In 2010, mankind experienced one of the worst environmental disasters in history. The Deepwater Horizon oil spill off the Gulf of Mexico led to the discharge of 4.9 million barrels of oil, causing irreparable damage to the local ecosystem that is still felt to this day. There are, however, thousands of smaller spills that occur every year, but since they’re not that important you never hear about them in the news.
With this huge environmental challenge in mind, researchers at Imperial College London and the University of Toronto have developed a cheap sponge that can soak up oil relatively fast. The best thing about this sponge is that it can also work on wastewater from fracking (up to over 100 billion barrels a of such water are produced each year). At the moment, the toxic fracking byproduct is either injected deep underground or stored in huge tanks.
The team of chemical engineers led by Pavani Cherukupally sought to find a solution by turning to polyurethane foam, a common material used in everyday household items like mattresses. Although polyurethane foam has good oil absorption properties, it only works well under certain conditions of acidity, which can strengthen or weaken the affinity between oil droplets and the sponge.
“It’s all about strategically selecting the characteristics of the pores and their surfaces. Commercial sponges already have tiny pores to capture tiny droplets. Polyurethane sponges are made from petrochemicals, so they have already had chemical groups which make them good at capturing droplets,” said Cherukupally.
“The problem was that we had fewer chemical groups than what was needed to capture all the droplets.”
The researchers developed a coating that alters the foam’s texture, chemistry, and charge, thus making it more suitable for a broad range of situations. When viewed under a microscope, the coating contains hair-like particles of nanocrystalline silicon that act like fishing rods for the oil droplets.
“The critical surface energy concept comes from the world of biofouling research—trying to prevent microorganisms and creatures like barnacles from attaching to surfaces like ship hulls,” Dr. Cherukupally said in a statement.
“Normally, you want to keep critical surface energy in a certain range to prevent attachment, but in our case, we manipulated it to get droplets to cling on tight.”
When tested under four different scenarios of acidity, the coated foam soaked up between 95% and 99% of the oil and did so in no more than three hours.
The material can be washed with a solvent that extracts the oil, crucially allowing the foam to be reused.
Hopefully, this technology will soon become commercially available because, right now, our options are extremely limited and not very effective. For instance, British Petroleum used controversial chemicals called dispersants to clean up the Deepwater Horizon spill by breaking up the oil into smaller drops. The small size of the droplets allows microbes to digest the oil more easily while also emulsifying the oil in the process, harming the ocean ecosystems.
“Current strategies for oil spill cleanup are focused on the floating oil slick, but they miss the microdroplets that form in the water,” said Amy Bilton, a professor at the University of Toronto and co-author of the new study.
“Though our sponge was designed for industrial wastewater, adapting it for freshwater or marine conditions could help reduce environmental contamination from future spills.”
In the future, the researchers would like to use sponges to treat contamination from the gas, mining, and textile industries.
The findings appeared in the journal Nature Sustainability.