Preparation of this fact sheet has been funded by the U.S. Environmental Protection Agency (EPA) under Contract Number 68-W07-078. Information in the fact sheet is derived from numerous sources (including personal communications with experts in the 

field), some of which have not been peer-reviewed. The fact sheet has undergone EPA and external review by subject-matter 

experts. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. 

United States Solid Waste and EPA 542-F-08-009 

Environmental Protection Emergency Response October 2008 

Agency (5203P) www.epa.gov

http://cluin.org

Nanotechnology for Site Remediation 

Fact Sheet 

INTRODUCTION

This fact sheet presents a snapshot of 

nanotechnology and its current uses in 

remediation. It presents information to help site 

project managers understand the potential 

applications of this group of technologies at their 

sites. The fact sheet also identifies contacts, 

such as vendors or project managers with field 

experience, to facilitate networking. 

Nanotechnology is still relatively in its infancy 

but it is rapidly evolving. It holds promise in 

remediating sites cost effectively and addressing 

challenging site conditions, such as the 

presence of dense nonaqueous phase liquids 

(DNAPL). For example, nanoscale iron is in use 

in full-scale projects with encouraging success. 

Ongoing research at the bench- and pilot-scale 

is investigating particles such as self-assembled 

monolayers on mesoporous supports 

(SAMMSTM), dendrimers, carbon nanotubes, 

and metalloporphyrinogens to determine how to 

apply their unique chemical and physical 

properties for full-scale remediation. There are 

many unanswered questions regarding 

nanotechnology. Further research is needed to 

understand the fate and transport of free 

nanoparticles in the environment, whether they 

are persistent, and whether they have 

toxicological effects on various biological 

systems. 

This fact sheet includes information on sites 

where nanoscale iron has been tested for site 

remediation. Because many of the remediation 

projects using nanoparticles are just beginning 

or are ongoing, there are limited cost and 

performance data at this point. In addition, due 

to proprietary concerns, information about cost 

is often not made publicly available. However, 

as the technology is applied at an increasing 

number of sites with varying geologies, more 

data will become available on performance and 

cost, providing site managers and other 

stakeholders additional information to determine 

whether the technology might be applicable to 

their sites. 

The following topics are covered in this fact 

sheet: 

• Background 

• Description of Nanoparticles Used in 

Site Remediation 

• Description of Nanomaterials with 

Potential Remediation Applications 

• Chemistry of Selected Nanoparticles 

• In situ Application of Nanoparticles 

• Limitations 

• Fate, Transport, and Toxicity Questions 

• Performance and Monitoring 

• Cost 

• List of Identified Vendors for 

Nanotechnology 

• Selected Sites Using or Testing 

Nanoparticles for Remediation 

Other potential environmental applications of 

nanotechnology are not addressed in this fact 

sheet.

BACKGROUND 

The definition of nanotechnology is multifaceted. 

For the purposes of this fact sheet, it is defined 

as the understanding and control of matter at 

dimensions between approximately 1 and 100 

nanometers, where unique phenomena enable 

novel applications (NNI, 2008). Figure 1 shows 

a micrograph of a nanowire compared to a 

human hair. Nano-sized particles have large 

surface areas relative to their volumes and may 

have enhanced chemical and biological 
2 

reactivity (U.S. EPA, 2007). They can be 

manipulated for specific applications to create 

novel properties not commonly displayed by 

particles of the same material at macroscale. 

Nanoparticles may be produced via a “top down” 

approach, such as milling or grinding of 

macroscale material, or, most commonly, via a 

“bottom up” approach, such as the chloride 

synthesis method, which creates nanoparticles 

from component atoms or molecules (Lien, 

2006; U.S. EPA, 2007). 

Figure 1. Micrograph of a looped nanowire 

against the backdrop of a human hair (Mazur 

Group, Harvard University, 2008)

An increasing variety of nanomaterials with 

environmental applications have been 

developed over the past several years. For 

example, NanoScale Corporation is marketing 

its product, FAST-ACT®, as a chemical 

containment and neutralization system that first 

responders can use to clean up toxic chemical 

releases of industrial chemicals or chemical 

warfare agents (NanoScale, 2008). A group of 

researchers at the Massachusetts Institute for 

Technology (MIT) have developed a “paper 

towel” for oil spills that is comprised of a 

membrane or mat of potassium manganese 

nanowires. According to the researchers, the 

nanowire membrane selectively absorbs oil with 

high efficiency. The oil can be recovered by 

heating the mat, which can then be reused. The 

membrane, which appears to be impervious to 

water, may have additional uses in water 

filtration (Thomson, 2008). 

Nanomaterials have also been used to 

remediate contaminated groundwater and 

subsurface source areas of contamination at 

hazardous waste sites. Early treatment 

remedies for groundwater contamination were 

primarily pump-and-treat operations. Because 

of the relatively high cost and often lengthy 

operating periods for these remedies, the use of 

in situ treatment technologies is increasing. 

Since the early 1990s, site project managers 

have taken advantage of the properties of 

metallic substances such as elemental iron to 

degrade chlorinated solvent plumes in 

groundwater. One example of an in situ 

treatment technology for chlorinated solvent 

plumes is the installation of a trench filled with 

macroscale zero-valent iron to form a permeable 

reactive barrier (PRB) (ITRC, 2005). 

