Novel Carbon-Based Nanoadsorbents for Removal of Synthetic Textile Dyes from Wastewaters - Green Chemistry for Dyes Removal from Wastewater - page 71

75.4 mg g -1 was achieved. Fixed-bed column adsorption studies were also
conducted in multiple cycles and the results thus obtained confirmed that
GSC could be used for water purification applications.
Ai and Jiang [134] reported the efficient removal of Methylene Blue
from its aqueous solution by a self-assembled cylindrical graphene-
carbon nanotube hybrid (G-CNT). The hybrid showed good adsorption
performance with a maximum adsorption capacity of 81.97 mg g -1 . Sui
et al. [135] fabricated graphene-CNT hybrid aerogels by supercritical CO 2
drying of their hydrogel precursors obtained from heating the aqueous
mixtures of GO and CNTs with vitamin C without stirring. The CNTs
used in the study were either pristine MWCNTs or acid-treated MWCNTs
(c-MWCNTs). The resulting hybrid aerogels, i.e., graphene/MWCNT
and graphene/c-MWCNT, showed excellent adsorption performance in
removal of basic dyes (Rhodamine B, Methylene Blue, Fuchsine) from their
aqueous solutions. The adsorption was found to be pseudo-second-order
with the binding capacity of graphene/c-MWCNT (150.2, 191.0 and 180.8
mg g -1 for Rhodamine B, Methylene Blue and Fuchsine, respectively) being
higher than that of graphene/MWCNT (146.0, 134.9 and 123.9 mg g -1 for
Rhodamine B, Methylene Blue and Fuchsine, respectively).
Zhang et al. [136] developed polyethersulfone (PES) enwrapped GO
porous particles to remove Methylene Blue from aqueous solutions. Batch
isotherm and kinetic studies were carried out to study the effects of con-
tact time, initial dye concentration (50-250 μmol L -1 ), pH (3.0-11.0),
and temperature (288-333 K) on the adsorption phenomena. Unlike
other adsorption systems with fast equilibration time, the adsorption of
Methylene Blue attained equilibrium after about 60 h. The delayed equi-
librium was ascribed to the porous structure of the particles. The interior
micropores were abundant for which the diffusion of dye molecules took
a long time. Both temperature and pH were found to have a significant
influence on the adsorption of Methylene Blue. The experimental adsorp-
tion equilibrium data correlated well with the Langmuir isotherm model.
The pseudo-second-order kinetic model provided a better correlation for
the experimental kinetic data in comparison to the pseudo-first-order
kinetic model. The dye uptake process was controlled by intraparticle dif-
fusion. Enwrapping of GO with PES facilitated its easy separation from
aqueous environment after adsorption. However, it was found that pure
GO had a higher adsorption uptake capacity than the prepared porous par-
ticles. After blending with PES, the adsorption capacity of GO decreased.
Moreover, the mass of GO in the particles did not show a linear relation-
ship with the adsorption capacity. This was mainly due to the coverage of
the adsorption sites by PES and the agglomeration between GO sheets. The