Summary of Lec 4.3 - Adsorption Applications and Material

Summary of Scientific Concepts and Discoveries

• Absorption Types:
  • Physical Absorption:
    • Weaker forces, typically reversible.
    • Small heat evolved (4 to 40 KJ per mole).
    • Non-specific surface coverage; entire surface available for absorption.
    • Can have multi-layer absorption.
    • Low activation energy.
    • Rapid absorption at low temperatures, decreases with increasing temperature.
    • Example: Absorption of gases like oxygen and hydrogen on charcoal.
  • Chemical Absorption:
    • Stronger, irreversible forces.
    • Larger heat evolved (40 to 400 KJ per mole).
    • Highly specific; restricted to active sites on the surface.
    • Incomplete surface coverage; only unimolecular layer.
    • High activation energy required for bond formation.
    • Insignificant absorption at low temperatures, increases with temperature.
    • Example: Absorption of hydrogen gas on nickel metal.
• Applications of Absorption:
  • Dye Removal: Use of powdered taline to remove red dye from solutions.
  • High Vacuum Formation: Activated charcoal used to absorb remaining molecules in a vacuum vessel.
  • Chromatography: Separation of components in a mixture using solid-phase absorption.
  • Air Purification: Absorption of oil vapors from compressed air using carbon-rich materials.
  • Personal Protective Equipment (PPE): Masks with carbon-based filters for organic substance absorption.
  • Biological Applications: Viruses absorb onto cells to initiate infection.
• Materials Used for Absorption:
  • Activated Carbon: Highly porous, used for absorbing organic substances and treating wastewater.
  • Activated Alumina: Good desiccant for dehydrating vapors.
  • Silica Gel: Absorbs moisture, commonly found in product packaging.
  • Zeolites: Used in various industrial processes including gas purification and ion exchange.
  • Activated Clay: Enhanced absorption through acid treatment and drying.
  • Bone Char: Used for removing fluoride and metal ions from water.
• Regeneration and Reactivation:
  • Regeneration: Process of desorbing absorbed substances by applying heat.
  • Reactivation: Combustion process to burn off substances on the surface of the absorbent.

Methodology

• Absorption Experiment:
  • Insert gas at specific pressure and measure absorbed volume.
  • Plot data to identify isotherm models (e.g., BET, Langmuir).
  • Use equations to calculate monolayer volume and surface area.

Researchers/Sources Featured

The lecture references various research studies, specifically mentioning a 2018 study on powdered taline for dye removal, but does not provide specific researchers' names. Other materials and applications discussed are based on general scientific knowledge in the field of absorption and materials science.

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