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The BET method is widely used in materials science for the calculation of surface areas of solids by physical adsorption of gas molecules. The total surface area S t o t a l {\displaystyle S_{\mathrm {total} }} and the specific surface area S B E T {\displaystyle S_{\mathrm {BET} }} are given by
Brunauer, Emmett and Teller's model of multilayer adsorption is a random distribution of molecules on the material surface. Adsorption is the adhesion [1] of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. [2] This process creates a film of the adsorbate on the surface of the adsorbent.
Gas separation can refer to any of a number of techniques used to separate gases, either to give multiple products or to purify a single product. Swing adsorption techniques [ edit ]
Pressure swing adsorption (PSA) is a technique used to separate some gas species from a mixture of gases (typically air) under pressure according to the species' molecular characteristics and affinity for an adsorbent material.
The adsorption sites (heavy dots) are equivalent and can have unit occupancy. Also, the adsorbates are immobile on the surface. The Langmuir adsorption model explains adsorption by assuming an adsorbate behaves as an ideal gas at isothermal conditions. According to the model, adsorption and desorption are reversible processes.
The invention of gas chromatography is generally attributed to Anthony T. James and Archer J.P. Martin. [6] [7] Their gas chromatograph used partition chromatography as the separating principle, rather than adsorption chromatography. The popularity of gas chromatography quickly rose after the development of the flame ionization detector. [8]
The capacity to discriminate based on both molecular size and adsorption affinity makes zeolite membranes an attractive candidate for CO 2 separation from N 2, CH 4, and H 2. Scientists have found that the gas-phase enthalpy (heat) of adsorption on zeolites increases as follows: H 2 < CH 4 < N 2 < CO 2. [13]
A nitrogen generator Bottle of 4Å molecular sieves. Pressure swing adsorption provides separation of oxygen or nitrogen from air without liquefaction. The process operates around ambient temperature; a zeolite (molecular sponge) is exposed to high pressure air, then the air is released and an adsorbed film of the desired gas is released.