Introduction of activated carbon | What is Activated Carbon?Adsorption
Adsorption
Adsorption is a surface phenomenon. Molecules in a fluid (gas or liquid) are adsorbed by the attractive force (Van der Waals force) of the surface of the solid body (activated carbon) to cause adsorption. Difficulty of adsorption is affected, in many cases, by the condensation characteristics of the gas when the adsorbed material is a gas, and by the solubility of the dissolved material in the case of liquids. The micropores promote adsorption via capillarity. In the case of gas phase, gas is condensed by the capillarity and turns to liquid, which increases adsorption.
Taken together, these are called physical adsorption. The adsorption is rapid and reversible, which means it can be easily desorbed by heating or decompression.
In addition to physical adsorption, there is also chemisorption accompanied with chemical reactions. This phenomenon is seen with activated carbon impregnated with acid or alkali. Chemisorption selects only the material that reacts and the phenomenon is irreversible.