Recent research indicates that nanoscale zerovalent iron (nZVI) may prove more effective and 

less costly than macroscale ZVI under similar 

environmental conditions. For example, in 

laboratory and field-scale studies, nZVI particles 

have been shown to degrade trichloroethene 

(TCE), a common contaminant at Superfund 

sites, more rapidly and completely than larger 

ZVI particles. Also, nZVI can be injected directly 

into a contaminated aquifer, eliminating the need 

to dig a trench and install a PRB. Research 

indicates that injecting nZVI particles into areas 

within aquifers that are sources of chlorinated 

hydrocarbon contamination may result in faster, 

more effective groundwater cleanups than 

traditional pump-and-treat methods or PRBs. 

Research indicates that nanoparticles such as 

nZVI, bi-metallic nanoscale particles (BNPs), 

and emulsified zero-valent iron (EZVI) may 

chemically reduce the following contaminants 

effectively: perchloroethylene (PCE), TCE, cis1, 2-dichloroethylene (c-DCE), vinyl chloride 

(VC), and 1-1-1-tetrachloroethane (TCA), along 

with polychlorinated biphenyls (PCBs), 

halogenated aromatics, nitroaromatics, and 

metals such as arsenic or chromium. Two of the 

important degradation reactions for chlorinated 

solvents are reductive dechlorination and beta 

elimination. Beta elimination, which occurs most 

frequently when the contaminant comes into 

direct contact with the iron, follows the pathway 

of TCE + Fe0 → HC Products + Cl-

 + Fe2+/Fe3+
3 

(U.S. EPA, 2008). Reductive dechlorination, 

which occurs under the reducing conditions 

fostered by nZVI in groundwater, follows the 

pathway of PCE→ TCE→ DCE→ VC→

ethene (Elliot, 2006). 

Nanoparticles can be highly reactive due to their 

large surface area to volume ratio and the 

presence of a greater number of reactive sites. 

This allows for increased contact with 

contaminants, thereby resulting in rapid 

reduction of contaminant concentrations. 

Because of their minute size, nanoparticles may 

pervade very small spaces in the subsurface 

and remain suspended in groundwater, which 

would allow the particles to travel farther than 

macro-sized particles and achieve wider 

distribution. However, as discussed in the 

‘Limitations’ section, bare iron nanoparticles may 

not travel very far from the injection point. 

It is important to note that there is variability 

among iron nanoparticles, even if they have the 

same chemical composition (Liu, 2005). The 

properties of particles such as reactivity, 

mobility, and shelf-life can vary depending on 

the manufacturing process or the vendor 

providing the particle (Miehr, 2004). 

DESCRIPTION OF NANOPARTICLES USED 

IN SITE REMEDIATION 

Most of the bench-scale research and field 

application of nanoparticles for remediation at 

full-scale have focused on nZVI and related 

products, according to information obtained for 

this fact sheet. Particles of nZVI may range 

from 10 to 100 nanometers in diameter or 

slightly larger. Figure 2 shows transmission 

electron microscope (TEM) images of nZVI. 

An example of a site where nanotechnology 

showed positive results at full scale is a former 

fill area in Hamilton Township, New Jersey, 

which was treated with a nanoiron water slurry 

(NanoFe PlusTM). The groundwater at the site 

was contaminated with TCE and associated 

daughter products, with an initial maximum 

volatile organic compound (VOC) concentration 

of 1,600 micrograms per liter (μg/L). The nZVI 

was injected in two phases over a total of 30 

days. It was reported that post injection 

monitoring indicated a decrease in the 

concentration of chlorinated contaminants of up 

to 90 percent. The site is now in the monitoring 

phase (Varadhi, 2005). 

Figure 2. Transmission electron microscope (TEM) images of iron nanoparticles (Zhang, 2006b) 

Note: The scale bars in the figure are 200 nm. 
4 

Information on other sites using nZVI can be 

found in the ‘Performance and Monitoring’ and 

‘Selected Sites Using or Testing Nanoparticles 

for Remediation’ sections at the end of this fact 

sheet. 

Nanoscale iron particles can be modified to 

include catalysts such as palladium (Pd), 

coatings such as polyelectrolyte or triblock 

polymers (Saleh, 2007), or can be encased in 

emulsified vegetable oil droplets (Hydutsky, 

2007; He, 2007). Some nanoparticles are made 

with catalysts that enhance the intrinsic reactivity 

of the surface sites (Tratnyek, 2006). BNPs 

have been used for the remediation of 

contaminants in soil and groundwater. BNPs 

consist of particles of elemental iron or other 

metals in conjunction with a metal catalyst, such 

as platinum (Pt), gold (Au), nickel (Ni), and 

palladium. The combination of metals increases 

the kinetics of the oxidation-reduction (redox) 

reaction, thereby catalyzing the reaction. 

Palladium and iron BNPs are commercially 

available and currently the most common. 

In bench-scale tests, BNPs of iron combined 

with palladium showed contaminant degradation 

two orders of magnitude greater than microscale 

iron particles alone (Zhang, 2006b). These 

particles were 99.9 percent iron and less than 

0.1 percent palladium. Palladium can catalyze 

the direct reduction of TCE to ethane without 

producing other intermediate by-products such 

as vinyl chloride (Nutt, 2005). Research is 

ongoing using gold and palladium BNPs to 

degrade TCE and other chlorinated compounds 

(Nutt, 2005); however, unlike nanoiron, these 

nanoparticles require a source of reductant such 

as dissolved hydrogen. They may be used in 

conjunction with nZVI to supply hydrogen, or an 

external source of reductant must be applied. 

