Highly porous activated carbons were fabricated from sunflower
seed hull by ZnCl2 activation and used as adsorbents to remove
Cr(VI) ions from aqueous solution. The activated carbons can be
dominantly microporous or mesoporous depending on the ZnCl2/
SSH impregnation ratios and activation temperatures. The
adsorption experiments indicated that the micropore dominant
samples were more favorable for Cr(VI) removal, and the existence
of some mesopore could facilitate the intra-particle diffusion,
hence enhance the Cr(VI) removal. The optimum pH for Cr(VI)
adsorption varied with the change of initial Cr(VI) concentration in
the solutions. In general, more acidic environment was required to
promote Cr(VI) adsorption in solutions with higher initial Cr(VI)
concentrations. However, acidic solution (pH 2.0 in this study)
would result in reduction of Cr(VI) to Cr(III), and consequently
reduce the overall removal efficiency of chromium element