Abstract
Pistachio wood-derived activated carbon prepared by a two-stage process (PWAC-2), conducting two consecutive chemical activation processes with NH4NO3 and NaOH, respectively. The results showed that explosive characteristic of NH4NO3 can primarily be employed to produce a char, with a large surface area and a highly-ordered pore structure, which can be subjected to a second activation process with NaOH to prepare a more suitable activated carbon, with a highly porous structure and useful functional groups, for removal of lead ions from aqueous media. An L25 Taguchi experimental design was used by varying impregnation ratio, activation time and temperature in both pre- and post-activation stages, and the results showed that, in both stages, a small activating agent/precursor and a proportional low activation time suffice for preparation of an advantageous activated carbon for Pb(II) adsorption. A comprehensive study was performed on the equilibrium, kinetic and thermodynamic aspects of Pb(II) adsorption by the new activated carbon. The results exhibited that, having had a high lead adsorption capacity (190.2 mg g−1), a high adsorption rapidness, and thermodynamic favorability, PWAC-2 is a beneficial alternative for utilization in full-scale plants of lead removal from waters and wastewaters.
•Suitable activated carbon for Pb(II) removal was produced by two-stage activation process.•NH4NO3 and NaOH were, respectively, used as pre- and pro-activation agents.•A small activating agent/precursor and a low activation time were enough for activation.•Explosive characteristic of NH4NO3 resulted in a char with a highly-ordered pore structure.•NaOH as pro-activating agent raised the activated carbon efficiency for Pb(II) sorption.