Effect of long-range interactions on ion equilibria in liquid–liquid extraction (original) (raw)

Liquid–liquid extraction: An adsorption isotherm at divided interface?

Comptes Rendus Chimie, 2007

We show that liquideliquid extraction can be described as the equilibrium between two pseudophases of ions: the hydrated state in the water phase and the solvation state when the ions are adsorbed on an organized interface. The extractant is considered as a potential surface where the ions can adsorb. Unlike phenomenological binding ''constants'', ion extraction/stripping can be seen as the sum of Langmuir isotherms. The number of aggregated extractants in one reverse micelle in the solvent is at least equal to or higher than the number of extracting molecules complexed at a given instant to the ion to be extracted. Considering extraction equilibrium as a sum of isotherms corresponding to the different states of aggregation of extractant molecule in the solvent, the resulting constant is representative of both the efficiency of the extraction and the structure of the solution. This is a first step toward the development of predictive models for the apparent distribution coefficients. To cite this article: F. Testard et al., C. R. Chimie 10 (2007). Ó 2007 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.

CHE504 - Lab Report on Liquid - liquid Extraction (L7) (2018)

Liquid-liquid extraction is one of the separation technology used in industries. This process is quite different with distillation because it focuses on relative solubility of the species rather than volatility. Usually, extraction is more preferable than distillation for separation application that is not cost efficient and applicable for distillation. This experiment was carried out to determine the distribution coefficient and mass transfer coefficient of LLE. The sample collected from extraction equipment, namely raffinate, extract and feed were titrated with sodium hydroxide with different concentration. An indicator, phenolphthalein were added into the sample in order to detect alkaline ion. The sample is titrated until the solution turns light pink. The amount of 0.025M sodium hydroxide needed to turn the colourless feed, extract and raffinate solution to light pink were 253.8 mL, 52 mL and 4 mL respectively. While for 0.1M sodium hydroxide, the samples need 81.5 mL, 15.9 mL and 2.2 mL in the same order as mentioned previously. The mass transfer coefficients in 0.025M NaOH are 6.1402x10-3 m/min and 6.1632x10-3 m/min for K value 1.9272 and 1.8415 respectively. Meanwhile, for 0.1M NaOH, the mass transfer coefficients are 5.8451x10-3 m/min and 5.8620x10-3 m/min for K value 1.9272 and 1.8415 respectively. As the concentration of sodium hydroxide, NaOH solution and the distribution coefficient, K values increases, the mass transfer coefficient of propionic acid will decreases. The experiment is considered successful since all the objectives are successfully achieved. Turnitin : Percentage Similarity (18%)