Thermodynamics of clouding process in 1-butanol + water mixtures in the presence and absence of sugars

Soluting-In, Soluting-Out, and Washing-Out Effects of Various Additives on Aqueous 1-Butanol Solutions

“…The clouding phase diagram of binary 1-butanol + water mixtures in both water-rich and butanol-rich regions (namely, 1-butanol in water and water in 1-butanol mixtures) has been previously determined by us and other research groups. − In this work, aiming at investigating the effect of additives on the clouding behavior of the 1-butanol + water mixture in the water-rich region, the following systematic study was performed in a wide temperature range (283–353 K). Cloud point determination for ternary systems of 1-butanol in aqueous solutions of 0.2, 0.4, and 0.6 mol·kg –1 of the amino acids, glycine, alanine, serine, and proline, as well as in aqueous solutions of 0.2 mol·kg –1 of glutamine. Because of the low water solubility of glutamine, its higher molality could not be investigated. Cloud point determination for ternary systems of 1-butanol in aqueous solutions of 0.2, 0.4, and 0.6 mol·kg –1 of the ILs 1-butyl-3-methylimidazolium bromide ([C 4 mim]­Br) and 1-methyl-3-octylimidazolium bromide ([C 8 mim]­Br). Cloud point determination for ternary systems of 1-butanol in aqueous solutions of 0.05, 0.10, and 0.15 w/w of the polymers poly­(ethylene glycol) 400 (PEG400) and poly­(ethylene glycol) 10 000 (PEG10000). Cloud point determination for ternary systems of 1-butanol in aqueous solutions of 0.05, 0.10, and 0.15 w/w of the primary and secondary propanol. …”

“…The clouding (liquid–liquid demixing) phase diagrams for ternary systems of 1-butanol in aqueous amino acid/IL/poly­(ethylene glycol) (PEG)/propanol solutions were determined by the visual turbidity titration method. The methods’ procedure and apparatus details have been explained in our previous works. ,, Here, to determine 1-butanol mass fraction corresponding to the clouding phenomenon at each temperature (283.1–353.1 K with an increase of 10 K), binary aqueous solutions of the investigated additives {amino acids (0.2, 0.4, and 0.6 mol·kg –1 ), ILs (0.2, 0.4, and 0.6 mol·kg –1 ), polymers (0.05, 0.10, and 0.15 w/w), and 1-/2-propanol (0.05, 0.10, and 0.15 w/w)} were first prepared and poured into a transparent double-walled glass cell. Then, pure 1-butanol was dripped on each binary limpid solution until a cloudy mixture was detected at each temperature.…”

“…To study the clouding process in the viewpoint of thermodynamics, the Gibbs free energy (Δ G m,C ), entropy (Δ S m,C ), and enthalpy (Δ H m,C ) changes of phase separation in the 1-butanol aqueous mixtures were calculated from the following equations , where R is the universal gas constant, T Cp is the cloud point temperature, and X b is the 1-butanol mole fraction corresponding to each T Cp . The relative contributions of entropy (ζ S ) and enthalpy (ζ H ) to clouding Gibbs free energy were determined using the equations below , …”

Soluting Effects of Various Additives on the Clouding Behavior of Poly(propylene glycol) 1000 in Aqueous Media

“…The liquid–liquid demixing temperatures (cloud point temperatures, T C ) for the aqueous solutions of the thermoresponsive polymer PPG1000 in the presence of additives were determined by the visual cloud point measuring method. This method has been successfully used to determine the liquid–liquid phase diagrams of several systems, and the manner details have been described previously. ,, Briefly, the understudy samples were prepared using a high-resolution Sartorius analytical balance (model: CP225D, precision: ±1 × 10 –5 g) and placed in a double-shell glassy container; then the container was sealed to avoid water evaporation. The container was located on a stirrer plate to provide continuous stirring of samples during measurements, and it was also connected to a Julabo thermostat (model: F 25, precision: ±0.1 K) to circulate thermostatically regulated water in the outer shell of the container.…”

“…In other words, additives can behave as a stimulus on the phase separation behavior of thermoresponsive materials. When a solute is added to the solution containing a thermoresponsive substance, depending on the soluting-in or soluting-out effect of the additive, a wider or narrower homogeneous region in the clouding diagram ( T C against the concentration of a thermoresponsive substance) may be observed. − This fact provides a means to adjust the clouding behavior of these systems, which leads to optimized design of their applications, especially in the cloud point extraction implementation.…”