Wood charcoal is formed when carbon-containing raw wood is carbonized in a limited supply of air with no oxygen called Pyrolysis. The wood substance is forced to decompose into Wood charcoal, a black porous solid consisting mainly of elemental carbon.
Wood Activated Carbon
Wood charcoal is an important raw material for Activated Carbon. It is not a very active adsorption material for either liquids or vapors because its fine structure is blocked by residues. To convert the charcoal to “Activated Mode” this structure must be opened up by removing the tarry residues and volatiles. The most widely used method today consists in heating the granulated wood charcoal in a rotary kiln to low red heat in an atmosphere of superheated steam. The steam prevents the charcoal from burning away by excluding oxygen. Meanwhile the volatile tars can be distilled away and are carried off with the steam, leaving the pore structure open. The treated charcoal is run off into closed containers and allowed to cool.
Properties of Wood Activated Carbon
Surface Area – Generally, higher the internal surface area, the higher is the adsorption capacity of carbon. The surface area of activated carbon is 500 to 1500 m2/g or even more; a spoonful of activated carbon easily equates the surface area of a soccer field.
It is in the activation process that this vast surface area is created. The most common process is steam activation; at around 900°C steam molecules selectively burn holes into the carbonized raw material, thus creating a multitude of pores inside the carbonaceous matrix.
Total Pore Volume – Refers to all pore spaces inside a particle of activated carbon . It is expressed in milliliters per gram (ml/g), volume in relation to weight. In general, the higher the pore volume, the higher the effectiveness. However, the selection of carbon mainly depends upon matching the molecular size of impurities to be adsorbed by the carbon with suitable pore diameter and pore volume.
Pore Volume Distribution – Wood Charcoal has its own unique distribution of Mesopores r > 1-25nm.
Typical Parameters of Wood Activated Carbon
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