2/26'2015 CLU-IN 

### ITeclllologies> Remediation>AlxURemediationTechnclogies > Nanotecmology:Applicationsfor Envirormental Remeclalion >Application 

# U.S. EPAContaminated Site Cleanup Information (CLU-IN)

CLU-IN 

### ITechnologies 

### I Remediation 

### IAbout Remediation Technologies 

### I Nanotechnology: Applications for Environmental Remediation 

# C FormoreInformationon Nanomaterlals,please

### contact: 

### G1911 G81V819 Technology.AaeumantBranch 

# _J PH: (703)**60~0690**

### IEmall: geaals.gregoty@eoa.gov 

# Nanotechnology: Applications for Environmental Remediation Application Since the early 1990s, site project managers have taken advantage of the properties of metallic substances such as elemental iron todegrade chlorinated solvent plumes in groundwater. One example ofan insitu

### treatment technology for chlorinated solvent plumes is the installation 

### of a trench filled with macroscale zenrvalent iron (ZVI) toform a permeable 

### reactive barrier 

### (PRB) (ITRC 

## 2005). Based on the success of using macroscale metallic substances for environmental remediation, nanoscale materials are being researched and applied as 

### in situ contamination reduction technologies. Following are 

### brief descriptions 

### ofnanoscale materials forenvironmental remediation. Jumptoa Subsection 

### Nanoscale Materials 

## I Contaminants Known

### to beTreated Using Nanoscale Materials 

## I Reactive ChemistryofNanoscale Materials 

## I In SituApplication of Nanoscale Materials 

## I FactorsAffecUng Performance 

## I Fate,Transport. and Toxicity 

## I Field Demons1rations and Case Studies 

## ICost 

## I Nanotechnology Vendors 

## I NanotechnologyProductswith Potential Remediation Applications 

## Nanoscale Materials Overview Guidance 

### Application Training 

### Additional Resources Technology FocusHome Suggest Resource Comments



### Most 

### of

### the bench-6cale research and field application of nanoscale materials for remediation at full scale has focused on nanoscale zenrvalent iron (nZVI) and r91ated products. However, other nanoscale materials, such as titanium dioxide**(Ti~).** 

### are in the research and development stages for use in environmental remediation 

### (see Nanotacbnology

### Produc;ts

## with Potlntlal RlmtcUatlonAppllcatloQI). Nanoscala 

### zero-valent Iron (nZVI): 

### Particles of nZVI may range from 10 to 100 nanometers in diameter or slightly larger. Macroscale ZVI has 

### been shown to be 

### effective for treating groundwater contaminants within PRBs. Particles 

### of nZVI provide the same environmental remediation benefits as macroscale ZVI but have larger surface areas 

### pervolume 

### of material; this larger surface area provides more reactive sites allowing for more rapid degradation 

### ofcontaminants when compared tomacroscale ZVI (.U.S. EPA20088). A disadvantage of nZVI is the agglomeration 

### or clumping of particles to each otherorto the soil surface. Agglomeration may be 

### caused by 

### groundwaterconditions, surface properties of the particles, the 

### age ofthe materials, orshipping conditions (.U.S. EPA 

### 2007A). Modifications to nanoscale iron particles have been made to enhance their mobility, reactivity, orstability. Examples include adding coatings such as polyelectrolyte ortriblock polymers (Saleb 

## at al. 

### 2007: Hydutskv 

## at al. 

### 2007; He 

## at al. 2007) to improve mobility, or encasing in emulsified**~/cl~in.crg.ltecliocusldefUtfac~Sldectn:Jlogy:_Applicalions_for_Envin:nnenbll_Remediatioricat/Applicali<n'** 1/132J26l2015 CW-IN

### ITechnologies> Remeclation>About RemedationTectwlologies>Nanotechnology:Applicationsfa'Envirormental Remeclalion>Application vegetable oil droplets (Quinn 

### et

### al. 2005) to improve stability and to improve reactivity by improving contact with the contaminant (see EZVI section below}. Some nanoscale materials are made with catalysts (see Bimetallic nanoscale particles section below)that enhancethe intrinsic reactivity ofthesurfacesites (!rablyek and Johnson

