14-17 October 2008 The Fifth Eurasian Conference
CARBON NANOTUBES FOR
CARBON NANOTUBES FOR
POTENTIAL APPLICATIONS IN THE
POTENTIAL APPLICATIONS IN THE
FIELD OF NUCLEAR WASTE
FIELD OF NUCLEAR WASTE
MANAGEMENT
MANAGEMENT
Ceren Kütahyalı
Ceren Kütahyalı11, Fabio Belloni, Berkan Çetinkaya, Fabio Belloni, Berkan Çetinkaya11, , JoaquínJoaquín Cobos, Vincenzo V. Cobos, Vincenzo V.
Rondinella
Rondinella
1Ege University Institute of Nuclear Sciences, 35100 Bornova, Izmir, Turkey
European Commission, Joint Research Centre, Institute for Transuranium Elements P.O. Box 2340, 76125 Karlsruhe, Germany
Outline
•
Carbon nanotubes definitions and main features•
Nuclear fuel cycle and (potential) nanotubes applications•
Adsorption experiments 14-17 October 200814-17 October 2008
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Discovery
What are Carbon Nanotubes?
“In June, 1991, I found an extremely thin needle-like material when examining carbon materials under an electron microscope. Soon thereafter the material was proved to have a graphite structure basically, and its details were disclosed. I named these materials "carbon nanotubes" since they have a tubular structure of carbon atom sheets, with a thickness scaled in less than a few nanometers. The name has been widely accepted now. Carbon nanotubes have attracted a lot of researchers in a wide range of fields from academia to industry, not only because of their uniqueness when compared with conventional
materials, but also because they are very promising materials in nanotechnology in future technology.”
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•
Carbon nanotube is a new carbon allotrope•
A tubular form of carbon with diameter as small as 1nm. Length: few nm to microns.•The cylinders are typically closed at their ends by semi-fullerene-like structures.
•
Discovered in 1991 by Dr. Sumio Iijima•
Its unique and promising properties have attracted the attention of researcher around the worldWhat are Carbon Nanotubes?
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What are Carbon Nanotubes?
Carbon nanotubes (CNTs) have extraordinary properties:
electrical mechanical optical
thermal chemical
Nanotubes are formed by
rolling up a graphene sheet into a cylinder and capping each end with half of a fullerene molecule. Depending on how the graphene plane is 'cut' before rolled up, the three types of carbon nanotubes are obtained.
The diameter of the nanotubes depends on the values of n and
m.
If n=0, the nanotubes are called zigzag. If n=m, the
nanotubes are called armchair. Otherwise, they are called
chiral.
What are Carbon Nanotubes?
http://www.wikipedia.org
3D model of three types of single-walled carbon
nanotubes.
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Types of CNTs
Single Wall CNT (SWCNT)
made by rolling up a single graphite sheet to a narrow but long tube
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(Iijima, Nature, 354, 56, 1991)
Multi Wall CNT (MWCNT)
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MWCNT
High-resolution TEM image of a MWCNT
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• Novel electronic properties.
• High electrical and thermal conductivity. • Excellent chemical and thermal stability. • High chemical storage capacity.
• Tensile strength and elastic modulus (CNTs are the strongest and stiffest material presently known) • Sorption capacity (Large surface area, >600 m2/g)
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• Telecommunication, cell phones • Batteries
• Medical image equipment • Computer display
• Multi-functional composites for aircraft • Materials science
• Micro-electronics • Nano electronics • Supercapacitors
• Conducting composites
• Nanotube reinforced composites • Chemical processing
• Gas storage
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Fabrication routes of CNT
Many different ways to make nanotubes Chemical vapor deposition
Arc discharge Laser ablation Catalytic growth
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Introduction I
Due to their highly porous and hollow structure, large specific surface
area, light mass density and strong interaction between carbon and
hydrogen molecules, CNTs have been applied as sorbents for gases by many researchers.
CNT adsorption and retention properties make this material a promising
candidate for applications in:
environmental remediation,
treatment of liquid effluents from nuclear plants,
conditioning/immobilization of fission products and actinides. Superior sorbent for dioxin removal
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Functionalization of modification of carbon nanotubes has attracted
increasing attention over the past years.
To achieve this, it is essential to be able to functionalize the carbon
nanotubes with chemical groups.
Carboxylate groups have been introduced onto the surface of carbon
nanotubes by reaction with strong oxidizing agents such as HNO3.
