Environmental Engineering Reference
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adsorption isotherm data were better fitted by pseudo second-order kinetic model
and by Langmuir isotherm, respectively [58, 62, 72, 73].
Recently developed a novel adsorbent by inserting MWCNTs into the cavities
of dolomite for scavenging of ethidium the foam line CNTs/dolomite adsorbent.
Foam like ternary composite PUF/diatomite/dispersed-MWCNTs, gave the high-
est capacities for adsorption of these dyes, followed by PUF/agglomerated-MW-
CNTs, and then PUF/dispersed-MWCNTs. Adsorption isotherm study revealed
the monolayer adsorption at higher concentration and multilayer adsorption at
lower concentration. Pseudo first order kinetics gives the best-fitted results com-
pared to the pseudo second order. Self-assembled cylindrical graphene-MCNT
(G-MCNT) hybrid, synthesized by the one pot hydrothermal process was used as
adsorbent for the removal of methylene blue in batch process. G-MCNT hybrid
showed good performance for the removal [72, 73].
Most important CNT-based as adsorbent composites include: CNT-Chitosan,
CNT-ACF, CNT-Dolomite, CNT-Cellulose, CNT-Magnetic and Metal Oxide
composites, CNT-Fiber composites, CNT-CF(PAN),CNT-Alginate, CNT-PANI
composites and CNTs-Graphene. These composites are investigated in next sec-
tion.
1.1.6.1 CNT-CHITOSAN COMPOSITES AS ADSORBENT
Chitosan (CS) is one of the best adsorbents for the removal of dyes due to its
multiple functional groups, biocompatibility and biodegradability, but its low me-
chanical strength limits its commercial applications. Impregnation of CS hydrogel
beads with CNTs (CS/CNT beads) resulted in significant improved mechanical
strength. In CS/CNT composite, CNTs and CS are like a symbiosis, CNTs help
to improve the mechanical strength of CS while CS help to reduce the cost of
CNTs for adsorption, while the resulted composite solves the problem of sepa-
rating CNTs from aqueous medium. Impregnation of 0.05 wt.% cetyl trimethyl
ammonium bromide (CTAB) increased the maximum adsorption capacity of CS
beads from media. The small difference in maximum adsorption capacity of CS/
CNT beads and CS/CTAB beads indicated that CTAB molecules played a sig-
nificant role in enhancing the adsorption performance of both varieties of beads.
However, higher maximum adsorption capacity of CS/CNT beads than CS/CTAB
beads suggested that CNTs itself in the beads adsorb CR during adsorption. This
work suggests that surfactant played an important role in the removal of dyes. In
his further studies [72, 73] on CS/CNTs, some researchers reported the effect of
anionic and cationic surfactants as dispersant on impregnated MWCNTs/CS for
the removal of CR dye.
The adsorption capacity of CNT-impregnated CSBs was found to be depen-
dent on the nature of dispersant for CNTs. CNT-impregnated CSBs were prepared
by four different strategies for dispersing CNTs: (a) in CS solution (CSBN1), (b)
in sodium dodecyl sulfate (SDS) solution (CSBN2), (c) in CS solution contain in
cetyl trimethyl ammonium bromide (CTAB) (CSBN3), and (d) in SDS solution for
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