### 2006). It should 

### be noted that modifications toenhance mobility may result in reduced reactivity (Phenrat

### etal. 2009). Bimetallic nanoacale 

### partides (BNP): BNPs have been used to remediate contaminants in soil and groundwater. BNPs consist of particles ofelemental iron orother metals in conjunction with a metal catalyst, such as platinum, gold, nickel, 

### and palladium. 

### The combination of metals increases the kinetics 

### of the oxidation-reduction (redox) reaction, thereby catalyzingthe reaction. Palladium and iron BNPs are commercially available and currently the most common. In bench-scale tests, BNPs of iron combined with palladium achieved contaminant degradation two orders of magnitude greaterthan microscale iron particles alone: these particles were

### 99.9 percent iron and less than 

### 0.1 percent palladium <Zhang and 

### Elllot 20QI). Palladium can catalyze the direct reduction 

### of trichloroethane (TCE} to ethane without producing other intermediate byproducts suchas vinyl chloride 

### (Nutt

### atal. 

### 2005), BNPs are generally incaporated intoa sluny

### for injection and can beinjected 

### bygravityorby pressurefeed 

### CGil! 

## 2006).
Emulslftad 

### zero-valent Iron (EZVI): EZVI is commercially available and has been used 

### to remediate chlorinated solvents. EZVI consists of nano- or microscale ZVI sunounded 

### by an emulsion membrane that facilitates treatment of chlorinated hydrocarbons. The exterior emulsion membrane is made from food-grade surfactant 

### and biodegradable oil 

### and the inside of the droplets contain water and the ZVI particles. Figure 

### 2 illustrates the structure ofan EZVI particle. 

### Theexterioremulsion membranes are hydrophobic, similar to the properties of dense 

### nonaqueous phase liquid {DNAPL) contaminants such as TCE. 

### EZVI particles (or "droplets") therefore mix directly with DNAPL. When the emulsion droplets come into contact with with 

## a TCE DNAPL, the TCE partitions into the oil membrane and then diffuses into the interior 

### of the emulsion droplet, where it comes into contact with the ZVI and is degraded. A concentration gradient is established by migration ofthe TCE molecules into the interior 

### aqueous phase of the emulsion droplet and by migration of the by-products out 

### of the droplet and into the surrounding water phase, further driving the degradation reactions 

### CO'Hara 

# at al. 

### 2QQ6l. The vegetable oil can also provide 

### "food" (electron donors) to microorganisms 

### and enhance biological activity, which in tum contributes to the destruction 

### of the Figure2.Sb"uc:tureofan EZVIparticle (modifiedfromQ'Hamet

### •I· 2006}


# 0

contaminant (Quinn 

## at al. 

### 2005). In addition, 

### EZVI can 

### be especially effective when DNAPL is present because DNAPLtends to be miscible in vegetable oil. When DNAPLcontacts EZVI, the DNAPLcan mixwith the EZVI, afterwhichthecontaminants 

### are inclose proximitywiththeZVI and can 

### be effectivelydegraded. Top of Page



## Contaminants Knowntobe

## Treated Using Nanoscale Materials

http://clu-in.Q'9"tBctmcuslda'ault.focuslseclNlrdactmlogy:_Applicalions_fcr_Environmental_Remeclalicnlcat/Applicalionf 2/132/2El2015 CLU-IN 

### ITectr.ologies >Remediation>About RemediationTechnologies> Nanotechnology:Applications fa Environmental Remediation>Application INanoscale Iron Research indicates that nanoscale mater1als such as nZVI, BNPs, and EZVI may chemically reduce the following contaminants effectively: tetrachloroethene (PCE), TCE, cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and 1-1-1-tetrachloroethane (TCA), polychlorinated biphenyls (PCBs), halogenated aromatics, nitroaromatics, metals such as arsenic and chromium (U.S. EPA. 2008A), and nitrate, perchlorate, sulfate, and cyanide (Tratnyek

### et al

.. as cited inTarr2003). Two of the most important reductive dechlorination reaction mechanisms are hydrogenolysis and beta elimination. Beta elimination, which occurs most frequently when the contaminant comes into direct contact with elemental iron (Fe0), follows the degradation pathway below: TCE + Fe0

- Chlorinated Acetylene
- Hydrocarbon Products+ 

### c1- + Fe2+/Fe3+ (U.S. EPA. 2008A). The hydrogenolysis pathway for reductive dechlorination of PCE, which occurs under the reducing conditions fostered by nZVI in groundwater, follows thefollowing degradation pathway: PCE

- TCE

- DCE

- VC

- ethene (Tratnyak

## at al

.. 

