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

Effect of Sulfate, Citrate, and Tartrate Anions on the Liquid-Liquid Equilibrium Behavior of Water + Surfactant

Cloud point extraction is a versatile method aimed at separating compounds from complex mixtures and arouses great technological interest, particularly among the biochemical industries. However, one must have deep knowledge of the liquid–liquid equilibrium behavior of systems to properly use the method. Thus, we used thermodynamic parameters to evaluate the effect of citrate, sulfate, and tartrate anions on the phase separation of water + Triton X-114® mixtures at 283.2 K, 293.2 K, and 303.2 K. In these systems, increasing the temperature and the anion molar fraction expanded the biphasic region in the following order: C6H5O73-> SO42- >  C4H4O62−. Unlike other studies based on the Hofmeister series, the Gibbs free energy of micellization correlated the anion effect on the biphasic region with the spontaneity of the micelle formation. The water molecules structured around these anions were evaluated according to the shell volume of the immobilized water by electrostriction, volume of water around the hydration shell, Gibbs free energy of hydration, and Gibbs free energy of electrostriction (ΔGel12). The citrate anion presented a higher ΔGel12 of −1781.49 kJ mol−1, due to the larger number of electrons around it. In addition, the partition coefficient of the surfactant in the two liquid phases revealed a linear dependence upon the anion mole fractions by following the previous anion sequence and temperature in the phase separation.

Thermodynamic factor and vacuum crystallization

Sucrose crystallization depends on various thermal phenomena, which makes them an important scientific issue for the sugar industry. However, the rationale and theory of sucrose crystallization still remain understudied. Among the least described problems is the effect of time and temperature on the condensation rate of sucrose molecules on crystallization nuclei in a supersaturated sugar solution. This article introduces a physical and mathematical heat transfer model for this process, as well as its numerical analysis. The research featured a supersaturated sugar solution during sucrose crystallization and focused on the condensation of sucrose molecules on crystallization nuclei. The study involved the method of physical and mathematical modeling of molecular mass transfer, which was subjected to a numerical analysis. While crystallizing in a vacuum boiling pan, a metastable solution went through an exothermal reaction. In a supersaturated solution, this reaction triggered a transient crystallization of solid phase molecules and a thermal release from the crystallization nuclei into the liquid phase. This exogenous heat reached 39.24 kJ/kg and affected the mass transfer kinetics. As a result, the temperature rose sharply from 80 to 86 °C. The research revealed the effect of temperature and time on the condensation of solids dissolved during crystalline sugar production. The model involved the endogenous heat factor. The numerical experiment proved that the model reflected the actual process of sucrose crystallization. The obtained correlations can solve a number of problems that the modern sugar industry faces.