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Nanoremediation: Information for Decision Makers from NanoRem

Thematic Page 3: Implementation Issues for Using Nanoparticles in Remediation

Contents
 

1.  Aim
2.  Introduction
3.  Quality Assurance/Quality Control Issues
4.  Relative Cost of Nanoremediation
5.  Ease of Use
6.  Hazards from nZVI Handling in Remediation
7.  NanoRem Activities
8.  Additional Resources on the NanoRem Web Site
9.  References
10.  Feedback and Opinions


1 Aim



The aim of this page is to highlight the specific implementation issues affecting the application of nZVI for the remediation of contaminated groundwater. nZVI has been the most widely used nanoparticle type in practice to date.
 

This thematic page summarises information provided by a chapter of the NanoRem report: 'A Risk/Benefit Appraisal for the Application of Nano-Scale Zero Valent Iron (nZVI) for the Remediation of Contaminated Sites'. The full report including additional information, detail and referencing can be downloaded from: 
www.nanorem.eu/Displaynews.aspx?ID=525


2 Introduction



As with all other in situ remedial technologies, the successful implementation of nanoremediation is dependent upon:
 
  • Good site characterisation
  • The development of a robust site conceptual model
  • Good remedial design with clear objectives
  • Good implementation of technology on site
  • Experienced field operatives
  • A good system of quality assurance/quality control (QA/QC)
 
A full list of the operating parameters that should be considered can be found in “A Risk/Benefit Appraisal for the Application of Nano-Scale Zero Valent Iron (nZVI) for the Remediation of Contaminated Sites in the Environment” (Table 2 - Parameters for consideration in the deployment of nZVI)
www.nanorem.eu/Displaynews.aspx?ID=525


3 Quality Assurance/Quality Control Issues



nZVI particles are highly reactive and their properties are not static but change over time (see: Thematic page 4: Factors Affecting Potential Deployment Risks from nZVI into the Environment). The result of this is that the handling, environmental stability and contamination issues (e.g. retention in pore spaces) associated with bulk products are of considerably more importance for nanoparticles compared to other chemical agents used in in situ remediation (Baer et al. 2007). For example, nZVI particles manufactured well in advance of the injection time may experience loss of reactivity. Site operatives should therefore confirm the particles’ reactivity prior to injection, and be aware of how any changes from the reactivity specified in the design might influence the effectiveness of the remediation.  


4 Relative Cost of Nanoremediation



There is little robust data within the scientific literature relating to the costs of implementing nanoremediation. As of 2001, nZVI material costs in the USA were typically in the order of $30-40/lb (€ 23 - 31kg), while micro-scale ZVI was around $1-5/lb (€ 0.8 – 3.9 /kg), and millimetre-scale iron was generally in the range of $0.25-0.75/lb (€ 0.25 -0 0.75/kg) (conversion rate dollars to euro as of September 2014). However, it is postulated that economies of scale would be likely to drive down the relative cost of nZVI. In addition, at least at laboratory scale, nZVI is more reactive than conventional ZVI and thus less material is needed to treat the same quantity of contaminant. However, it is difficult to extrapolate these results into the field for a number of reasons including the possibility that the higher reactivity of the nZVI may make it more susceptible to passivation, as a result of reacting with groundwater and the aquifer material, and so may require multiple injections to achieve the same groundwater clean-up.
 

However, as is the case with the majority of in situ remediation technologies, the cost of the active reagent can be a relatively small proportion of the overall site budget, when site investigation, consultant and contractor labour, and analytical laboratory costs are considered.


5 Ease of Use 



Most field operations have used direct injection techniques to deliver the nanoparticles into the subsurface (see: Thematic Page 1: Application of nZVI in Remediation) and for ease of operation, the particles have usually been introduced as pumpable slurry, e.g. in water, vegetable oil or in gaseous nitrogen. However, Siskova et al. (2012) demonstrated an air-stable nZVI formation coated with an inner shell of amorphous ferric oxide/hydroxide and an outer shell of glutamic acid. Despite the double coating, Siskova and colleagues still found the nZVI to be highly reactive. 
 

One problem reported in the literature is the limited distance travelled by the nanoparticles from the point of injection. In the case of nZVI, particle mobility has often been limited to several metres, or significantly less, from injection points with daylighting being reported in a number of cases (Uyttebroek et al. 2010). Modified or stabilised nanoparticles have been shown to travel the furthest from the point of injection, but they are typically less reactive than the unmodified particles. Designers have to make the balance between reactivity and distance travelled from point of injection. 


6 Hazards from nZVI Handling in Remediation 



Once manufactured, the most significant health and safety risks for people working with nZVI occur during the transportation, handling, and injection of the nanoparticle slurries. If dry nanomaterials are delivered to site then the higher surface reactivity and surface-area-to-volume ratio of the nanopowders increases the risk of dust explosion. However, as stated previously, the majority of projects utilise nanoparticles delivered as slurries so this issue does not generally arise. Such handling concerns are not unique to nanoparticles and the remediation sector has recognised the need for good handling, storage and transportation procedures for other hazardous substances, such as those used for in situ chemical oxidation. 
 

