Intelligent sponge could clean up oil spills
A team led by Northwestern University has developed a highly porous, intelligent sponge that selectively absorbs oil in water.
With its ability to absorb more than 30 times its weight in oil, the sponge could be used to clean up oil spills in a cost-effective and efficient way without harming marine life. Once the oil has been squeezed out of the sponge, it can be reused many dozens of times without losing its effectiveness.
"Oil spills have devastating and immediate effects on the environment, human health and the economy," said Vinayak Dravid of Northwestern, who led the research. "Although many oil spills are small and may not make the evening news, they are still deeply invasive to the ecosystem and surrounding communities. Our sponge can clean up these spills in a more economical, efficient and environmentally friendly way than any of today's most advanced solutions".
The research was published in the journal Industrial Engineering and Chemical Research. Dravid is the Abraham Harris Professor of Materials Science and Engineering at McCormick School of Engineering at Northwestern. Vikas Nandwana, a senior research fellow in Dravid's laboratory, is the lead author of the paper.
Oil spill cleanup is an expensive and complicated process that often harms marine life and further pollutes the environment. Current solutions include burning the oil, using chemical dispersants to break the oil into very small droplets, skimming the oil floating on the water and/or absorbing the oil with expensive, non-recyclable sorbents.
"Each approach has its own drawbacks and none is a sustainable solution," Nandwana said. "Combustion increases carbon emissions, and dispersants are terribly harmful to marine life. Skimmers do not work in rough waters or with thin layers of oil. And sorbents are not only expensive, they also generate a huge amount of physical waste - similar to the problem of diaper landfills".
The Northwestern solution overcomes these challenges by selectively absorbing oil, leaving clean water and unpolluted marine life behind. The secret lies in a nanocomposite coating of magnetic nanostructures and a carbon-based substrate that is oleophilic (attracts oil), hydrophobic (resists water) and magnetic. The nanoporous 3D structure of the nanocomposite selectively interacts with and binds to the oil molecules, captures the oil and stores it until it is squeezed out. The magnetic nanostructures give the intelligent sponge two additional functionalities: the controlled movement in the presence of an external magnetic field and the desorption of adsorbed components, such as oil, in a simulated and remote-controlled manner.
The OHM (oleophobic, hydrophobic, magnetic) nanocomposite slurry can be used to coat any cheap, commercially available sponge. The researchers applied a thin layer of the slurry to the sponge, squeezed out the excess and allowed it to dry. The sponge can be quickly and easily converted into a smart sponge (or "OHM sponge") with a selective affinity for oil.
Vinayak and his team tested the OHM sponge with many different types of crude oils of different density and viscosity. The OHM Sponge consistently absorbed up to 30 times its weight of oil and left the water behind. To imitate the natural waves, the researchers placed the OHM sponge on a shaker immersed in water. Even after vigorous shaking, the sponge releases less than 1% of the absorbed oil back into the water.
"Our sponge works effectively under different and extreme water conditions with different pH and salinity levels," said Dravid. "We believe we can solve a giga-ton problem with a nanoscale solution.
"We are pleased to introduce such smart sponges as a platform for environmental remediation that selectively removes and recovers pollutants present in water, soil and air, such as excess nutrients, heavy metal contaminants, VOCs/toxins and others," Nandwana said. "The nanostructured coating can be tailored to selectively adsorb (and later desorb) these pollutants".
The team is also working on another type of OHM sponge that can selectively absorb (and later recover) excess dissolved nutrients, such as phosphates, from fertilizer runoff and agricultural pollution. Stephanie Ribet, a PhD student in Dravid's laboratory and co-author of the paper, is pursuing this topic. The team plans to develop and commercialize the OHM technology for environmental remediation.
Quelle: Chemie.de - Intelligenter Schwamm könnte Ölverschmutzungen säubern
Original article: Industrial & Engineering Chemistry Research - OHM Sponge: A Versatile, Efficient and Ecofriendly Environmental Remediation Platform