Figure 3 shows a schematic of gold and 

palladium BNPs from a study where the 

amounts of palladium were varied to optimize 

the contaminant degradation rate by maximizing 

the percentage of surface cover. In that study, 

the TCE reaction rate was maximized at 12.7 

percent palladium content. Using palladium in 

BNPs may improve the reaction kinetics and 

more effectively distribute the injected slurry or 

mixture. 

BNPs can be injected by gravity or by pressure 

feed (Gill, 2006). BNPs were used in an 

application at the Naval Air Engineering Station 

in Lakehurst, New Jersey, where the soil and 

groundwater were contaminated with PCE, TCE, 

and other daughter products. Data indicate that 

the BNP treatment resulted in a decrease in the 

average total VOC concentration by 74 percent 

within six months (NAVFAC, 2005). 

Figure 3. Schematic of Pd/Au BNPs idealized as clusters, with a 4-nm Au core and variable Pd 

surface coverage from 0 to 100 percent (with corresponding Pd content). (Nutt, 2006) 

Another product, EZVI, is also commercially 

available and has been used for the remediation 

of chlorinated solvents. The product consists of 

ZVI surrounded by an oil-liquid membrane that 

facilitates the treatment of chlorinated 

hydrocarbons. EZVI is made from food-grade 

surfactant, biodegradable oil, water, and either 

nanoscale or microscale iron to form emulsion 

droplets. Figure 4 illustrates the structure of an 

EZVI particle. The exterior oil membranes of the 

droplets are hydrophobic, as are DNAPL 

contaminants such as TCE. The droplets are 

therefore miscible with the DNAPL, allowing 

increased contact between the TCE DNAPL and 
5 

the ZVI within the droplets. It is believed that 

when the emulsion droplets combine with the 

TCE, the contaminant dissolves and diffuses 

into the droplet where it comes into contact with 

the ZVI and is degraded. A concentration 

gradient is established from the migration of the 

TCE molecules into the aqueous emulsion 

droplet and by the migration of the by-products 

out of the particles and into the surrounding 

water phase, further driving the degradation 

reactions (O’Hara, 2006). While both nZVI and 

EZVI have been shown to reduce TCE DNAPL, 

according to one researcher, EZVI appears to 

be more effective in treatment, lowering TCE 

concentrations to a greater extent than nZVI. 

The vegetable oil also enhances biological 

activity, which contributes to the destruction of 

the contaminant (Quinn et al, 2005). 

Figure 4. Structure of an EZVI particle 

(modified from O’Hara, 2006) 

EZVI can be made from nanoscale ZVI, 

microscale ZVI (larger than 100 nm), or a 

combination. Using larger particles could make 

the emulsion more difficult to emplace. Because 

microscale particles are less costly to produce 

than nanoscale EZVI, using a mixture of nano 

and microscale particles provides cost savings 

while maintaining the benefits of nanoscale iron. 

EZVI has been used to clean up TCEcontaminated soil and groundwater at an 

industrial site on Patrick Air Force Base in 

Florida. The particles were introduced via highpressure pneumatic injection. While initial TCE 

concentrations were as high as 150,000 μg/L, 

the highest concentration measured after 

treatment was 3,580 μg/L. The remediation 

project was still in operation at the time this fact 

sheet was prepared. More information on EZVI 

applications can be found at the Web site link 

provided in the ‘Selected Sites Using or Testing 

Nanoparticles for Remediation’ section at the 

end of this fact sheet. 

DESCRIPTION OF NANOMATERIALS WITH 

POTENTIAL REMEDIATION APPLICATIONS 

Researchers are developing a variety of 

nanomaterials for potential use to adsorb or 

destroy contaminants as part of either in situ or 

ex situ processes. These particles include 

SAMMSTM, ferritin, dendrimers, and 

metalloporphyrinogens. The stage of 

development ranges from bench to pilot scale. 

Some materials can be made with surface 

functional groups to serve as adsorbents to 

scavenge specific contaminants from waste 

streams. SAMMSTM particles consist of a 

nanoporous ceramic substrate coated with a 

monolayer of functional groups tailored to 

preferentially bind to the target contaminant. 

The functional molecules covalently bond to the 

silica surface, leaving the other end group 

available to bind to a variety of contaminants. 

According to researchers, SAMMSTM particles 

maintain good chemical and thermal stability 

and can be readily reused or restored (Fryxell, 

2007). Figure 5 shows a schematic of a 

functionalized nano-sized pore within a 

SAMMSTM particle. The particle has a large 

surface area to allow for quick sorption kinetics. 

