Would condensation of water below its dew point on charcoal be considered adsorption?
2. Would the conversion of solid NaOH by HCl gas to NaCl be considered adsorption?
3. Would the drying of moist air by charcoal be considered adsorption?
4. Can more than one component be removed simultaneously from a gas or liquid by a solid adsorbent?
Problems
1. One hundred pounds per minute of moist air at 70°F that has a humidity of 0.01 lb H2O/lb dry air is dehumidified to 0.002 lb H2 O/lb dry air in a dryer. If 7 lb/min of dry silica gel enter the dryer at 70°F, how many pounds of H2 O leave the dryer per pound of silica gel entering?
2. The dissertation of Blaney (see Example 13.1) contains the following data for the adsorption of N2 on activated coconut charcoal at 298 K:
| P (mm Hg) | y (g mol N2/g Charcoal) × 104 |
|---|---|
| 0 | 0 |
| 26.8 | 0.1562 |
| 45.93 | 0.2945 |
| 67.72 | 0.4149 |
| 88.21 | 0.5354 |
| 108.05 | 0.6360 |
| 127.91 | 0.7406 |
| 147.42 | 0.8477 |
| 166.77 | 0.9458 |
| 246.86 | 1.3786 |
| 369.93 | 1.9808 |
| 428.79 | 2.2396 |
| 492.32 | 2.5430 |
| 587.86 | 2.9713 |
| 688.05 | 3.3996 |
| 761.10 | 3.6851 |
Determine the coefficients in the Langmuir relation y = k0 k1 p /1 + k1 p.
3. Water contains organic color, which is to be extracted with alum and lime. Five parts of alum and lime per million parts of water will reduce the color to 25% of the original color, and 10 parts will reduce the color to 3.5%.
Estimate how much alum and lime as parts per million are required to reduce the color to 0.5% of the original color.
Thought Problems
1. Why might a solid adsorbent be used rather than distillation to separate a liquid mixture?
2. How might you regenerate an adsorbent used for the separation of a mixture of (a) gases and (b) liquids?
Glossary
adsorbent A solid surface on which gas or liquid molecules condense to form a film.
adsorption The physical process that occurs when gas or liquid molecules are brought into contact with a solid surface and condense on the surface.
adsorption isotherm The mathematical or experimental relation between the amount a single component adsorbed (the adsorbate) on the adsorbent, and the bulk amount of the adsorbate in a different phase expressed in terms of the partial pressure in the gas phase, or the concentration in the liquid phase, at some temperature.
chemisorption Adsorption when interaction between the solid and the condensed molecules is relatively strong as contrasted with physical adsorption.
Freundlich isotherm Mathematical relation for adsorption that takes place at equilibrium.
Langmuir isotherm Mathematical relation for adsorption that takes place at equilibrium.
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