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. The Cr
(VI) adsorption on SSH activated carbons can be well explained by
the Langmuir isotherm model and the pseudo-second-order
kinetic model, i.e., the adsorption occurred through monolayer
formation on the surface of adsorbents via chemical interactions
such as ionic or covalent bonds. Generally considering the low cost
and abundant raw material, easy fabrication process, high carbon
yield and high adsorption capacity, SSH-derived activated carbons
can be potentially used as attractive low-cost adsorbent for largescale
treatment of Cr(VI) containing industrial wastewaters