Physicochemical basis for separation

The preceding chapters introduced first the notion of separation and then a variety of indices to describe separation. These indices were used to characterize quantitatively the amount of separation achieved in a closed or an open separation vessel. The quantitative description included systems at steady or unsteady state involving chemical or particulate systems. Systems studied were either binary or multicomponent or a continuous mixture. Not considered in these two chapters was the fundamental physicochemical basis for these separations appropriately, this is the focus of our attention in this chapter. 

In Section 3.1, we distinguish between hulk and relative displacements and describe the external and internal forces that cause separation-inducing displacements. This section then identifies species migration velocities and the resulting fluxes as a function of various potential gradients. Section 3.2 is devoted to a quantitative analysis of separation phenomena and multicomponent separation ability in a closed vessel as influenced by two basic types of forces. The criteria for equilibrium separation in a closed separator vessel and individual species equilibrium between immiscible phases are covered in Section 3.3. Section 3.4 treats flux expressions containing mass-transfer coefficients in multiphase systems. Flux expressions for transport through membranes are also introduced here. 

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