How does activated carbon achieve adsorption

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Activated carbon is prepared by pyrolysis and activation processing of carbon-containing raw materials such as wood, coal and petroleum coke. It has developed pore structure, large specific surface area and abundant surface chemical groups, and has strong specific adsorption capacity. A collective term for carbon materials.
Activated carbon is usually in powder, granular or columnar form. Activated carbon has a strong adsorption capacity. powdered carbon activated  It is carbonized by solid carbonaceous matter (such as coconut shell, fruit shell, coal, petroleum coke, etc.) at a high temperature of 600-900°C under air isolation. It is obtained after oxidation and activation with air, carbon dioxide, water vapor or a mixture of the three at 1000-1100°C.
Activated carbon achieves adsorption through its huge specific surface area. Adsorption is divided into: physical adsorption and chemical adsorption.
Physical adsorption
The specific surface area of micropores in activated carbon accounts for more than 95% of the specific surface area of activated carbon, which largely determines the adsorption capacity of activated carbon. The mesoporous specific surface area accounts for about 5% of the activated carbon specific surface area, which is the adsorption site of larger molecules that cannot enter the micropores, and capillary agglomeration occurs under higher relative pressure.
The specific surface area of the macropores generally does not exceed 0.5m2/g, which is only the channel through which the adsorbate molecules reach the micropores and mesopores, and has little effect on the adsorption process. Some scholars have proposed that the pore size of activated carbon is divided into three categories: pores smaller than 2nm are micropores, pores between 2-50nm are mesopores, and larger than 50nm are
During the preparation of activated carbon, the edge chemical bonds of aromatic hydrocarbons formed in the carbonization stage are broken to form edge carbon atoms with unpaired electrons. These edge carbon atoms have unsaturated chemical bonds and can react with heterocyclic atoms such as oxygen, hydrogen, nitrogen and sulfur to form different surface groups. The existence of these surface groups will undoubtedly affect the adsorption performance of activated carbon. Adsorption is mainly achieved by means of chemical bonds.
Posted 20 Mar 2021

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Posted 20 Mar 2021

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