Reactive Extraction of Glycolic Acid Using Tri-n-Butyl Phosphate and Tri-n-Octylamine in Six Different Diluents: Experimental Data and Theoretical Predictions

Abstract

The present study deals with the equilibrium reactive extraction of glycolic acid from aqueous solution by two different extractants [tri-n-butyl phosphate (TBP) and tri-n-octylamine (TOA)] at constant concentration of 0.573 kmol·m−3 dissolving in a wide range of diluents [n-hexane, decane-1-ol, n-hexane + decane-1-ol (1:1 v/v), 4-methylpentan-2-one (MIBK), benzene, and dichloromethane (DCM)] at isothermal conditions (298 ± 1 K). The effects of various parameters such as acid concentration (0.10−0.57 kmol·m−3), extractant type, and type of diluent on the recovery of glycolic acid from aqueous solution are derived. The values of equilibrium constants (K E), number of reacting acid molecules (m) per extractant molecule, and also the equilibrium constants (K 11 and K 21) for individual complexes between acid and extractant are estimated through the proposed mathematical model. Further, the experimental values of the distribution coefficients (K D) are correlated using the linear solvation energy relationship (LSER) model which is based on solute−solvent interaction parameters. The extraction power of TBP and TOA in terms of K D increases in the order of DCM ≥ MIBK > decan-1-ol > n-hexane + decan-1-ol (1:1 v/v) ≥ benzene ≥ n-hexane, and DCM ≥ decan-1-ol > MIBK > n-hexane + decan-1-ol (1:1 v/v) > benzene > n-hexane, respectively.

New insights in reactive extraction mechanisms of organic acids: An experimental approach for 3-hydroxypropionic acid extraction with tri-n-octylamine

“…Potentiometric titration with colorimetry is often used to determine extraction yields in reactive extraction with phenolphthalein as a pH indictor [18,20,21,23,29,34]. However, the usual color turning point of phenolphthalein is at pH=8.2 [46] which means that acidic species at pH > 8.2 are not titrated.…”

“…In the case of hydrophilic carboxylic acids, these reagents can be hydrophobic basic molecules being able to interact with acidic groups [15]. Among such molecules, long chained aliphatic amines have been widely studied for a large set of carboxylic acids, such as hydroxycarboxylic acids like citric [16][17][18], glycolic [19,20], malic [21,22] and tartaric [23][24][25][26] acids, C3 monocarboxylic acids like acrylic [27], propionic [28][29][30][31] and pyruvic [32][33][34] acids and even lactic acid, an α-hydroxylated C3 monocarboxylic acid (positional isomer of 3-HP) [22,23,35].…”

Thermodynamic equilibrium of hydroxyacetic acid in pure and binary solvent systems

“…Hydroxyacetic acid (HA, CAS: 79-14-1，Figure 1), the smallest and simplest compound of α-hydroxy acid family [1], is a fundamental organic compound and an important organic synthesis intermediate. HA is widely used in chemical cleaning and daily-used chemical industrial [2,3].…”

Synergistic Extraction of Glycolic Acid from Glycolonitrile Hydrolysate

“…Matsumoto M. et al 15À17 and Datta D. 18 reported that positive synergism appears in the extraction of dilute organic acids with trin-octylamine (TOA) by adding TBP as an additive. In our previous work: "Separation of glycolic acid from glycolonitrile hydrolysate by reactive extraction with tri-n-octylamine", 19 result was reported.…”