Salting-out effect of NaCl on the rate of mass transfer of liquid-liquid extraction in a two impinging-jets contacting device

The effect of very low NaCl addition in the recommended liquid-liquid extraction chemical system of toluene-acetone-water was investigated using a two impinging-jets contacting device with a high velocity of jet flows. By Adding salt within the concentration range of 10(-6)-10(-4) mol/L, while the pH was constant and with the jets colliding force within 70.34-214.6 mN, the extraction efficiency and overall volumetric mass transfer coefficient found enhancements to about 22.7% and 35.6% respectively. A high trend of variation is observed for the salt concentrations till only about 10(-5) mol/L. This phenomenon can be attributed to the hydration of ions which favours acetone to be transferred easier. Increasing jets force in the impingement of the streams provides a higher efficiency in the extraction process within the range used. In this regard, the variation of interfacial tension with salt concentration was investigated and using the dimensionless Weber and Eotvos numbers in accord with the conditions, an empirical correlation was developed for the prediction of extraction efficiency in the impinging-jets contacting device. (C) 2009 Taiwan Institute of Chemical Engineers. Published by Elsevier BM. All rights reserved.