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Nanotechnology in Geotechnical Engineering: Benefits and Risks
Amro El Badawy, Ph.D. W.M. Keck Foundation Postdoctoral Fellow
Global Waste Research Institute
CE 381- Fall 2014
Nov 13th, 2014
Scope of Nanotechnology?
• It is all-purpose-technology (no single focus)
• U.S. Agencies involved: • Department of Defense
• Department of Energy
• NASA
• National Institute of Occupational Safety and Health
• National Institute of Standards and Technology
• National Institute of Health
• National Science Foundation
• Industry: large number of world leading industries are investing in nanotechnology
Nanotechnology Is the Transformative Technology of the 21st Century
• In the last 50 years there has been
more technology innovation than in
the previous 5000 years
http://www.petroleumhistory.org/
http://www.walltecno.com/
http://sites.psu.edu/designingthinking/2013/11/23/nanotechnology/
http://www.nanostart.de/en/nanotechnology/tiny-structures-with-a-big-future
What are Nanomaterials?
Nanomaterials (1-100 nm) • 1 nm= 10-9 m • Have high surface area to volume ratio • Highly reactive • Exhibit unique properties compared to their bulk
counterparts
Source: http://www.civil.uwaterloo.ca/cpatt/Symposium%202006/G%20Kennepohl%20Nanotechnology%20for%20Engineers.pdf
http://www.webexhibits.org/causesofcolor/9.html
Gold nanoparticles
Transition from Micro to Nano
• Nanomaterials have significantly high surface area to volume ratio and thus higher reactivity and higher cation exchange capacity as compared to micron size materials
http://www.nano.gov/nanotech-101/special
• Examples of nanomaterials:
• Metals (Ag and Au),
• Metal oxides (TiO2 and ZnO)
• Carbon-based (carbon
nanotubes and fullerenes)
• Shapes of Nanomaterials:
• Spheres, rods, wires, nanotubes,
sheets, and many others
http://www.cfs.gov.hk/english/programme/programme_rafs/files/RA_41_Nanotechnology_and_Food_Safety_Briefing_e.pdf
http://phys.org/news/2013-09-teams-similar-method-non-oxidizing-silver.html
Geo-Denver 2007: New Peaks in Geotechnics
Nanomaterials for Soil Improvement?
http://blog.geotechpedia.com/index.php/category/geotechnical-information-2/
http://www.engineer.ucla.edu/newsroom/featured-news/archive/2011/geotechnical-earthquake-engineer-professor-jonathan-stewart-answers-questions-regarding-his-trip-to-japan-after-the-great-tohoku-earthquake
Soil Stabilization
• Soil stabilization improves soil properties such as durability, permeability, and strength
• Stabilization can be chemical or mechanical or a combination of both
• Chemical stabilization is achieved by changing the chemical make of the soil matrix through addition of polymers, enzymes, cement, NANOMATERIALS and other compounds
• Mechanical stabilization is the reinforcement of soil through mechanical means such as compaction
Examples of Soil Improvement using Nanomaterials
Polypropylene Nanocomposite Improves CH Clay
• Changes in microstructure by addition of nanocomposites leads to changes in clay consistency
• Nanocomposite fill internal voids in clay soil and increase density
• Nanocompoistes can make clay surface hydrophobic-> reduction in liquid limit (LL)
• Nanocompoistes can reduce charge on clay surface -> Reduction in swelling
Alexandria Engineering Journal, 2014, 53(1), 143-150
Polymer Nanocomposite Reduces Atterberg Limits
• Polymer nanocomposite reduced Atterberg limits of CH clay
• Increase soil strength
Alexandria Engineering Journal, 2014, 53(1), 143-150
Polymer Nanocomposite Improves Compaction
• Polymer nanocomposite acted as a nanofiller and improved compaction of clay soil
Alexandria Engineering Journal, 2014, 53(1), 143-150
Polymer Nanocomposite Increases Shear Strength
• Unconfined compression stress–strain behavior:
• Significant increase in peak axial stress with slight decrease in the corresponding strain
• Increased shear strength and cohesion
• Nanocomposites in clay voids increased interconnection between clay particles producing a homogenous compressible isotropic material
Alexandria Engineering Journal, 2014, 53(1), 143-150
Non treated clay: Brittle failure (well-defined shear plane) Treated clay: Plastic failure (buckling)
http://homepage.usask.ca/~mjr347/prog/geoe118/geoe118.036.html
Polymer Nanocomposite Reduces Volumetric Shrinkage
• Addition of nanomaterials considerably reduces the volumetric shrinkage strain of the tested sample
Alexandria Engineering Journal, 2014, 53(1), 143-150
Polymer Nanocomposite Reduces Desiccation Cracks
• Untreated clay specimens left in air: deep and wide cracks formed
• Treated clay samples with polymer nanocomposites significantly reduced the intensity and depth of desiccation cracks without decreasing hydraulic conductivity of the clay
• Minimization of surface cracking of landfill clay covers is critical
Silica Nanoparticles Reduce Clay Swelling
Source: J Nanopart Res (2014) 16:2137
Carbon Nanotubes in Clay
Source: http://www.damascusfortune.com/uploads/9/6/6/3/9663001/1340304820.png http://wjoe.hebeu.edu.cn/sup.2.2010/T/Taha,%20M.R.%20(U.%20Kebangsaan%20Selangor,%20Malaysia)%20721.pdf
Capacity for water is higher with the addition of nanotubes (more water can be taken inside the tubes)
Increase LL -> Higher capacity for water -> Reduced strength and increase compressibility (settlement)
Increased PI means reduction in hydraulic conductivity (good for landfill clay covers and liners)
Geo-environmental Improvement of Soil Using Nanomaterials
• Nanomaterials can be used for:
• Improving Cation Exchange Capacity (good from contaminant standpoint, for example in landfill liners)
• Nanomaterials for soil remediation
Challenges of Using Nanomaterials for Soil Improvement
• COST of nanomaterials is high
• Potential environmental and health risks of nanomaterials
Potential Risks of Nanomaterials?