Contaminants successfully sorbed to SAMMSTM 

particles include radionuclides, mercury, 

chromate, arsenate, pertechnetate, and selenite 

(Mattigod, 2003; Tratnyek, 2006). According to 

the SAMMSTM Adsorbents Web site 

(http://sammsadsorbents.com/page/resourcecenter), SAMMSTM has shown positive results in 

pilot scale tests in the remediation of mercury in 

well water with a high concentration of dissolved 

solids, aqueous mercury in low concentrations, 

highly radioactive mercuric waste, and gaseous 

elemental mercury. 
6 

Figure 5. Schematic of functionalized nanosized pore within a SAMMSTM particle 

(modified from Mattigod, 2004) 

Nanotubes are engineered molecules most 

frequently made from carbon. They are 

electrically insulating, highly electronegative and 

easily polymerized. Nanotubes have also been 

made from titanium dioxide (see Figure 6) and 

have demonstrated potential for use as a 

photocatalytic degrader of chlorinated 

compounds (Chen, 2005). Bench-scale 

research has shown titanium dioxide nanotubes 

to be particularly effective at high temperature, 

capable of reducing contaminant chemicals by 

greater than 50 percent in three hours 

(Xu, 2005). 

Figure 6. Scanning electron microscope 

image of titanium dioxide nanotubes 

(Chen, 2005)

Bench-scale tests using ferritin, an iron storage 

protein, have indicated that it can reduce the 

toxicity of contaminants such as chromium and 

technetium in surface water and groundwater to 

facilitate remediation (Temple University, 2004). 

Like titanium dioxide, ferritin is photocatalytic; in 

one bench-scale project, the addition of visible 

light caused ferritin to reduce toxic, watersoluble hexavalent chromium to the less toxic 

trivalent chromium, which is not water soluble 

and precipitates out of solution. 

Dendrimers are hyper-branched, well-organized 

polymer molecules made up of three 

components: core, branches, and end groups. 

Dendrimer surfaces terminate in several 

functional groups that can be modified to 

enhance specific chemical activity. Fe0

/FeS 

nanocomposites, synthesized using dendrimers 

as templates, could be used to construct 

permeable reactive barriers for the remediation 

of contaminated groundwater. Bench-scale 

research has indicated that dendrimers have 

flexible delivery options (Diallo, 2006). 

Metalloporphyrinogens are complexes of metals 

with naturally occurring, organic porphyrin 

molecules. Examples of biological 

metalloporphyrinogens are hemoglobin and 

vitamin B12. Batch-reactor experiments have 

shown that metalloporphyrins are capable of 

reducing chlorinated hydrocarbons such as 

TCE, PCE, and carbon tetrachloride under 

anoxic conditions to remediate contaminated soil 

and groundwater, with some structures showing 

a reduction of TCE and PCE by greater than 990 

percent from the original concentration 

(Dror, 2005). 

Researchers are also using nanotechnology to 

develop membranes for water treatment, 

desalination, and water reclamation. These 

membranes incorporate a wide variety of 

nanomaterials, including nanoparticles made of 

alumina, zero-valent iron, and gold (Theron, 

2008). Carbon nanotubes can be aligned to 

form membranes with nanoscale pores to filter 

organic contaminants from groundwater 

(Mauter, 2008; Meridian Institute, 2006). 

These and other types of nanoscale materials 

are chemical substances as defined under the 

Toxic Substances Control Act (TSCA). Pursuant 

to TSCA section 5(a)(1), any person 

manufacturing (including importing) a new 

chemical substance must file with EPA a 
7 

premanufacture notice (PMN) at least 90 days 

prior to manufacture, unless the substance is 

exempt from PMN reporting. 

CHEMISTRY OF SELECTED 

NANOPARTICLES 

Zero-valent, or elemental, iron is a reducing 

reagent that can react with both dissolved 

oxygen (DO) and water (Zhang, 2003). In the 

presence of an oxidizing agent, Fe0

 becomes 

oxidized to ferrous ions (Fe2+), and the two 

released electrons become available to reduce 

other compounds. In aerobic conditions, Fe0

reacts with dissolved oxygen to form ferrous 

ions and water. Fe0

 can also reduce water to 

form ferrous ions, hydrogen, and hydroxide ions. 

These reactions are shown below: 

2Fe0 + 4H+

 + O2 → 2Fe2+ + 2H2O 

(Matheson, 1994) 

2Fe0 + 2H2O → 2Fe2+ + H2 + 2OH-

 

(Matheson, 1994) 

In addition to the above reactions, ZVI can also 

react with contaminants. Figure 7 illustrates a 

reaction that shows the reducing ability of 

elemental iron with a chlorinated hydrocarbon. 

In this example, the Fe0

 (in the form of a BNP) 

transforms TCE to ethane, releasing Fe2+ ions 

and chloride ions. 

Figure 7. Reaction of iron in a bimetallic 

nanoscale particle with TCE (image courtesy 

of Wei-Xian Zhang, Lehigh University) 

The reductive capacity of Fe0

 when it comes into 

contact with chromium contamination in soil and 

groundwater can be seen in the following 

equation, where iron is oxidized to its ferrous 

form and chromium is reduced from chromium 

(VI) to the less toxic chromium (III) (Cao, 2006): 

3Fe0

 + 2Cr2+ → 3Fe2+ + 2Cr3+

Nanosized titanium dioxide has been shown to 

mineralize a variety of herbicides, insecticides, 

and pesticides via photocatalysis and can 

convert other contaminants to less toxic 

compounds (Konstantinou, 2003). When 

aqueous titanium dioxide suspensions are 

irradiated with light energy greater than 3.2 eV, 

titanium dioxide is activated and can combine 

with water and/or dissolved oxygen to form 

highly reactive species, including the hydroxyl 

radical and the superoxide radical anion, which 

can oxidize many contaminants. 

