Photocatalytic Processes for the Removal of Dye - Green Chemistry for Dyes Removal from Wastewater - page 188

Table 5.23 Surface chemical characteristics of the activated carbons derived
from coffee waste [117].

Functional
group

Calculation
Method

CGAC30 * CGAC60 * CGAC120 * CGAC180 *

Carboxylic
( meqg -1 )

BET 0.466 0.390 0.266 0.266

Lactonic
( m 2 g -1 )

t-Plot 0.200 0.200 0.234 0.014

Phenolic
( m 2 g -1 )

t-Plot 0.709 0.700 1.033 0.786

Carbonyl
( m 2 g -1 )

BJH
Desorption

0.125 0.133 0.124 0.434

Total
oxygenated
( cm 3 . g -1 )

Single-Point
Adsorption

1.500 1.312 1.657 1.500

Total basic
( m 2 g -1 )

t-Plot 0.000 0.000 0.000 0.000

pH BJH

Desorption

3.7 3.6 3.6 6.9

pH PZC 3.7 3.6 3.9 7.4

*CGAC(n) represents the activated carbon with an impregnation ratio of “n” wt%.

activated carbons which verified the successful activation of the carbon
(see Figure 5.28). As the impregnation ratio increased, the adsorption of
the methylene blue was enhanced. The activated carbons with the lowest
and highest impregnation ratios showed methylene blue uptake capacities
of 96 and 182 mg.g -1 , respectively. The dye-covered surface areas have been
compared with the BET surface area and also mesoporous surface area
of the activated carbons in Table 5.24. The MB coverage ratio is virtually
independent of impregnation ratio, whereas mesopore volume increases
significantly with an increase in the impregnation ratio. This indicates that
the MB molecules do not completely fill the mesopores of CGAC120 and
CGAC180. Akar et al. [118] prepared an activated carbon from spent tea
leaves by impregnating the raw material in dilute NaOH and carbonizing
the material at 450 C under nitrogen atmosphere. The BET and micropore
surface areas of the carbon after the activation process were increased to
134 and 21.5 m 2 .g -1 , respectively, while the untreated material showed a
BET surface area of 30 m 2 .g -1 with no microporosity. The BJH pore diam-
eter was 22.5 Å for the unactivated material, whereas it decreased consid-
erably to 5.1 Å after the activation process. The surface functional group