• It depends on many factors (type of ENMs, dose, etc.)
• Toxic effects of nanomaterials has been reported on: • Bacteria
• Archea
• Algae
• Marine Species
• Earthworms
• Soil Microbes
• Plants
• Fish
• Animals and Humans
Are Nanomaterials Toxic?
Anthony, et al. 2013, Journal of Industrial and Engineering Chemistry, In Press
Science of the Total Environment, 2014, 466-467, 232-241
• Toxicity of AgNPs to Bacillus marisflavi
Nanomaterials Toxicity
• Abnormalities in zebra fish embryos exposed to AgNPs
• Toxic impacts of nanomaterials have been widely reported on a wide spectrum of living species
http://phys.org/news/2014-03-peril-nanotechnology.html
• YES
• Evidence: • Laboratory studies
• Real environmental samples
Will Nanomaterials Reach the Environment
How Much?
Transport in Natural Environment
Chemosphere 2012, 88, 670-675
How Nanomaterials Are Made?
Example: Bottom Up Technique
• For example, the synthesis of silver nanoparticles:
• Solvent
• Salt precursor
• Reducing agent
• Stabilizing agent
J. Mater. Chem., 2011, 2991-2996
• Charge is not the only way to stabilize
nanomaterials
• Stabilization Mechanisms for nanomaterials:
• Electrostatic (charge)
• Steric (uncharged polymers)
• Electrosteric (cationic and anionic
polymers)
Other Stabilization Mechanisms
http://uniqchem.com/?page_id=409
http://de.academic.ru/dic.nsf/dewiki/339576
Electrostatic
Steric
Electrosteric
1- Properties of Nanomaterials
2- Surrounding Conditions
• pH, ionic strength, background electrolyte valence
• Oxygen (redox conditions)
• Light
• Temperature
• Presence of macromolecules (e.g., natural organic matter)
• Presence of bio-macromolecules (e.g., proteins and polysaccharides)
• Presence of certain chemical species such as ammonia, chlorides and reduced sulfur species
• Soil chemistry and the presence of microbes
Factors Governing Transport and Toxicity of Nanomaterials
Nanomaterials properties + Surrounding conditions
Transformations of nanomaterials
Determine the exposure, fate, transport and toxicity of nanomaterials
Nanomaterials Transformations
• Physical Transformations (e,g., aggregation)
• Chemical Transformations (e.g., oxidation, sulfidation, adsorption of macromolecules, and dissolution)
• Biological Transformations (e.g., adsorption of proteins and polysaccharides)
Citrate-AgNPs
pH
pH7 3 6 9
HD
D (
nm
)
1
10
100
1000
Zet
a P
ote
nti
al (
mV
)
-50
-40
-30
-20
-10
0
As Prepared
PVP-AgNPs
pH
pH8.5 3 6 9
HD
D (
nm
)
1
10
100
1000
Zet
a P
ote
nti
al (
mV
)
-50
-40
-30
-20
-10
0
Polyvinylpyrrolidone-coated AgNPs
Citrate-coated AgNPs
Environ. Sci. Technol., 2010, 44 (4), pp 1260–1266
• Same NMs having different coatings act differently under acidic conditions
Pore Volume
1 10 100 1000
C/C
0
0.0
0.2
0.4
0.6
0.8
1.0
QS
FcS
KcS
Citrate-AgNPs
No Humic Acid
Blocking Effect
Straining
Conservative
Pore Volume
1 10 100 1000
C/C
0
0.0
0.2
0.4
0.6
0.8
1.0QS-HA
FcS-HA
KcS-HA
ADE-Model
Citrate-AgNPs
Environ. Sci. Technol. 2013, 47, 4039−4045
No Humic Acid
With Humic Acid
Same NMs with same coating behave different in different soils Same NMs, same coating, same soil but adding humid acid change behavior
Regulations
• Currently, nanotechnology is not regulated because of the lack of sufficient data on their environmental and health impacts
Summary
Sustainable Development of Nanotechnology is the Key
Acknowledgement
This lecture is part of an educational project “ Exploring Emerging Waste Streams Created by Advances in Technology: Bringing Real World Issues into the Undergraduate STEM curriculum at Cal Poly, San Luis Obispo” implemented by the Global Waste Research Institute at Cal Poly and funded by W.M. Keck Foundation