The sponge that cleans oil spills
Oil and water don’t mix, the saying goes, but in the event of a big oil spill, they do a pretty good imitation
That is one reason offshore crude-oil clean-ups can be so tough. One option is corralling the oil so that it can be skimmed or suctioned, which is difficult in roiling seas. Other options have serious environmental trade-offs—including burning the oil in place, dispersing it with chemicals or spreading various disposable materials to soak it up. Offshore drilling mishaps can be especially troublesome, producing not just a large surface slick but also masses of droplets suspended in a towering plume below.
Enter Oleo Sponge, a new invention meant to remedy these shortcomings. It is the brainchild of scientists at Argonne National Laboratory, operated by the University of Chicago for the U.S. Energy Department. They have developed a way to treat common household foam—used in cushions and the like—so that it will rapidly suck up oil from water, even below the surface. In addition, a hunk of Oleo Sponge can be wrung out and used again and again. Oil squeezed from the sponge also can be reused, which makes it a potential asset instead of a hazardous waste problem.
The results, while still preliminary, have been encouraging. The scientists report that their invention takes in—the technical term is “adsorbs”—up to 90 times its weight in oil.
Oleo Sponge has performed not just in the lab but also in tests at the National Oil Spill Response Research and Renewable Energy Test Facility in Leonardo, N.J. Operated by a contractor for the Interior Department, the facility’s centrepiece is a huge tank filled with 2.6 million gallons of saltwater, enabling equipment to be tested on something like a real-world scale. At the facility, large segments of foam were used and squeezed out repeatedly, with no significant degradation.
In its ordinary state, a piece of common foam will soak up fluid indiscriminately. How to make it especially attractive to oil? It depends on a process called “sequential infiltration synthesis,” which the Argonne scientists had previously invented for other purposes. This is a way of getting inorganic materials such as metal oxides into polymers such as polyurethane. In this case, the researchers adapted the technique so they could bind aluminium oxide to the fibres within the foam.
Thus primed, the foam was treated with carbon-based chemicals to make it oleophilic, or “oil loving.” Seth Darling, a co-inventor of the Oleo Sponge, notes that in this second step, he and his colleagues could also easily treat the foam with a different chemical to make it soak up some other unwanted substances, such as heavy metals, pesticide-laden runoff or waste pharmaceuticals.
From there, it is just a matter of getting the sponge into contact with oily water. Surface spills could be handled by towing a large sponge through the spill; once contact is made, oil’s property of “cohesion” encourages the molecules to pull one another in.
For underwater oil, Dr Darling envisions fishing trawlers dragging net-mounted sponges through oily waters. Saturated sponges could be hauled aboard and wrung out, the oil could be collected, and the process could be repeated as needed. Depending on their long-term durability, precautionary arrays of the sponges might even be used to surround offshore oil wells as protection against a spill.
photo: Scientists say that they have invented a sponge made of common polyurethane foam treated to absorb up to 90 times its weight in oil