BLOG: How magnetic nanoparticles can be used to clean up oil spills
After the huge oil spill that occurred in the Gulf of Mexico in 2010,¹ there has been an increased effort by oil companies to reduce the financial and environmental costs of spills.² Further complications can occur during other processes, such as the extraction of crude oil, which causes oil to leak into the ocean.³ In cases such as these, the oil either floats to the surface or, if heavy enough, sinks to the seabed. In the first case, oil that settles on the water’s surface spreads continuously.⁴ These sheets of oil are poisonous to birds (if ingested) and can damage their feathers, resulting in birds freezing to death (i.e., because they have lost their means of insulation).⁵
One current method for cleaning up oil spills involves using boats (`skimmers’) to scoop up oil from the water’s surface.⁶ Skimmers are not very efficient, however, as they are only able to remove oil from the surface of the water. Furthermore, their efficiency reduces with increased turbulence, meaning that about 50% of the oil can be lost. Another method currently in use involves burning oil from the water’s surface. Although this approach provides a quick and easy way to remove oil that has spread, it has a greater negative impact on the environment because it causes the release of greenhouse gases. An additional drawback of these methods is that they require a great deal of labour.⁷
The main challenge lies in quickly removing any oil that has been spilled and thus ensuring minimal damage to the environment.⁸ One method that could help to achieve these aims is based on bioremediation, where bacterial microbes ingest and break the oil down into smaller compounds (e.g., carbon dioxide and ethane). The benefits of this approach include that it is relatively inexpensive, requires minimal labour, and only a small amount of equipment is necessary. However, oil is not recovered using this approach and greenhouse gases are again produced, which causes further damage to the environment.⁹
Researchers at MIT are currently looking into new ways that allow oil to be separated from water quickly and efficiently. One such technique involves coating magnetic nanoparticles—particles smaller than 100nm in diameter—with polymers. The nanoparticles are coated in a polymer that has a positive charge. The positively charged nanoparticles can then attract the negatively charged oil droplets through the electrostatic force of attraction. Once the positively charged nanoparticle is bonded to the oil droplet, it can be separated from the water using magnets.
Fluids with magnetic nanoparticles are known as ‘ferrofluids’. Previously, research has been carried out to separate the nanoparticles from the water by letting the ferrofluids pass through channels. These channels are surrounded by magnets which separate the magnetic nanoparticles (i.e., that are bonded to the oil) from the water. The eventual goal of this approach is to separate the oil from the water such that it can be reused, and the money thus acquired can offset the cost of the clean-up.² However, this method is not practical enough with regards to oil spills as it is difficult to know the exact concentration of the nanoparticles that would need to be extracted.¹⁰
To overcome this problem, MIT researchers immersed the magnet directly into the fluid containing the nanoparticles which carried the oil. They also decided to orientate the cylindrical-shaped magnets so that they were perpendicular to the flow of water, such that the oil would travel up the sides of the magnet and accumulate around the point with the strongest area of magnetism – the edge. The researchers plan to conduct this process in an oil-recovery vessel so that the nanoparticles will not contaminate the environment or the oil, and so that the nanoparticles (which can be removed using magnets) can be reused.¹¹
The main advantage of using magnetic nanoparticles is that they enable most of the oil to be recovered. The magnetic nanoparticles attach directly to the oil droplets, making the separation process quick and simple. Moreover, the process is continuous and no additional power is required.¹² The problems associated with the use of magnetic nanoparticles are primarily that they are not tested on a larger scale. However, the team at MIT are currently conducting research which involves testing the nanoparticles in larger tanks before they trial them in open water.
Magnetic nanoparticles provide a quick, non-toxic and efficient way of separating oil from water. Furthermore, a magnetic-nanoparticle-based approach enables recovered oil to be reused and, as such, any money thus saved couldbe used to help offset the expense of the clean-up. In addition to being more environmentally friendly compared to existing methods, this technique does not produce the harmful greenhouse gases that are created during bioremediation,¹³ making magnetic nanoparticles a promising new technology for cleaning up oil spills in the future.
1 Gulf Oil Spill. Smithsonian (2018). Accessed 29 June, 2018.
2 M. Treacy. 10 impressive innovations for cleaning up oil spills developed since the Gulf disaster. TreeHugger (2017). Accessed 29 June, 2018.
3 How are oil and gas extracted from under the sea bed? GridClub. Accessed 29 June, 2018.
4 New oil spill dispersant made from ingredients in peanut butter, chocolate, ice cream PhysOrg (2017). Accessed 29 June, 2018.
5 Magnets could pull oil out of ocean before wildlife is harmed. New Scientist (2016). Accessed 29 June, 2018.
6 10 methods for oil spill cleanup at aea. Marine Insight (2018). Accessed 29 June, 2018.
7 How do spills happen? Office of Response and Restoration, National Oceanic and Atmospheric Administration (2018). Accessed 29 June, 2018.
8 Nanoparticles and magnets offer new, efficient method of removing oil from water. ScienceDaily (2017). Accessed 29 June, 2018.
9 A citizens guide to bioremediation. (2017). [ebook] Environmental Protection Agency, pp.1-2. Accessed 29 June, 2018.
10 Water-Repellent Ferrous Nanoparticles May Help Clean Oil Spills. SciTech Daily (2017). Accessed 29 June, 2018.
11 Larry Hardesty. How to clean up oil spills. MIT News (2017). Accessed 29 June, 2018.
12 Tom Levitt. Cleaning up oil spills with magnets and nanotechnology. CNN (2017). Accessed 29 June, 2018.
13 Nina Dombrowski and Brett J. Baker T. Scientists Want to Use Bacteria to Clean Up Oil Spills – And It Could Actually Work ScienceAlert (2017). Accessed 29 June, 2018.