### as cited inTarr2003; U.S. EPA 1999). The reactions of Fe0 with contaminants may be especially complicated, involving multiple competing pathways. lather Nanoscale Materials Nanoscale Ti02 has been shown to mineralize a variety of herbicides, insecticides, and pesticides via photocatalysis and can convert othercontaminants to less toxic compounds (Konstantinou and Albanis 2003). Top of Page



## Reactive ChemistryofNanoscale Materials
INanoscale Iron/Iron Zero-valent, or elemental, iron is a reducing reagent that can react with both dissolved oxygen (DO) and water (Zhang 20()3). The chemical processes of nZVI are driven by the oxidation of Fe0

. However, the exact transformation mechanism may involve competing pathways and depends on the nature of the contaminant and targeted media (Dickinson 2010). 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+ + 

### 02 -2Fe2+ 

### +2H20 (Matheson andTratnyek 1994) 2Fe0 

### + 2H20-2F&.!+ 

### + H2 + 20W !Matheson andTratnyek 1994) The reactions of Fe0 with contaminants (such as TCE) may be more complicated and may involve multiple competing pathways, including beta elimination, where Fe0 releases electrons and TCE is transformed to ethane and releases chloride ions. The equations above and these reactions apply to iron particles in general; however, the advantages of using nanoscale iron over macro- or microscale iron is that reactions may proceed ata faster rate. The reductive capability 

### of Fe0 when it comes into contact with chromium contamination in soil and http://clu-in.orgltechfocus/da'ault.focus/sec/Nanotechnology:_Applications_fa _Environmenlal_Remediation/cat/Application/ 31132/26'"2015 CW-IN 

### ITechnologlea > Ranedlatlm>AboutRernedlatlmTechnologlea > Nadeclnllcgy:Appllcallaisfor Environmental Ranedlatlm>Appllcallm 

### groundwatercan 

### beseen inthefollOY1ing equation, where iron is oxidized to itsferrous form and chromium is reduced from chromium (VI)tothe lesstoxicchromium (Ill)<Cao andZhang

### 200§):

Aftergroundwatertreatment using nanoscale iron particles, post-injection observations 

### of the subsurface have indicated an increase in pH 

### (caused bytheformation 

### ofhydroxide ions)

### and a decrease in oxidationreduction potential (ORP) (a result 

### of the reducing conditions that 

### are created). A IOY1er ORP favors anaerobic bacterial growth, which may promote increased degradation for certain contaminants 

### (for example, chlorinated solvents). Other chemicals formed when particles such 

## as nZVI are used may include hydrogen gas 

### and Fe2 ions, whichalsowould promote microbial growth. Afteran nZVI injection, theORPtends todecrease sharply before

### it becomes stable

## <Zhang2003). 

# l<>ther Matarlals When aqueous**Ti~** 

### suspensions are irradiated with light energy greaterthan 

### 3.2 electronvolts 

### (eV),**Ti~** 

### is activated and 

## can combine with water or dissolved oxygen {or both) to fonn highly reactive species, including the hydroxyl radical 

### and the superoxide radical anion, which can oxidize and degrade a range 

### of contaminants 

## ru.s. EPA2008Al. InSitu

## Appllcatlonof

## Nanoscale Materlals
The application 

### of nanoscale materials for

### in situapplication is sitespecific. The method 

### of injection, and spacingand distribution

### ofinjection points, will depend on thetype

### ofgeologyfound in thetreatment zone, the type and distribution of contaminants, 

### and the fonn of the nanoscale materials that will 

### be injected. Injection 

### of nanoscale iron is typically 

### done via direct injection through gravity feed or under pressure. Direct injection

## can bedonevia several options including, but not limited to, direct pushtechnology orvia various types 

### of wells (e.g., temporary or permanent injection wells). Recirculation is another option that involves injecting nanoscale materials, while extracting groundwater and reinjecting it in the treatment zone, possibly adding more nanoscale materials inthe process. This method 

