Evaluation of mean diameter and drop size distribution of an emulsion liquid membrane system in a horizontal mixer-settler

Abstract

A W/O emulsion consisting of distillated water, kerosene and Span 80 was prepared to be employed in a horizontal mixer settler. The effect of stirring speed, flow ratio, total flow, Span 80 concentration and the internal to membrane phase volume ratio on the Sauter mean diameter (D32) of emulsion, drop size distribution and also the holdup were investigated without mass transfer effect. The results revealed that, with increasing the stirring speed, the D32 decreased and the emulsion holdup increased. However, the emulsion globules breakage incremented due to producing high shear forces. For the ELM system with the surfactant concentration higher than 3wt.%, the D32 increased due to the emulsion swelling and the holdup reduced. In addition, raising the flow ratio and the total flow increased the drop size which led to the reduction in the holdup. Besides, for the internal to membrane phase volume ratio higher than 0.4, the drop size increased. Empirical correlation was presented to predict the D32 with average absolute relative errors (AAREs) of 3.9%. The drop size distribution was conformed to normal distribution, and α and β parameters have been correlated with AAREs of 3.4% and 3.7%, respectively.