be achieved. Moreover, activated carbon from coconut shells,
coal dust, husk and pods of M. oleifera is an H-type activated
carbon (which adsorbs H+ ions). Numerous studies on H-type
activated carbon state that pH of the solution increases as they
adsorb more and moreH+ ions. The removal efficiency for heavy
metals is supposed to increase from 10 to 95% in the equilibrium
pH values ranging from 2.3 to 7. Modification of activated
carbon with HCl, HF and HNO3 introduce oxygen surface complexes
that alter the surface chemistry and can change the surface
area and porosity of the original samples [18–20]. The ability
of surfactant to accelerate the removal efficiency of toxic, noble
and rare metals can be ascribed to wettability alterations and/or
micellar solubilization [13]. Moreover, carbon surface have both
negative (anionic) and positive (cationic) functional groups to
attract free ions in solution or suspension. Apart from wetting
and solubilization surfactants are also capable to produce the
electrostatic charge on surface of activated carbon and in turn
creating more available active sites for adsorption. That may be
the reason for carbon adsorbents modified by CTAB to increase
the removal of Pb(II) as compared to the acidic treatment.
Moreover, in case of CTAB-modified carbon sorption of lead
is rapid, indicating maximum penetration of adsorbate in less
time, due to easy transport of the metal ions to mesopores and
micropores