Post on 12-Nov-2014
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MULTI WALLED CARBON NANOTUBES
(MWCNT) & GRAPHENE NANO-SHEETS
FOR DYES REMOVAL
M. H. Khedr, A. A. Fargali M. Bahgat and W.M.A.EL Rouby
Beni-Suif University
What are carbon nanotubes?
• Tubes with walls made of carbon (graphite) Nanometers
in diameter
• Up to tens of micrometers
in height
• Extremely good strength and
field emission properties
Roll up
Classification of CNTs:
Single-wall Carbon nanotubes (SWNTs,1993)
• one graphite sheet seamlessly wrapped-
up to form a cylinder
• typical radius 1nm, length up to mm
Classification of CNTs:
Ropes • Ropes: bundles of SWNTs
– triangular array of individual SWNTs
– ten to several hundreds tubes
– typically, in a rope tubes of different
diameters and chiralities
Classification of CNTs:
Multiwall nanotubes (Iijima 1991)
• russian doll structure, several inner
shells
•typical radius of outermost shell > 10
nm
(From Iijima, Nature 1991) (Copyright: A. Rochefort, Nano-CERCA, Univ. Montreal)
CNTs Current Applications
•Technological applications – conductive and high-strength
composites – energy storage and conversion
devices – sensors, field emission displays – nanometer-sized molecular
electronic devices
• Pipe
• Wires
• Springs
• Gears
• Pumps
CNTs Production Methods
• Arc discharge
• Laser ablation
• Chemical Vapor Deposition
(CVD)
Arc–Discharge Process
• High-purity graphite rods
under a helium
atmosphere.
• T > 3000oC
• 20 to 40 V at a current in
the range of 50 to 100 A
• Gap between the rods
approximately 1 mm or
less
• Lots of impurities:
graphite, amorphous
carbon, fullerenes
Arc-discharge apparatus
Laser Ablation Process
• Temperature 1200oC
• Pressure 500 Torr
• Cu collector for carbon
clusters
• MWNT synthesized in
pure graphite
• SWNT synthesized
when Co, Ni, Fe, Y are
used
• Laminar flow
• Fewer side products
than Arc discharge but
still high temperature
Laser ablation apparatus
Chemical Vapor Deposition (CVD)
• Catalysts: Fe, Ni, Co, or alloys of the three metals
• Hydrocarbons: CH4, C2H2, etc.
• Temperature: First furnace 1050oC
Second furnace: 750oC
• Advantages:
Higher production of CNTs High Purity
Fewer by-Products Low Temperature
What is Graphene?
• “Imagine a piece of paper but a million times thinner. This is how thick graphene is.
• Imagine a material stronger than diamond. This is how strong graphene is [in the plane].
• Imagine a material more conducting than copper. This is how conductive graphene is.
• Imagine a machine that can test the same physics that scientists test in, say, CERN, but small enough to stand on top of your table. Graphene allows this to happen.
• Having such a material in hand, one can easily think of many useful things that can eventually come out. As concerns new physics, no one doubts about it already...''
Allotropes of Carbon
Diamond, graphite, lonsdalerite, C60, C70,
carbon, amorphous carbon, carbon nanotube
And Graphene
What is Graphene?
• Is a 2D structure and 1
atom thick
• Hexagonal array of sp2
carbon atoms.
– Sigma orbital = valence
band
– Pi orbital = conduction
band (2)
• C-C bond is 120° and ~
0.142nm bond length
• Is electrically “metallic”
What is Graphene?
