Oil spill cleanup is an expensive and complicated process that often harms marine life and further damages the environment. Currently used solutions include burning the oil, using chemical dispersants to breakdown oil into very small droplets, skimming oil floating on top of water, and/or absorbing it with expensive, unrecyclable sorbents. Burning increases carbon emissions and dispersants are harmful for marine wildlife. Skimmers don’t work in rough waters or with thin layers of oil. Sorbents are not only expensive but generate a huge amount of physical waste.
With an ability to absorb more than 30 times its weight in oil, a highly porous sponge was developed that could be used to inexpensively and efficiently clean up oil spills without harming marine life. After squeezing the oil out of the sponge, it can be reused many dozens of times without losing its effectiveness.
The solution selectively absorbs oil and leaves clean water and unaffected marine life behind. It uses a nanocomposite coating of magnetic nanostructures and a carbon-based substrate that is oleophilic (attracts oil), hydrophobic (resists water), and magnetic. The nanocomposite’s nanoporous 3D structure selectively interacts with and binds to the oil molecules, capturing and storing the oil until it is squeezed out. The magnetic nanostructures give the smart sponge two additional functionalities: controlled movement in the presence of an external magnetic field and desorption of adsorbed components, such as oil, in a simulated and remote manner.
The OHM (oleophilic hydrophobic magnetic) nanocomposite slurry can be used to coat any inexpensive, commercially available sponge. The researchers applied a thin coating of the slurry to the sponge, squeezed out the excess and let it dry. The sponge is quickly and easily converted into a smart sponge (or OHM sponge) with a selective affinity for oil.
The OHM sponge was tested with many different types of crude oils of varying density and viscosity. The OHM sponge consistently absorbed up to 30 times its weight in oil, leaving the water behind. To mimic natural waves, researchers put the OHM sponge on a shaker submerged in water. Even after vigorous shaking, the sponge release less than 1% of its absorbed oil back into the water.
The smart sponges serve as an environmental remediation platform for selectively removing and recovering pollutants present in water, soil, and air such as excess nutrients, heavy metal contaminants, VOC/toxins, and others. The nanostructure coating can be tailored to selectively adsorb (and later desorb) these pollutants.
The team also is working on another grade of OHM sponge that can selectively absorb (and later recover) excess dissolved nutrients, such as phosphates, from fertilizer runoff and agricultural pollution.