Deep eutectic solvent (DES) has demonstrated its ability to improve the yield and selectivity in the 5-hydroxymethylfurfural (HMF) production process. Liquid−liquid extraction is a beneficial process in HMF production to recover HMF from the reaction medium. In the present study, the effect of DES (choline chloride urea) on the liquid−liquid equilibria (LLE) of HMF−water−organic solvent (methyl isobutyl ketone (MIBK) or 2pentanol) systems in the absence and presence of sodium chloride (NaCl) was investigated at 313.15 K and atmospheric pressure (0.1 MPa). The tie-lines of the multicomponent systems were measured using several analytical methods. According to the experimental results, the extraction performance decreased with an increase in DES concentration. However, the addition of 10 wt % NaCl into the HMF aqueous DES solution can induce stronger liquid− liquid phase splitting, enhancing the separation factors and distribution coefficients of HMF by around 2.7 and 1.6 times, respectively. Additionally, MIBK showed better extraction performance in the presence of DES and NaCl with the separation factors 2.6 times higher than those of 2-pentanol and the HMF distribution coefficients above 1.8. The LLE of the multicomponent systems were correlated well with the nonrandom two-liquid (NRTL) model.

The capacity of methyl isobutyl ketone (MIBK) containing 5 wt % 4-(2-hydroxyethyl)-1-piperazine propanesulfonic acid (EPPS) buffer has been demonstrated to boost the distribution coefficient and separation factor in the extraction process of carboxylic acids (acetic acid or propionic acid). Liquid–liquid extraction is a useful technique for recovering acetic acid and propionic acid from an aqueous fermentation broth. In this study, the effect of EPPS buffer on the liquid–liquid equilibria (LLE) of water–acetic acid–MIBK and water–propionic acid–MIBK systems were measured at a temperature range of 298.15–318.15 K and atmospheric pressure (P = 0.1 MPa). The distribution coefficient (D) and separation factor (S) were calculated at each tie-line, and the reliability of the tie-lines was evaluated using the Othmer–Tobias and Hand plot correlations. With the addition of 5 wt % EPPS in the water–carboxylic acids–MIBK system, the separation factor increased by 7.2 times of the EPPS-free system. The NRTL model predicts the new LLE tie-lines within reasonable accuracy for this quaternary system. By adjusting constituent binary parameters, the NRTL model satisfactorily correlated the liquid–liquid equilibria of the water + acetic acid + MIBK + EPPS and the water + propionic acid + MIBK + EPPS system.

Biofuel, that is, n-butanol, production from plant-based biomass represents a renewable energy resource that can be a substitute for fossil fuel. Thus, it is important to study the separation of n-butanol from its aqueous solution to obtain a high-purity product. Liquid–liquid extraction is a beneficial process in alcohol production to recover alcohol from the aqueous medium. Liquid–liquid equilibrium (LLE) data are needed for rational design and optimal separation operation, such as biological separation and extraction processes. The objective of this study is to determine LLE data for quaternary systems of n-butanol, methyl isobutyl ketone (MIBK), water, and a biological buffer at 303.15 K and atmospheric pressure (P = 0.1 MPa). The effect of biological buffer addition into aqueous solution was also studied. Three different biological buffers, 4-(2-hydroxyethyl)-1-piperazine propanesulfonic acid (EPPS), 4-morpholinepropanesulfonic acid (MOPS), and 4-(2-hydroxyethyl)­piperazine-1-ethanesulfonic acid (HEPES), were applied in this study for the comparison. The separation factor and distribution coefficient were evaluated in this study to interpret the extraction performance of n-butanol. According to the experimental results, the extraction performance was in the order of HEPES > EPPS > MOPS, describing the strength of buffering-out as well. Furthermore, it was found that the aid of a biological buffer in the LLE systems consisting of n-butanol, MIBK, and water resulted in better extraction performance than that of the LLE systems in the absence of a biological buffer. The reliability of the experimental LLE tie-line data was satisfactorily ascertained by the Hand correlation. The non-random two-liquid and universal quasi-chemical thermodynamics models correlated well the experimental LLE tie-line data with the root mean square deviation of less than 1%. The binary interaction parameters of both models were also obtained in this study.

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