Chemical activation is principally used for the activation of wood-based activated carbon and activated carbon made from stones, e.g., olive stones. This differs from steam activation in that carbonification and activation occur simultaneously. The raw material, usually wood chips, is mixed with an activating and dehydrating substance, usually phosphoric acid or zinc chloride. The activation takes place at a low temperature: 500°C is the norm, but sometimes it can go up to 800°C. The phosphoric acid causes the wood to swell and open its cellulose structure. During the activation, the phosphoric acid acts as a stabilizer and ensures that the carbon does not collapse again. The result is a very

porous activated carbon full of phosphoric acid. This is later washed out and re-used in the next production.
 

 

As a result of the manufacturing process, no “chips” (crystalline plates) are to be found in this carbon. Instead, the carbon acquires a very open pore structure, which is ideal for the absorption of large molecules, e.g., in the clarification of liquids. As a rule, this carbon is ground down to powdered carbon.