Preparation of activated carbon from Iris tectorum with different ammonium phosphates activation and removal of nickel from aqueous solution

The preparation of activated carbons (AC-(NH4)(x)HyPO4) from Iris tectorum (IT) with three kinds of ammonium phosphates ((NH4)(2)HPO4, NF4H2PO4 and (NH4)(3)PO4) activation was investigated, with a special attention paid to the effect of these (NH4)(x)HyPO4 on both physical and chemical properties. The prepared carbons were characterized by scanning electron microscope (SEM), N-2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR), and Boehm's titration. The surface area and total pore volume of AC-(NH4)(3)PO4 were much higher than AC-(NH4)(2)HPO4 and AC-NH4H2PO4, while AC-(NH4)(2)HPO4 had largest micropore volume ratio. Boehm's titration results suggested that AC-(NH4)(2)HPO4 possessed more acidic functional groups than AC-NR4H2PO4 and AC-(NH4)(3)PO4. Batch adsorption studies were carried out to compare adsorptive performances of the carbons toward Ni(II). The adsorption equilibrium data were in good agreement with Langmuir model. The maximum Ni(II) adsorption capacities of AC-(NH4)(2)HPO4 (40.00 mg/g) was higher than that of AC-NH4H2PO4 (38.61 mg/g) and AC-(NH4)(3)PO4 (34.60 mg/g), resulting from the carbons higher content oxygen-containing functional groups which could adsorb more Ni(II) by cation exchange and electrostatic attraction. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.