A team from Northwestern University has developed a highly porous smart sponge that can selectively soak up oil spills in water. With an ability to absorb more than 30 times its weight in oil, the sponge could be used to inexpensively and efficiently clean up 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 secret lies in a nanocomposite coating of magnetic nanostructures and a carbon-based substrate that is Oleophilic (attracts oil), Hydrophobic (resists water) and Magnetic (OHM). The nanocomposite’s nanoporous three-dimensional structure selectively interacts with and binds to the oil molecules, capturing and storing the oil until it is squeezed out.
“We all know oil spills have a catastrophic effect on the environment, wildlife and human health and the economy as well,” Professor Vinayak Dravid, who led the research, told Forbes. “Typically we only hear about the large scale disasters, but there are smaller spills all the time that are equally as destructive to the local ecosystem and neighboring 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.”
The Costco Busan spilled over 58,000 gallons of heavy fuel into San Francisco Bay in 2007
For as long as fossil fuels are still used, there will always be oil spills. Just three weeks ago, Russia declared a state of emergency after six million gallons of diesel fuel from a power plant in Norilsk leaked into the Ambarnaya river that flows into the ecologically sensitive Arctic Ocean. Greenpeace estimates the cost of environmental damage to waters in the region at $1.4 billion and at least 10 years until biodiversity returns to normal in the area.
Oil spill clean-up is an unpleasant, expensive and complicated process that frequently harms marine life and further damages the surrounding 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.
Each of those approaches has its own drawbacks and none of them are sustainable solutions. Burning increases carbon emissions and dispersants are extremely harmful for marine wildlife. Skimmers are ineffective 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.
The OHM sponge can absorb 30 times its weight in oil and be reused several dozen times
The research undertaken by the team at Northwestern was published in the journal Industrial Engineering and Chemical Research. Their solution bypasses these challenges by selectively absorbing oil and leaving clean water and unaffected marine life behind. The OHM nanocomposite slurry can be used to coat any cheap, commercially available sponge. The researchers applied a thin coating of the slurry to the sponge, squeezed out the excess and let it dry.
Dravid and his team tested the OHM sponge with 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.
“Our sponge works effectively in diverse and extreme aquatic conditions that have different pH and salinity levels,” Dravid said.
The OHM nanocomposite slurry can be used to coat any commercially available sponge
The Deepwater Horizon disaster is considered to be the largest marine oil spill and environmental disaster in American history. In April 2010, a methane gas explosion engulfed the drilling platform, releasing over 21 million gallons of oil into the Gulf of Mexico.
Just three years later, in April 2013, it was reported that dolphins and other marine life were dying in record numbers with infant dolphins dying at six times the normal rate. In 2014, it was reported that tuna and amberjack that were exposed to oil from the spill developed deformities of the heart and other organs that would probably be fatal or at least life-shortening.
In fact, the Gulf of Mexico is so polluted, that every year an event known as the dead zone occurs. Annual spring rains wash the nutrients used in fertilizers and sewage into the Mississippi river. They then flow out into the open sea. That fresh water, which is less dense than sea water, sits on top of the ocean, preventing oxygen from properly mixing.
Eventually those freshwater nutrients can spur a burst of algal growth, which consumes oxygen as the plants decompose. The resulting patch of low-oxygen waters leads to a condition called hypoxia, where animals in the area suffocate and die. Last year, scientists estimated the dead zone in the Gulf of Mexico spread about 7,800 square miles across the continental shelf situated off the coast.
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.
“The same OHM sponge, with a slight modification, can absorb almost 95% of phosphorus. And that's something we have recently done with the Chicago Water Reclamation District. So we are very excited,” Dravid said.
The Deepwater Horizon disaster released 21 million gallons of oil into the Gulf of Mexico
The team is currently talking to the US Coast Guard and Schmidt Marine, the philanthropic ocean technology group. Cost issue and scalability are the primary concerns for investors, but because of the extremely low cost and potentially high return of this concept, Dravid is optimistic that the full potential of this game-changing green technology will be realized.
For instance, the oil returned from the spill clean up can be sold back to whoever is responsible for the spill and as an added bonus, once the OHM slurry has eventually lost its oil-soaking properties, it has a second life as an anode for lithium ion batteries
“Our dream and ambition is that after the oil recovery, instead of throwing away that sponge, we actually control burn it and use that soot as an electrode for lithium ion battery, and it actually does much better than the current graphitic anodes,” Dravid said.
