Photocatalytic Processes for the Removal of Dye - Green Chemistry for Dyes Removal from Wastewater - page 179

( a )
( b )
Figure 5.21 SEM images of (a) coconut husk and (b) the derived activated carbon [110].
husk-based activated carbon was relatively large (434.8 mg.g -1 ) when com-
pared with some other literature, which can be attributed to the nature of
the precursor used, the activation process applied or a mixture of these two.
An increase in the temperature led to a reduction in the adsorption capacity
of the material due to the weakening of the adsorbent-adsorbate bonds and
the increase in the solubility of the dye. The activation of coconut coir dust
was also attempted by zinc chloride [111]. The impregnation of the precur-
sor in ZnCl 2 and subsequent activation at 800 C under CO 2 atmosphere
resulted in the production of a mesoporous activated carbon with surface
area of 1884 m 2 .g -1 with a variety of functional groups on the surface. The N 2
adsorption-desorption isotherm curve, illustrated in Figure 5.22, depicts a
hysteresis loop typical of Type IV isotherm, verifying the development of a
mesoporous structure. The mechanism of the dye uptake by the adsorbent