acid from aqueous solutions.