Environmental Engineering Reference
In-Depth Information
of 820 m 2 .g -1 with a pore volume of 0.219 cm 3 .g -1 was obtained for the acti-
vated carbon. The average pore diameter of the activated carbon was cal-
culated to be 2.46 nm. The increase in the surface area was attributed to the
intercalation of the potassium metal ions into the carbon structure. A lot
of functional groups were observed on the surface of the activated car-
bon, namely O-H, N-H, C-O, C = O and Si-O-Si. The presence of extra
functional groups on the surface of the dye-loaded activated carbon, such
as NH 2 , NO 2 and C-N, signified the contribution of the activated carbon
for color removal. The titration results confirmed the presence of 1.57 and
2.56 mmol/g acidic and basic functional groups, respectively. A maximum
uptake capacity of 203.3 mg.g -1 was determined for the Acid Blue 25. It was
found that the optimum adsorption capacity was observed at pH values of
7-11 due to the interaction of the carboxyl groups of the activated carbon
with the amine groups of the dye molecule. Moreover, the high adsorption
at both acidic and basic media was ascribed to the amphoteric nature of the
silica and amino groups. The dye uptake capacities of tea and coffee waste-
based materials have been compiled in Table 5.25.
Table 5.25 Comparison of adsorption capacities of tea and coffee waste-based
materials.
Modification
Surface
Area
( m 2 g -1 )
Dye Type
pH
Adsorption
Capacity
( m 2 g -1 )
Ref.
N/A
Methylene Blue
300
[113]
N/A
Methylene Blue
6
147
[114]
N/A
Methylene Blue
7
173
[134]
N/A
1.71
Methyl Violet
294
[115]
N/A
Methylene Blue
5
18.7
[135]
N/A
Methylene Blue
8
90.1
[136]
N/A
3
Remazol Blue
2
175
[116]
Basic Blue
10
240
N/A
Methylene Blue
85.2
[137]
NaOH
6.5
Methylene Blue
7
242.1
[138]
NaOH
173.2
Malachite Green
55.3
[139]
NaOH
134
Malachite Green
256.4
[118]
CH 3 CO 2 K - Activation
854.3
Methylene Blue
554.3
[140]
Acid Blue
453.1
( Continued )
 
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