Sponge can soak up and release spilled oil hundreds of times
Difficult clean up
US Coast Guard Photo/Alamy Stock Photo
A new material can absorb up to 90 times its own weight in spilled oil and then be squeezed out like a sponge and reused, raising hopes for easier clean-up of oil spill sites.
This contrasts with most commercial products for soaking up oil, called “sorbents”. These are generally only good for a single use, acting like a paper towel used to mop up a kitchen mess and then tossed away. The discarded sorbents and oil are then normally incinerated.
But what if the oil could be recovered and the sorbent reused? The new material, created by Seth Darling and his colleagues at Argonne National Laboratory in Illinois, seems to allow for both of these processes, cutting waste.
The oil sponge consists of a simple foam made of polyurethane or polyimide plastics and coated with “oil-loving” silane molecules with a sweet spot for capturing oil. Too little chemical attraction would render the sponge useless as an absorber, whereas too much would mean the oil could not be released.
In laboratory tests, the researchers found that when engineered with just the right amount of silane, their foam could repeatedly soak up and release oil with no significant changes in capacity.
But to determine whether this material could help sort out a big spill in marine waters, they needed to perform a special large-scale test.
Recreating a spill
To do this, the team made an array of square pads of the sponge material measuring around 6 square metres. “We made a lot of the foam, and then these pieces of foam were placed inside mesh bags – basically laundry bags, with sewn channels to house the foam,” Darling says.
The researchers suspended their sponge-filled bags from a bridge over a large pool specially designed for practising emergency responses to oil spills.
They then dragged the sponges behind a pipe spewing crude oil to test the material’s capability to remove oil from the water. They next sent the sponges through a wringer to remove the oil and then repeated the process, carrying out many tests over multiple days.
This so-far unpublished test was conducted in early December at the National Oil Spill Response Research & Renewable Energy Test Facility in Leonardo, New Jersey.
“Our treated foams did way better than either the untreated foam that we brought or the commercial sorbent,” says Darling.
The team does not yet know, however, whether this material can perform well under the high pressures of the deep sea.
Even so, this material could be used for spills near shores, where clean-up is particularly difficult. “I see it as a major advance in cleaning small spills and spills close to coastlines where dispersants cannot be used easily,” says Vijay John at Tulane University in New Orleans, Louisiana.
“In an ideal world, you would have warehoused collections of this foam sitting near wherever there are offshore operations… or where there’s a lot of shipping traffic, or right on rigs… ready to go when the spill happens,” says Darling.
The next challenge for the team is to optimise the process for scale-up.
Journal reference: Journal of Materials Chemistry A, DOI: 10.1039/C6TA09014A