Environmental Engineering Reference
In-Depth Information
Owing to the decoration of CNTs, the specific capacitance was found to have an
increase of up to 42%.
1.1.6.3 CNT-METAL OXIDES AND MAGNETIC COMPOSITES AS
ADSORBENT
Incorporation of magnetic property in CNTs is another good technique to separate
CNTs from solution. The magnetic adsorbent can be well dispersed in the water
and easily separated magnetically. Magnetic-modified MWCNTs were used for
removal of cationic dye crystal violet (CV), thionine (Th), janus green B (JG),
and methylene blue (MB). To find the optimum adsorption, effect of various pa-
rameters including initial pH, dosages of adsorbent and contact time have been
investigated. The optimum adsorption was found to be at pH 7.0 for all dyes.
In recent work they prepared guar gum grafted Fe
3
O
4
/MWCNTs (GG/MWCNT/
Fe
3
O
4
) ternary composite for the removal of natural red (NR) and methylene blue
(MB). The removal efficiency of cationic dyes using GG/MWCNT/Fe
3
O
4
is high-
er as compared with other adsorbents such as MWCNTs and MWCNT/Fe
3
O
4
. The
higher adsorption capacity of GG/MWCNT/Fe
3
O
4
could be related to the hydro-
philic property of GG, which improved the dispersion of GG-MWCNT-Fe
3
O
4
in the solution, which facilitated the diffusion of dye molecules to the surface of
CNTs. The magnetic GG/MWCNT/Fe
3
O
4
possesses the high adsorption proper-
ties and magnetic separation and can therefore be used as magnetic adsorbents to
remove the contaminants from aqueous solutions. Starch functionalized MWCTs/
iron oxide composite was prepared to improve the hydrophilicity and biocompat-
ibility of MWCNTs. Synthesized magnetic MWCNT-starch-iron oxide was used
as an adsorbent for removing anionic methyl orange (MO) and cationic methylene
blue (MB) from aqueous solutions. MWCNT-starch-iron oxide exhibits super
paramagnetic properties with a saturation magnetization and better adsorption
for MO and MB dyes than MWCNT-iron oxide. The specific surface areas of
MWCNT/iron oxide and MWCNT-starch-iron oxide were 124.86 and 132.59
m
2
/g. However, surface area of the composite was small but adsorption capacity
was higher compared to the parent one, the adsorption capacities of MB and MO
onto MWCNTs-starch-iron oxide were 93.7 and 135.6 mg/g, respectively, while
for MWCNTs-iron oxide were 52.1 and 74.9 mg/g. This is again confirming that
ternary composite has the higher removal capacity than the binary composite and
as grown CNTs. A novel magnetic composite bio adsorbent composed of chi-
tosan wrapping magnetic nanosized γ-Fe
2
O
3
and multi-walled carbon nanotubes
(m-CS/γ-Fe
2
O
3
/MWCNTs) was prepared for the removal of methyl orange. The
adsorption capacity of MO onto m-CS/γ-Fe
2
O
3
/MWCNTs was 2.2 times higher
than m-CS/γ-Fe
2
O
3
. The adsorption capacity of MO onto m-CS/γ-Fe
2
O
3
/MW-
CNTs (66.90 mg/g) was also higher than MWCNTs (52.86 mg/g). Kinetics data
and adsorption isotherm data were better fitted by pseudo second-order kinetic
model and by Langmuir isotherm, respectively. On the comparison of nature of
Search WWH ::
Custom Search