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Studies concerning application of CNTs for radionuclide adsorption are
scarce. Only a few studies reported adsorption of Th, Am and Eu on MWCNTs:
- Wang et al. examined the use of uncapped MWCNTs as adsorbents for radionuclide 243Am(III).
- Chen et al. , investigated the adsorption of Th(IV) on oxidized MWCNTs.
- Tan et al. (9), studied the use of MWCNTs as adsorbents for radionuclide152+154Eu(III).
Introduction III
Wang, X.; Chen, C.; Hu, W.; Ding, A.; Xu, D.; Zhou, X. Environ. Sci. Technol. 2005, 39, 2856-2860. Chen, C.; Li, X.; Zhao, D.; Tan, X.; Wang, X. Colloids Surf., A 2007, 302, 449-454.
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Aim of the present campaign
The aim of the work is to discuss potential applications of CNTs in the
field of nuclear waste management.
Carbon nanotubes may have great potential use as an effective
adsorbent for radioactive solutions.
Nuclear Fuel Cycle
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Some conventional methods for removing heavy metals,
radionuclides and lanthanides from aqueous solutions,
Adsorption Ion exchange Coagulation Floatation Chemical precipitation Reverse osmosis
Removal of long lived radionuclides from nuclear waste solutions is
an important environmental concern in nuclear waste management.
CNT and Nuclear Fuel Cycle
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Experimental characterization of CNT
Multiwalled carbon nanotubes (Sigma-Aldrich)
20-30 nm outer and 5–10 nm inner diameter with length 0.5-200 µm, Surface area of 40–600 m2/g
Purity above 95%.
Modification of the surface with HNO3 (8 M HNO3) Functional groups generation on the surface Adsorption experiments
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Modification of The Surface
CNT 8 M HNO3, 16h, room temp Filtered, 0.1 µm membrane filter Washing
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In adsorption experiments
50 mg of MWCNTs were mixed with 10 mL of metal ion solution. The initial metal concentration was 10 mg L-1.
The mixture was shaken in an orbital shaker at room temperature.
After 4 h shaking, solutions were filtered through 0.45 µm membrane filters metal concentration in the aqueous solutions was determined by ICP-OES.
The amounts of metal ions adsorbed on MWCNTs were calculated as
the difference between initial and final concentration at equilibrium.
m
V
)
C
C
(
q
0
e (mg/g)Adsorption tests
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• 50 mg of MWCNTs
• Initial metal concentration: 10 mgL-1
• orbital shaker at RT • 4 h shaking time
Results
Effect of acid treatment on adsorption
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pH effect
•Initial Sr concentration: 10 mgL-1 •Amount of the adsorbent: 50 mg •Room temperature
•4 h shaking time Effect of initial pH
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• Initial Sr concentration: 10 mg L-1
• amount of the adsorbent: 50 mg • room temperature
• pH 10
Stirring effect
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• Initial Sr concentration: 10 mg L-1
• amount of the adsorbent: 50 mg • pH 10
Effect of temperature
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G° (kj/mol)
H° (kj/mol) S°(kj/molK) 296K 303K 323K 333K 343K
4,701 0,068 -15,39 -15,86 -17,22 -17,90 -18,59
H positive and G negative Endothermic and spontaneous
Effect of temperature
Thermodynamic considerations
RT H R S K ln d 0 0 0 0 0 S G 14-17 October 2008
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Langmuir Isotherm Freundlich Isotherm
Adsorption isotherms
m e m e e n C bn q C 1 Ce: equilibrium concentration (mg/L), qe: amount absorbed at equilibrium (mg/g) nm:monolayer capacity b: energy of adsorption n / e e KC q 1q: amount of solute adsorbed per mass unit
adsorbent
C: equilibrium concentration K and n: Freundlich constants
Freundlich Constants Langmuir Constants
R2 n K R2 n
m (mg/g) b (L/mg)
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Conclusions
•CNTs adsorption and retention properties make this material a promising candidate for
applications in environmental remediation, e.g. treatment of liquid effluents from nuclear plants, and conditioning / immobilization of fission products and actinides.
•Preliminary results showed that their application on the nuclear waste management deserves further studies, particularly with respect to sorption and retention capacity of fission products and actinides
•Impregnated CNTs and CNT composite materials can be investigated for increasing the adsorption capacity and selectivity for the special radionuclides.
•Radiation damage and structural stability will be examined.
•MWCNTs can be a promising candidate for pre-concentration and solidification of some
lanthanides and actinides from large volumes of aqueous solution, as required for remediation purposes.
Thank you very much for your attention…
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