Environmental Engineering Reference
In-Depth Information
1.1.6.4 CNT-DOLOMITE, CNT-CELLULOSE AND CNT-GRAPHENE AS
ADSORBENTS
Recently developed a novel adsorbent by inserting MWCNTs into the cavities
of dolomite for scavenging of ethidium the foam line CNTs/dolomite adsorbent.
Adsorptions reached equilibrium within 30 min for the cationic dyes, acridine
orange, ethidium bromide, and methylene blue while it was about 60 min for the
anionic dyes, eosin B and eosin Y. Foam like ternary composite PUF/diatomite/
dispersed-MWCNTs, gave the highest capacities for adsorption of these dyes,
followed by PUF/agglomerated-MWCNTs, and then PUF/dispersed-MWCNTs.
Langmuir adsorption isotherm was best fitted to the equilibrium data. The re-
moval of methylene blue onto natural tentacle type wale gum grafted CNTs/cel-
lulose beads was investigated by some researchers. The maximum adsorption of
MB was observed at pH 5 and 150 min. Adsorption isotherm study revealed the
monolayer adsorption at higher concentration and multilayer adsorption at lower
concentration. The equilibrium adsorption capacity onto the adsorbent was de-
termined to be 302.1 mg/g at pH 6.0 from Sips model. Pseudo first order kinet-
ics gives the best-fitted results compared to the pseudo second order. From the
results, it is evident that carboxylic group on the adsorbent plays the important
role for the removal of MB as ionized to COO− at higher pH and bind with MB
through electrostatic force [1]. 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 of MB from aqueous solution with a
maximum adsorption capacity of 81.97 mg/g. The kinetics of adsorption followed
the pseudo second-order kinetic model and equilibrium data were best fitted to
Freundlich adsorption isotherm. The adsorption capacity of G-MCNTs is much
higher than MCNTs. Therefore, G-CNTs hybrid could be used as an efficient
adsorbent for environmental remediation [72-73].
1.1.6.5 CNT-CF (PAN) AS ADSORBENT
In order to combine carbon nanotubes with carbon fibers, most studies report the
direct synthesis of carbon nanotubes on carbon fibers by CVD (chemical vapor
deposition) with special attention paid to the control of CNT length, diameter and
density as well as arrangement and anchorage on carbon fibers. The approach,
which was mostly investigated, consists in impregnating carbon fibers with a liq-
uid solution of catalyst precursors (nickel, iron or cobalt nitrates, iron chloride)
followed by CNT growth from carbonaceous gaseous precursors such as ethyl-
ene and methane. Carbon fibers can also be covered by catalyst particles (iron,
stainless steel) using sputtering or evaporation techniques or even electrochemi-
cal deposition before introducing a gaseous carbon source (methane, acetylene)
for CNT growth. In order to improve the CNT growth efficiency on carbon fibers,
different modifications have been made such as addition of H 2 S in the reactive
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