Environmental Engineering Reference
In-Depth Information
in the composite, while it decreased with increasing solution pH. Based
on the Langmuir isotherm, the maximum equilibrium adsorption capacity
of Methyl Orange was 14.13 mgg -1 . Recently, Bhagat et al. [100] prepared
NiFe 2 O 4 /MWCNT composite materials for removal of Toluidine Blue. The
amount of dye adsorbed increased with NiFe 2 O 4 /MWCNT dosage. he
activation energy of the adsorption process calculated using the Arrhenius
equation suggested that adsorption of Toluidine Blue onto NiFe 2 O 4 /CNTs
involved physisorption.
In order to resolve the aggregation and dispersion problem of CNTs,
Wa n g et al. [101] prepared CNTs/activated carbon fabric (CNTs/ACF)
composite and tested its efficacy for the removal of Basic Violet 10 from
aqueous solutions. The experimental data obtained showed that the dye
uptake process was very fast and could be well characterized by three
different types of isotherm models: Freundlich, Langmuir, and Dubinin-
Radushkevich. The maximum monolayer adsorption of Basic Violet 10
onto CNTs/ACF was 220 mgg -1 .
The incorporation of magnetic property in CNTs is another useful
approach to separate CNTs from test solutions. The magnetic adsor-
bent can be well dispersed in the aqueous environment and can also
be easily separated magnetically. Madrakian et al. [105] developed
magnetic-MWCNTs, by depositing Fe 2 O 3 nanoparticles onto MWCNTs,
for removal of cationic dyes Thionine, Crystal Violet, Janus Green B and
Methylene Blue. Batch adsorption experiments were conducted to study
the effect of different operating parameters including initial pH, adsorbent
dosage and contact time on the dye uptake process. Optimum adsorption
occurred at pH 7.0 for all the dyes. The maximum monolayer adsorption
capacities for Crystal Violet, Thionine, Janus Green B and Methylene Blue
dyes were calculated as 227.7, 36.63, 250.0, and 48.08 mg g -1 , respectively.
Desorption studies were conducted by washing the spent adsorbent with
different eluents such as methanol, N,N-dimethyl formamide and aceto-
nitrile. For all the studied dyes, the desorption equilibrium time was 2
min and the desorption efficiency was found in the order: methanol <
N,N-dimethyl formamide < acetonitrile. After five successive cycles, no
change in the adsorption behavior was observed. It was therefore rec-
ommended that magnetic MWCNTs could be used as a good reusable
and economical adsorbent for treatment of colored effleunts. Magnetic
MWCNTs have also been identified as a suitable adsorbent for removal of
Brilliant Cresyl Blue [106], Methylene Blue [103,104,106], Methyl Orange
[102], and Neutral Red [104,106] by several other researchers.
Also, a number of ternary nanocomposites have also been devel-
oped and tested for the decoloration of textile effluents. Gao et al. [107]
Search WWH ::




Custom Search