(1) The longan seed activated carbon (LSAC) was synthesized from
longan seed by chemical activation with sodium hydroxide and
applied for the removal of Cr(VI) from its aqueous solutions in
batch adsorption experiments. LSAC has a porous and
homogenous structure, high BET surface area (1511.8 m2/g)
and total pore volume (0.7420 cm3/g), which is an effective
adsorbent for Cr(VI).
(2) The batch adsorption experiments show that the external
diffusion is eliminated at 170 rpm, the maximum chromium
removal was found at pH 3.0 and the percent removal of Cr(VI)
increases with the increase of LSAC dosage.
(3) The process of removal of Cr(VI) was better governed by pseudo
second-order kinetic model, and the adsorption activation
energy is 84.4 kJ/mol.
(4) The adsorption isotherms data of Cr(VI) on LSAC were
described better by the Langmuir isotherm equation. The
thermodynamics parameters, DH = 2.73 kJ/mol, DS = 28.14 J/
mol K and DG < 0, show that the adsorption process is
spontaneous, endothermic and entropy driven.