What is adsorption? It is one of the important and most asked questions in chemistry. In 1881 the German physicist Heinrich Kayse named the term “adsorption.” Adsorption is the adhesion (the action or process of sticking to a surface or object) of atoms, ions or molecules onto a surface from a gas, liquid or dissolved material. It is not to be confused with absorption which occurs in the bulk stage.
Process of Adsorption
Adsorption is a surface process which results in a molecule being transferred from a bulk of fluid to a solid surface. It will be due to physical actions or by chemical bonds. This process is normally reversible. It not only helps in subtraction but also in the release of substances. This mechanism is defined in equilibrium by means of certain equations that calculate the amount of substance bound to the surface given the fluid concentration.
Because of dependence on temperature these equations are also defined as isotherms. Thes equations are famous such as 1.1 Linear equation, Freundlich equation, Langmuir equation, BET equation, Kisliuk equation.
- It is Molecular material deposition in the bottom instead of the liquid or base.
- It is a surface phenomenon.
- Heat exchange involved in this process is an exothermic process.
- It is influenced by low temperatures.
- In adsorption rate of reaction increases steadily and reaches equilibrium.
- Concentration is no as absorption here concentration is mostly at bottom and different from the bulk.
Types of adsorbents which help in adsorption
- Oxygen-containing compounds : They are naturally hydrophilic and polar such as silica gel and zeolites.
- Carbon-based compounds: They are naturally hydrophilic and non-polar such as activated carbon and graphite.
- Polymer-based compounds : They are mostly polar or non-polar mainly depends on functional groups in the polymer matrix.
Uses and roles of adsorption
In many human, physical, biological and chemical processes, adsorption occurs. This is commonly used in industrial applications such as heterogeneous catalysts, activated charcoal, the capture and use of excess heat to supply air conditioning with cold water. And Other process criteria such as, synthetic resins, improved carbide-derived carbon storage capability and water purification. It also has Pharmaceutical industry applications, That use adsorption as a way to extend neuronal access to, or portions of, particular medications.
Adsorption in Environment
It plays a key function in biodiversity. It governs the interaction between the geosphere and the hydrosphere and the environment, accounts for the transfer of materials in the ecosystems and activates other essential processes such as ionic interaction and enzymatic processes.
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