Oil and water famously don’t mix, and yet it’s very difficult to extricate the former from the latter. When light crude oil spills at sea, it rapidly spreads out into a thin sheen that is notoriously tough to clean up, especially when spills happen in remote areas. But the trick to doing so in an easy, environmentally sustainable way may lie just beneath the water’s surface, according to new research.

A team of chemists from the City College of New York has created an eco-friendly version of a “chemical herder.” The term describes a class of molecules that have been used in oil spill cleanup since the early 1970s. Typically they’re sprayed on the water surrounding a spill, where they alter the surface tension of the water and cause a thin film of oil to condense into a slick several millimeters thick. This can then be siphoned from the water or burned off the surface.

But this strategy may simply exchange one form of marine pollution for another. The most common chemical herders currently in use are based on silicone. They aren’t biodegradable, and their long-term effects on marine organisms are unknown.

The new, eco-friendly chemical herders are based on phytol, a naturally occurring small molecule that is a component of chlorophyll, the photosynthetic pigment that enables plants to turn sunlight into energy. Phytol is abundant in the layer of water just below the sea’s surface and is harmless to marine life.

Phytol-derived herders have some powerful advantages, the researchers report in the June 26 issue of Science Advances. Phytol is cheap and easy to produce – marine algae provide a ready source. And phytol-derived herders, just like their parent molecule, break down quickly into non-toxic components.

Best – and most important – of all, the green herders work. The researchers tested their molecules on miniature crude oil spills in laboratory trays, under various temperature and salinity conditions. When a dose of herder was added to the tray, “instantaneously, the thin oil layer contracted to a thick slick,” the researchers write.

One phytol-derived molecule, nicknamed PIm (that’s short for 1-methyl-3-(2-oxo-2-((phytyl)oxy)ethyl)-1H-imidazol-3-ium bromide, so thank goodness for nicknames), matched the performance of a commonly used silicone-based herder, Silsurf, in head-to-head trials. Both of these chemicals thickened the laboratory oil slicks by 1,000 percent within 30 minutes.

The results demonstrate that phytol-based herders are both safe for the marine environment and effective at condensing oil slicks, the researchers say, news that should nudge oil spill cleanup in a more sustainable direction. – Sarah DeWeerdt | 30 June 2015

Source: Gupta D. et al. 2015 Sacrificial amphiphiles: Eco-friendly chemical herders as oil spill mitigation chemicals. Science Advances DOI: 10.1126/sciadv.1400265

Header image: An oil spill cleanup drill off the coast of Cameroon. (Chemical herders are used to clean up spills in conditions where the booms shown here are not effective.) Credit: International Maritime Organization via Flickr.