Activated carbon can be produced through physical and chemical activation. In the physical activation, there are two steps: carbonization
step and activation step. The raw material isfirst carbonized under
inert atmosphere and then resulting char is activated at high temperature by steam or carbon dioxide. In the chemical activation, raw material
is impregnated with an activation reagent and heated in an inert atmosphere. The chemicals used in the chemical activation are alkali (KOH,
K2CO3, NaOH and Na2CO3), alkali earth metal salts (AlCl3and ZnCl2)
and some acids (H3PO4and H2SO4). These chemicals are dehydrating
agents that influence pyrolytic decomposition and inhibit formation of
tar. In the case of chemical activation, the effect of KOH and ZnCl2on
the carbonization of precursors has been particular interest and ZnCl2
in particular is a widely used chemical agent in the preparation of activated carbon[21,22].