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

Abstract

This work addresses the liquid−liquid demixing (clouding) behavior of 1-butanol aqueous solutions in the presence of various additives, including amino acids, imidazolium-based ionic liquids (ILs), polymers, and 1-/2-propanol, in a wide temperature range (283.1−353.1 K) and at atmospheric pressure (845 hPa). The visual cloud point data revealed that the studied amino acids reduce the water solubility of 1-butanol and expand the immiscibility region (soluting-out effect). At the same amino acid's molality, the soluting-out aptitude follows the trend serine > glycine > alanine > proline > glutamine. However, the ILs and polymers [poly(ethylene glycol) (PEG)] act as cosolvents for 1butanol in aqueous media and broaden the miscibility region (soluting-in effect). An increase in the cation alkyl chain length of ILs and a decrease in PEG molar mass strengthen the soluting-in effect. The clouding phase behavior of aqueous 1-butanol + 1-/2propanol ternary systems at lower temperatures reveals the expansion of the immiscibility region due to the washing-out effect but at higher temperatures exhibits the soluting-in effect. An increase in the concentration of 1-/2-propanol decreases the extent of the washing-out effect. In all cases, the soluting-in/out effects increase with the increase in the concentration of additives. Soluting effects occurring in the studied systems have been quantified by correlating the experimental cloud point data with Setschenow's equation, and the clouding process in the systems studied has been carefully discussed from the thermodynamic point of view. From the gathered results, at higher temperatures, the relative contribution of enthalpy to clouding Gibbs free energy in the presence of soluting-in agent additives is mostly higher than that in the presence of soluting-out agents. However, at lower temperatures, the entropy increase is the driving force of clouding in most of the investigated systems.

Vapor–Liquid Equilibrium Study on Amino Acid + Quaternary Ammonium Salt Aqueous Ternary Systems

“…As shown in Figure , for a given salt, at similar water activities, the greatness of negative deviations from the semi-ideality, which is a measure of the soluting-out intensity, decreases in the order S­(+)-serine > glycine > dl -alanine > S(−)-proline. The same trend was observed for the extent of the soluting-out effect in amino acid–polymer and amino acid–butanol aqueous ternary systems. Glycine is the smallest amino acid with a hydrogen atom side chain.…”

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

“…It has become evident that inorganic salts usually cause an increase in the upper critical solution temperature (UCST) and an expansion in the immiscibility (two-phase) region of the BuOH–water solubility curve, indicating the salting-out effect (with some exceptions like sodium thiocyanate that decrease the UCST and inserts the salting-in effect). Besides, the soluting-out aptitude of sugars (maltitol ≈ maltose > sucrose > glucose > fructose > xylitol > xylose) and amino acids (serine > glycine > alanine > proline > glutamine) in the BuOH–water system is demonstrated by our research group. On the other hand, it has been shown that imidazolium-based ionic liquids and polyethylene glycols increase the water-solubility of BuOH and decrease the immiscibility region (soluting-in effect) of BuOH–water mixtures .…”

“…Although interfacial properties and pseudo-ternary phase behavior of {water/[organic ammonium salt surfactant-BuOH (cosurfactant)]/ n -heptane} have been well studied for some alkyltrimethylammonium halides with long alkyl chain length, , the effect of these salts on the liquid–liquid phase behavior of BuOH–water has not been studied. In this work, in continuation of the previous studies, , the salting effects of ammonium chloride (NH 4 Cl), ammonium bromide (NH 4 Br), and a wide range of tetraalkylammonium salts, including 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) on the water-solubility of BuOH have been investigated in a wide temperature range (283.1–353.1 K). The effects of anion type, cation alkyl chain length, and concentration of the salts on the type and strength of the salting (out/in) effects and thermodynamic quantities of the clouding process have been scrutinized.…”

“…On the other hand, it has been shown that imidazolium-based ionic liquids and polyethylene glycols increase the water-solubility of BuOH and decrease the immiscibility region (soluting-in effect) of BuOH−water mixtures. 24 Making an overview of the literature reveals that there is no systematic study regarding the salting effect of organic and inorganic ammonium salts on the clouding diagram of the BuOH−water system, and only a few scattered studies have been performed with NH 4 Cl. 25−28 Because of the tunability of hydrophilic/hydrophobic properties by changing their ammonium alkyl chain length and also their anion, quaternary ammonium salts are a good choice for investigating the soluting effects in aqueous BuOH solutions.…”