Liquid–Liquid Demixing Behavior of Aqueous 1-Butanol Solutions in the Presence of Various Organic and Inorganic Ammonium Salts: Effect of Temperature, Cation Alkyl Chain Length, and Anion Type of Salts on Salting Coefficients and Thermodynamic Functions

Abstract

In this work, the effects of various organic and inorganic ammonium salts on the liquid−liquid demixing (clouding) behavior of aqueous 1-butanol (BuOH), as a thermoresponsive material, solutions were investigated in the temperature range of 283.15−353.15 K. The inorganic salts used are NH 4 Cl and NH 4 Br, and the organic ones are tetramethylammonium bromide (TMAB), tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride (TBAC), tetrabutylammonium hydrogen sulfate (TBAH), dodecyltrimethylammonium bromide (DTAB), and cetyltrimethylammonium bromide (CTAB). The inorganic ammonium halides reduced the water-solubility of BuOH and induced the salting-out effect. As the concentration of inorganic ammonium salts increased, the strength of the salting-out effect and the area of the biphasic region increased. However, all the investigated tetraalkylammonium salts had the salting-in effect on BuOH and increased its solubility in water. The extent of the monophasic region and also the intensity of the salting-in effect (co-solvency) enhanced with increasing the concentration of the tetraalkylammonium salts. The effects of the charge density of the salt anion as well as the alkyl chain length of the salt cation, on the immiscibility region of aqueous BuOH solutions, were studied. From the correlation of the measured cloud point data with Setschenow's relation, the salting effects occurring in the investigated systems were also quantified. Finally, the values of different thermodynamic functions of phase separation were determined, from which the driving force of clouding at different conditions was discussed.

Comparative Study of the Aggregation Behavior of Some Ionic Surfactants with Nonionic Triton X-114 in Water and a Water/2,2,2-Trifluoroethanol Mixture

“…In this context, various additives, including salts, solvents, polymers, drugs, etc., have been introduced to the micellar environment of amphiphilic systems to achieve the desired features with various industrial importance in cosmetics, food products, enhanced oil recovery, and pharmaceuticals . Among all the additives, nonaqueous alcohol solvents have been examined mostly in amphiphile-water-solvent ternary systems using both theoretical and experimental approaches. − The exceptional solubilizing and hydrogen bonding potential of alcohols distinguish them as solvents of choice . Moreover, alcohols possess a dual character of serving as either cosurfactants or cosolvents as a motif to modify the critical micelle concentration (CMC) in the self-assembly of amphiphilic systems .…”