When the Deepwater Horizon drilling pipe blew out seven years ago, beginning the worst oil spill in U.S. history, those in charge of the recovery discovered that the millions of gallons of oil bubbling from the sea floor weren’t all collecting on the surface where it could be skimmed or burned. Some of it was forming a plume and drifting under the surface of the ocean.
A new foam, called Oleo Sponge, was developed to address this problem. The material not only easily absorbs oil from water, but is also reusable and can pull dispersed oil from the entire water column — not just the surface. Many molecules can grab oil, but the problem is how to get them into a useful structure and bind them there permanently.
The inventors started with common polyurethane foam that is used in everything from furniture cushions to home insulation. This foam has nooks and crannies that could provide ample surface area to grab oil, but it needed a new surface chemistry to firmly attach the oil-absorbing molecules. A technique called sequential infiltration synthesis (SIS) was adapted to grow an extremely thin layer of metal oxide “primer” near the foam’s interior surfaces. This serves as the perfect glue for attaching the oil-absorbing molecules, which are deposited in a second step; they hold onto the metal oxide layer with one end, and reach out to grab oil molecules with the other.
The result is the Oleo Sponge, a block of foam that easily absorbs oil from the water. The material, which looks a bit like an outdoor seat cushion, can be wrung out to be reused, and the oil recovered. In tests, the Oleo Sponge successfully collected diesel and crude oil from both below and on the water surface.
Oleo Sponge could potentially also be used routinely to clean harbors and ports, where diesel and oil tend to accumulate from ship traffic. The technique can be adapted to other types of cleanup besides oil in seawater — a different molecule can be attached to grab any specific substance.