An activated carbon is amorphous-based material and can be defined as “a material exhibiting a high degree of porosity and a prolonged inter-particulate surface area” (Bansal et al. 1988). A black solid substance resembling granular or powder charcoal regarded as activated carbon that possesses highly internal surface area, highly developed porosity, relatively high mechanical strength (Sahu et al. 2010). Activated carbon is the best example of heterogeneous acid catalyst. Adsorption and desorp­tion are the process through which catalyst works. The two processes help in the reaction of molecules to make them attract and attach to one another. Activated carbon is best, effective adsorbents for the purification or recovery of different chemicals. Turnover frequency usually expresses the efficiency of a catalyst. It is a chemical reaction rate and not a rate constant. Equation 15.1 is used for calculating the TOF of a catalytic process (Boudart 1995)

TOF = number of molecules of a given product /

(number of active sites) x(times) (15.1)

It is the best method of comparing the activities of different catalysts, however seldom used for the heterogeneous catalysts.

The ultimate product of an activation process of carbonaceous materials is acti­vated carbon with carbon contents in the range 72-90 %. The activation sequence generally commences with an initial carbonization of the raw material to obtain samples with high carbon content (Daza et al. 1986). Any organic material that is rich in carbon content but with low content in inorganic matter can be used as pre­cursor material for the preparation of activated carbon.