Study Questions for
“Separation Process Principles” by
J. D. Seader and Ernest J. Henley
Chapter 15
1. In adsorption operations, what is the adsorbate and the adsorbent?
2. How is a high surface achieved for adsorption?
3. What is meant by ion exchange? How does ion exchange differ from deionization?
4. What kinds of sorbents are used in chromatography?
5. In adsorption processes, what distinguishes a purification from a bulk separation?
6. What three inventions made possible the bulk separation of mixtures by adsorption?
7. What is meant by regeneration?
Section 15.1:
8. What are the 10 major requirements of an effective adsorbent?
9. Can the specific surface area of an adsorbent be estimated from its average pore diameter? If so, what equation is used and under what assumptions is it derived?
10. Why is it easy to measure the amount of adsorption of a pure gas, but difficult to measure the adsorption of a pure liquid?
11. Name five of the most important commercial adsorbents? What is the distinguishing feature of the molecular-sieve zeolites?
13. What experimental techniques can be used to measure pore-size distribution?
14. What kinds of materials are most commonly used as ion exchangers? How are they made?
15. What are the different types of chromatographic methods?
16. How is possible to use a liquid sorbent in chromatography?
Section 15.2:
17. What is meant by loading in adsorption?
18. What is an adsorption isotherm? How can the heat of adsorption be determined from a series of isotherms?
19. What is capillary condensation? What effect does it have on an adsorption isotherm?
20. In Figure 15.9, which isotherm(s) is (are) favorable and which unfavorable?
21. What is the equation for a linear adsorption (also called Henry's law)?
22. What is the major difference between the shapes of the isotherms predicted by the Freundlich and Langmuir isotherms? Which is based on theory?
23. What is meant by an extended adsorption isotherm?
24. What makes the determination of an equation for an adsorption isotherm of a binary or multicomponent liquid mixture difficult, leading to weird shaped curves as shown in Figure 15.13?
25. Why is the maximum loading of an ion exchanger fixed? What fixes it?
26. Does the valences of the ions being exchanged influence the equilibrium expression? How?
Section 15.3:
27. What are the four steps that occur during the adsorption of a solute from a gas or liquid mixture? Which step is almost instantaneous such that equilibrium can be assumed?
28. Within the particle, why are mass and heat transfer not analogous?
29. For mass transfer outside a spherical particle, what is the smallest value of the Sherwood number? What is the basis for this value?
30. What is the recommended equation for predicting the external mass-transfer coefficient for flow through a packed bed of particles?
31. What mechanisms of internal mass transfer must be considered for gas adsorption?
Section 15.4:
32. What is the difference between slurry adsorption (contact filtration) and fixed-bed adsorption (percolation)? When should each be considered and not
considered?
33. How do pressure-swing and thermal-swing adsorption differ?
34.. What are inert-purge swing and displacement purge?
35. What is meant by a simulated countercurrent adsorption system?
36. What is the advantage of the rotating, cross-current, annular chromatograph?
37. What are the three common modes for conducting slurry adsorption? Which mode requires the smallest residence time of the liquid mixture? What controls the rate of slurry adsorption, external or internal mass transfer?
38. What is ideal fixed-bed adsorption? What assumptions are necessary for it to apply? What is meant by the stoichiometric front? What is meant by
breakthrough?
39. What is a mass-transfer zone (MTZ) and what causes it? Is it desirable? If not, why not?
40. For fixed-bed adsorption, what is the difference between the superficial velocity, interstitial velocity, and the concentration wave velocity? Which is the largest and which is the smallest?
41. Explain what each term means in Equation (15-102).
42. What is the linear driving force (LDF) model of Glueckauf? Why is it so useful?
43. Why is Equation (15-106) useful? Does it account for both external and internal mass transfer?
44. What is the Klinkenberg approximation? Why is it useful in computing concentration and loading profiles, and breakthrough curves for fixed-bed adsorption?
45. What is the Collins technique for sizing a fixed-bed adsorption vessel?
46. Describe a typical thermal-swing adsorption cycle.
47. What is meant by the delta loading?
48. What is the basis for the method of lines for solving partial differential equations?
49. What is the difference between pressure-swing and vacuum-swing adsorption?
50. Describe the steps in the Skarstrom cycle.
51. How is the McCabe-Thiele diagram used for continuous, countercurrent adsorption-desorption?
52. Describe a typical ion exchange cycle.
53. In chromatography, what causes different solutes to pass through the chromatograph with different residence times?
54. In chromatography, what is the difference between the equilibrium wave pulse theory and the rate-based theory?
