Sorption

Absorption_vs_adsorption.svg

Sorption is a physical and chemical process by which one substance becomes attached to another. The term encompasses both absorption and adsorption, which are different processes. Sorption is a key concept in various scientific fields, including chemistry, biology, and environmental science.

Types of Sorption

Sorption can be classified into two main types:

• Absorption: This is the process in which a substance is taken up into the volume of another substance, such as a liquid or solid. An example of absorption is the uptake of water by a sponge.
• Adsorption: This is the process in which a substance adheres to the surface of another substance. An example of adsorption is the accumulation of gases on the surface of activated charcoal.

Mechanisms

The mechanisms of sorption can vary depending on the nature of the substances involved. Common mechanisms include:

• Physisorption: This involves weak van der Waals forces and is usually reversible.
• Chemisorption: This involves the formation of chemical bonds and is usually irreversible.

Applications

Sorption has a wide range of applications in various fields:

• Environmental Science: Sorption is used in the removal of pollutants from air and water. For example, activated carbon is used to adsorb contaminants from drinking water.
• Pharmacology: Sorption processes are crucial in drug delivery systems where the drug needs to be absorbed by the body.
• Chemical Engineering: Sorption is used in separation processes, such as in the purification of gases and liquids.

Factors Affecting Sorption

Several factors can influence the sorption process:

• Temperature: Higher temperatures can increase the rate of sorption but may also lead to desorption.
• Pressure: Higher pressures can increase the amount of gas adsorbed on a solid surface.
• Surface Area: Larger surface areas provide more sites for adsorption.
• Concentration: Higher concentrations of the sorbate can increase the rate of sorption.

Sorption Isotherms

Sorption isotherms describe how a sorbate interacts with a sorbent at constant temperature. Common models include:

• Langmuir Isotherm: Assumes monolayer adsorption on a surface with a finite number of identical sites.
• Freundlich Isotherm: An empirical model that describes adsorption on heterogeneous surfaces.

See Also

• Absorption
• Adsorption
• Desorption
• Physisorption
• Chemisorption
• Langmuir Isotherm
• Freundlich Isotherm