### of in situ application 

### keeps thewater in the aquiferin contact with the nZVI and also prevents largeragglomerated iron particles from settling out, promoting continuous contact with the contaminant. Figure 

### 3 shows an 

### example 

### of the recirculation 

### in situ application 

### of nanoscale materials. Another common 

### in situ application method 

### for nZVI is the direct push method. This method involves driving direct-push rods, similar in size to small drilling augers, progressively 

### deeper into the ground. This method allOY1s materials to 

### be injected without the need to install pennanentwells (Butler

### 2000). Additional methods 

### and processes to apply nanoscale material for 

### in situtreatment include pressure pulse technology, liquid atomization injection, pneumatic fracturing, and hydraulic fracturing. Pressure pulse technology uses large-amplitude pulses 

### of pressureto insertthe nZVI slun-y into

### porous media

### atthewater table; the pressure then excites the media 

### and increases fluid level and 

### flOYI COCETA 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 nZVl..fluid mixture into the subsurface using a carrier 

### gas. The nZVI liquid gas combination aerosolizes, allowing for more effective distribution; this method Figure3. Conceptualdesign afrectcula'llon (Hann2005)

....**~** •M•

.....

41132J26l2015 CW-IN

### ITechnologies> Remeclation >About RemedationTectwlologies>Nanotechnology:Applicationsfa'Envirormental Remeclalion >Application 

### can be used in geologic fonnations with lower penneability CNAVFAC 

### 2008). Fracturing injection {pneumatic or hydraulic) is a high-pressure injection technique using compressed gas {pneumatic) or a water-based, highly viscous slurry containing sand (hydraulic) that fractures rock orother low-penneability fonnations and allows liquids and vapors to be transported quickly through the channels created. Pneumatic fracturing uses compressed gas 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 thefractured rock; pneumatic fracturing improves access to contaminants and allows liquids to flow freely (Pneumatic 

### Fracturing Inc.2008; Zbana2003). Figure 

### 4 illustrates the basic principles 

### of two methods 

### of remediating contaminated groundwater using nZVI. The imageatthe topshows treatment

### of DNAPLcontamination by injection 

### ofnanoscale materials. In the second image, a reactive treatment zone is fanned by a series 

### of injections 

### of 

### nZVI. These injections create overtapping zones 

### of particles that become lodged within the native aquifer material {Tratnyek

### and Johnson

### 2006). Research is underway into methods 

### of injection that will allOYt' nanoscale materials to better maintain their reactivity 

### and increase their access to recalcitrant contaminants by achieving wider distribution in the subsurface. For example, creating nZVI on site could reduce the amount 

### of oxidation the iron undergoes 

### between production 

### and use, thereby reducing potential losses 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, allOYt's greater access to the contaminant 

### and creates less hazardouswaste in the manufacturing process 

### <vanna 

### 211111).

!Qp

### of

### page



## FactorsAffecting Performance A



### BFigure4. SChematlcoftwo methodsofgroundwaterremediation using nanoscale**~n** (CGR20091

Conuiminated Groundwater

GroundwaterFlow

ConGmjnatfll Groundwattr**PH~able** RH<tiw Barnet"

lnjtttlon

Well



## • •

# --;- / !----- Treated Grounclwatet"

Tr.ated Groundw.ter



### A number 

### of factors can affect nanoscale performance for site remediation, including: {1) site specific conditions, (2) agglomeration, 

### and (3) passivation. Eachofthese is discussed below. Si11Hpecific conditions such as the site location and layout, geologic conditions, concentration 

### of contaminants, and types ofcontaminants may limittheeffectiveness ofnanoscale materials. Before nanoscale materials are injected, geologic, hydrogeologic, and subsurface conditions should be evaluated to assess whether injected particles would offerthe perfonnance expected. Factors that affectthesubsurface mobility 

### of nanoscale materials include the surface features 

### of nanoscale materials and site-specific factors including: http://clu-in.a9'ta:tmcuslda'ault.focuslseclNlrdactmlogy:_Applicalions_fcr _Environmental_Remeclalicnlcat/Applicalionf 51132/2El2015 CLU-IN 

### ITectr.ologies >Remediation>About RemediationTechnologies> Nanotechnology:Applications fa Environmental Remediation>Application composition 