Graphene: A Honeycomb Lattice
Types of Graphene:
• Theoretical graphene (1947 -present)
• Mechanically exfoliated/cleaved graphene (1997-2004)
• Epitaxially grown graphene (1986-2004)
• Chemically exfoliated and intercalated graphene (c.1980-2004)
• Chemical decomposition graphene (1997-still under development)
1. Drawing – mechanical exfoliation of 3D graphite crystals
2. Epitaxial growth – use of the atomic structure of substrate to grow graphene
3. Silicon Carbide Reduction – heating of silicon carbide to 1100C and reduce it to form graphene (5)
4. Other processes
– Hydrazine Reduction
– Sodium Reduction of Ethanol
– CVD (4)
• Transistors
• Sensors
• TEM
• Inert Coatings
• Nanoribbons and Semiconductors
• Integrated circuits
• Ultracapacitors
• Biodevices (6)
1- Preparation of Fe-Co/CaCO3
catalyst/support:
1- The support material
(CaCO3) Ball milled
10 hrs
2- Fe(NO3)3·9H2O +
Co(NO3)2·6H2O +
milled CaCO3
Ball milled
2 hrs
4- The paste dried in oven at 120oC for 12 hrs
3- The produced
fine powder
dispersed in a few drops of water and
mixed well to get a homogeneous paste
cooled and ground well to obtain a fine powder of
Fe-Co/CaCO3 catalyst/support mixture
Mass flow
controllerGas
regulator
CO
CO
N2
Purification
towerKanthal wire
Balance
Alumina tube
Tube furnace
Kanthal basket
Fig. 2.1: Schematic diagram for the reaction system
Mass flow
controllerGas
regulator
CO
CO
N2
Purification
towerKanthal wire
Balance
Alumina tube
Tube furnace
Kanthal basket
Mass flow
controllerGas
regulator
CO
CO
N2
Purification
tower
Mass flow
controllerGas
regulator
CO
CO
N2
Purification
tower
Mass flow
controllerGas
regulator
CO
CO
N2
Purification
tower
CO
CO
N2
Purification
tower
CO
N2
COCO
N2
Purification
towerKanthal wire
Balance
Alumina tube
Tube furnace
Kanthal basket
Fig. 2.1: Schematic diagram for the reaction system
C2H2
Flo
w
C2H2
C % = [W3 – (W1 – W2) / (W1 – W2)]*100 W1 is the initial weight of the catalyst (Fe - Co ),
W2 is the weight loss of catalyst at operating temperature,
W3 is the weight of carbon deposited and catalyst.
Influence of reaction time and temperature
on Carbon yield and morphology
400 oC
500 oC
600 oC
700 oC
800 oC
2. Influence of reaction time and temperature on Carbon yield:
Figure 2: Effect of growing
time on the deposited
carbon percent during
acetylene decomposition
over Fe- Co /CaCO3
catalyst/support at
different temperatures
(400-800 oC)
M. Bahgat, M. Khedr and M. Shaaban, Materials Technology: Advanced Performance Materials, 2008, 23, 13-18.
M. Bahgat, M. Khedr, M. Radwan and M. Shaaban, Mineral Processing and Extractive Metallurgy, 2007, 116, 217-220.
4. CNTs Purification:
purification process was achieved by using chemical oxidation method.
Specific amount
of the as-grown
carbon nanotubes
added to mixture of conc.
HNO3 &H2SO4
(3:1 by volum)
refluxed oil bath
for 4 hrs
at 120 °C
cooling to room
temperature the reaction mixture is
diluted with distilled water
filtered through
a filter paper
(3 μm porosity)
washing drying at 100 °C.
For nonpolar and/ or planer
chemicals: Adsorption decreased.
For polar chemicals : Adsorption
increased.
Adsorption
increased
O=C
HO
HOOC
COOH
OH
C=O
COOH HOOC
COOH
As-growing CNTs Acid treated Functionalized
Inner pores blocked Catalyst removed Functional group added
The effect of CNT functional groups on organic molecule adsorption
M. H. Khedr, A. A. Farghali and A. Abdel-Khalek, Journal of analytical and applied pyrolysis, 2007, 78, 1-6.
A. A. Farghali, M. H. Khedr and A. A. Abdel Khalek, Journal of materials processing technology, 2007, 181, 81-87.
6. Effect of acid treatment on MWCNTs
a
b
Figure 6 : TEM (a) and SEM (b) image of CNTs
synthesized at 600 oC and oxidized in
concentrated acid for 4 hrs.
MWCNT Oxidized MWCNT
Scheme 1: Schematic preparation of the functionalized carbon
nanotubes.
Figure 8: FTIR spectra of MWCNTs
synthesized at 600 oC and then oxidized in
concentrated acid for 4 hrs.
3. Effect of operating temperature on MWCNTs morphology:
a
15 nm
60 nm
22 nm
b
Figure 3 : TEM image of the synthesized
MWCNTs at 600 oC (a) and 700 oC (b).
Walls of MWCNT with thickness about 36
nm the inner and outer diameter of the
tube about 28 and 112 nm respectively
Internal diameters of approximately
12–15 nm and external diameters of
55–60 nm.
