The influence of aqueous phase pH on the rate of liquid−liquid extraction was investigated, using single drop experiments for a range of drop size and in either of the mass transfer directions. The chemical system of toluene−acetone−water was employed with the advantage of high accuracy and repeatability when analyzed with gas chromatography. The pH of continuous aqueous phase was adjusted within 5.5−8, a range in which most industrial waters are lain. An extraction column was used to introduce the drops into the aqueous phase. Results have demonstrated the impact of pH on the mass transfer performance giving a significant reduction in mass transfer with increasing pH and nearly independent of the kind of accompanied cation for two utilized bases. This matter can be attributed to the adsorption of hydroxyl ions from the aqueous phase which causes small drops to be more prone to this effect. The rate of mass transfer is greater for the dispersed to continuous phase direction under similar conditions.

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Temperature can alter the performance of conventional liquid–liquid extraction columns in which one phase is dispersed inside another phase. In this research, the influence of temperature on the extraction process was investigated using a toluene–acetic acid–water chemical system with dominant mass transfer resistance in the organic phase. Single drop experiments with a range of drop size within 2.49–3.77 mm and temperature within 15–40 °C were performed. Results demonstrate significant impact of temperature on the rate of mass transfer with an average enhancement of 93.6% in overall mass transfer coefficient while small drops are benefited more. Having lower contributions by drop size and terminal velocity, the extraction efficiency is the most effective term in this regard which itself is increased by increasing molecular diffusivity in the organic dispersed phase. For the aim of modeling, effective diffusivity was substituted for molecular diffusivity in Newman’s equation and consequently, a reliable empirical equation was derived for the enhancement factor of diffusivity as a function of dimensionless variables.

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