To address some of the serious concerns surrounding the methods in which oil is removed from water in the event of a serious spill, such as those that have occurred several times over the past few decades around the world, a team of Researchers from the Cockrell School of Engineering at the University of Texas at Austin have developed a way in which up to 99.9% of the oil is removed from water.
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While modern oil separation methods have been recorded to separate approximately 95% of oil from water, the accumulation of the small oil droplets that remain are not only difficult to remove, but can cause deleterious effects to the environment and marine wildlife present within the affected waters. By synthesizing magnetic nanoparticles (MNPs) that were specifically coated to treat water, these Researchers were able to successfully remove oil and other potential contaminants through a method that relies primarily on the electrostatic force between the oil and the engineered magnet.
In the event of an oil spill, there are several traditional methods to clean up large bodies of water that are affected by this type of incident. Through a method of physically removing the oil present on the surface of the water, workers use long and buoyant booms, or inflatable tubes, to surround, isolate and scoop the oil slick onto the shore or a nearby vessel. Once the majority of the oil spill is captured, chemical dispersants are used to break down oil into droplets that can be more easily mixed and absorbed by the water.
While this method is used to speed up the natural biodegradation process, which occurs when bacteria and other microorganisms that are naturally present in the water breakdown the oil into components such as fatty acids and carbon dioxide, chemical agents can cause extremely deleterious effects to the marine organisms present within the affected area1. In fact, as marine animals absorb these harmful chemical agents, the likelihood of subsequent human consumption of the dispersants rises, as affected seafood enter the food chain. Those responsible for cleaning up oil spills in our large bodies of water, such as the Coast Guard and the Environmental Protection Agency within the United States, therefore face a particularly challenging task of ensuring a complete reversal of the oil spill while eliminating additional threats to the environment during this process.
Derived from a previously determined mathematical model that estimated the total time and velocity in which the MNPs could magnetically separate oil droplets from water solutions, the Texas team applied this hypothesized schematic by use of superparamagnetic magnetite MNPs that had an average size of 66 nm. By coating the MNPs with positively charged polymers, the negatively-charge possessing oil droplets were attracted to the MNPs through an electrostatic attractive force.
Once the MNPs latched onto the oil droplets, a subsequent neutral charge was applied to the surface of the MNP/oil-droplet aggregate that forms from the magnetic attraction2. In a process that was inspired by high gradient magnetic separation, a process typically used in both mining and food industries to ensure the removal of toxic particles, the aggregates can be magnetically separated from water in a rapid manner that can occur both on their own, as well as following the application of an external magnetic field.
What is especially remarkable about the engineered MNPs devised in this study involves the possible extensions of this application that reaches far beyond removing oil from water. By manipulating the surface coating design to specifically attract a contaminant or toxic particle of interest, Researchers can utilize the magnetic properties of the MNPs for a wide variety of important applications. For example, by simply reversing the magnetic attraction of the MNPs to a negatively charged polymer surface to target positively charged particles, lead (Pb+2/+3) or mercury (Hg+1/+2)2, both extremely harmful neurotoxins, for example, could be successfully removed from an aquatic environment, which could have significant impacts on marine life and human consumption of such seafood. As the Texas team of Researchers continue to work towards expanding the MNP design to handle a high volume of oil and water, such as that could occur in the event of a large oil spill within the ocean, they are hopeful that this discovery will significantly impact the way in which we utilize nanotechnology for the greater good of our environment.
References
- “How are Oil Spills Cleaned?” – LiveScience
- “Amine functionalized magnetic nanoparticles for removal of oil droplets from produced water and accelerated magnetic separation” S. Ko, E. Kim, et al. Journal of Nanoparticle Research. (2017). DOI: 10.1007/s11051-017-3826-6.
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