Polar Mixed-Solid Solute Systems in Supercritical Carbon Dioxide: Entrainer Effect and Its Influence on Solubility and Selectivity

Abstract

The equilibrium solubilities of benzoic acid (BA), salicylic acid (SAL), and acetylsalicylic acid (ASA) were determined in binary (solute + CO 2 ), ternary (two solutes + CO 2 ), and quaternary systems (three solutes + CO 2 ) at temperatures ranging from (308 to 328) K and pressures ranging from (10.1 to 28.0) MPa. Solubility data were obtained using a dynamic approach with a simple and reliable apparatus. Polar mixed-solid solute systems demonstrated solubility enhancements, which were consistent with the entrainer effect. In all the polar ternary systems studied, at least one component exhibited solubility enhancements. In the polar quaternary system studied, the solubility of each component increased in comparison to each binary system; the solubility of ASA, SAL, and BA was enhanced up to 484 %, 248 %, and 43 %, respectively. The high solubility enhancements observed in our study indicate that solute-solute interactions are significant in the supercritical fluid (SCF) phase. The solubility enhancements observed in the polar mixed-solid solute systems studied resulted in a decrease in selectivity of SCF CO 2 . However, in a quaternary system consisting of BA, SAL, and fluoranthene (FLU), the selectivity of SCF CO 2 for SAL versus FLU increased by a factor of 2.7 due to specific solute-solute interactions. This study showed that solute-solute interactions in mixed solid solute systems can result in an increase in the solubility of solutes and also the selectivity of SCF CO 2 .

Influence of matrix composition on the ternary solubility of cholesteryl esters in supercritical carbon dioxide

“…This mutual solubility diminution is far less reported in the literatures [11,[19][20][21], but is quite different from the solubility enhancement commonly reported [1][2][3][4][5][6][7][8][9][10]. For this reason, the ternary solubilities of CBE/CBU solid mixtures in SCF CO 2 at the other bed compositions were measured and the experimental results at 318.15 K are presented in Table 2.…”

“…Unfortunately, most of these solubility databases concern the solubility of a single solute in a supercritical solvent with or without a cosolvent while solubility data for multi-solute systems have been reported far less frequently [1][2][3][4][5][6][7][8][9][10][11], which indicates that further research on the solubility of solid mixture is needed. The study of multi-solid systems is of industrial importance and theoretical as well as practical interests because many potential applications of supercritical fluid technology involve the extraction of high-value compounds from a matrix of components such as extracting the effective main component from Chinese herbs for medical uses [12][13][14].…”

“…The study of multi-solid systems is of industrial importance and theoretical as well as practical interests because many potential applications of supercritical fluid technology involve the extraction of high-value compounds from a matrix of components such as extracting the effective main component from Chinese herbs for medical uses [12][13][14]. Because of the presence of another solute, the intermolecular interactions between two solute components may significantly alter the solubility behavior of the solute mixture in supercritical fluids, particularly in situations where the solutes contain potential hydrogen-bonding sites [4,9,15]. Thus the solubility of individual solutes in a multi-solute/solvent system can be sometimes considerably different from that observed in their respective binary systems [1][2][3][4][5][6][7][8][9][10][11].…”

“…Because of the presence of another solute, the intermolecular interactions between two solute components may significantly alter the solubility behavior of the solute mixture in supercritical fluids, particularly in situations where the solutes contain potential hydrogen-bonding sites [4,9,15]. Thus the solubility of individual solutes in a multi-solute/solvent system can be sometimes considerably different from that observed in their respective binary systems [1][2][3][4][5][6][7][8][9][10][11]. This effect on ternary solubility due to the presence of a cosolute may be named the cosolute effect, following the definition of the cosolvent effect on single solute solubility in a solute/supercritical solvent/cosolvent system.…”

Applications of SSAFT EOS for determination of the solubilities of solid compounds in supercritical CO₂.

“…Carbon dioxide is inexpensive, widely available, non-toxic, non-flammable; inert chemically suitable for use in food and pharmaceutical processes and has good critical situations (31.3 ℃ and 72.9 atm) is [5]. Given the characteristics of supercritical fluids and increasing use of them, modeling and simulating these types of systems is of particular importance.…”