Researchers from Northwestern University created a smart sponge that can selectively soak up oil and leave behind clean water. The sponge can absorb over 30 times its own weight in oil and be reused dozens of times without losing effectiveness. It could serve as a cheap and effective way to clean up oil spills and preserve marine life.

Smart sponge selectively absorbs oil (on the left) while resisting water (on the right). Source: Northwestern UniversitySmart sponge selectively absorbs oil (on the left) while resisting water (on the right). Source: Northwestern University

Any size oil spill is harmful to the environment. Current solutions to clean up oil spills include burning the oil, using chemical dispersants to break down the oil and skimming or absorbing oil with unrecyclable sorbents. These options are harmful to the environment or expensive. The new sponge is sustainable and cheap.

The oleophobic hydrophobic magnetic (OHM) nanocomposite mixture can turn any commercially available sponge. To create OHM sponges a thin slurry is spread over a sponge, the excess is squeezed out and, once it is dry, the sponge is ready to go.

The mixture creates a nanoporous 3D structure that selectively interacts with and binds to oil molecules, capturing and storing the oil until it is squeezed out. The magnetic nanostructures have two other functionalities, controlled movement in the presence of external magnetic field and desorption of the absorbed components.

The team tested the OHM sponge with many types of crude oils with varying density and viscosity. The sponge was placed on a shaker and submerged in water to mimic natural waves. After shaking, the team found that the sponge only released less than one percent of the absorbed oil back into the water.

Researchers say that the coating could be tailored to selectively absorb and desorb a variety of contaminants. Currently, the team is working on another grade of OHM sponge that can absorb/desorb excess dissolved nutrients from fertilizer runoff and agricultural pollution.

A paper on the new sponge was published in Industrial Engineering and Chemical Research.