Salt Influence on Liquid-Liquid Equilibria
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Beschreibung
In biotechnological processes, salts might be present during reaction steps and in downstream processes. Salts are known to have a strong impact on phase equilibria of aqueous systems and this work systematically investigates in this work a systematically the influence of salts on the liquid-liquid equilibria (LLE). The LLE of the ternary water/methyl isobutyl ketone (MIBK)/salt mixtures were measured in this work at 298.15 K and 1 bar up to the salt solubility limit. From these LLE measurements it was found that a high amount of salt is dissolved in the aqueous phase whereas only a very small amount of salt was detected in the MIBK phase. This work also investigated the influence of salts on the performance of extracting 5-Hydroxymethylfurfural (HMF) from aqueous media using MIBK. For that purpose, the LLE of quaternary systems containing HMF, water, MIBK and salts were measured wiht the same condition and salts as for the ternary systems. Based on these LLE data, the partition coefficient of HMF between the aqueous and the MIBK phase KHMF was determined. It could be shown that KHMF significantly depends on the kind and concentration of the added salt. Weak electrolytesNitrates caused salting-in, whereas strong electrolytes (e.g. sulfates, acetates) caused salting-out of HMF from the aqueous phase. Unexpectedly, LiCl caused salting-out at low LiCl concentrations and salting-in at LiCl concentrations higher than 3 mol/kgH2O.
The electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was used for modeling the binary system water/MIBK and ternary water/MIBK/salt, water/1-butanol/salt, water/toluene/salt, water/benzene/salt systems and the quaternary water/MIBK/HMF/salt and water/1-butanol/HMF/salt systems. Ion-specific binary interaction parameters between organic solvent and ions were fitted to experimental and literature LLE data of the ternary systems water/organic solvent/salt. ePC-SAFT allows for almost quantitative correlations of experimental data for the ternary systems. Nevertheless, the salt influence on the LLE in the quaternary systems water/MIBK/HMF/salt and water/1-butanol/HMF/salt was predicted in good agreement with the experimental data. Based on ePC-SAFT it could be concluded that the different salting-out/salting-in behavior of the various salts on the HMF partition in organic solvents are caused mainly by their different tendency to form ion pairs in aqueous solutions.
Autor*in
Sultan Mohammad
Themen in »Salt Influence on Liquid-Liquid Equilibria«
Liquid-Liquid Equilibria Quaternary Systems Salt Influence