Influence of Inorganic Salts on the Phase Equilibrium of Triton X-114 Aqueous Two-Phase Systems

Abstract

In this work, we studied the liquid–liquid equilibrium of ternary systems containing nonionic surfactant Triton X-114, inorganic salts, and water. The salt impact of five different sodium salts (NaCl, NaBr, NaI, Na2SO4, and Na2HPO4) and four different chlorides (NaCl, KCl, LiCl, NH4Cl) was investigated. The influence of the inorganic additives was studied at 30 °C because at this temperature all prepared mixtures faced a separation above the cloud point temperature (CPT) in micellar (surfactant-rich) and aqueous (surfactant-lean) phase. The salting-out ability of the cations follows the series Na+ > K+ > NH4 + > Li+. We observed a more pronounced effect among the anions, where the salting-out effect decreased in the order HPO4 2– ≈ SO4 2– > Cl– > Br– > I–. All salts, except NaI, lead to an increase in the Triton X-114 concentration in the micellar phase and to a decrease of the surfactant fraction in the aqueous phase. Inorganic salts also distributed unevenly between both phases and, thus, accumulated in the aqueous phase. In the case of stronger salting-out kosmotropic anions (HPO4 2–, SO4 2–), the salt load of water in the aqueous phase was higher compared to the weaker agents Br– and I–.

Continuous Countercurrent Extractive Biocatalysis in Aqueous Surfactant Two‐Phase Systems

“…However, the continuous extraction was performed in presence of a phosphate buffer, which influences the miscibility gap. In a previous study it was shown that phosphate salt increases the miscibility gap, which even enhances the suitability of the system for extraction processes . Nevertheless, due to the small phosphate concentration (100 mM), the impact of the buffer solution on the LLE used in this work is rather small.…”

“…At 37 °C, which is a tolerable temperature for many biotechnological processes, a density difference of around 0.01 g cm −3 was found. Despite that the density difference might be a limiting parameter in case of other surfactants, the density difference determined at 37 °C in the system with Tergitol NP‐7 was in a range suitable for continuous extraction processes as shown in former studies , .…”

“…During the reaction progress, penicillin degrades and the CPT decreases linearly. However, the addition of salts, e.g., potassium phosphate, leads to an increase of the miscibility gap in aqueous surfactant solutions and can be used to overcome such limitations . Thus, one has to keep in mind that the LLE can dramatically change during the reactive process, especially when treating streams with high reactant concentrations.…”

“…A MCP standard hose pump from Ismatec was used to introduce the surfactant solution at the top of the column. The feed‐to‐solvent ratio was 4 in both experiments (all operating parameters were chosen based on preliminary work , ). The surfactant weight fraction in the solvent was w Tergitol NP‐7 = 23.5 wt % (according to the liquid‐liquid equilibrium of the binary system at 37 °C).…”

Impact of different diols/polyols on the phase separation behavior as well as thermodynamic properties of tween 80

“…Knowledge of the CP helps us to evaluate the storage steadiness since storing formulations at temperatures considerably above the CP causes in phase partition as well as instability. The employment of nonionic surfactants in engineering, as well as pharmaceutical formulation, is remarkable and in the solid medium withdrawal of numerous kinds of diverse organic molecules by means of hydrated phase . Nonionic surfactants also show the best possible efficiency when utilized close or under their CP.…”