It is proposed that oxygen be separated from nitrogen by absorbing and desorbing air in water. Pressures from 101.3 to 10,130 kPa and temperatures between 0 and 100^οC are to be used. 

(a) Devise a scheme for the separation if the air is 79 mol% N₂ and 21 mol% O₂.
(b) Henry’s law constants for O₂ and N₂ are given in Figure 4.26. How many batch absorption steps would be necessary to make 90 mol% oxygen? What yield of oxygen (based on the oxygen feed) would be obtained?

4 Values of mole fraction per atmosphere 2 10-1 -00 to 8 6 4 2 y 00 co -10-2 st N m00 CD 10 -18 6 st 2 104 8 6 4 IL 10-5 I 2 CO Cl 0 CHA NH CH 0, I I 10 20 30 H 50 HS CH CO Brz HS IN 1 40 50 60 70 80 Temperature, C 11 L 90 100 Figure 4.26 Henry's law constant for solubility of gases in water. [Adapted from O.A. Hougen, K.M. Watson, and R.A. Ragatz, Chemical Pro- cess Principles. Part I, 2nd ed., John Wiley & Sons, New York (1954).]