Batch extraction cell

Figure 5.9. Schematic illustration of batch extraction cell used in liquid-liquid mass transfer studies.

Since thermodynamic nonidealities are of the essence for phase separation in liquid-liquid systems, and such nonidealities contribute to multicomponent interaction effects, it may be expected that liquid-liquid extraction would offer an important test of the theories presented in this book. Here, we present some experimental evidence to show the significance of interaction effects in liquid-liquid extraction. The evidence we present is largely based on experiments carried out in a modified Lewis batch extraction cell (Standart et al., 1975 Sethy and Cullinan, 1975 Cullinan and Ram, 1976 Krishna et al., 1985). The analysis we present here is due to Ej-ishna et al. (1985). The experimental system that will be used to demonstrate multicomponent interaction effects is glycerol(l)-water(2)-acetone(l) this system is of Type I. The analysis presented below is the liquid-liquid analog of the two bulb gas diffusion experiment considered in Section 5.4. 

Figure 5.10. Equilibration paths during mass transfer in the system glycerol (1), water (2), and acetone (3) in a batch extraction cell. The point M is the mixture point and P represents the plait point. Experimental data correspond to Run C of Krishna et al. (1985).

Example 5.6.1 Equilibration Paths in a Batch Extraction Cell... 

Equation 6.2.3 has exactly the same form as Eq. 5.1.3 for binary systems. This means that we may immediately write down the solution to a multicomponent diffusion problem if we know the solution to the corresponding binary diffusion problem simply by replacing the binary diffusivity by the effective diffusivity. We illustrate the use of the effective diffusivity by reexamining the three applications of the linearized theory from Chapter 5 diffusion in the two bulb diffusion cell, in the Loschmidt tube, and in the batch extraction cell. 

The batch extraction cell experiments of Krishna et al. (1985) were discussed at some length in Section 5.6, where it was shown that the diffusion fluxes could be calculated from... 

Total moles of mixture in batch extraction cell [mol]... 

---