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Nanoparticles are used in a broad range of applications, such as food processing, disinfectants, water purification, and household appliances. Interest in applying nanotechnology to environmental cleanup has been increasing, by preventing, detecting, monitoring, and remediating pollution.
Current Cleanup Issues and the Nanoparticle Solution
Environmental cleanup projects are of global and local interest, involving the cleanup of landfills, oil fields, and industrial sites which can contain and leak pesticides, oils, heavy metals, and other dangerous chemicals. Affected resources, such as aquifers and groundwater, risk harming surrounding populations.
Current cleanup techniques include thermal treatment, chemical oxidation, and surface cosolvent flushing. These methods are expensive, time-consuming, and only partially effective, which is pushing industries to turn to nanoparticles, as a more cost-effective solution.
Nanotechnology methods currently used to tackle environmental cleanup include nanoscale zeolites, metal oxides, carbon nanotubes, and bimetallic nanoparticles. These technologies can transform and detoxify pollutants. Nanoscale zero-valent iron is currently the most popular nanoparticle technique used for environmental cleanup, partly due to high surface area and high reactivity which increases cleanup efficiency.
Applications of Nanoparticles to Environmental Cleanup
Nanoparticles have important uses in cleaning groundwater and soil for the environmental sector. Nanoscale zero-valent iron is particularly diverse. By injecting it to the affected area, it can dechlorinate organic solvents, detoxify pesticides, immobilize metals, and transform fertilizers, such as nitrates. Other nanoparticles can also be applied to these issues, such as bimetallic nanoparticles for dechlorinating organic solvents and carbon nanotubes for detoxifying pesticides.
The textile industry is over increasing scrutinization for its role in environmental damage. Dyes, which can be carcinogenic and mutagenic, can leak into the environment from textile factories. Nanoparticles can detoxify dyes and prevent issues associated with dyes’ long lifetime and deleterious environmental effects. Similarly, nanoparticles have been successfully applied to the removal of toxic metals. Magnetic nanoparticles with their high magnetic properties and large surface area have worked well for metal removal and can do so with high efficiency and high removal rate.
So far, nanoparticles have been applied for the cleanup of groundwater, water, wastewater, crude oil spills, and soils. In addition to remediating pollution, nanoparticles have been successfully used in detection and monitoring. Magnetic nanoparticles, which are nanoparticles that do not have magnetic memory (including nanoscale zero-valent iron nanoparticles), have been used to analyze organic compounds and pesticides present in water, methanol, and fresh produce. This is done by combining nanotechnology with mass spectrometry methods and/or chromatography techniques, such as gas chromatography or high-performance liquid chromatography.
Risks of Nanoparticles
Along with the benefits of this growing technology, there are risks associated with nanoparticles which have often not been fully explored. Overall, there are five main issues with nanoparticle application: aggregation of nanoparticles when present at high concentrations into larger clusters or bioaccumulation, uncharacterized mobility and dispersal ability, potential unknown dangers to human or ecological health, longevity in natural environments, and whether or not its possible to remove nanoparticles from the environment after they have been introduced.
Studies looking at the environmental effects of nanoparticles on the environment and human health have covered several organisms. In bacteria, nanoparticles have been shown to cause reactive oxygen species in living cells, thereby damaging the DNA and cell survival. In plants, nanoparticles caused toxicity when present at concentrations higher than 200 mg/L. In soil microorganisms, nanoparticles were toxic when in dry soil.
The effects of nanoparticles in humans, ingested by water or food, inhalation, or exposure through contaminated air, are numerous. To name a few, nanoparticles have been associated with oxidative stress, DNA mutations, lung diseases, and inflammation. The adverse effects demonstrated on both the environmental and human health likely mean its widespread use in environmental cleanup will be limited unless safety concerns can be overcome and unless the contaminant is significantly more harmful. More so than other nanotechnologies, nanoparticles could be of huge benefit if in situ applications can be safely carried out.
Sources and Further Reading
- Patil S.S., et al. (2016). Nanoparticles for environmental clean-up: a review of potential risks and emerging solutions. Environmental Technology and Innovation. http://dx.doi.org/10.1016/j.eti.2015.11.001
- Kaur R., et al. (2014). Synthesis and surface engineering of magnetic nanoparticles for environmental cleanup and pesticide residue analysis: a review. Journal of Separation Science. https://doi.org/10.1002/jssc.201400256
- Tratnyek P.G. and Johnson R.L. (2006). Nanotechnologies for environmental cleanup. Nanotoday. https://doi.org/10.1016/S1748-0132(06)70048-2