1. The document discusses the use of multi-walled carbon nanotubes (MWCNTs) and graphene nano-sheets for removing dyes. It describes methods for synthesizing MWCNTs using chemical vapor deposition and graphene using Hummers method. 2. Characterization of the materials is discussed including SEM, TEM, XRD, and FTIR which show the morphology, structure, and functional groups of the MWCNTs and graphene. 3. Experiments are described where MWCNTs or graphene are added to solutions of organic dyes at different concentrations and temperatures to test their ability to remove dyes through adsorption.

1. 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

2. 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

3. Classification of CNTs:
Single-wall Carbon nanotubes (SWNTs,1993)
• one graphite sheet seamlessly wrappedup to form a cylinder
• typical radius 1nm, length up to mm

4. 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

5. 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)

6. 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

7. CNTs Production Methods
• Arc discharge
• Laser ablation
• Chemical Vapor Deposition
(CVD)

9. 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

10. 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

11. 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

12. 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...''

13. Allotropes of Carbon
Graphene
And
Diamond, graphite, lonsdalerite, C60, C70,
carbon, amorphous carbon, carbon nanotube

14. 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”

15. What is Graphene?
Graphene: A Honeycomb Lattice

16. 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)

17. 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
4. Other processes
(5)
– Hydrazine Reduction
– Sodium Reduction of Ethanol
– CVD (4)

18. • Transistors
• Sensors
• TEM
• Inert Coatings
• Nanoribbons and Semiconductors
• Integrated circuits
• Ultracapacitors
• Biodevices (6)

20. 1- Preparation of Fe-Co/CaCO3
catalyst/support:
1- The support material
(CaCO3)
2- Fe(NO3)3·9H2O +
Co(NO3)2·6H2O +
milled CaCO3
3- The produced
fine powder
Ball milled
10 hrs
Ball milled
2 hrs
dispersed in a few drops of water and
mixed well to get a homogeneous paste
dried in oven at 120oC for 12 hrs
4- The paste
cooled and ground well to obtain a fine powder of
Fe-Co/CaCO3 catalyst/support mixture

21. Influence of reaction time and temperature
on Carbon yield and morphology
400
oC
Balance
Purification
tower
Kanthal wire
500 oC
Alumina tube
Tube furnace
600 oC
700 oC
800
oC
C2H2
Kanthal basket
CO
C2H2
Flo
CO
w
Mass flow
controller
Gas
regulator
C % = [W3 – (W1 – W2) / (W1 – W2)]*100
W is the initial weight of the catalyst (Fe Co ),
Fig. 12.1: Schematic diagram for the -reaction system
W2 is the weight loss of catalyst at operating temperature,
W3 is the weight of carbon deposited and catalyst.
N2

22. 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.

23. 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 refluxed
(3:1 by volum)
the reaction mixture is
diluted with distilled water
filtered through
a filter paper
(3 μm porosity)
washing
oil bath
for 4 hrs
at 120 °C
cooling to room
temperature
drying at 100 °C.

24. As-growing CNTs
Acid treated
Functionalized
HOOC
COOH
C=O
O=C
OH
HO
COOH
HOOC
COOH
Inner pores blocked
Catalyst removed
Adsorption
increased
Functional group added
For nonpolar and/ or planer
chemicals: Adsorption decreased.
For polar chemicals : Adsorption
increased.
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.

25. 6. Effect of acid treatment on MWCNTs
a
MWCNT
Oxidized MWCNT
Scheme 1: Schematic preparation of the functionalized carbon
nanotubes.
b
Figure 6 : TEM (a) and SEM (b) image of CNTs
synthesized at 600 oC and oxidized in
concentrated acid for 4 hrs.
Figure 8: FTIR spectra of MWCNTs
synthesized at 600 oC and then oxidized in
concentrated acid for 4 hrs.

26. 3. Effect of operating temperature on MWCNTs morphology:
Figure 3 : TEM image of the synthesized
MWCNTs at 600 oC (a) and 700 oC (b).
a
Walls of MWCNT with thickness about 36
nm the inner and outer diameter of the
tube about 28 and 112 nm respectively
b
60 nm
22 nm
15 nm
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.

27. Graphene preparation:
1-Preparation of graphite oxide
2-Preparation graphene
10 g Natural
Graphite
powders
Treated by 5%
HCl twice
temperature was
held at 353 ◦C
for 30 min
filtered, Washed
and dried at 110 ◦C
for 24 h
distilled water (460 mL)
was added slowly to an
increase in temperature
to 98 ◦C
distilled water (1.4 L)
and 30% H2O2 solution
(100 mL) were
added after the reaction
The mixture was
stirred for 40 min
“Hummers method”
“Hummers method”
placed (0 ◦C)
concentrated
H2SO4 (230 mL)
The solution was
Graphite
filtered, washed and
dried at 60 oC 24h
oxide
Graphene
Added to distilled water
and sonicated for 30 min
solution temperature was not
allowed to go up to 20 ◦C
The solution was
the mixture was filtered
held atThe solution was
room temperature
50 µ of
and washed with 5% HCl
for with
treated 24 h microwave
900 W for 3 min “On
and Off”
KMnO4 (30 g) was
added gradually with
stirring and cooling
The reaction product was dried
hydrazine
under vacuum at 50 ◦C for 24 h
hydrate was added

28. 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.

29. Graphene characterizations
SEM of graphene sheets decorated with CoFe2O4 nanoparticles
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.

30. Graphene characterizations
TEM of graphene sheets decorated with CoFe2O4 nanoparticles
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.

31. Organic dyes Removal:

32. Organic dyes Removal:
50 ml of dye solution
dye solution of increased
initial concentrations (C0)
from 50 to 400 mg/L.
5 ml separated
0.05 g oxidized CNTs or graphene was added
equilibrium
(UV-Vis) spectrophotometer (Jasco 530)
temperature control box to
maintain water temperature
(298, 313,323K)

34. X-Ray analysis for Catalyst:
X-ray diffraction pattern for Fe, Co supported on CaCO3.
( 1: CaCO3, 2: Fe2O3, 3: CoO)

35. FTIR spectra for CNTs:
871
a
3369
2916 2848
1428
b
3369
2916 2848
1146
674
596
1704 1569
FTIR spectra of (a) as grown MWNT , (b) acid treated purified MWNT.
HNO3/H2SO4
MWCNT
Oxidized MWCNT
schematic preparation of the functionalized carbon nanotubes.

36. Electron microscope examination for CNTs
TEM for nonoxidized CNTs
TEM for oxidized CNTs

37. Electron microscope examination for CNTs
SEM image of the oxidized CNTs synthesized at 600 oC and refluxed in concentrated acid for 4 hrs.

38. Electron microscope examination for Graphene
SEM of prepared graphene

39. Adsorption studies:
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.
Effects of dye concentration on the adsorption of methyl
green dye (CNTs = 0.1 g/100 ml and T = 298 K).

40. 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).

41. Adsorption Isotherm:
Adsorption isotherms of methyl green
onto Graphene at different
temperature.
Adsorption isotherms of methyl green
onto MWCNTs at different
temperature.

42. 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