Drop size distribution in a batch mixer under breakage conditions

Abstract

The equilibrium size distribution, F 0( v), of organic drops produced in a batch mixing vessel has been determined experimentally for very low dispersed phase fractions (0.006) in order to reduce the coalescence between drops to negligible values. The organic phase used was a 1:1 mixture of a salicylaldoxime (LIX 860N-IC) and a ketoxime (LIX 64-IC) in an aliphatic diluent (Escaid 103). The aqueous phase was a 0.25-M sodium sulfate solution. The results indicated that the system reaches an equilibrium drop size distribution in less than 30 min of stirring time. An increase in the stirring speed increased the tendency of the organic drops to break, shifting the drop size distribution toward the smaller drop sizes. An increase in temperature from 22 to 32 °C decreased the size of the organic drops, while a change in the concentration of the extractant in the organic phase from 7% to 20% by weight had little effect. Both effects can be attributed to changes in the physical properties of the system. A decrease in pH of the aqueous phase from 5.7 to 2.0 increased progressively the tendency of the organic drops to undergo breakage giving finer drop size distributions due to changes in the surface charge of the organic drops produced by the pH change. In all cases, the experimental drop size distributions could be accurately represented by a lognormal distribution.