IN SITU APPLICATION OF NANOPARTICLES 

The method of application for nanoparticles is 

usually site-specific and is dependent on the 

type of geology found in the treatment zone and 

the form in which the nanoparticles will be 

injected. The most direct route of injection 

utilizes existing monitoring wells, piezometers, 

or injection wells. Recirculation is a technique 

that involves injecting nanoparticles in 

upgradient wells while downgradient wells 

extract groundwater. The extracted 

groundwater is mixed with additional 

nanoparticles and reinjected in the injection well. 

The wells keep the water in the aquifer in 

contact with the nZVI, and also prevent the 

larger agglomerated iron particles from settling 

out, allowing continuous contact with the 

contaminant. 

Additional methods and processes to inject the 

nanomaterials include direct push, pressurepulse technology, liquid atomization injection, 

pneumatic fracturing, and hydraulic fracturing. 

The direct push method involves driving directpush rods, similar to small drilling augers, 

progressively deeper into the ground. This 

method allows materials to be injected without 

having to install permanent monitoring wells 

(Butler, 2000). Pressure pulse technology 

utilizes large-amplitude pulses of pressure to 

insert the nZVI slurry into porous media at the 

water table; the pressure then excites the media 

and increases fluid level and flow (OCETA, 

C2H6+3Cl5[H]

Pd0

Fe2+

C2HCl3
8 

2003). Liquid atomization injection is a 

technology that is proprietary to ARS 

Technologies, a company that specializes in 

pneumatic fracturing and injection field services. 

It introduces an nZVI-fluid mixture into the 

subsurface using a carrier gas. The nZVI liquidgas combination aerosolizes, allowing for more 

effective distribution; this method can be used in 

geologic formations with lower permeability 

(NAVFAC, 2008). Fracturing injection 

(pneumatic or hydraulic) is a high pressure 

injection technique using compressed air 

(pneumatic) or a water-based, highly viscous 

slurry containing sand (hydraulic) that fractures 

rock and allows liquids and vapors to be 

transported quickly through the channels 

created. Pneumatic fracturing uses air to create 

a fracture network of preferential flow paths in 

rock around the injection point to allow liquids 

and vapors to be transported quickly through 

fractured rock. This method of injection 

improves access to contaminants and allows 

liquids to flow freely (Pneumatic Fracturing Inc., 

2008; Zhang, 2003). 

Research is ongoing into methods of injection 

that will allow nanoparticles to better maintain 

their reactivity and increase their access to 

recalcitrant contaminants by achieving wider 

distribution in the subsurface. Creating nZVI on 

site reduces the amount of oxidation the iron 

undergoes, thereby reducing loss in reactivity. 

Researchers in green chemistry have 

successfully created nZVI in soil columns using 

a wide range of plant phenols, which, according 

to the researchers, allows greater access to the 

contaminant and creates less hazardous waste 

in the manufacturing process (Varma, 2008). 

Figure 8 illustrates the basic principles of two 

methods of remediating contaminated 

groundwater using nanoscale iron. The image 

at the top shows treatment of DNAPL 

contamination by injection of nanoparticles. In 

the second image, a reactive treatment zone is 

formed by sequential injections of nZVI. This 

creates overlapping zones of particles that 

adsorb to the native aquifer material. 

Post-injection observations of the subsurface 

indicate an increase in pH (due to the formation 

of hydroxyl ions) and a decrease in the 

oxidation-reduction potential (ORP) (due to the 

reducing conditions that are created). A lower 

ORP would most likely favor anaerobic bacteria 

growth, which in turn may promote increased 

degradation. Other chemicals formed when 

using particles such as nZVI may include 

hydrogen gas and Fe2+ ions, which would further 

promote microbial growth. After an nZVI 

injection, the ORP tends to decrease sharply 

before becoming stable (Zhang, 2003). 

LIMITATIONS 

Site-specific conditions such as the site location 

and layout, geologic conditions, concentration of 

contaminants, and types of contaminants may 

limit the effectiveness of nanoparticles. For 

example, the research conducted for this fact 

sheet documents only two sites that have used 

nanoparticles in fractured bedrock, although 

several pilot studies have been undertaken 

(Macé, 2006). Prior to injection of nanoparticles, 

geologic, hydrogeologic, and subsurface 

conditions should be evaluated to determine 

whether injected particles would have adequate 

subsurface infiltration. Factors that affect 

subsurface mobility include composition of the 

soil matrix, ionic strength of the groundwater, 

hydraulic properties of the aquifer, depth to the 

water table, and geochemical properties 

(including pH, dissolved oxygen, ORP, 

concentration of nitrate, nitrite, and sulfate), 

among others. Performance will be site specific 

and depend on the presence of competing 

oxidants such as DO and NO3

-

 (nitrate ion), 

contaminant concentration, and soil/groundwater 

pH (Liu, 2006; Liu, 2007). 

Studies have shown that nanoparticles may not 

achieve widespread distribution in the 

subsurface due to agglomeration prior to 

complete dispersion within the soil or 

groundwater matrix, limiting the radius of 

influence. Nanoscale zero-valent iron particles 

are attracted to one another, which can cause 

them to agglomerate into larger micron-sized 

particles (greater than 100 nm) (Tratnyek, 2006; 

Phenrat 2007). Agglomeration also reduces the 

exposed reactive surface area of the particles. 

