Activated carbon is a popular choice among all owing to its good adsorption capacity, active free valancies, high surface area, porous structure, surface reactivity, inertness, and thermal stability (Cheremisinoff and Ellerbusch, 1978; Babel and Kurniawan, 2003). Activated carbons can be used in various forms: powdered activated carbon (PAC) has finer particle size of about 44 µm which allows faster adsorption, but it is difficult to handle in fixed adsorption beds. The granulated activated carbon (GAC), having granules of 0.6–4.0 mm in size, are hard and resistant to abrasion (Uddin, 2017). Although GAC is costlier than PAC and can be regenerated easily. The fibrous activated carbon fibers are expensive, but they can be molded easily into the shape of the adsorption system and produce low hydrodynamic resistance to flow (Uddin, 2017).

Due to the versatility, various researchers attempted to use activated carbon to work on cost reduction by generating carbon from cheap sources or by doing surface modification. Kadirvelu and Namasivayam (2003) prepared activated carbon from coir pith for adsorption of Cd(II) from aqueous solution with the adsorption capacity of 93.4 mg/g. Activated carbon modified using tetrabutyl ammonium iodide and sodium diethyl dithiocarbamate was used to remove Cu, Zn, and Cr found to be effective than plain carbon (Monser and Adhoum, 2002). Sawdust activated carbon was used to remove Cr(VI) (Karthikeyan et al., 2005). Pb(II) was removed using treated activated carbon (Goel et al., 2005). Karnib et al. (2014) performed batch experiments to evaluate removal efficiency of activated carbon for the removal of lead, cadmium, nickel, chromium, and zinc from water. Activated carbon has limitations such as cost inefficiency, expensive raw material, difficult to separate powdered form from the effluent, and costly regenerating methods. Complexing agents are required by activated carbon to improve its removal performance for inorganic matters (Babel and Kurniawan, 2003).