A sponge coated with a paraffin-like material can suck up 99 per cent of oil from water at low temperatures, offering a solution to crude oil spills in Arctic environments.
Such spills happen with worrying frequency, but in the cold, oil can be more difficult to clean up. At low temperatures, crude oil’s heavier compounds, including the roughly 2.44 per cent of oil that is natural paraffin wax, begin to crystallise. The paraffin crystals then try to link together, which creates larger, stickier masses. Pre-existing clean-up technologies struggle to pick up this thicker, stickier oil.
Previous experimental removal methods weren’t that practical, as they included heating oil-laden water to break down these molecules or running the oily water through a large centrifuge to separate the molecules.
Pavani Cherukupally at Imperial College London and her colleagues have come up with a different approach. “We’re trying to keep the oil as it is, then develop the sponge to capture it,” she says. “This means we don’t have to do the pre-heating process and can directly tackle the problem.”
She analysed the molecular structure of the sticky oil and engineered a nanocoating with a near-identical structure. A sponge carrying this paraffin-like nanocoating is particularly likely to bind to any sticky oil it encounters. In tests, such a sponge was able to adsorb up to 99 per cent of Texas raw crude oil mixed into 100 millilitres of water within 3 hours, at temperatures as low as 5°C.
The oil was drained from the sponge by soaking it in a solvent that released the crude. The sponge’s coating withstood at least 10 further uses. “I haven’t tested it beyond 10,” admits Cherukupally. “Experiments take a long time.”
Previous research has developed similar sponges that can suck up oil, though past work hasn’t focused on the lower temperatures found in the Arctic, where a significant proportion of oil exploration and production is located.
Cherukupally hopes to improve her laboratory tests by improving the sponge and coating’s efficiency, and testing it on different crude oil grades, which have different microstructures.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abc7926