Novel aqueous biphasic system based on ethyl lactate for sustainable separations: Phase splitting mechanism

Abstract

Ethyl lactate is a hydrophilic green solvent which is bio-renewable and biodegradable with low toxicity towards humans and animals. For the first time, we report that aqueous solutions of ethyl lactate separate into two aqueous phases upon addition of salts. The performance of trisodium citrate, disodium tartrate and disodium succinate as salting-out media for the separation of natural organic compounds, such as caffeine and catechin, from their aqueous solutions was examined. In this respect, cloud points for the ternary solutions composed of ethyl lactate, water and salt were determined at ambient pressure (0.1 MPa) at 298.2 K. Partition coefficients of caffeine and catechin between two phases were determined by chemical analysis of phases in equilibrium for different initial compositions at 298.2 K. The obtained results clearly demonstrate the ability of the ternary mixture to phase separate, providing good salting-out media for the efficient and sustainable separation from aqueous solution. 1 H-NMR spectroscopy was employed to elucidate the mechanisms of phase splitting in the ternary (ethyl lactate + water + salt) systems at molecular level. The discovery of aqueous biphasic system (ABS) containing ethyl lactate as hydrophilic solvent opens a new and green platform for extraction of various compounds from aqueous solutions.

Liquid–Liquid Phase Equilibria of Aqueous Biphasic Systems Based on Glycerol Formal: Application on Tetracycline Recovery from Water

“…Solubility curves of the ternary mixtures containing glycerol formal, water and salt (either K3PO4 or K2HPO4 or K2CO3) were determined by the cloud point titration method at a constant temperature of 298 K at pressure of 0.1 MPa as described in our previous papers 15,16 .…”

“…Solubility curves of the ternary mixtures containing glycerol formal, water, and salt (either K 3 PO 4 or K 2 HPO 4 or K 2 CO 3 ) were determined by the cloud point titration method at a constant temperature of 298 K at pressure of 0.1 MPa as described in our previous papers. , Gravimetrically prepared binary mixtures, containing salt and water of known compositions, were placed in septum-sealed conical glass vials equipped with magnetic stirrer and immersed in the temperature-controlled bath (Thermo Scientific) heated with SAHARA SC150 S19T circulator with a stability of 0.02 K. The transparent acrylic bath walls allowed full visualization of the mixture content. The binary mixtures were titrated with glycerol formal very slowly at a constant temperature, until the first turbidity was observed, which was taken as a cloud point.…”

“…Recently, we discovered novel ATPS based on ethyl lactate, which is capable to efficiently extract amino acids and alkaloids from aqueous solutions. 15,16 Our further search for ATPS focuses on glycerol formal, commercially available as a mixture of two fiveand sixmembered ring isomers, which has attracted attention as hydrophilic solvent due to its very low toxicity. 17 Glycerol formal (GF) is an industrially important compound derived from glycerol that has a massive surplus globally due to increased biodiesel demand.…”

“…Recently, we discovered novel ATPS based on ethyl lactate, which is capable to efficiently extract amino acids and alkaloids from aqueous solutions. , …”

Extraction of antibiotics using aqueous two-phase systems based on ethyl lactate and thiosulphate salts

“…Previous works have shown efficient separations of natural compounds, such as caffeine and catechin [23], amino acids [24] as well as rutin and quercetin [25], from aqueous solutions using ATPS based on ethyl lactate and various salts (citrate, tartrate, succinate, phosphate, dihydrogen phosphate and carbonate). In this paper, we further investigate using a systematic study the role of different extractants namely, thiosulphate salts.…”