### ofthe soil matrix, ionicstrength 

### ofthe groundwater, hydraulic properties 

### ofthe aquifer, depth tothe water table, and geochemical properties (including pH, DO, ORP, and the concentration 

### of nitrate, nitrite, and sulfate), among others. Perfonnance will be site specific and will depend on the presence 

### of competing oxidants such as DOand No3- (nitrate ion), contaminant concentration, and the pH 

### ofthe soil and groundwater (Liu and Lowry2006; Liu

### etal. 2007). Agglomeration
- Studies have shown that nanoscale materials may not achievewidespread distribution in the subsurface because 

### of agglomeration before they completely disperse within the soil or groundwater matrix, limiting the radius 

### of influence. nZVI particles are attracted to one another, which can cause them to agglomerate into larger micron-sized particles (greater than 100 nanometers) (Tratnyek and Johnson 2006; Phenrat

### et al. 2007). Because 

### of agglomeration, the effective size might range up to hundreds 

### of nanometers. Some vendors refer to their materials as nanoscale even though they are larger than 100 nanometers and therefore do not meetthe NNI definition of nanotechnology. Agglomeration also reduces the exposed reactive surface area 

### of the particles. The pH ofthe subsurface may also limitthe effectiveness 

### ofnanoscale materials because the sorption strength, agglomeration, and mobility of the particles are all affected by the pH 

### ofthe groundwater (U.S. EPA 20078). 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 nanoscale materials (Saleh

## etal. 2008). Passivation, ordeactivation, may limit the effectiveness 

### of iron nanoscale materials. The high surface energy 

### of nanoscale materials makes them highly reactive and susceptible to oxidation in the open air, resulting in the fonnation of iron oxide and a decrease in the chemical reactivity ofthe iron nanoscale materials (Wang 

### et al. 2010). 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 larger volumes are used, deoxygenated water can minimize the iron passivation, but other oxidants may still be present to react with the iron 

### (Gavaskar

### etal. 2005). A challenge in evaluating the perfonnance 

### of nanoscale material injection is monitoring the distribution of injected particles in the subsurface. It is therefore important to identify the appropriate parameters to measure perfonnance. Typically, geochemical measures such

## as ORP are monitored as a surrogate. Dissolved iron can also be monitored. Reaction kinetics are difficult to monitor; however, post-injection chemical concentrations are measured using standard approaches. Additionally, the kinetics and reactivity of nanoscale materials in a DNAPL source zone may vary from the kinetics and reactivity in a dissolved plume (U.S. EPA 2008A; Liu 

### et al. 2007). 

### Fate, Transport, andToxicity Although nanoscale materials that contain iron are the most widely used nanoscale materials in site remediation, knowledge is limited on the fate and transport 

### of iron nanoscale materials in the environment. Furthennore, research is ongoing regarding the potential toxicological effects of nanoscale materials. There are insufficient data on the potential for bioaccumulation 

### ofnanoscale materials in environmentally relevant species (Krey!ing 

### et al. 2006), and there have been few studies on the effects of any nanoscale materials on environmental microbial communities (Klaine 

### et al. 2008). As described in the "Factors Affecting Performance" section, agglomeration often affects transport 

### of nanoscale materials in the subsurface. The particles may become associated with the aquifer matrix as oxidized iron particles after they react with contaminants. Under standard environmental conditions (aerated water and 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 nanoscale materials within aquifers and to optimize contact betweenthe nanoscale material and contaminant. Ongoing studies are evaluating surface coatings and other modifications that would reduce agglomeration 

### of nanoscale materials and maximize subsurface mobility (Phenrat 2008). Preliminary research indicates that polymers, surfactants, and organic proteins (such as soy) stabilize nanoscale material suspensions in aquifers, inhibiting their agglomeration and allowing greater dispersal without compromising the ability ofthe iron to remediate contaminants (He etal. 2007, Zhana 2009). Based on laboratory research, soils high in clay content have been shown to allow greater dispersal 

### ofnZVI as well; anionic clay particles appearto function as a natural stabilizer, allowing for more effective transport (Schrick 

### et al. 2004; Hydutsky 

### et al. 2007). Increasing mobility without sacrificing reactivity needs to be tempered with methods to control the migration 

