Agricultural by products
have proved to be promising raw materials for the production
of activated carbons because of their availability at a low price. They can
be used for the production of activated carbon with a high adsorption
ation.
In the physical activation, there are two steps: carbonization
step and activation step. The raw material is first 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 (AlCl3 and ZnCl2)
and some acids (H3PO4 and 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 ZnCl2 on
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].