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

aelbadaw@calpoly.edu amrelbadawy@yahoo.com