### ofthe nanoscale particles due to lack 

### of toxicological infonnation (Lowry

## etal. 2007). http://clu-in.orgltechfocus/da'ault.focus/sec/Nanotechnology:_Applicalions_fa _Environmenlal_Remediation/cat/Applicalion/ €1132/2El2015 CLU-IN 

### ITectr.ologies >Remediation>About RemediationTechnologies> Nanotechnology:Applications fa Environmental Remediation>Application Studies are being conducted on the potential toxicity ofvarious types of manufactured nanoscale material. The increased surface area and larger number of reactive sites of nanoscale materials may equate to greater biological activity per unit mass than with micro- or macroscale particles ofthe same composition. Substances considered nontoxic at the macroscale may have negative impacts on human health when nanoscale particles are inhaled, absorbed through the skin, or ingested (Kreyling 

### et al. 

### 2006). Because of the small size of nanoscale materials, the particles have the potential to migrateto, oraccumulate in, places that larger particles cannot, such as the alveoli in the lungs (Grassian 

### et al. 

### 2007), thereby potentially increasing toxicity. Some nanoscale materials have demonstrated an ability to increase the bioavailability of certain hydrophobic contaminants, for example, by increasing the mobility of contaminants bound to soil and sediment surfaces CTungittiplakom 

### et al. 

### 2005). Potential health effects 

### of nanoscale materials have been reviewed in Nanoparticles: Health Effects--Pros and Cons, written by Maureen Gwinn and Val Vallyathan. Issues of toxicity and safety have limited the use of nanoscale materials for remediation by some private-sector companies. For example, DuPont has ruled out the use of nZVI for remediation at 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 announc:ecm;i that it will no longer cover injury or damage arising from nanotubes or nanotechnology, as used in products orprocesses. U.S. Environmental Protection Agency's (EPA) Office 

### of Research and Development (ORD) published a 

### Nanomaterial Research Strateav <NRS>m in June 

### 2009 to act as a guide for nanotechnology research within ORD. The NRS centers around progressing EPA's understanding of nanomaterials for decision support and focuses on four research themes:

• Identifying sources, fate, transport, and exposure • Understanding human health and ecological research to inform risk assessment and test methods • Developing risk assessmentapproaches • Preventing and mitigating risks (U.S. EPA

### 2009). In addition, EPA ORD has prepared a document, Nanomaterial CSH Studies: Nanoscale Titanium Dioxide in Water Treabnent and in Topical Sunscreen. The document discusses two case studies on the use of nanoscale**Ti~:** 1) to remove arsenic from drinking water, and 2) as an active ingredient in topical sunscreen. The document was designed to define the information required to perform a comprehensive environmental assessment ofthe potential risks associated with nanoscaleTi02. Top of Page



## Field Demonstrations and Case Studies

As of November

### 2011, datathat exhibit varying degrees ofcomprehensiveness were obtained for 36 sites using or testing nanoscale materials for remediation or in the planning stages. Details on these selected sites are available at http://clu-in.om/products/nanozvi and will be updated periodically as new information is received. Performance data are limited because many 

### of the remediation projects using nanoscale materials are just beginning or are ongoing. However, as the technology is applied at an increasing number of sites with varying geologies, more data will become available on performance, providing site managers and other stakeholders with additional information toevaluatewhetherthetechnology might be applicable fortheirsites. Top of Page



## Cost

In 

### 2001, when field demonstrations of nZVI technology first took place, the cost of nZVI was considered high (nearty $500/kilogram [kg]) due to a limited number of commercial suppliers. In addition, the effectiveness and quality 

### of commercially-available nanoscale material products were highly variable when compared to laboratory-prepared nanoscale material due to insufficient characterization and quality assurance/quality control procedures 

### (Li 

### 2006). By 

### 2006, nZVI costs had reduced to about 

### $50 to 

### $100 per kg. Decreasing nZVI costs and improved quality control procedures that provide better homogeneity are making this technology more viable http://clu-in.orgltechfocus/da'ault.focus/sec/Nanotechnology:_Applications_fa _Environmenlal_Remediation/cat/Application/ 7/132/2El2015 CLU-IN 

