Although scientists have created many materials to absorb oil spills, most of them are used only to capture most of the oil slicks. However, a new sponge is designed to capture tiny suspended oil droplets that might otherwise be missed. The sponge was originally developed by Pavani Cherukupally, Ph.D., of Imperial College London.
Earlier versions of this sponge were made of ordinary polyurethane foam, although their aperture, surface chemical properties and surface area have been adjusted. This improves the ability of foams to attract and capture oil droplets while still allowing water to pass through. Even if it can capture more than 95% of the oil in a water sample, it takes three hours to complete, which is impractical in the real world.
In addition, it works best at a pH of 5.6 in water. According to Cherukupally, the pH of water that needs to be treated can be as high as 10, at which point the original sponge can capture only 6 to 7 percent of the oil droplets.
Cherukupally is now working with its colleagues to address these shortcomings in the new version of the material. The main improvement came from the addition of tiny nanocrystalline silicon particles. These coatings better adjust the surface area and surface chemistry of the sponge to capture oil droplets more quickly over a wide acidity range. In fact, it can now capture 90% of the oil droplets in 10 minutes.
Once the sponge is soaked in oil, it can be simply removed from the water and treated with a solvent to remove the captured oil before being used. Although scientists now intend to use the material for wastewater treatment, they point out that the material could also be used for freshwater and offshore oil spills.
The paper on the study was recently published in the journal Nature-Sustainable Development.