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We have a wide range of activated carbon, whether for the gas phase or the liquid phase,
available in spun, granulated, crushed or powdered form.
Activated carbon is an adsorbent because we are talking here about the phenomenon of adsorption and not absorption.
Adsorption is a physical process in which molecules are attached to the large inner surface of the activated carbon in the pores.
The substances adsorbed in the activated carbon can be desorbed again by heat treatment; Accordingly, for example in the case of adsorbed solvents, these substances can be reused in the sense of preserving valuable materials. One can take as an example a bath sponge which adsorbs water, which is desorbed again by squeezing the sponge.
Absorption, on the other hand, describes the absorption of a substance by capillary forces into another body. This is not surface accumulation, as in adsorption, but absorption in the free volume of the absorbent phase.
Activated carbon is obtained from raw materials containing carbon (wood, peat, coal, lignite, coconut shells, fruit stones, etc.).
Any organic raw material containing carbon is a priori suitable for the production of activated carbon.
After selecting the raw materials, they are physically or chemically activated in an activation furnace.
Through this activation, a carbonaceous structure is obtained thanks to the reaction of gas and water vapour.
To find the origins of coal, we have to go back 200 to 300 million years.
At that time, the earth was like a vast greenhouse: covered with swamps and lush vegetation that were surrounded by a warm, humid climate.
Some of the land subsides, plant debris accumulates, ferments and is buried under sediment.
This repeated process of layering deposits in a carbon dioxide laden atmosphere gave rise to the solid, combustible, high carbon substances, coal.
This stage is necessary to transform the raw material into carbonised coal.
Coal from carbonaceous raw materials has an infinite number of pores (a few Angstroms) blocked by organic matter.
To be transformed into activated coal, this carbonaceous material is heated to a high temperature (300 °C) in a rotary or vertical kiln to remove all organic products, this is carbonisation.
After carbonisation comes activation.
Activation is the process of opening the pores of the activated carbon.
The coal is mixed with steam and nitrogen.
The organic matter is then destroyed.
The whole thing is heated to 700 - 1000 °C.
The carbonaceous material is mixed with sulphuric acid, phosphoric acid or zinc chloride.
The whole is heated to between 400 °C and 800 °C.
This activation method is used for powdered activated carbons.
Following activation, we can see that:
It is not uncommon to have an activated carbon with an internal surface area of more than 1,200 m²/gram of activated carbon.
The more the activated carbon is activated, the more the volume of the micro, meso and macro pores increases.