### ITectr.ologies >Remediation>About RemediationTechnologies> Nanotechnology:Applications fa Environmental Remediation>Application 

### in today's remediation market. While costs may remain high in some applications, the total costs of deploying the technology at asite compared tothe life cycle cost of

### an ex situ technology can be quite competitive. In addition to the costs associated with the nanoscale material, other factors contribute to the cost of site remediation such as site type, contaminant type, contaminant concentration, extent of

### the contaminant plume, and any challenges that may occur during remediation. Additional factors that may increase the total cost of 

### nanoscale material application may include operational requirements connected with any contamination found underneath a building, orthe need totreat ordispose extracted fluids (Wilson 

### 2004). Currently, project-specific financial information is limited because many ofthe remediation projects using iron nanoscale materials arejust beginning orare ongoing. Proprietary concerns may also preclude cost data from being made publicly available. However, as the use 

### of the technology increases at sites with varying geologies, more cost data will become available, providing site managers and other stakeholders with additional information to evaluate the applicability and cost-effectiveness of

### the technology fortheirsites. Top 

### of Page



## NanotechnologyVendors
The properties of particles such as reactivity, mobility, and shelf life can vary depending on the manufacturing process or the vendor that provides the particle (Miehr 

### et al. 

### 2004). Several vendors supply nanoscale materials for site remediation. See http://clu-in.om/products/nanozvi for information about vendors associated with site-specific applications. More information about vendors and other types of 

### nanoscale materials can be found on the Internet at sites such as htm://www.nanovip.com or http://www.nanotechnow.com/business.htrn. The inclusion ofthese websites should not be considered to be an endorsement by EPA. Top 

### of Page



## Nanotechnology Productswith Potential RemediationApplications
Researchers are developing a variety of 

### other nanoscale materials for potential use to adsorb or destroy contaminants as part 

### ofeither in situor exsitu.p,rocesses. The stage of

### development ranges from bench to pilot scale. These particles include Ti02, 

### SAMMS M, 

### nanotubes, ferritin, dendrimers, metalloporphyrinogens, and swellable organically modified silica (SOMS). NanoscaleTi02 

### is being pilot tested for exsitu treatment of 

### contaminated groundwater as part 

### of a pump and treat system. Additional information on nanoscale Ti02 

### is available within Contaminants Known

### to be Treated Using Nanoscale Materialsand Reactive ChemistryofNanoscale Materials. Some materials can be made with surface functional groups to serve as adsorbents to scavenge specific contaminants from waste streams. SAMMSTM materials 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. Though SAMMSTM materials are larger than the nanoscale range,

### the~ are considered a nanotechnology because of 

### their nanoscale pores. According to researchers, SAMMS M 

### maintains good chemical and thermal stability and can be readily reused or restored (Frvxell et 

### al. 2007). SAMMSTM has a large surface area to allow for quick sorption kinetics. Contaminants successfully sorted toSAMMSTM include radionuclides, mercury, chromate, arsenate+ pertechnetate, and selenite (M@Miaod 

### 2003; Tratnyek and Johnson 

### 2006). According to the SAMMsi.M Adsorbents website, SAMMSM materials have produced positive results in pilot-scale tests for remediation of 

### mercury in well water with a high concentration of dissolved solids, aqueous mercurr in low concentrations, highly radioactive mercuric waste, and gaseous elemental mercury. Since SAMMS M 

### materials adsorb the contaminants, these materials are used primarily as an exsitutreatment technology (!ratnyekand Johnson

### 200§). Nanotubes are engineered molecules mostfrequently made from carbon. They are electrically insulating, highly electronegative, and easily polymerized. Nanotubes have also been made from Ti02 

### and have demonstrated the potential for use as a photocatalytic degrader of 

### chlorinated compounds (Chen 

### et al. 

### 2005). Bench-scale http://clu-in.orgltechfocus/da'ault.focus/sec/Nanotechnology:_Applications_fa _Environmenlal_Remediation/cat/Application/ &'132/2El2015 CLU-IN 

### ITectr.ologies >Remediation>About RemediationTechnologies> Nanotechnology:Applications fa Environmental Remediation>Application research has shown Ti02 nanotubes are particularty effective at high temperatures and are capable 

