As the Deepwater Horizon incident showed us, oil spills can be huge environmental disasters. That said, there are also considerable challenges in dealing with the waste products generated by the forestry and agriculture industries. Now, scientists from Switzerland's Empa research group have come up with a method of addressing the one problem with the other – they've developed sponges made from cellulose waste, that can soak up 50 times their own weight in oil.
The sponges are made from a chemically-modified version of what's called nanofibrillated cellulose (NFC), also known as nanocellulose.
Regular NFC is made by adding water to cellulose-containing materials (such as wood waste, discarded paper or agricultural by-products), extruding the resulting pulp at high pressure to create a gel, then freeze-drying the gel to remove the water. This results in a sponge made up of "long and interconnected cellulose nanofibres," that soaks up both oil and water.
For the sponges to be effective at cleaning up oil spills, however, it wouldn't do if they filled up with water before they could soak up much oil. Therefore, the Empa team mixes a reactive alkoxysilane molecule into the gel, before the freeze-drying process. This causes the sponge to lose its hydrophilic (water-absorbing) qualities, so it only sucks up oily liquids.
In lab tests, the sponges effectively removed substances such as engine oil, silicone oil, ethanol, acetone and chloroform from water samples, within a matter of seconds. Additionally, the oil-saturated sponges remain floating for easy retrieval, and they're biodegradable.
Empa is now working on scaling up the technology for use on a much larger (oil spill-sized) scale, and is seeking partners for its commercial development.
A paper on the research was recently published in the journal Chemistry of Materials.
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