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.
FAQs
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