Applications of Adsorption

Adsorption underpins a wide range of practical uses:

• Production of high vacuum: charcoal adsorbs the last traces of air left after a vacuum pump, giving a very high vacuum.
• Gas masks: a mask packed with activated charcoal (or a mix of adsorbents) adsorbs poisonous gases, allowing safe breathing in coal mines.
• Control of humidity: silica and alumina gels adsorb moisture and regulate humidity.
• Removal of colouring matter: animal charcoal decolourises solutions by adsorbing coloured impurities.
• Heterogeneous catalysis: reactants adsorbed on a solid catalyst react faster — e.g. iron in ammonia manufacture, the contact process for $H_2SO_4$, and finely divided nickel for hydrogenating oils.
• Separation of inert gases: noble gases are separated on coconut charcoal because they are adsorbed to different extents at different temperatures.
• Curing diseases: some drugs act by getting adsorbed onto germs and killing them.
• Froth floatation: low-grade sulphide ores are concentrated, separating ore from silica and earthy matter using pine oil and a frothing agent. …