CLARIMEX - Classification

CLASSIFICATION

Classification Activated carbons are generally classified into two groups:

Purification carbons in a LIQUID PHASE
Purification carbons in a GASEOUS PHASE

The most important properties that should be considered when choosing a carbon are the diameter and the characteristic of the pores. The pores of activated carbon, depending on their size, are classified as follows:

Micropores
Macropores
Macropores

Micropores are pores with a 20 A° radius or smaller and are the ones that provide a larger area. There are useful to adsorb very tiny molecules, generally present in purification of gases.

Macropores range between 20 and 500 A°. Although they provide a smaller total area, their size allows them to adsorb big molecules that are generally present in the purification of liquids.

Macropores do not contribute much in the total area of a carbon, but they are important because they act as an access route towards the mesopores and the micropore, thus affecting the speed of diffusion of impurities in the carbon.

Unfortunately, the total area and the size of the pores are not easy to measure, and consequently the following indexes are used:

Iodine index
Molasses index
Methylene blue index
Carbon tetrachloride index
Butane index

This indexes give of us an idea of how easily different size molecules are adsorbed; therefore we can imagine the kind of pore a certain carbon has.

It is generally difficult for a carbon to only have one size pores; what it does have is a certain distribution.

When the average leans towards the micropores, it is said that the carbon is "gas phase"; such not being the case, the carbon will be "liquid phase".