Chapter 15, Problem 15.32P

A liquid-process feed stream F contains 99 mol-% of species 1 and 1 mol-% of impurity. species 2. The impurity level is to be reduced to 0.1 mol-% by contacting the feed stream with a stream S of pure liquid solvent, species 3. in a mixer/settler. Species 1 and 3 are essentially immiscible. Owing to “good chemistry.” it is expected that species 2 will selectively concentrate in the solvent phase.

(a) With the equations given below, determine the required solvent-to-feed ratio $n_S/n_F$ .

(b) What is mole fraction x₂ of impurity in the solvent phase leaving the mixer/settler? M

(c) What is “good" about the chemistry here? With respect to liquid-phase nonidealities. what would be “bad” chemistry for the proposed operation?
Given: $G_{12}^E/RT=1.5x_1{x}_2$ $G_{23}^E/RT=-0.8x_2{x}_3$