Pore Structure Of Activated Carbon

According to the appearance of activated carbon, it is usually divided into two categories: powdery and granular. Granular activated carbon can also be cylindrical, spherical, hollow cylindrical, hollow spherical, and irregularly shaped crushed carbon. With the development of modern industry and scientific technology, many new types of activated carbon have emerged, such as carbon molecular sieves, microsphere carbon, activated carbon nanotubes, activated carbon fibers, etc.
pore structure
Activated carbon is composed of graphite microcrystals, single planar reticulated carbon and Amorphous carbon, of which graphite microcrystals are the main part. The microcrystalline structure of activated carbon is different from that of graphite, with a interlayer spacing of 0.34~0.35nm and a large gap. Even at temperatures above 2000 ℃, it is difficult to convert into graphite. This microcrystalline structure is called non graphite microcrystalline, and the vast majority of activated carbon belongs to non graphite structure. The arrangement of microcrystals in a graphite like structure is relatively regular and can be transformed into graphite after treatment. The non graphite like microcrystalline structure gives activated carbon a well-developed pore structure, which can be characterized by pore size distribution. The pore size distribution range of activated carbon is very wide, ranging from less than 1nm to thousands of nm. Some scholars have proposed to divide the pore size of activated carbon into three categories: micropores with a pore size less than 2nm, mesopores with a pore size between 2-50nm, and macropores with a pore size greater than 50nm.
The microporous specific surface area in activated carbon accounts for over 95% of the specific surface area, which largely determines the adsorption capacity of activated carbon. The mesoporous specific surface area accounts for about 5% of the specific surface area of activated carbon, which is the adsorption site of larger molecules that cannot enter the micropores, resulting in capillary condensation under high relative pressure. The specific surface area of macropores generally does not exceed 0.5m2/g, which is only the channel for adsorbate molecules to reach micropores and mesopores and has little impact on the adsorption process.