Foam solution mops up oil

A team of researchers from Queensland University of Technology (QUT) has developed a non-toxic, low-cost foam for cleaning up oil spills. The team’s findings are published in The Journal of Physical Chemistry.

When an oil spill occurs, the foam can be sprayed onto its surface to quickly absorb the waste. The foam is then scraped away for safe disposal. The same principle could be applied to oil spills in the home.

“Thousands of tons of oil have been disgorged into our oceans over the decades,” said Associate Professor Jingsan Xu.

“One of the most memorable was the Exxon Valdez oil spill in Prince William Sound, Alaska, in 1989, which spilled 37,000 metric tons of crude oil and is considered one of the worst ever human-caused environmental disasters.

“More recently, the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 had the dubious honour of becoming the largest marine oil spill in the history of the petroleum industry.”

Prof Xu explained that current methods for cleaning up oil spills are usually messy and difficult to contain, while some methods such as in situ burning create more hazards for the environment. He said that the key to saving the environment from maximum damage is to mop up the oil as quickly as possible.

“So what we have focused on is the adaptability and possibilities associated with surfactants which are already widely used in research, industrial production and daily lives via household cleaning products,” Prof Xu said.

“Surfactants are compounds that lower the surface tension between two liquids, between a gas and a liquid, or between a liquid and a solid — in other words, they can be detergents, wetting agents, emulsifiers, foaming agents and dispersants.

“One way to remove the floating oil from [the] sea surface is adsorption. Hydrophobic porous foam — low-density material that can float on liquid — is a promising candidate to achieve that and we recently reported on the synthesis of a hydrophobic hybrid foam which showed excellent adsorption performance to a range of organic liquids.”

Prof Xu and the team have created what they call a ‘hybrid surfactant’ by combining stearic acid, an oil-soluble molecule, with water-dispersible alumina nanofibres via chemisorption at the oil−water interface.

“Our hybrid surfactant exhibits reversible switching between hydrophilic (molecules attracted to water) and lipophilic (able to dissolve in fats, oils, lipids and non-polar solvents) states by manipulating the adsorption−desorption volume of stearic acid attached to the alumina nanofibres,” he said.

“Therefore, the emulsions stabilised by this organic−inorganic hybrid can reversibly transform between oil-in-water and water-in-oil type by simple mechanical manipulation.

“Unlike conventional approaches, no other external stimulus is needed to set the amphiphilic properties of the hybrid surfactant. This protocol may have significant applications in cosmetic, food and other fields.

“As a bonus, organic−inorganic three-dimensional solid foams can be readily prepared based on the emulsion system, which demonstrates a strong potential for use in evaporating oil spills — in the ocean or the kitchen — in a very quick fashion.”

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