May 29 2020
A research team under the guidance of Northwestern University has designed a highly porous smart sponge that selectively soaks up oil from water.
The sponge can absorb over 30 times its weight in oil, and thus can be utilized to cheaply and efficiently clean up oil spills without any harm to the marine life. Once the oil is squeezed out of the sponge, it can be reused several dozens of times without losing its efficiency.
Oil spills have devastating and immediate effects on the environment, human health and economy. Although many spills are small and may not make the evening news, they are still profoundly invasive to the ecosystem and surrounding community. Our sponge can remediate these spills in a more economic, efficient and eco-friendly manner than any of the current state-of-the-art solutions.
Vinayak P. Dravid, Study Lead Researcher, Northwestern University
The study was published in the Industrial Engineering and Chemical Research journal on May 27th, 2020.
Dravid is also the Abraham Harris Professor of Materials Science and Engineering at Northwestern’s McCormick School of Engineering. Vikas Nandwana, a senior research associate in Dravid’s laboratory, is the first author of the study.
Cleaning up oil spills is a costly and tough process that often causes harm to marine life and further impacts the environment. The solutions used at present are to burn the oil, making use of chemical dispersants to disintegrate oil into very tiny droplets, skimming oil that floats on top of the water, and/or absorbing it using costly and unrecyclable sorbents.
Each approach has its own drawbacks and none are sustainable solutions. Burning increases carbon emissions and dispersants are terribly harmful for marine wildlife. Skimmers don’t work in rough waters or with thin layers of oil. And sorbents are not only expensive, but they generate a huge amount of physical waste—similar to the diaper landfill issue.
Vikas Nandwana, Senior Research Associate, Northwestern University
The Northwestern solution overcomes such difficulties through selective absorption of oil and leaving only clean water and unaffected marine life behind. The secret behind this ability is a nanocomposite coating of magnetic nanostructures and a carbon-based substrate that is hydrophobic (resists water), oleophilic (attracts oil), and magnetic.
The nanoporous 3D structure of the nanocomposite selectively interacts with and attaches to the oil molecules, thus trapping and storing the oil until it is pressed out. The magnetic nanostructures offer the smart sponge two extra functionalities: regulated movement when there is an external magnetic field and desorption of adsorbed components, like oil, in a remote and simulated way.
The oleophilic hydrophobic magnetic (OHM) nanocomposite slurry can be utilized to coat any low-cost and commercially available sponge. The scientists applied a thin coating of the slurry over the sponge, squeezed out the surplus, and allowed it to dry. The sponge can be easily and rapidly transformed into a smart sponge (or “OHM sponge”) with a selective attraction for oil.
Vinayak together with this research team tested the OHM sponge with several kinds of crude oils of different viscosity and density. The OHM sponge constantly absorbed up to 30 times its weight in oil and left water behind. The natural waves were simulated by placing the OHM sponge on a shaker immersed in water. Even after strong shaking, the sponge liberated less than 1% of its absorbed oil back into the water.
According to Dravid, “Our sponge works effectively in diverse and extreme aquatic conditions that have different pH and salinity levels. We believe we can address a giga-ton problem with a nanoscale solution.”
We are excited to introduce such smart sponges 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.
Vikas Nandwana, Senior Research Associate, Northwestern University
Additionally, the researchers are working on OHM sponge of another grade, with the ability to selectively absorb (and later recover) surplus dissolved nutrients, like phosphates, from agricultural pollution and fertilizer runoff.
Stephanie Ribet, a PhD candidate in Dravid’s laboratory and co-author of the paper, is pursuing this subject. Furthermore, the researchers plan to design and commercialize OHM technology for environmental clean-up.
The study titled “OHM Sponge: A versatile, efficient and eco-friendly environmental remediation platform” was financially supported by the National Science Foundation. The co-authors of the paper are Stephanie Ribet, Roberto Reis, Yuyao Kuang, and Yash More—all from Northwestern.
Journal Reference:
Nandwana, V., et al. (2020) OHM Sponge: A Versatile, Efficient, and Ecofriendly Environmental Remediation Platform. Industrial Engineering and Chemical Research. doi.org/10.1021/acs.iecr.0c01493.
Source: https://www.northwestern.edu/