Temperature Effect on the Phase Equilibrium of Polyethylene Glycol 2000 + Trilithium Citrate + Water Aqueous Two-Phase Systems at T = 288.15, 298.15, 308.15, and 318.15 K

Abstract

Binodal and tie-line mass fractions for ternary polyethylene glycol 2000 + trilithium citrate + water aqueous two-phase systems (ATPSs) were reported at T = 288.15, 298.15, 308.15, and 318.15 K experimentally and modeled thermodynamically. It was found that the extent of the two-phase area of the liquid–liquid equilibrium region was increased as the temperature increased. Also, binodal curves were properly modeled with two nonlinear models, and both models have been successful in fitting the binodal data. Furthermore, the osmotic virial, modified nonrandom two-liquid (m-NRTL), and electrolyte-Wilson models have successfully been implemented in the modeling of the tie-line mass fractions. The quality of fitting with the electrolyte-Wilson and specially m-NRTL models is good, and the uncertainty of the modeled data is in the range of the uncertainty of the experimental data. Also, the salting-out coefficient (k s) of a Setschenow-type equation was applied as a quantitative measure of the salting-out ability. The results of the present work introduce a green and environmentally friendly ATPS for liquid–liquid extraction and purification purposes, which can be used in the separation and purification of drugs, biomaterials, and foods.

Effect of Temperature on the Phase Equilibria of Poly(vinylpyrrolidone) 10000 + Trilithium Citrate + Water Aqueous Two-Phase System and Partitioning of Curcumin at T = 298.15, 308.15, and 318.15 K

“…The chemicals used in this work are described in Table 1. Following our previous work, 35 trilithium citrate was heated at the temperature of T = 423 K to remove the water and obtain dehydrated salt. Other materials were used as provided by suppliers.…”

“…Furthermore, the top and bottom phases were totally separated from each other using the method described in our previous work. 35 The pH of the separated solutions was then measured by a laboratory pH meter (Metrohm Ltd., Model 780, Switzerland). Finally, the mass of each phase in each tieline was measured, and the separated phases were kept in closed containers at T = 283.15 K for further use in determining the partition coefficient of curcumin.…”

“…Electrolyte-Wilson (e-Wilson) 43 and electrolyte-NRTL (e-NRTL) 45,50 local composition models were recently used by our group in the modeling of the LLE data of PEG 2000 + trilithium citrate + water ATPSs. 35 Only the general equations are represented here, and the detailed information and equations can be found in our previous work. 35 The excess Gibbs free energy (G E ) expression for both models is the sum of a local composition term for the short range (SR) and a Pitzer−Debye−Huckel (PDH) 51 term for the long-range (LR) contributions along with the Flory− Huggins expression 52,53 for the combinatorial terms.…”

“…Citrate salts are watersoluble and can be an alternative to nontoxic and inflammable salts to form environmentally friendly ATPSs. 10,15,35 Various thermodynamic or empirical models are used to model the liquid−liquid equilibrium (LLE) of various ATPSs. Binodal models of the polymer/alcohol + electrolyte ATPSs are simple nonlinear empirical equations, in which the fitting function represents the concentration of one component (i.e., polymer/alcohols or electrolyte) as a function of the other one.…”

“…Moreover, the modified version of the segment-based nonrandom two-liquid model (e-NRTL) is developed by Sadeghi 45 for vapor−liquid systems and has been used to correlate the tie-line compositions of numerous systems. 10,14,19,35 In this work, the PVP 10000 + trilithium citrate + water ATPS at T = 298.15, 308.15, and 318.15 K was investigated. The experimental binodal curves at different temperatures were obtained and correlated using a new empirical equation.…”