To understand the difference between absorption and adsorption we will first discuss the terms apart from each other:
Absorption is a term in chemistry which is used to describe the process in which the atoms, molecules or ions change their state and enter a phase of bulk transforming into a solid, liquid or gas. Absorption is the general process in which a substance takes in another like an ion being taken into and being part of a bulk phase like a solid, liquid or gas material. In other words, the capture of energy from one substance and transforming it is also known as absorption.
Absorption follows the Nernst law and it has two types, it may be chemical meaning it is reactive or it may be physical meaning it is non-reactive.
In chemical absorption the reaction takes place between the absorbed and the species which is absorbing it and it can sometimes also combine with physical absorption but that type of absorption depends upon the reaction and the stoichiometry of the reaction.
The adhesion of molecules or ions from gas, liquid or solid state into a surface is known as the process of Adsorption. Adsorption is said to be the consequence of surface energy, in a bulk material all the spores or holes of the material are filled by atoms, ions, or molecules of the other.
Adsorption is present in natural systems and is widely used in industrial applications which include processes such as water purification, synthesis resins and activated charcoal using heat to capture other state molecules to name a few.
In 1881, a German Physicist Heinrich Kayser coined the word Adsorption.
Adsorption is also a very important phenomena in our daily life as it takes place inside our body when proteins and other important stuff enters into the blood through adsorption.
The main difference between absorption and adsorption is that the process in which a fluid gets dissolved into a solid or liquid is known as absorption while when the atoms, ions and molecules from one substance adhere to the substance in which they are meant to adsorb it is known as Adsorption.
Another difference being in the way the process takes place; Absorption occurs when the atoms or molecules of a substances enter through a bulk or a bulky substance and the molecules, atoms or ions are entirely dissolved into the fluid to form a solution while the forces involved in adsorption are weak van der Waals forces, weak covalent bonding or electrostatic attraction in which the molecules are held loosely and they can be easily removed and used for other bond formations.
Space cooling applications, cold storage and turbine inlet cooling is the common commercial usage of absorption while air conditioning and adsorption chiller are some of the industrial uses of adsorption.
Absorption is an endothermic process while absorption is an exothermic process and the stead increase and reaching of equilibrium state happens in adsorption while the rate of reaction is uniform in absorption.