Risks to human health and the environment from nanoparticles are mitigated by compliance with appropriate regulatory procedures, namely following procedures outlined in Safety Data Sheets (SDS) for countries where REACH regulations apply and in the USA (see: FAQ How safe is nanoremediation to use and what are the possible risks associated with it). These sheets typically accompany the manufactured product and include the specific information relating to physical and chemical properties, identified hazards, acute and chronic health effects, first aid measures, fire-fighting measures, accidental release measures, handling and storage, exposure controls and personal protection, transport, and regulation. For modified nZVI, SDS should also contain information related to coatings. However, it should be noted, that documentation with this type of information or level of detail are not commonplace in the emergent nZVI marketplace. Generally speaking, over the past several years, SDS supplied with nZVI purchases tended to provide relatively generic data as very little toxicological, emergency response, and clean-up information was available. The NanoRem project aims to provide the NanoRem SDS information on the external web site for all particles which will be used on the project’s field sites. 
 

Method statements relating to the implementation of the technology should ensure that practitioners wear appropriate personal protective equipment (PPE) during slurry handling and injection. Recognition of potential hazards such as hydrogen gas evolution from aqueous nZVI slurries in mixing tanks and direct-push injection equipment is important. 
 

Although there is no explicit reference to nanomaterials, the European Commission concluded that REACH (Regulation on the Registration, Evaluation, Authorisation and Restriction of Chemicals) and CLP (European Regulation on classification, labelling and packaging of substances and mixtures) offered the best possible framework for the risk management of nanomaterials when they occur as substances or in mixtures. However, within this framework more specific requirements for nanomaterials have proven necessary and this is currently under review. 


7 NanoRem Activities



Nanoremediation is an emerging technology in many countries, but many of the factors leading to successful implementation are similar to those associated with other in situ technologies utilising other chemical reagents. 
 

The NanoRem project aims to undertake fully documented nanoremediation trials at a number of test sites across the European Union, and to ensure that this information is widely disseminated to interested parties.  The distribution of this information should hopefully reassure decision makers on the efficacy of the process, and thus encourage the uptake of this emerging promising technology for the remediation of contaminated groundwater.
 

This information will include, but not be limited to:
 
  • Fully documented case studies where nanoremediation has been utilised.
  • The continual monitoring of nanoparticles within the sub-surface post injection using dedicated equipment to provide information on the distance travelled by nanoparticles from the point of injection.
  • Laboratory analysis from a series of water samples to establish the fate of nanoparticles and their degradation products within the groundwater. 
  • The relative costs of implementing nanoremediation, and how it compares with alternative in situ remediation technologies.
  • The production of appropriate SDS for all particles which will be used on the field sites.
  • The efficiency of NPs.


8 Additional Resources on the NanoRem Web Site


This thematic page summarises information provided by a chapter of the NanoRem report: 'A Risk/Benefit Appraisal for the Application of Nano-Scale Zero Valent Iron (nZVI) for the Remediation of Contaminated Sites'. The full report including additional information, detail and referencing can be downloaded from:  www.nanorem.eu/Displaynews.aspx?ID=525.
 

Additional summary information is also available on the following online pages:
 


FAQs
 

Currently we have the following FAQ pages:

 



 
THEMATIC PAGES
 


 

 


9 References


BAER, D. R., TRATNYEK, P. G., QIANG, Y., AMONETTE, J. E., LINEHAN, J., SARATHY, V., NURMI, J. T., WANG, C-M. AND ANTONY, J. 2007 ’Synthesis, Characterisation, and Properties of Zero-Valent Iron Nanoparticles’. In FRYXELL, G.E. AND CAO, G. (eds.) Environmental Applications of Nanomaterials: Synthesis, Sorbents and Senors, Imperial College Press, London, 49-86.  http://books.google.co.uk/books?hl=en&lr=&id=CqIH3eklveQC&oi=fnd&pg=PA49&dq=%E2%80%99Synthesis,+Characterisation,+and+Properties+of+Zero-Valent+Iron+Nanoparticles&ots=nen2vRzm-i&sig=nIGDyDRtlcfObnhsNLMn7Rnzypw#v=onepage&q=%E2%80%99Synthesis%2C%20Characterisation%2C%20and%20Properties%20of%20Zero-Valent%20Iron%20Nanoparticles&f=false
 

SISKOVA, K., TUCEK, J., MACHALA, L., OTYEPKOVA, E., FILIP, J., SAFAROVA, K., PECHOUSEK, J. AND ZBORIL, R. 2012 ‘Air-stable nZVI formation mediated by glutamic acid: solid-state storable material exhibiting 2D chain morphology and high reactivity in aqueous environment’, Journal of Nanoparticle Research, 14,4, 1-13.
http://dx.doi.org/10.1007/s11051-012-0805-9
 

UYTTEBROEK, M., BAILLIEUL, H., VERMEIREN, N., SCHOLIERS, R., DEVLEESCHAUWER, P., GEMOETS, J. AND BASTIAENS, L. 2010 ‘In Situ Remediation of a Chlorinated Ethene Contaminated Source Zone by Injection of Zero-valent Iron: From Lab to Field Scale’, Proceedings of the 4th International Symposium on Permeable Reactive Barriers & Reactive Zones, July, 2010.
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCUQFjAA&url=http%3A%2F%2Fwww.multibarrier.vito.be%2Fdocs%2FPRB2010-Proceedings.pdf&ei=_78RVKvGAqmN7Qbs1YG4DQ&v6u=https%3A%2F%2Fs-v6exp1-ds.metric.gstatic.com%2Fgen_204%3F
 

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