Environmental Engineering Reference
In-Depth Information
cadmium at pH 6.0. They determined that the C=O and S=O functional
groups, present on the carbon surface, worked as the adsorption sites
responsible for removing the metallic ions from the solution. The equilibrium
process was well described by a Langmuir isotherm model with maximum
sorption capacity of 19.5 mg g
-1
of cadmium ion. The initial uptake was fast
and equilibrium was established in less than 40 min. The highest desorbability
was 88% using a 0.2 M HCl aqueous solution.
Inbaraj and Sulochana [105] evaluated the removal of cadmium by
carbonized jackfruit peel. The results showed that at the beginning, the
adsorption of Cd (II) ions was very fast and the equilibrium time was 180 min.
When the Cd
2+
concentration increased from 20 to 40 mg L
-1
the amount of
Cd
2+
, adsorbed at equilibrium time, increased from 28.3 to 50.6 mg g
-1
. The
removal of Cd
2+
ions increased from 13.1% to 98.7% when pH increased from
2.0 to 5.0. Thereafter, the removed quantity remained constant (98.7-99.4%)
over the pH range of 5.0-10.0. A complete recovery of the adsorbed metallic
ions from the spent adsorbent was achieved by using a 0.01 M HCl aqueous
solution.
The sorption of Cd
2+
from aqueous solution by activated carbon derived
from husk and pods of
Moringa oleifera
was investigated by Nadeem
et al.
[106]. The adsorption process took place very quickly, being almost completed
in 120 min. Triton X-100-modified carbon, SDS-modified carbon and CTAB-
modified carbon treatments resulted in the increase of the sorption capacity of
unmodified carbon from 207.3 mg g
-1
to 232.9, 263.2 and 279.5 mg g
-1
,
respectively.
Bamboo charcoal, produced from the fast growth of the moso bamboo
plants, was studied as adsorbent for Cd
2+
removal by Wang
et al.
[107]. The
results showed that the adsorption of Cd (II) ions was initially very fast and the
equilibrium time was reached in 6 h. High pH (≥8.0) was favorable for the
adsorption and removal of Cd (II) ions. Higher initial Cd
2+
concentrations led
to lower removal percentages but higher adsorption capacity. The removal of
Cd
2+
increased as the adsorbent dose also increased, however the adsorption
capacity decreased. The highest monolayer adsorption capacity was 12.08 mg
g
-1
for the adsorption of Cd (II) ions by bamboo charcoal.
Wang
et al.
studied the effects of the synthesis preparations of the Makino
bamboo charcoal on its adsorption capacity of heavy metallic ions [108]. The
results showed that the specific surface area and the iodine number of the
bamboo charcoal activated at 900 ºC were larger than those of the bamboo
charcoal activated at 800 ºC. The specific surface area of bamboo charcoal
activated at 900 ºC by steam was larger than that of charcoal activated by CO
2
.
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