Mass Transfer Enhancement in Liquid−Liquid Extraction with Very Dilute Aqueous Salt Solutions

Abstract

The effect of very low salt addition in the recommended liquid−liquid extraction chemical system of toluene−acetone−water was investigated with circulating single drops and in both of the mass transfer directions. By adding sodium chloride, potassium chloride, and potassium iodide, within the concentration range of 10−6−10−4 mol/L, into the continuous phase and under constant pH, the mass transfer rate finds enhancements to about 425%. A high trend of variation was observed for the salt concentrations until only about 10−5 mol/L. This phenomenon can be attributed to the hydration of ions which favors acetone to be transferred easier in the aqueous phase. Small drops are usually more benefited, and the rate of mass transfer is greater for the dispersed to continuous phase direction under similar conditions due to a higher dominant extraction fraction, whereas the drop size decreases in this direction. The effectiveness of salts in this matter appeared to be in the order of NaCl > KCl > KI.

Low interfacial tension liquid–liquid extraction with impinging-jets contacting method: Influencing parameters and relationship

“…9, it is obvious that the rate of mass transfer for the organic to aqueous direction is more than the inverse direction which does conform the results previously reported in a rotating disc contactor (RDC) using single drop experiments with the same chemical system [12] and the chemical system of TAW [16]. It is notable that since the local mass transfer coefficients are unknown, it is difficult to predict this result with theoretical aspects, for instance mass transfer resistance in each phase.…”

(Liquid+liquid) equilibria for the ternary (water+acetic acid+toluene) system at different temperatures: Experimental data and correlation

“…There are practical concerns when choosing extraction solvents, toluene can be considered as a suitable solvent for extraction of carboxylic acids from water, having low vapour pressure, capability to form two phases, and rapid phase separation due to its low density (0.8669 kg Á m À3 at T = 298.2 K) and low viscosity (5.90 Á 10 À4 Pa Á s at T = 298.2 K) [5,6].…”

Equilibrium interfacial tension and the influence of extreme dilutions of uni-univalent salts: An expression of the “Jones–Ray effect”

“…It has been shown, for instance, that waters containing a very low amount of salts provide a higher rate of mass transfer in liquidliquid extraction which can be attributed to interfacial phenomena [7].…”