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Nanoremediation: Information for Decision Makers from NanoRem

Thematic Page 2: Benefits of Using Nanoparticles in Remediation

Contents

1. Aim

2. Broad Benefits of In Situ Treatments in General

3. Benefits of Nanoremediation

4. Additional Resources on the NanoRem Web Site

5. Feedback and Opinions

 

1 Aim 

This page summarises the benefits of using nano-scale zero valent nanoparticles  in remediation, compared to the use of alternative in situ technologies.  More detailed information is available from the NanoRem Tool Box (http://www.nanorem.eu/toolbox/index.aspx#TB1).

 

2 Broad Benefits of In Situ Treatments in General

Over the last 30 years, approximately 80,000 sites have been remediated in European countries. Early efforts were largely based on containment, “pump and treat” and/or removal to landfill. However, treatment based approaches began to become widely available from the late-1980s. In the majority of remediation projects, the contaminated materials (solid or liquid) are removed to the surface prior to treatment (ex situ). However, in many cases the excavation of contaminated material may be neither desirable, nor even feasible; e.g. the contamination may be inaccessible: either at significant depth or below operational plant infrastructure or building footprints. In such cases the contamination can be addressed using in situ remediation technologies. 

A range of in situ technologies are in use that exploit biological, chemical, physical and/or thermal processes to treat soil and/or groundwater in the sub-surface. In situ remediation is now a significant remediation market segment. These enable remediation to be undertaken with minimal disruption to site operations and with minimal exposure of site workers and others to the contaminants (e.g. in dust, gas or vapours). The “footprint” of an in situ remediation project tends to be much smaller than for an ex situ scheme, meaning that treatment can usually be carried out where access and available space are restricted.

The use of nanoparticles potentially extends the range of available in situ remediation technologies, and may offer particular benefits in some applications.

 

3 Benefits of Nanoremediation

The broad potential benefits seen for using nanoremediation fall into a number of categories: improving the range, extent and rate of contaminant destruction; extending the treatable range of contaminants; extending the range of treatable conditions; providing source term treatment capability; synergies and enhancement effects.

 

3.1 Extending the Range of Treatable Contaminants

Nanoremediation can extend the range of treatable contaminants leading to the destruction of organic contaminants and the transformation and/or precipitation of inorganic contaminants such as the treatment of hexavalent chromium (Cr(VI)). Additional studies have demonstrated the treatment of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pentachlorophenol (PCPs), and the chlorinated benzenes. nZVI has also been considered as a treatment for radionuclides such as radium, uranium and pertechnetate.

Note:  treatability of contaminant categories by nZVI based on bench scale work can be found in Annex 2 of the report “A Risk/Benefit Appraisal for the Application of Nano-Scale Zero Valent Iron (nZVI) for the Remediation of Contaminated Sites” www.nanorem.eu/Displaynews.aspx?ID=525.

 

3.2 Improving the Extent and Speed of Contaminant Destruction

Due to their small particle size, nanoparticles have a very high specific surface area, which significantly increases their reactivity. In addition, the enhanced surface area allows the particles to be in more intimate contact with the contaminants. In theory, the combination of these two features should make nanoparticles more efficient compared with other solid chemical reactants, including microscale ZVI, in treating identical contaminant masses. This effect can be significantly enhanced by the use of catalytic bimetallic nanoparticles (BNP). 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). However, it should be noted that this claim has been difficult to verify in the field largely due to the heterogeneous nature of in situ conditions.

 

3.3 Providing Source Term Treatment Capability

There are limitations to the effectiveness of any in situ approach to source removal / destruction. However, nanoremediation may be effective for mopping up small source terms, for example, what are often termed as secondary sources. Secondary sources may be used to describe two types of sources: (a) free product that has migrated away from the original term source and (b) more colloquially, smaller sources on a contaminated site.

 

3.4 Extended range of environmental conditions

nZVI has been shown to be effective across a broad range of soil pHs, temperatures, and nutrient levels.  Nanoremediation would also not be subject to conditions which might be inhibitory to biological processes.

 

3.5 Compatibility with Other Treatments

A number of researchers have suggested that nZVI may be suitable for deployment alongside other remediation technologies, with some studies demonstrating a synergistic effect. In particular, the synergy between nZVI addition and supporting biological processes of dehalorespiration is a significant opportunity for nZVI deployment.

The literature also describes a number of other emerging approaches include combined treatments including nZVI with other treatments, for example, thermal destruction, electrokinetic treatments (Gomez et al. 2015a and b) and in situ bioremediation.  Of these combined bioremediation and chemical dechlorination in situ is most developed, and

 

4 Additional Resources on the NanoRem Web Site

Comprehensive resources are available from the NanoRem Tool Box, shown below (http://www.nanorem.eu/toolbox/index.aspx):



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

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Taking Nanotechnological Remediation Processes from Lab Scale to End User Applications for the Restoration of a Clean Environment.
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