Adsorption of gases with activated carbon
Adsorption is the process of retaining liquid or gaseous molecules on a solid surface. This differs from absorption, where the molecules are taken up by the internal structure of the absorbent (e.g., water absorption by a sponge). Activated carbon has the strongest physical adsorption forces, or the highest volume of adsorbing porosity, of all known materials. Activated carbon can have a surface area of more than 1000 m² / g, which means that 3 g of activated carbon has the surface area of a football field. Due to its very large surface area, carbon can adsorb thousands of types of organic and inorganic gases, generally with the adsorption of a compound increasing as its molecular weight increases.
There are two types of adsorption, physisorption and chemisorption.
- Physisorption: with this type of adsorption, organic molecules will physically attach themselves to the surface by weak electromagnetic forces (Vanderwaal forces). Physisorption is reversible, the adsorbed molecules can be released back into the environment by desorption.
- Chemisorption: with this type of adsorption, inorganic molecules will be adsorbed on and in the activated carbon by means of a covalent bond (chemical bond). Chemisorption is in principle irreversible.
- Hydrogen sulfide (H2S)
- Ammonia (NH3)
- Mercury (Hg)
- Chlorine (Cl)
- Municipal and industrial odor control
- Emissions from industrial installations
- Wastewater from refineries and chemical plants
- Emissions from waste treatment activities
- Air stripper waste gas VOC removal
- Venting of waste water and product storage tanks
- Pelletized activated carbon
- Granular activated carbon
- Impregnated carbon
- Powdered charcoal
- Catalytic coal
Types of activated carbon
Three types of activated carbon can be distinguished:
- Extruded activated carbon, cylindrical shaped with diameters from 2 to 5 mm. This type of coal is mainly used for gas phase applications due to their low pressure drop, high mechanical strength and low dust content. Our standard is 3 and 4 mm.
- Granular activated carbon - irregularly shaped particles with sizes ranging from 0.2 to 5 mm. This type is used in both liquid and gas phase applications for smaller molecule capture. Mesh size 4x8 is the most commonly used shape.
- Powdered activated carbon - pulverized carbon with a size of typically less than 0.18 mm. This type of coal is mainly used for flue gas treatment.
Removal of:
In practice, activated carbon is used for the adsorption of mainly organic compounds and some inorganic compounds with a higher molecular weight. These include the removal of:
• Volatile organic compounds (VOC) such as benzene, PAH, MEK.