The pH of the subsurface may also limit the 

effectiveness of nanoparticles because the 

sorption strength, agglomeration, and mobility of 

the particles are all affected by the pH of the 

groundwater (U.S. EPA, 2007). The ionic 

strength and types of cations in the 

groundwater, as well as the chemical and 

physical characteristics of the aquifer materials, 

also affect the agglomeration and movement of 

iron nanoparticles (Saleh, 2008). 
9 

Figure 8. Schematic of two methods of groundwater remediation using nanoiron 

(Tratnyek, 2006) 

Passivation is another factor that may limit the 

effectiveness of iron nanoparticles. If nZVI is 

being used, improper handling can result in the 

iron becoming oxidized and passivated prior to 

reacting with the contaminants. As a rule, 

injection mechanisms should limit the volume of 

water injected along with the iron, to limit 

exposure to oxygen and other oxidants that 

could passivate the iron before and during 

injection. If using larger volumes, deoxygenated 

water can minimize the iron passivation, but 

other oxidants may still be present to react with 

the iron (Gavaskar, 2005). 

A challenge with evaluating the effectiveness of 

nanoparticle injection is monitoring the 

distribution of injected particles in the 

subsurface. It is therefore important to identify 

the appropriate parameters to measure 

performance. Typically, geochemical measures 

such as ORP are monitored as a surrogate. 

Dissolved iron can also be monitored. Reaction 

kinetics are difficult to monitor; however, postinjection chemical concentrations are measured 

using standard approaches. Additionally, the 

kinetics and reactivity of nanoparticles in a 

DNAPL source zone may vary from the kinetics 

and reactivity in a dissolved plume (U.S. EPA, 

2008; Liu, 2007). 
10 

FATE, TRANSPORT, AND TOXICITY 

QUESTIONS 

While nZVI is the most widely used nanoparticle 

in site remediation, knowledge is limited on the 

fate and transport of iron nanoparticles in the 

environment, and little research has been done 

on the potential toxicological effects 

nanomaterials might pose. There are 

insufficient data on the potential for 

bioaccumulation of nanoparticles in 

environmentally-relevant species (Kreyling, 

2006) and there have been few studies on the 

effects of any nanoparticles on environmental 

microbial communities (Klaine, 2008). 

As described in the ‘Limitations’ section, 

agglomeration often affects transport of 

nanoparticles in the subsurface. The particles 

may become associated with the aquifer matrix 

as oxidized iron particles after reacting with 

contaminants. Under standard environmental 

conditions (aerated water, pH 5 to 9), Fe2+ will 

readily and spontaneously oxidize to Fe3+ and 

precipitate out of the groundwater as insoluble 

iron oxides and oxyhydroxides. Researchers 

have developed methods, some of which are in 

use commercially, to improve the mobility of iron 

nanoparticles within aquifers and to optimize 

contact between the nanoparticle and 

contaminant. Ongoing studies are evaluating 

surface coatings and other modifications that 

would reduce agglomeration of nanoparticles 

and maximize subsurface mobility (Phenrat, 

2008). Preliminary research indicates that 

polymers and surfactants stabilize nanoparticle 

suspensions in aquifers, inhibiting their 

agglomeration and allowing greater dispersal 

without compromising the ability of the iron to 

remediate contaminants (He, 2007). Soils high 

in clay content have been shown to allow 

greater dispersal of nZVI as well; anionic clay 

particles appear to function as a natural 

stabilizer, allowing for more effective transport 

(Schrick, 2004, Hydutsky, 2007). While 

increased mobility would allow more efficient 

remediation, it could also result in the possibility 

of the nanomaterials migrating beyond the 

contaminated plume area, seeping into drinking 

water aquifers or wells, or discharging to surface 

water during the remediation process. 

Studies are being conducted on the potential 

toxicity of various types of manufactured 

nanomaterials. The increased surface area and 

larger number of reactive sites of nanomaterials 

may equate to greater biological activity per unit 

mass than micro- or macro-scale particles of the 

same composition. Substances considered 

nontoxic at macroscale may have negative 

impacts on human health when nanoscale 

particles are inhaled, absorbed through skin, or 

ingested (Kreyling, 2006). Because of the 

minute size of nanomaterials, the particles have 

the potential to migrate to or accumulate in 

places that larger particles cannot, such as the 

alveoli in the lungs (Grassian, 2007), thereby 

potentially increasing toxicity. Some 

nanoparticles have demonstrated an ability to 

increase bioavailability of certain hydrophobic 

contaminants, for example, by increasing 

mobility of contaminants bound to soil and 

sediment surfaces (Tungittiplakorn, 2005). 

Issues of toxicity and safety have limited the use 

of nanotechnology for remediation by some 

private sector companies. For example, DuPont 

has ruled out the use of nZVI for site 

remediation at any of its sites until issues 

concerning fate and transport have been more 

thoroughly researched. The company has cited 

questions of post-remediation persistence and 

potential human exposure to the particles as 

areas of particular concern (DuPont, 2007). As 

another example of a cautionary approach, the 

Continental Western Group of insurance 

companies announced that it will no longer 

cover injury and/or damage arising from 

nanotubes or nanotechnology, as used in 

products or processes. See: 

http://cwgins.com/mike/documents/CW3369060

8NanotubesExclusion.pdf. 

