The carbon-based materials are converted to AC by thermal decomposition in a furnace using a controlled atmosphere and heat by physical activation or chemical activation (Hsieh and Teng 2000; Mohan et al. 2005) involving the following steps: (1) removal of all water (dehydration), (2) conversion of the organic matter to elemental carbon, driving off the non-carbon portion (carbonization), and (3) burning off tars and pore enlargement (activation) (Ahmadpour and Do 1997). The two common methods for the preparation of activated catalyst are physical and chemical activation, the differ­ence between the two methods and their advantages (Table 15.5).

Different chemical activating agents and related recent studies are presented in Table 15.6. Different physical forms of AC that usually can be found, including: (1) granular activated carbon (GAC); (2) powdered activated carbon (PAC); (3) acti­vated carbon fibers (ACF); and (4) activated carbon cloths (ACC). GAC and PAC

Table 15.5 Comparison between physical activation and chemical activation method Physical activation Chemical activation

Diasa et al. (2007), with permission

are the most widely used activated catalyst. Hard materials are used to prepare GAC, such as coconut shells, including particles retained in an 80-mesh sieve (0.177 mm); PAC obtained when small particles are the raw materials, like wood sawdust, (includes particles <0.177 mm); ACF prepared from homogeneous poly­meric raw materials and, in contrast to GAC and PAC, they show a mono dispersed pore size distribution (Kasaoka et al. 1989).

Phenolic or viscose rayon initially used to develop ACC in the early 1970s (Bailey et al. 1971). Thus the utilization of discarded materials possesses several advantages, mainly involve the eco-friendly nature and their economically feasibility.