M. Bahgat, M. Khedr and S. Abdel-Moaty, Materials Technology: Advanced Performance Materials, 2007, 22, 139-146.
M. Bahgat and M. Khedr, Materials Science and Engineering: B, 2007, 138, 251-258.
Graphene preparation:
1-Preparation of graphite oxide “Hummers method” 10 g Natural
Graphite
powders
The mixture was
stirred for 40 min
Treated by 5%
HCl twice
placed (0 ◦C)
concentrated
H2SO4 (230 mL)
KMnO4 (30 g) was
added gradually with
stirring and cooling
solution temperature was not
allowed to go up to 20 ◦C
distilled water (460 mL)
was added slowly to an
increase in temperature
to 98 ◦C
temperature was
held at 353 ◦C
for 30 min
The solution was
held at room temperature
for 24 h
filtered, Washed
and dried at 110 ◦C
for 24 h
distilled water (1.4 L)
and 30% H2O2 solution
(100 mL) were
added after the reaction
the mixture was filtered
and washed with 5% HCl
The reaction product was dried
under vacuum at 50 ◦C for 24 h
Graphite oxide
2-Preparation of graphene “Hummers method”
Added to distilled water
and sonicated for 30 min
50 µ of hydrazine
hydrate was added
The solution was
treated with microwave
900 W for 3 min “On
and Off”
The solution was
filtered, washed and
dried at 60 oC 24h
Graphene
Graphene characterizations
SEM of graphene sheets prepared by hummer method
M. Bahgat, A. Farghali, W. El Rouby and M. Khedr, Journal of analytical and applied pyrolysis, 2011, 92, 307-313.
A. Farghali, M. Moussa and M. Khedr, Journal of alloys and compounds,2010, 499, 98-103.
SEM of graphene sheets decorated with CoFe2O4 nanoparticles
Graphene characterizations
M. Khedr, A. Farghali, A. Moustafa and M. Zayed, International Journal of Nanoparticles, 2009, 2, 430-442.
M. Khedr, K. Abdel Halim and N. Soliman, Materials Letters, 2009, 63, 598-601.
TEM of graphene sheets decorated with CoFe2O4 nanoparticles
Graphene characterizations
M. Bahgat, A. Farghali, W. El Rouby and M. Khedr, Journal of analytical and applied pyrolysis, 2011, 92, 307-313.
A. Farghali, M. Moussa and M. Khedr, Journal of alloys and compounds,2010, 499, 98-103.
Organic dyes Removal:
0.05 g oxidized CNTs or graphene was added 50 ml of dye solution dye solution of increased
initial concentrations (C0) from 50 to 400 mg/L.
temperature control box to
maintain water temperature
(298, 313,323K) equilibrium 5 ml separated
(UV-Vis) spectrophotometer (Jasco 530)
Organic dyes Removal:
X-ray diffraction pattern for Fe, Co supported on CaCO3.
( 1: CaCO3, 2: Fe2O3, 3: CoO)
X-Ray analysis for Catalyst:
FTIR spectra for CNTs:
a
b
FTIR spectra of (a) as grown MWNT , (b) acid treated purified MWNT.
HNO3/H2SO4
MWCNT Oxidized MWCNT
schematic preparation of the functionalized carbon nanotubes.
3369
3369
1569 1704 1146 674 596
871
1428 2916
2916
2848
2848
Electron microscope examination for CNTs
TEM for nonoxidized CNTs TEM for oxidized CNTs
SEM image of the oxidized CNTs synthesized at 600 oC and refluxed in concentrated acid for 4 hrs.
Electron microscope examination for CNTs
Electron microscope examination for Graphene
SEM of prepared graphene
Adsorption studies:
Effects of dye concentration on the adsorption of methyl
green dye (CNTs = 0.1 g/100 ml and T = 298 K).
The amount of dye
adsorbed per unit of CNT
mass increased as initial
dye concentration
increased due to the
increase in the driving
force of the concentration
gradient for mass transfer
with the increase in initial
dye concentration.
Adsorption studies:
Effects of CNTs dosage on the adsorption of methyl green dye
(dye concentration = 4.36 x 10-5 M and T = 298 K).
Adsorption Isotherm:
Adsorption isotherms of methyl green
onto MWCNTs at different
temperature.
Adsorption isotherms of methyl green
onto Graphene at different
temperature.
Electron microscope examination for CNTs
• The adsorption capacity of methyl green onto MWCNTs and
Graphene nano-Sheets
298 K 313 K 323 K
MWCNTs 119.05 mg/g-1 160.12 mg/g-1 181.2 mg/g-1
Graphene 203.51 mg/g-1 258.39 mg/g-1 312.80 mg/g-1