EPA’s Office of Research and Development 

(ORD) published a Draft Nanomaterial Research 

Strategy (NRS) in January 2008. The initial 

emphasis of the NRS will be to evaluate and 

assess the extent to which nanomaterials and 

products impact the environment and human 

health. Results from this research will directly 

inform future policy decisions regarding how to 

address possible adverse implications 

associated with the production, use, recycling, or 

disposal of nanomaterials and nanoproducts 

(that is, products containing nanomaterials). 

Initially, a smaller portion of the proposed 

research will focus on beneficial environmental 

applications, such as more effective control 

technologies and enhanced production 

processes that reduce emissions and releases 

of conventional pollutants. As the program 
11 

evolves over time, ORD will augment its efforts 

in this area. 

In the Draft NRS, ORD identified four key 

research themes for investigating nanomaterials 

for EPA: 

• Sources, Fate, Transport, and Exposure 

• Human Health and Ecological Research 

to Inform Risk Assessment and Test 

Methods 

• Risk Assessment Methods and Case 

Studies 

• Preventing and Mitigating Risks 

(USEPA 2008A). 

PERFORMANCE AND MONITORING

As of September 2008, data exhibiting varying 

degrees of comprehensiveness were obtained 

for a total of 26 sites using or testing 

nanoparticles for remediation. Details on these 

selected sites are available at http://cluin.org/products/nanozvi, and will be updated 

periodically as new information is received. 

One site is located in Quebec, Canada; the 

remaining 25 sites cover seven states in the 

United States. Of these 25 sites, data for 16 

were independently verified through peerreviewed sources or by government regulators. 

Data for the other nine sites were not 

independently verified. There are seven fullscale remediation applications and 19 pilot-scale 

projects represented. Thirteen remediation 

projects used nZVI, eight used BNPs, four used 

EZVI, and one used nanoscale calcium ions with 

a noble metal catalyst. The most frequently 

treated contaminants of concern were 

chlorinated solvents, such as TCE, PCE, TCA, 

and VC. 

Of the seven full-scale projects, five indicated 

that site-specific cleanup goals were met, 

according to the points of contact. The other 

two demonstrated decreasing trends in 

contaminant concentrations. Of the 12 pilotscale projects, six indicated that cleanup goals 

had been met. The other six either did not meet 

cleanup goals or sufficient information on 

cleanup goals was not provided to assess 

performance. 

Details for two projects in the list of sites are 

provided below. 

Use of nZVI at a former Manufacturing site in 

Passaic, New Jersey. nZVI was applied at a 

former manufacturing site in Passaic, New 

Jersey, where chlorinated solvent contaminants 

such as TCE had been found in groundwater. A 

pilot scale test was conducted from September 9 

to 13, 2005, to treat a shallow sand aquifer. The 

technology design included the injection of 108 

pounds of nZVI slurry and 1,200 pounds of 

emulsified oil into 3 points within the silt unit. 

Pneumatic fracturing injections were used at two 

of the injection points and hydraulic injection 

was used at the third. At the end of the pilotscale test, there was a 90 to 100 percent 

reduction in TCE concentrations throughout the 

contaminant plume. Monitoring occurred weekly 

during the first month of the project and was 

conducted monthly thereafter (Zhang, 2006a). 

Use of nZVI at Fill Area in Hamilton Township, 

New Jersey. Contaminants at the Klockner 

Road Site in Hamilton Township, New Jersey 

were treated using nZVI. The site was a former 

fill area, where contaminants such as TCE, TCA, 

DCE, and dichloroethane (DCA) were found in 

the groundwater. A full-scale project was 

implemented using nZVI (NanoFe PlusTM). 

NanoFe PlusTM is manufactured by PARS 

Environmental Inc. and consists of nZVI with an 

added catalyst to enhance the speed and 

efficiency of remediation. The nanoscale iron 

was injected in three phases. Phase I injection 

contained 3,000 pounds of slurry and was 

injected at the northern end of the site over a 

period of 20 days. Phase II injection contained 

1,500 pounds of slurry and was injected 

throughout the northern half of the site over a 

period of 10 days. Information on Phase III was 

not available at the time this fact sheet was 

prepared. The results of the full-scale injections 

showed up to 90 percent reduction in the overall 

contaminant concentrations. ORP, pH, and 

groundwater elevations were monitored during 

each phase of the injection. The first postinjection monitoring event was conducted one 

week after the first injection and the second 

event was conducted two weeks after 

completion of the Phase II injection. At 

preparation of this fact sheet, monitoring 

activities were ongoing and included collecting 

groundwater samples to monitor trends in any 

remaining groundwater contamination. Cost 

information was not available in the materials 

reviewed to prepare this fact sheet (Gill, 2006). 
12 

COST 

Three site-specific examples of project costs are 

shown in Table 1 below. The first two sites 

achieved their remedial objectives; information 

on performance for the third site was not 

available. The cost information that was 

provided is limited; therefore, a comparison of 

nanotechnology costs with the costs of 

traditional technologies cannot be accurately 

conducted at this time. Factors contributing to 

the costs include site type, type of contaminants, 

concentrations of contaminants, extent of the 

plume, and any challenges that may have 

occurred during remediation. The factors that 

were included in the total cost for the Naval Air 

Engineering Station in New Jersey included 

monitoring well installation, sampling, nZVI 

injection, post-injection sampling, and reporting. 