### of reducing contaminant chemical concentrations by more than 50 percent in 3 hours (Xu 

### et al. 2005). Ti02 is considered an 

### ex situ strategy because effective illumination usually requires that treatment occur in a reactor that is designed forthis purpose (!ratnvekand Johnson200§). 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 Ti02, ferritin is photocatalytic; in one bench-scale project, the addition of visible light caused ferritin to reduce toxic, water-soluble hexavalent chromium to the less toxic trivalent chromium, which is not water soluble and precipitates out of solution (U.S. EPA 2008A). Ferritin is being researched for

### in situ use ITemple Universitv200fl. Dendrimers are hyper-branched, well-organized polymer molecules with 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 remediation of contaminated groundwater. Bench-scale research has indicated that delivery options for dendrimers are flexible (Diallo

## etal. 2006). Dendrimers can be used 

### in situorex 

### situ (Xu 200§). Metalloporphyrinogens are complexes 

### of metals with naturally occurring, organic porphyrin molecules. Examples of biological metalloporphyrinogens are hemoglobin and vitamin B12. Batch-reactorexperiments have shown that metalloporphyrins are capable 

### of reducing chlorinated hydrocarbons such as TCE, PCE, and carton tetrachloride under anoxic conditions to remediate contaminated soil and groundwater. Laboratory research using metalloporphyrinogens is being performed forthe potential 

### in situ remediation of groundwater (Dror

### et al. 

### 21m). SOMS (commercial name Osort) is organically modified silica that swells and captures small molecule organic compounds such as gasoline, natural gas, acetone, ethanol, pharmaceuticals, and solvents. When organic compounds are introducedtoSOMS, the powder swells, capturing the organic compounds. SOMS may 

### be able to capture up to eight-times its volume in organic compounds that are present either

### as neat liquids, vapors, or dissolved in water. The SOMS material is hydrophobic and does not absorbwater(Edmiston 2009).

• lron-Osorb incorporates nZVI into Osorb, forming a material that can dechlorinate captured organics. The glass matrix concentratesthe chlorinated solventsand protects the embedded metal particles from deactivation by dissolved ions. Afterthe lron-Osorb has captured the organic compounds, it can be put through athermal or rinsing process to release the compounds allowing forthe capture ofthe organiccompound and the reuse ofthe lron-Osorb. lron-Osort can gothrough this regeneration process over 

### 100 times (ABS Materials 20108). The manufacturer reports that lron-Osort material is designed to last over 10years in the subsurface. For long-term remediation, it can be injected as a 

### soft curtain barrierto protect groundwaterareas from incoming plumes. 

### In situ pilot scale testing was performed at several sites in Ohio in 2009 for groundwater remediation of

### TCE1**l** • Palladium-Osorb is a similar metal-glass hybrid material used in exsitutreatment systems forremediation of chlorinated volatile organic compounds (VOCs) (Edmiston 2010). Palladium nanoparticles are incorporated into the Osortto remove halogenated VOCsfrom groundwater pumped through the system. A hydrogen gas source supplies a proton that completes the reductive dehalogenation 

### of contaminants inside the Palladium-Osort, and reduces contaminantsto benign products ofethane gas and salts (in the reduction ofTCE) (ABS Materials 2010A). Pilot scale testing at an Ohiosite has shown the continuous reduction ofTCE from 5800 parts per millionto no detect bythe 

### exsitu system. The manufacturer reports that Palladium-Osorb isa catalytic material that does not break down orneed replacement. An above ground unit has been designed totreat 1

### O gallons per minute of produced water 

### (ABS Materials2010A) and the unit has been modified to 

### be able totreat the oil sheens and moussesthat result from oil spills. The unit is being field-tested for possible use in the Gulfof Mexico (Boccieri 2010). Researchers are also using nanotechnology to develop membranes forwatertreatment, desalination, and water reclamation. These membranes incorporate a wide variety 

### of nanoscale materials, including those composed 

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

### et al. 2008). Carbon nanotubes can be aligned to form membranes with nanoscale 

### pores to filter organic contaminants from groundwater (Mauter

## et al. 2008; Meridian Institute 2006). Top of Page
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### ITectr.ologies >Remediation>About RemediationTechnologies> Nanotechnology:Applications fa Environmental Remediation>Application 

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