Environmental Engineering Reference
In-Depth Information
of 5
K.min
-1
. The adsorption capacity of the pyrolyzed bamboo activated
carbon was determined to be 16.9, 35.3 and 319.2
mg.g
-1
for Acid Blue 25,
Acid Yellow 117 and methylene blue, respectively. The more favorable
adsorption of methylene blue was attributed to the molecular sieve effect
of the activated carbon with narrow micropore sizes.
A number of studies have been conducted to activate the bamboo by
orthophosphoric acid. Chan
et al.
[73] impregnated bamboo with phos-
phoric acid and activated it in a two-step process, where the impregnated
slurry was first subjected to 150 C and the temperature was raised to either
400 or 600 C under flowing nitrogen. The results showed that the surface
area increased considerably with an increase in both the acid-to-bamboo
ratio and the temperature. The highest surface area and total pore volume
obtained were determined to be 2517
m
2
.g
-1
and 1.4
cm
3
.
g
-1
(see Figure 5.10).
The highest adsorption capacities of the bamboo-based activated carbon
were measured as 785.3
mg.g
-1
for Acid Blue 25 and 111.2
mg.g
-1
for Acid
Yellow 117. The higher adsorption capacity for Acid Blue 25 compared to
Acid Yellow 117 was assigned to the smaller molecular size of the former.
The same reason accounts for the preferential adsorption of the former dye
to the latter in a multicomponent system. Using the hybrid fractional error
function, it was shown that the Sips model was the best it model for the
adsorption of dyes by bamboo-derived activated carbons [74,75]. A sim-
ilar activation method was employed to modify the bamboo to remove
Reactive Black 5 [76]. Two bamboo activated carbons with impregnation
ratio of 2 and 6, namely BACX2 and BACX6, were prepared. It was found
that the activated carbon with lower impregnation ratio gives higher sur-
face area and micropore volume, whereas the one with higher impreg-
nation ratio has higher mesopore volume. The adsorption capacities of
BACX2 and BACX6 adsorbents were found to be 281.2 and 441.7
mg.g
-1
,
respectively, for Reactive Black 5. The higher adsorption capacity of the
activated carbon with lower surface area (BACX6) was ascribed to the pore
widening at higher impregnation ratio, enabling the dye molecules to pen-
etrate the pores more effectively. Ahmed and Hameed have determined the
surface functional groups of phosphoric acid-activated bamboo as phe-
nols, carboxylic acid and carbonyl [77]. A high surface area bamboo-based
activated carbon prepared by similar activation method showed a very tiny
adsorption capacity for the Disperse Red 167 [78]. Choy and McKay [79]
prepared bamboo charcoal at 500 C under a nitrogen atmosphere. Also,
activated bamboo was produced by mixing the raw material with sulfu-
ric acid at 160 C and carbonizing the resulting material at 750 C. These
adsorbents were used to study the multilayer dye adsorption behavior.
The single-component adsorption study indicated that bamboo, bamboo
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