Carbonization is a process where a fuel is heated without air to remove solid carbon. Activated C is produced from carbonaceous materials like coal, pitch, petroleum, bamboo, coconut husk etc. In this way spontaneous breakdown of wood is occurred at 280oC that liberates energy i.e, it is a exothermic reaction. This process continues until the carbonized residue called charcoal remains.

Activated carbon is produced in two step 1. characterized by carbonization, i.e., the removal of undesirable by-products from the raw materials 2. about activation of the material.

Dear Mawar Hasyikin Abu Seman

Activated carbons have been prepared from a number of precursors, such

as lignite, coconut shell, wood, and grains, through one-stage or two-stage

processes.

In the one-stage process, activated carbons are generated

directly from raw materials via physical or chemical activation. Physical

activation is carried out most frequently by burning off some of the raw

carbon in an environment of oxidizing gas to create micropores. The usual

choices of oxidizing gas are steam, CO2, air, or their mixtures. Activation

normally takes place at temperatures between 700 and 1000 °C in steam

and CO2 and lower temperatures in air. In chemical activation, a carbon

precursor is impregnated with a dehydrating agent before heated between

500 and 800 °C. The most widely used dehydrating agents include zinc

chloride, potassium sulfide, potassium thiocyanate, phosphoric acid, sulfuric

acid, hydroxides of the alkali metals, magnesium chloride, and calcium

chloride. The resultant activated carbons from the one-stage process have

small surface areas and high mesoporosities.

The two-stage process comprises carbonization followed by physical or

chemical activation. Carbonization is performed by pyrolyzing raw materials

at a temperature less than 700 °C to produce char. The char obtained is

physically activated through oxidation in the presence of an oxidizing gas

or chemically activated through pyrolysis in an inert gas after mixing with

the dehydrating agent. The resultant activated carbons usually have high

surface areas and high microporosities.