Sorption heavy metal ions by activated carbons with well-developed microporosity and amino groups derived from Phragmites australis by ammonium phosphates activation

Activated carbons (ACs) were prepared from Phragmites australis impregnated with phosphoric acid (PPA) and ammonium phosphates (APs). APs include triammonium phosphate (TAP), diammonium phosphate (DAP), and monoammonium phosphate (MAP). The activation process of ACs was simulated by thermo-gravimetric analysis. The physicochemical properties of AC-PPA and AC-APs were systematically examined by N-2 adsorption/desorption, elemental analysis, Boehm's titration, and XPS. AC-PPA exhibited much higher values of the BET surface area (894.5 m(2)/g) and total pore volume (1.108 cm(3)/g) than that of AC-APs (< 500 cm(2)/g and < 0.3 cm(3)/g), but less Smic/SBET (29.3%) and Vrnic/Vtot (14.9%) of AC-PPA than that of AC-APs (>60% and >50%). Nevertheless, the results of elemental analysis, Boehm's titration, and XPS showed that AC-APs contained much more surface nitrogen-containing functional groups. The sorption equilibrium data for heavy metal ions Ni(II), Cu(II), and Cd(II)) sorption onto the carbons was analyzed by the Langmuir and Freundlich model. The differences of the carbons in the physicochemical and adsorption properties suggested that AC-APs exhibited higher heavy metal ions sorption capacities than AC-PPA due to well-developed microporosity and abundant amino groups. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.