The components contributing to the total cost at 

the Naval Air Station in Jacksonville, Florida, 

included mobilization, monitoring well 

installation, nZVI injection, sampling and 

analysis, and other miscellaneous costs 

(Gavaskar, 2005). nZVI production is included 

in the injection costs for both of these sites. The 

final costs for the Patrick Air Force Base Site 

include mobilization and site setup, monitoring 

well installation, recirculation/ injection events, 

surveying, disposal of demonstration derived 

waste, and monitoring. Administrative costs 

associated with project management, work plan 

generation, and bench-scale treatability study 

costs were not included. 

Additional factors that may increase the total 

cost of nanoparticle application may include 

operational requirements connected with any 

contamination found underneath a building, or 

the need to treat or dispose extracted fluids 

(Wilson, 2004). 

Table 1. Costs for example projects using nanotechnology for site remediation

Cost Components 

Site Name 

Remediation 

Cost (Total) 

Capital 

Costs 

O & M Costs Unit 

Cost 

Naval Air Engineering Station 

Lakehurst, NJ1

$255,500 - $213,000 - 

Naval Air Station 

Jacksonville, FL2 $260,000 - $110,000 $269/cy 

Patrick Air Force Base, FL3 $4,000,000 $2,000,000 $70,000 $180/cy 

1. O&M costs: Monitoring Well Installation $24,400, Sampling and Analysis $58,400, Reporting $18,100. 

2. nZVI cost: $37,000. O&M costs: Monitoring Well Installation $52,000, Sampling and analysis $110,000. 

967 cubic yards (cy) soil treated. 

3. Capital costs: $1,000,000 for EZVI, $1,000,000 for pneumatic injection contractor. 22,222 cy soil treated. 

LIST OF IDENTIFIED VENDORS FOR 

NANOTECHNOLOGY 

Several vendors supply nanomaterials for site 

remediation. Some of the suppliers that were 

identified and their products are shown in 

Table 2. This list should not be considered to be 

comprehensive or as an endorsement by EPA. 

More information about the vendors and other 

types of nanomaterials can be found at 

http://www.nanovip.com. 

SELECTED SITES USING OR TESTING 

NANOPARTICLES FOR REMEDIATION 

A list of sites using or testing nanoparticles for 

remediation is available at http://cluin.org/products/nanozvi. This list will be updated 

periodically as new information is received. 
13 

Table 2. Identified nanomaterial vendors

Vendors* Nanomaterial Produced Web site 

Crane Polyflon PolyMetallix www.polymetallix.com

Lehigh University Fe/B www.lehigh.edu/nano/environmental.html

Environmental Restoration 

Services, LLC 

Nano-Ox http://www.ersllccorp.com/index.html

OnMaterials LLC ZLoy www.onmaterials.com

PARS Environmental Inc. NanoFeTM and NanoFe 

PlusTM 

www.parsenviro.com

Toda Kogyo Corporation RNIP www.toda.co.jp/english/c02-02.html

VeruTEK Technologies, 

Inc. 

Green Chemistry and 

Nanotechnoloy 

www.verutek.com

Pacific Northwest National 

Laboratory 

SAMMSTM http://samms.pnl.gov/

* Mention of product does not imply endorsement. Vendors that would like to be included in future iterations of this table should 

submit their request in a comment to the Clu-in Web site at: http://www.clu-in.org/gbook.cfm

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NOTICE 

Preparation of this fact sheet has been funded 

wholly or in part by the U.S. Environmental 

Protection Agency under Contract Number EPW-07-078. For more information regarding this 

fact sheet, please contact Martha Otto, EPA, at 

(703) 603-8853 or otto.martha@epa.gov. This 

fact sheet is available for viewing or 

downloading from EPA’s Hazardous Waste 

Cleanup Information (CLU-IN) Web site at 

http://cluin.org/542F08009. A limited number of 

hard copies are available free of charge from: 

EPA/National Service Center for Environmental 

Publications 

P.O. Box 42419 

Cincinnati, OH 45242-2419 

Phone: (800) 490-9198 

Fax: (301) 604-3408 

Web site: www.epa.gov/nscep

ACKNOWLEDGMENT 

Special acknowledgment is given to the 

following individuals for their review and 

thoughtful suggestions to support the 

preparation of this fact sheet: Glen E. Fryxell 

(Pacific Northwest National Laboratory), Gregory 

V. Lowry (Carnegie Mellon University), Paul 

Tratnyek (Oregon Health and Science 

University), Don Zhao (Auburn University), 

Robert Ellis (ARCADIS), Florin Gheorghiu 

(Golder Associates, Inc.), Heather Henry 

(NIEHS), David A. Sheets (U.S. Army 

Environmental Policy Institute), and EPA staff: 

Joseph Freedman and Manisha Patel of the 

Office of the General Counsel, Bernard Schorle 

of U.S. EPA Region 5, Jim Alwood and Jed 

Costanza of the Office of Pollution Prevention 

and Toxics, Michael Gill, Jon Josephs, Nora 

Savage, and Katrina Varner of the Office of 

Research and Development, Elisabeth Freed of 

the Office of Site Remediation Enforcement, 

Catherine Davis of the Office of Solid Waste, 

Matt Charsky of the Office of Superfund 

Remediation and Technology Innovation, and 

Hal White of the Office of Underground Storage 

Tanks.